Article

NRF-1 – A transactivator of nuclear-encoded respiratory genes in animal-cells

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Abstract

The assembly of the respiratory apparatus requires the coordinate expression of a large number of genes from both nuclear and mitochondrial genetic systems. In vertebrate organisms, the molecular mechanisms integrating the activities of these distinct genomic compartments in response to tissue demands for respiratory energy remain unknown. A potential inroad to this problem came with the discovery of nuclear respiratory factor 1 (NRF-1), a novel transcriptional activator defined by mutational and DNA binding analysis of the somatic cytochrome c promoter. Functional NRF-1 sites are now observed in several other recently isolated nuclear genes whose products function in the mitochondria. Among these are genes encoding subunits of the cytochrome c oxidase (subunit VIc) and reductase (ubiquinone-binding protein) complexes. In addition, a functional NRF-1 site resides in the MRP RNA gene encoding the RNA moiety of a ribonucleoprotein endonuclease involved in mitochondrial DNA replication. Synthetic oligomers of these sites competitively displace NRF-1 binding to the cytochrome c promoter. NRF-1-binding activities for each site also have the same thermal lability, copurify chromatographically, and make similar guanosine nucleotide contacts within each recognition sequence. Moreover, NRF-1 recognition in vitro correlates with the ability of each site to stimulate expression in vivo from a truncated cytochrome c promoter. The presence of NRF-1-binding sites in nuclear genes encoding structural components of the mammalian electron transport chain, as well as the mitochondrial DNA replication machinery, suggests a mechanism for coordination of nuclear and mitochondrial genetic systems through the concerted modulation of nuclear genes.

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... The search for cis-elements and transfactors that specifically regulate transcription of nuclear genes encoding subunits of the OXPHOS system has resulted in a discovery of several specific elements and their binding proteins. The OXPHOS genes containing these cis-elements are listed in Table 3. Table 3. List of OXPHOS genes containing binding sites for some transfactors Nuclear respiratory factor-1 (NRF-1) Somatic cytochrome c (Evans and Scarpulla, 1989;Evans and Scarpulla, 1990) Ubiquinone-binding protein (Evans and Scarpulla, 1990) COX Vb (Bachman et al., 1996;Virbasius et al., 1993) COX Vic (Evans and Scarpulla, 1990) MRP-RNA (Evans and Scarpulla, 1990) MtTFA (Virbasius and Scarpulla, 1994) Fl-ATPase y-subunit (Chau et al., 1992) Nuclear respiratory factor-2 (NRF-2) COX IV (Carter and Avadhani, 1994;Carter et al., 1992;Virbasius md Scarpulla, 1991) COX Vb (Bachman et al., 1996;Sucharov et al., 1995) COX VIIaL (Seelan et al, 1996) Fl-ATPase y-subunit (Villena et al., 1994;Virbasius and Scarpulla, 1994) UCP (Villena et al., 1998; Yuberoef a/., 1994) MtTFA (Virbasius and Scarpulla, 1994) ...
... The search for cis-elements and transfactors that specifically regulate transcription of nuclear genes encoding subunits of the OXPHOS system has resulted in a discovery of several specific elements and their binding proteins. The OXPHOS genes containing these cis-elements are listed in Table 3. Table 3. List of OXPHOS genes containing binding sites for some transfactors Nuclear respiratory factor-1 (NRF-1) Somatic cytochrome c (Evans and Scarpulla, 1989;Evans and Scarpulla, 1990) Ubiquinone-binding protein (Evans and Scarpulla, 1990) COX Vb (Bachman et al., 1996;Virbasius et al., 1993) COX Vic (Evans and Scarpulla, 1990) MRP-RNA (Evans and Scarpulla, 1990) MtTFA (Virbasius and Scarpulla, 1994) Fl-ATPase y-subunit (Chau et al., 1992) Nuclear respiratory factor-2 (NRF-2) COX IV (Carter and Avadhani, 1994;Carter et al., 1992;Virbasius md Scarpulla, 1991) COX Vb (Bachman et al., 1996;Sucharov et al., 1995) COX VIIaL (Seelan et al, 1996) Fl-ATPase y-subunit (Villena et al., 1994;Virbasius and Scarpulla, 1994) UCP (Villena et al., 1998; Yuberoef a/., 1994) MtTFA (Virbasius and Scarpulla, 1994) ...
... The search for cis-elements and transfactors that specifically regulate transcription of nuclear genes encoding subunits of the OXPHOS system has resulted in a discovery of several specific elements and their binding proteins. The OXPHOS genes containing these cis-elements are listed in Table 3. Table 3. List of OXPHOS genes containing binding sites for some transfactors Nuclear respiratory factor-1 (NRF-1) Somatic cytochrome c (Evans and Scarpulla, 1989;Evans and Scarpulla, 1990) Ubiquinone-binding protein (Evans and Scarpulla, 1990) COX Vb (Bachman et al., 1996;Virbasius et al., 1993) COX Vic (Evans and Scarpulla, 1990) MRP-RNA (Evans and Scarpulla, 1990) MtTFA (Virbasius and Scarpulla, 1994) Fl-ATPase y-subunit (Chau et al., 1992) Nuclear respiratory factor-2 (NRF-2) COX IV (Carter and Avadhani, 1994;Carter et al., 1992;Virbasius md Scarpulla, 1991) COX Vb (Bachman et al., 1996;Sucharov et al., 1995) COX VIIaL (Seelan et al, 1996) Fl-ATPase y-subunit (Villena et al., 1994;Virbasius and Scarpulla, 1994) UCP (Villena et al., 1998; Yuberoef a/., 1994) MtTFA (Virbasius and Scarpulla, 1994) ...
Thesis
Biogenesis of mammalian mitochondria requires the participation of both nuclear and mitochondrial genes. This thesis presents studies that characterize the common features of several nuclear encoded mitochondrial promoter genes and proposes the identity of factors regulating the transcription and responsible for coordinated, constitutive expression of diverse mammalian oxidative phosphorylation (OXPHOS) genes. As a model, we chose to study the promoters of four nuclear-encoded OXPHOS genes, all which are constitutively expressed, but, in addition, exhibit different responses to hormone and/or growth-activation. They also represent functionally different OXPHOS complexes. These promoters are from the human cytochrome c1, the mitochondrial transcription factor, mtTFA, the F1-ATPase b-subunit, and the adenine nucleotide translocator isoform 2 (ANT2) genes. The results presented in this thesis can be summarized as follows: The General transcription factor Sp1 can activate and repress different mammalian OXPHOS genes. Sp1 binding elements (GC boxes) are present in most, if not all, OXPHOS promoter, which suggest that Sp1 may have a general role in regulating the expression of nuclear encoded mitochondrial genes. (b) Sp1-mediated repression and activation from the ANT2 promoter require the D transactivation domain of Sp1 bound to the Cbox. (c) Sp1-mediated repression from the ANT2 promoter is not due to steric interference with the assembly of the transcription machinery. Sp1 bound to the Cbox, under certain conditions, activates the ANT2 promoter (d) Different Sp family members (Sp2, Sp3 and Sp4) differentially affect transcription of the OXPHOS promoters studied. (e) AP-2 enhances Sp1-dependent transactivation of the ANT2 promoter gene. (f) Sp3, but not Sp4, can repress the ANT2 promoter via the Cbox, suggesting that different members of the Sp family can have different roles when they bind to the ANT2 Cbox. (g) Thyroid hormone activates reporter gene expression driven from the ANT2 and cytochrome c1 promoters, which suggests that thyroid hormone induction of some OXPHOS genes is at the transcriptional level.
... The search for cis-elements and transfactors that specifically regulate transcription of nuclear genes encoding subunits of the OXPHOS system has resulted in a discovery of several specific elements and their binding proteins. The OXPHOS genes containing these cis-elements are listed in Table 3. Table 3. List of OXPHOS genes containing binding sites for some transfactors Nuclear respiratory factor-1 (NRF-1) Somatic cytochrome c (Evans and Scarpulla, 1989;Evans and Scarpulla, 1990) Ubiquinone-binding protein (Evans and Scarpulla, 1990) COX Vb (Bachman et al., 1996;Virbasius et al., 1993) COX Vic (Evans and Scarpulla, 1990) MRP-RNA (Evans and Scarpulla, 1990) MtTFA (Virbasius and Scarpulla, 1994) Fl-ATPase y-subunit (Chau et al., 1992) Nuclear respiratory factor-2 (NRF-2) COX IV (Carter and Avadhani, 1994;Carter et al., 1992;Virbasius md Scarpulla, 1991) COX Vb (Bachman et al., 1996;Sucharov et al., 1995) COX VIIaL (Seelan et al, 1996) Fl-ATPase y-subunit (Villena et al., 1994;Virbasius and Scarpulla, 1994) UCP (Villena et al., 1998; Yuberoef a/., 1994) MtTFA (Virbasius and Scarpulla, 1994) ...
... The search for cis-elements and transfactors that specifically regulate transcription of nuclear genes encoding subunits of the OXPHOS system has resulted in a discovery of several specific elements and their binding proteins. The OXPHOS genes containing these cis-elements are listed in Table 3. Table 3. List of OXPHOS genes containing binding sites for some transfactors Nuclear respiratory factor-1 (NRF-1) Somatic cytochrome c (Evans and Scarpulla, 1989;Evans and Scarpulla, 1990) Ubiquinone-binding protein (Evans and Scarpulla, 1990) COX Vb (Bachman et al., 1996;Virbasius et al., 1993) COX Vic (Evans and Scarpulla, 1990) MRP-RNA (Evans and Scarpulla, 1990) MtTFA (Virbasius and Scarpulla, 1994) Fl-ATPase y-subunit (Chau et al., 1992) Nuclear respiratory factor-2 (NRF-2) COX IV (Carter and Avadhani, 1994;Carter et al., 1992;Virbasius md Scarpulla, 1991) COX Vb (Bachman et al., 1996;Sucharov et al., 1995) COX VIIaL (Seelan et al, 1996) Fl-ATPase y-subunit (Villena et al., 1994;Virbasius and Scarpulla, 1994) UCP (Villena et al., 1998; Yuberoef a/., 1994) MtTFA (Virbasius and Scarpulla, 1994) ...
... The search for cis-elements and transfactors that specifically regulate transcription of nuclear genes encoding subunits of the OXPHOS system has resulted in a discovery of several specific elements and their binding proteins. The OXPHOS genes containing these cis-elements are listed in Table 3. Table 3. List of OXPHOS genes containing binding sites for some transfactors Nuclear respiratory factor-1 (NRF-1) Somatic cytochrome c (Evans and Scarpulla, 1989;Evans and Scarpulla, 1990) Ubiquinone-binding protein (Evans and Scarpulla, 1990) COX Vb (Bachman et al., 1996;Virbasius et al., 1993) COX Vic (Evans and Scarpulla, 1990) MRP-RNA (Evans and Scarpulla, 1990) MtTFA (Virbasius and Scarpulla, 1994) Fl-ATPase y-subunit (Chau et al., 1992) Nuclear respiratory factor-2 (NRF-2) COX IV (Carter and Avadhani, 1994;Carter et al., 1992;Virbasius md Scarpulla, 1991) COX Vb (Bachman et al., 1996;Sucharov et al., 1995) COX VIIaL (Seelan et al, 1996) Fl-ATPase y-subunit (Villena et al., 1994;Virbasius and Scarpulla, 1994) UCP (Villena et al., 1998; Yuberoef a/., 1994) MtTFA (Virbasius and Scarpulla, 1994) ...
Thesis
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... Under normoxia, metastatic and low-metastatic cancers (bladder-urothelial, breast, and colon adenocarcinomas; head and neck squamous cell carcinoma) maintain high mRNA levels of NRF-1 [174]. A high NRF-1 protein level is linked to an increment in the transcription of nuclear genes encoding some subunits of several respiratory chain complexes [90,91] and ATPS in cervix HeLa cancer cells (Figure 2; Table 3). It has been suggested that NRF-1 may also induce the expression of several components of mtDNA transcription and replication machinery as well as the mitochondrial heme biosynthetic pathway [175]. ...
... Cont.Abbreviations: 2OGDH, 2 oxoglutarate dehydrogenase; ACO, aconitase; AIF, apoptosis-inducing factor; ATG13, autophagy-related protein 13; ATPS, adenosine triphosphate synthase; ATT, total aspartate aminotransferase; BNIP3, BCL2/adenovirus E1B 19 kDa protein-interacting protein 3; COX, cytochrome c oxidase; CPT-I and CPTII, carnitine palmitoyl transferases; CS, citrate synthase; FH, fumarate hydratase; fum, fumarate; GA, glutaminase; HACoADH, β-hydroxyacyl-CoA dehydrogenase; IDH, isocitrate dehydrogenase; mal, malate; ND1, NADH dehydrogenase; NRF-1, nuclear respiratory factor 1; OxPhos, oxidative phosphorylation; OAA, oxaloacetate; PDH, pyruvate dehydrogenase complex; PDK, pyruvate dehydrogenase kinase; SDH, succinate dehydrogenase; SLC38A5 and SLC1A5, Solute Carrier (Family 38 Member 5 and Family 1 Member 1); SOC2, Leucine-Rich Repeat Scaffold Protein. * Activities were normalized for transfection efficiency by Hirt DNA analysis[90]. ...
Article
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Cancer development, growth, and metastasis are highly regulated by several transcription regulators (TRs), namely transcription factors, oncogenes, tumor-suppressor genes, and protein kinases. Although TR roles in these events have been well characterized, their functions in regulating other important cancer cell processes, such as metabolism, have not been systematically examined. In this review, we describe, analyze, and strive to reconstruct the regulatory networks of several TRs acting in the energy metabolism pathways, glycolysis (and its main branching reactions), and oxidative phosphorylation of nonmetastatic and metastatic cancer cells. Moreover, we propose which possible gene targets might allow these TRs to facilitate the modulation of each energy metabolism pathway, depending on the tumor microenvironment.
... To identify the putative protein factors controlling this transcriptional response, we performed a motif analysis of the up-regulated genes using the Broad Molecular Signatures Database (MSigDB). Binding sites of the nuclear respiratory factor-1 (Nrf1), the key factor mediating mitochondrial biogenesis (35)(36)(37), was designed as one of the top-scoring motifs (Fig. 4C). Accordingly, we showed that the level of Nrf1 mRNA was elevated in PHOSPHO1 KO primary brown adipocytes, and PHOSPHO1 knocked down brown adipocytes cell lines (Fig. 4 D and E), compared to WT controls, consistent with increased the mitochondrial copy number in KO BAT (Fig. 2C). ...
... Nonetheless, our data show that BAT is a major target of PHOSPHO1 depletion, triggering elevated mitochondrial and thermogenic gene expression, oxygen consumption, and mitochondrial biogenesis, the latter evidenced by an increase in mitochondrial DNA copy number. Indeed, Nrf1 is a key transcription factor mediating mitochondrial biogenesis (35)(36)(37) and Nrf1 transcripts were elevated in PHOSPHO1 KO BAT and KO brown adipocytes. Supporting the role of Nrf1 in mediating the effects of (38). ...
Article
Phosphocholine phosphatase-1 (PHOSPHO1) is a phosphocholine phosphatase that catalyzes the hydrolysis of phosphocholine (PC) to choline. Here we demonstrate that the PHOSPHO1 transcript is highly enriched in mature brown adipose tissue (BAT) and is further induced by cold and isoproterenol treatments of BAT and primary brown adipocytes. In defining the functional relevance of PHOPSPHO1 in BAT thermogenesis and energy metabolism, we show that PHOSPHO1 knockout mice are cold-tolerant, with higher expression of thermogenic genes in BAT, and are protected from high-fat diet-induced obesity and development of insulin resistance. Treatment of mice with the PHOSPHO1 substrate phosphocholine is sufficient to induce cold tolerance, thermogenic gene expression, and allied metabolic benefits. Our results reveal a role of PHOSPHO1 as a negative regulator of BAT thermogenesis, and inhibition of PHOSPHO1 or enhancement of phosphocholine represent innovative approaches to manage the metabolic syndrome.
... Several reports have suggested that the activated Nrf2/ARE pathway also has a role in mitochondrial biogenesis which acts in concert with transcriptional co-activator PGC1α with the outcome of regulating mitochondrial-ETC subunit and enzyme synthesis [129][130][131]. In normal cellular conditions Keap1, a cytosolic inhibitory protein leads to proteasomal degradation of NRF2, contrary to this during oxidative stress conditions (high ROS level), Keap1 inactivation leads to NRF2 activation [132]. ...
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Cellular ROS production participates in various cellular functions but its accumulation decides the cell fate. Malignant cells have higher levels of ROS and active antioxidant machinery, a characteristic hallmark of cancer with an outcome of activation of stress-induced pathways like autophagy. Autophagy is an intracellular catabolic process that produces alternative raw materials to meet the energy demand of cells and is influenced by the cellular redox state thus playing a definite role in cancer cell fate. Since damaged mitochondria are the main source of ROS in the cell, however, cancer cells remove them by upregulating the process of mitophagy which is known to play a decisive role in tumorigenesis and tumor progression. Chemotherapy exploits cell machinery which results in the accumulation of toxic levels of ROS in cells resulting in cell death by activating either of the pathways like apoptosis, necrosis, ferroptosis or autophagy in them. So understanding these redox and autophagy regulations offers a promising method to design and develop new cancer therapies that can be very effective and durable for years. This review will give a summary of the current therapeutic molecules targeting redox regulation and autophagy for the treatment of cancer. Further, it will highlight various challenges in developing anticancer agents due to autophagy and ROS regulation in the cell and insights into the development of future therapies. Graphical Abstract
... Nrf1, an important transmembrane transcription factor, is located in the endoplasmic reticulum and forms a heterodimer with small Maf or other bZIP proteins. The combination of the heterodimer with an antioxidant response element (ARE) regulates various physiological processes such as energy homeostasis, apoptosis, and inflammatory response (Evans and Scarpulla, 1990;Scarpulla, 1996;Zhang and Manning, 2015). Previous studies have shown that Nrf1 might act as a novel renal fibrosis antagonist in renal fibroblast cells (Hsieh et al., 2016). ...
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Renal ischemia–reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and has no effective treatment. Exploring the molecular mechanisms of renal IRI is critical for the prevention of AKI and its evolution to chronic kidney disease and end-stage renal disease. The aim of the present study was to determine the biological function and molecular mechanism of action of miR-92a-3p in tubular epithelial cell (TEC) pyroptosis. We investigated the relationship between nuclear factor-erythroid 2-related factor 1 (Nrf1) and TEC pyroptosis induced by ischemia–reperfusion in vivo and oxygen–glucose deprivation/reoxygenation (OGD/R) in vitro . MicroRNAs (miRNAs) are regulators of gene expression and play a role in the progression of renal IRI. Nrf1 was confirmed as a potential target for miRNA miR-92a-3p. In addition, the inhibition of miR-92a-3p alleviated oxidative stress in vitro and decreased the expression levels of NLRP3, caspase-1, GSDMD-N, IL-1β, and IL-18 in vitro and in vivo . Moreover, Zn-protoporphyrin-IX, an inhibitor of heme oxygenase-1, reduced the protective effect of Nrf1 overexpression on OGD/R-induced TEC oxidative stress and pyroptosis. The results of this study suggest that the inhibition of miR-92a-3p can alleviate TEC oxidative stress and pyroptosis by targeting Nrf1 in renal IRI.
... In yeast, ROS can downregulate the pathway of mitochondrial biosynthesis through the action of Hap4p; in mammals, ROS can trigger PGC-1α and induce enhanced mitochondrial biosynthesis [31]. Previous studies have reported that in mammalian cells, mitochondrial biosynthesis is mainly performed through the NRF1 pathway [32]. NRF1 is a transcription factor that regulates the transcription of the mitochondrial gene body TFAM. ...
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... PGC-1α was discovered as a PPARγ-interacting protein that is expressed preferentially in brown adipose tissue (BAT) [1,2]. PGC-1α binds to transcription factors, such as nuclear respiratory factor (NRF)-1, NRF-2, and estrogen-related receptor α (ERRα), thereby coactivating downstream genes [3][4][5][6]. NRF-1 and NRF-2 transcriptionally regulate various mitochondrial genes involved in the respiratory chain, and replication and transcription of mitochondrial DNA (mtDNA), which encodes part of proteins comprising respiratory chain complexes [5]. ERRα modulates β-oxidation and the tricarboxylic acid cycle, as well as mitochondrial biogenesis [6][7][8]. ...
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Peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α) regulates mitochondrial DNA replication and mitochondrial gene expression by interacting with several transcription factors. White adipose tissue (WAT) mainly comprises adipocytes that store triglycerides as an energy resource and secrete adipokines. The characteristics of WAT vary in response to systemic and chronic metabolic alterations, including obesity or caloric restriction. Despite a small amount of mitochondria in white adipocytes, accumulated evidence suggests that mitochondria are strongly related to adipocyte-specific functions, such as adipogenesis and lipogenesis, as well as oxidative metabolism for energy supply. Therefore, PGC-1α is expected to play an important role in WAT. In this review, we provide an overview of the involvement of mitochondria and PGC-1α with obesity- and caloric restriction-related physiological changes in adipocytes and WAT.
... We took advantage of ChIP-seq data for NRF1 from other cell lines and observed a large overlap with PPARGC1A binding regions ( Supplementary Fig. S6B). NRF1 has previously been implicated in controlling mitochondrial function and its metabolic activities (Evans et al., 1990;Wu et al., 1999;Cam et al., 2004) and consistent with this, two of the top GO terms for genes associated with PPARGC1A binding regions are "mitochondrial organisation" and "TCA cycle and respiratory electron transport" (Supplementary Fig. S6E). ...
Preprint
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Oesophageal adenocarcinoma (OAC) patients show poor survival rates and there are few targeted molecular therapies available. However, components of the receptor tyrosine kinase (RTK) driven pathways are commonly mutated in OAC, typified by high frequency amplifications of the RTK ERRB2. ERBB2 can be therapeutically targeted, but this has limited clinical benefit due to the acquisition of drug resistance. Here we examined how OAC cells respond to ERBB2 inhibition through altering their regulatory chromatin landscapes and rewiring their gene regulatory networks to acquire a reversible resistant state. ERBB2 inhibition triggers widespread remodelling of the accessible chromatin landscape. This remodelling is accompanied by the activation of the transcriptional regulators HNF4A and PPARGC1A. Initially, inhibition of cell cycle associated gene expression programmes is observed, with compensatory increases in the programmes driving changes in metabolic activity. PPARGC1A is instrumental in promoting a switch to dependency on oxidative phosphorylation and both PPARGC1A and HNF4A are required for the acquisition of resistance to ERBB2 inhibition. Our work therefore reveals the molecular pathways that support the acquisition of a resistant state and points to potential new therapeutic strategies to combat drug resistance.
... The increasing of mitochondria requires the protein expression from both mitochondrial DNA (mtDNA) and nuclear genome and requires cross-talk between them. Mitochondrial biogenesis is highly regulated by the vast of genome-encoded transcriptional elements, such as peroxisome proliferator-activated receptor γ (PPARγ) coactivator 1α (PGC-1α), estrogen-related receptor (ERR), nuclear respiratory factors (NRFs) [32,33]. Under energy depletion or cell growth, PGC-1α can be activated, stimulating the increase in mitochondria and oxidative metabolic [34]. ...
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Mitochondria undergo structural and functional remodeling to meet the cell demand in response to the intracellular and extracellular stimulations, playing an essential role in maintaining normal cellular function. Merging evidence demonstrated that dysregulation of mitochondrial remodeling is a fundamental driving force of complex human diseases, highlighting its crucial pathophysiological roles and therapeutic potential. In this review, we outlined the progress of the molecular basis of mitochondrial structural and functional remodeling and their regulatory network. In particular, we summarized the latest evidence of the fundamental association of impaired mitochondrial remodeling in developing diverse cardiac diseases and the underlying mechanisms. We also explored the therapeutic potential related to mitochondrial remodeling and future research direction. This updated information would improve our knowledge of mitochondrial biology and cardiac diseases’ pathogenesis, which would inspire new potential strategies for treating these diseases by targeting mitochondria remodeling.
... Considering that Pgc-1α is responsible for transcribing Nrf1, which is in charge of nuclear-encoded electron transport chain mitochondrial complexes levels [100], and since Nrf1 controls Tfam [55,58,101], both gene expressions were also investigated. Our data corroborate the Pgc-1α expression observed herein, and following the reduction in mitochondrial mass induced by Rot in vitro [66,102,103]. ...
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Since psychiatric disorders are associated with changes in the development of the nervous system, an energy-dependent mechanism, we investigated whether mitochondrial inhibition during the critical neurodevelopment window in rodents would be able to induce metabolic alterations culminating in psychiatric-like behavior. We treated male Wistar rat puppies (P) with rotenone (Rot), an inhibitor of mitochondrial complex I, from postnatal days 5 to 11 (P5–P11). We demonstrated that at P60 and P120, Rot-treated animals showed hyperlocomotion and deficits in social interaction and aversive contextual memory, features observed in animal models of schizophrenia, autism spectrum disorder, and attention deficit hyperactivity disorder. During adulthood, Rot-treated rodents also presented modifications in CBP and CREB levels in addition to a decrease in mitochondrial biogenesis and Nrf1 expression. Additionally, NFE2L2-activation was not altered in Rot-treated P60 and P120 animals; an upregulation of pNFE2L2/ NFE2L2 was only observed in P12 cortices. Curiously, ATP/ADP levels did not change in all ages evaluated. Rot administration in newborn rodents also promoted modification in Rest and Mecp2 expression, and in synaptic protein levels, named PSD-95, Synaptotagmin-1, and Synaptophysin in the adult rats. Altogether, our data indicate that behavioral abnormalities and changes in synaptic proteins in adulthood induced by neonatal Rot administration might be a result of adjustments in CREB pathways and alterations in mitochondrial biogenesis and Nrf1 expression, rather than a direct deficiency of energy supply, as previously speculated. Consequently, Rot-induced psychiatric-like behavior would be an outcome of alterations in neuronal paths due to mitochondrial deregulation. Graphical abstract
... Another transcriptional factor YY1 (Yin-Yang-1) appears to be involved in the expression of C0X5B and C0X7C (Hahn, 1992;Seelan and Grossman, 1997). NRF1 is a third transcription factor involved in the regulation of COX genes (Evans and Scarpulla, 1990). NRF1 binding sites have been identified in the promoter regions of several genes involved in mitochondrial function, including cytochrome c, C0X5B, C0X7AL, the mitochondrial transcription factor mtTFA, the mitochondrial processing endoribonuclease mMRP and a gene encoding tyrosine aminotransferase, which catalyses the rate-limiting step of haem biosynthesis (Grossman and Lomax, 1997). ...
Thesis
The mitochondrial respiratory chain and oxidative phosphorylation system (complexes I-V) produce ATP by aerobic metabolism. Complex IV or cytochrome c oxidase (COX) catalyses transfer of electrons from reduced cytochrome c to molecular oxygen, coupled with proton pumping across the inner mitochondrial membrane. Human COX has 13 polypeptide subunits. Three subunits (I, II and III) constitute the enzyme's catalytic core and are encoded on the mitochondrial genome. The remaining subunits are nuclear-encoded. COX deficiency, either total or partial, is the most commonly recognised respiratory chain defect in childhood. This may be an isolated defect, or combined with deficiencies of other respiratory chain components. Clinical presentations are heterogeneous but most patients with COX deficiency remain uncharacterised at the molecular level. COX subunit expression patterns were analysed in 5 patients with known mitochondrial DNA (mtDNA) mutations and 36 uncharacterised patients. A specific pattern of COX subunit loss was identified in COX deficiency secondary to mtDNA mutations. This suggested that immunohistochemistry using monoclonal antibodies may distinguish between mtDNA defects and nuclear defects in COX deficiency. Subsequent sequence analysis, targeted by immunohistochemistry findings, led to identification of a missense mutation of COX subunit II that causes defective assembly and myopathy. Characterisation of this mutation provided information about assembly of the metal centres of COX. Thus identification of naturally occurring COX mutations allows insight into structure-function relationships within the enzyme. The majority of children with COX deficiency did not have selective loss of mtDNA- encoded subunits, suggesting that nuclear gene defects account for many cases of childhood-onset COX deficiency. One nuclear gene SURF1 is responsible for COX assembly or maintenance. Four patients had homozygous SURF1 mutations, associated with reduced expression of both mtDNA- and nuclear-encoded COX subunits. Studying patterns of subunit expression in COX-deficient patients is fundamental to understanding the pathogenesis of respiratory chain enzyme deficiencies.
... The major role of TFB1M is rRNA methylation and not its transcription factor function (Metodiev et al., 2009). Nuclear respiratory factors NRF1 and NRF2 regulate expression of the ETC subunits encoded by the nuclear genome (Evans and Scarpulla, 1990) and bind to the promoters of genes involved in mtDNA transcription. NRF1 binds to the specific promoter sites and regulates expression of TFAM (Virbasius and Scarpulla, 1994), TFB1M, and TFB2M (Gleyzer et al., 2005). ...
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Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis are a heterogeneous group of debilitating disorders with multifactorial etiologies and pathogeneses that manifest distinct molecular mechanisms and clinical manifestations with abnormal protein dynamics and impaired bioenergetics. Mitochondrial dysfunction is emerging as an important feature in the etiopathogenesis of these age-related neurodegenerative diseases. The prevalence and incidence of these diseases is on the rise with the increasing global population and average lifespan. Although many therapeutic approaches have been tested, there are currently no effective treatment routes for the prevention or cure of these diseases. We present the current status of our knowledge and understanding of the involvement of mitochondrial dysfunction in these diseases and highlight recent advances in novel therapeutic strategies targeting neuronal bioenergetics as potential approach for treating these diseases.
... Analysis of known motifs using the software HOMER identified nuclear respiratory factor-1 (Nrf1) as the highest ranking significant motif common in both male and female cells (Fig. 3d). Nrf1 is an important transcription factor that activates the expression of various key metabolic genes regulating mitochondrial function and oxidative stress response [25,26]. This finding strongly advocates for Nrf1 being a direct target of Nup133. ...
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Background: Hyperoxia is a well-known cause of cerebral white matter injury in preterm infants with male sex being an independent and critical risk factor for poor neurodevelopmental outcome. Sex is therefore being widely considered as one of the major decisive factors for prognosis and treatment of these infants. But unfortunately, we still lack a clear view of the molecular mechanisms that lead to such a profound difference. Hence, using mouse-derived primary oligodendrocyte progenitor cells (OPCs), we investigated the molecular factors and underlying mechanisms behind the differential response of male and female cells towards oxidative stress. Results: We demonstrate that oxidative stress severely affects cellular functions related to energy metabolism, stress response, and maturation in the male-derived OPCs, whereas the female cells remain largely unaffected. CNPase protein level was found to decline following hyperoxia in male but not in female cells. This impairment of maturation was accompanied by the downregulation of nucleoporin and nuclear lamina proteins in the male cells. We identify Nup133 as a novel target protein affected by hyperoxia, whose inverse regulation may mediate this differential response in the male and female cells. Nup133 protein level declined following hyperoxia in male but not in female cells. We show that nuclear respiratory factor 1 (Nrf1) is a direct downstream target of Nup133 and that Nrf1 mRNA declines following hyperoxia in male but not in female cells. The female cells may be rendered resistant due to synergistic protection via the estrogen receptor alpha (ERα) which was upregulated following hyperoxia in female but not in male cells. Both Nup133 and ERα regulate mitochondrial function and oxidative stress response by transcriptional regulation of Nrf1. Conclusions: These findings from a basic cell culture model establish prominent sex-based differences and suggest a novel mechanism involved in the differential response of OPCs towards oxidative stress. It conveys a strong message supporting the need to study how complex cellular processes are regulated differently in male and female brains during development and for a better understanding of how the brain copes up with different forms of stress after preterm birth.
... Therefore, the aim of the present study was to confirm the regulatory relationship between NRF-1 and TFE3, in order to explore the role of NRF-1/TFE3 in the process of tumorigenesis. A previous study on NRF-1 in the literature have focused on mitochondria and energy metabolism (31). Autophagy, as well as tumor-related autophagy and even cellular immunity (32-35). ...
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The role of transcription factor binding to IGHM enhancer 3 (TFE3) in renal cell carcinoma (RCC) is not well understood. Nuclear respiratory factor 1 (NRF-1) may be the positive upstream regulatory gene of TFE3. The aim of the present study was to determine whether NRF-1 could directly regulate the expression of TFE3 and regulate tumorigenesis and progression of RCC through TFE3. Short hairpin RNA (shRNA) was used to silence the expression of NRF-1 in the 786-O human kidney adenocarcinoma cell line and the 293T human embryonic kidney cell line. Luciferase reporter assays were used to determine the relationship between NRF-1 and TFE3. The CHIP experiment was used to verify the actual binding of NRF-1 and TFE3 promoter regions. MitoTimer staining was used to measure mitochondrial biosynthesis. Flow cytometry was used to detect cell cycle and apoptosis. The 786-O and 293T cells were used to examine the underlying mechanism of action. The results demonstrated that NRF-1 could bind to the promoter region of the TFE3 gene and directly regulate the expression of TFE3. Following NRF-1 knockdown, the protein levels of phosphorylated (p)-AKT and p-S6 of mTOR pathway was inhibited, cell cycle progression was blocked, the levels of apoptosis increased, and mitochondrial generation was reduced. Following overexpression of TFE3, the levels of mTOR-associated markers were restored in NRF-1 knockdown cells. These findings suggest that NRF-1 may regulate the mTOR pathway through TFE3 and regulate the energy metabolism, proliferation and growth of cancer cells by directly regulating the expression of TFE3.
... The connection between Nrf2 and mitochondrial biogenesis is a more recent discovery (Gureev et al., 2019). Piantadosi et al. (2008) first showed that HO-1, a well-known transcriptional target of Nrf2, enhances the nuclear translocation of nuclear respiratory factor 1 (NRF1), which controls the expression of several ETC components encoded in the nucleus (Evans and Scarpulla, 1990;Li et al., 2017b) and is an ARE target (Picca and Lezza, 2015). NRF1 subsequently promotes the expression of mitochondrial transcription factor A (TFAM), a protein that enters the mitochondrial matrix and binds to the "D-Loop" promoter region of the mitochondrial genome, thereby stimulating mtRNA expression and mtDNA replication (Piantadosi and Suliman, 2006). ...
Article
Mitochondria are both a primary source of reactive oxygen species (ROS) and a sensitive target of oxidative stress; damage to mitochondria can result in bioenergetic dysfunction and both necrotic and apoptotic cell death. These relationships between mitochondria and cell death are particularly strong in both acute and chronic neurodegenerative disorders. ROS levels are affected by both the production of superoxide and its toxic metabolites and by antioxidant defense mechanisms. Mitochondrial antioxidant activities include superoxide dismutase 2, glutathione peroxidase and reductase, and intramitochondrial glutathione. When intracellular conditions disrupt the homeostatic balance between ROS production and detoxification, a net increase in ROS and an oxidized shift in cellular redox state ensues. Cells respond to this imbalance by increasing the expression of genes that code for proteins that protect against oxidative stress and inhibit cytotoxic oxidation of proteins, DNA, and lipids. If, however, the genomic response to mitochondrial oxidative stress is insufficient to maintain homeostasis, mitochondrial bioenergetic dysfunction and release of pro-apoptotic mitochondrial proteins into the cytosol initiate a variety of cell death pathways, ultimately resulting in potentially lethal damage to vital organs, including the brain. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a translational activating protein that enters the nucleus in response to oxidative stress, resulting in increased expression of numerous cytoprotective genes, including genes coding for mitochondrial and non-mitochondrial antioxidant proteins. Many experimental and some FDA-approved drugs promote this process. Since mitochondria are targets of ROS, it follows that protection against mitochondrial oxidative stress by the Nrf2 pathway of gene expression contributes to neuroprotection by these drugs. This document reviews the evidence that Nrf2 activation increases mitochondrial antioxidants, thereby protecting mitochondria from dysfunction and protecting neural cells from damage and death. New experimental results are provided demonstrating that post-ischemic administration of the Nrf2 activator sulforaphane protects against hippocampal neuronal death and neurologic injury in a clinically-relevant animal model of cardiac arrest and resuscitation.
... Nuclear factor-erythroid 2-related factor 1 (Nrf1) acts as a transcription factor belonging to the cap'n'collar (CNC) basic-region leucine zipper (bZIP) family, which serves as a crucial integrator of nuclear and mitochondrial interactions, modulating essential processes ranging from protein production to mitochondrial biogenesis (7)(8)(9). It also serves a prominent role in apoptosis (10,11), suggesting that NRF1 may be an important target for mediating chondrocytes apoptosis. ...
Article
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Osteoarthritis (OA) is a degenerative joint disease that affects the physical, and mental health of middle‑aged and elderly people. The aims of the present study were to determine the biological function and molecular mechanisms of miR‑363‑3p in chondrocyte apoptosis. Exploration of the molecular mechanisms of OA may be helpful in the understand of the causes, and facilitating the prevention and treatment of OA. In the present study, the expression of nuclear respiratory factor1 (NRF1) was downregulated in the articular cartilage of OA rats in vivo and lipopolysaccharide (LPS)‑treated chondrocytes in vitro. MicroRNAs (miRNA) are regulators of gene expression in the progression of OA. TargetScan software was used to predict that NRF1 was a potential target for miRNA (miR)‑363, and this was confirmed in subsequent experiments. The expression of miR‑363‑3p was negatively correlated with the expression of NRF1, and its expression was significantly upregulated in OA model rats and in LPS‑induced chondrocytes compared with the expression in the respective controls. In addition, the overexpression of miR‑363‑3p increased the levels of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α in vivo, and was demonstrated to promote chondrocyte injury and apoptosis by Safranin O staining and TUNEL. Moreover, the inhibition of miR‑363‑3p expression increased the expression of NRF1 and protected chondrocytes from apoptosis in vitro and in vivo, whereas the overexpression of miR‑363‑3p downregulated NRF1 expression and promoted LPS‑induced chondrocyte apoptosis through the p53 pathway in vitro. The results of this study suggested that miR‑363‑3p‑mediated inhibition of NRF1may be associated with chondrocyte apoptosis in OA.
... The gene-ontology pathways that were most significantly enriched after AM and NAM interventions (Extended Data Fig. 11d, e) were related to mitochondrial structure and function, nicotinamide adenine dinucleotide + (NAD + ) homeostasis and removal of superoxide radicals-canonical functions that are known to be disrupted in ALS. Notably, 28.6% of the promoters of the genes that showed significant changes in expression common to both AM and NAM treatments were found to share a binding site for the transcription factor nuclear respiratory factor-1 (NRF-1; Extended Data Fig. 12a), which is known to control mitochondrial biogenesis, electron transport chain activity and oxidative stress [24][25][26][27][28] . The potential contribution of NRF-1 to the modulatory effect of ALS merits further studies. ...
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Amyotrophic Lateral Sclerosis (ALS) is a genetically-driven neurodegenerative disorder, whose clinical manifestations may be influenced by unknown environmental factors. We demonstrate that ALS-prone SOD1-Tg mice feature a pre-symptomatic, vivarium-dependent dysbiosis and altered metabolite configuration, coupled with an exacerbated disease in germ-free or wide-spectrum antibiotic treatment conditions. We correlate 11 distinct commensals at our vivarium with mouse-ALS severity, and exemplify by their individual supplementation into antibiotic-treated SOD1-Tg mice that Akkermansia muciniphila (AM) ameliorates & Ruminococcus torques & Parabacteroides distasonis exacerbate mouse-ALS symptoms. Furthermore, AM-administered SOD1-Tg mice feature a CNS accumulation of AM-associated nicotinamide, which improves, upon systemic supplementation, motor symptoms and spinal-cord gene expression patterns in SOD1-Tg mice. in humans, we identify distinct microbiome/metabolite configurations, including impaired systemic & cerebrospinal-fluid nicotinamide levels, in a small preliminary study assessing ALS patients versus household-controls. Together, we suggest that environmentally-driven microbiome-brain interactions may modulate murine ALS, and call for similar investigations in human ALS.
... Active transcription of the mitochondrial genome has been demonstrated to initiate at various developmental stages, depending on the species [22]. Reports from many studies suggested that gene-specific transcription factors directly affect gene transcription in mitochondria [23]. ...
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In some cases of infertility in women, human oocytes fail to mature when they reach the metaphase II (MII) stage. Mitochondria plays an important role in oocyte maturation. A large number of mitochon-drial DNA (mtDNA), copied in oocytes, is essential for providing adenosine triphosphate (ATP) during oocyte maturation. The purpose of this study was to identify the relationship between transcript expression levels of the mitochondrial encoded gene (MT-CO1) and two nuclear encoded genes, nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) in various stages of human oocyte maturation. Nine consenting patients, age 21-35 years old, with male factors were selected for ovarian stimulation and intracytoplasmic sperm injection (ICSI) procedures. mRNA levels of mito-chondrial-related genes were performed by single-cell TaqMan® quantitative real-time polymerase chain reaction (qRT-PCR). There was no significant relationship between the relative expression levels in germinal vesicle (GV) stage oocytes (p = 0.62). On the contrary, a significant relationship was seen between the relative expression levels of TFAM and NRF1 and the MT-CO1 genes at the stages of meta-phase I (MI) and MII (p = 0.03 and p = 0.002). A relationship exists between the transcript expression levels of TFAM and NRF1, and MT-CO1 genes in various stages of human oocyte maturation.
... The NRF1 footprinting plot suggest an increased binding of transcription factors at the NRF1 binding site at 3hAm compared to UnT control myotubes (Fig. 5,E). One of the functions of NRF1 is to regulate mitochondrial respiration (37,38). Our observations of an increase in predicted binding at NRF1 motifs and on the transcription factor activation profiling array suggest that an increase in NRF1 may be a compensatory response to the mitochondrial defects during hyperammonemia that we have reported earlier (15). ...
Article
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Ammonia is a cytotoxic molecule generated during normal cellular functions. Dysregulated ammonia metabolism, which is evident in many chronic diseases such as liver cirrhosis, heart failure and chronic obstructive pulmonary disease, initiates a hyperammonemic stress response (HASR) in tissues including skeletal muscle and in myotubes. Perturbations in levels of specific regulatory molecules have been reported, but the global responses to hyperammonemia are unclear. In this study we used a multiomics approach to vertically integrate unbiased data generated using transposase-accessible chromatin sequencing (ATACseq), RNA sequencing (RNAseq), and proteomics. We then horizontally integrated these data across different models of hyperammonemia, including myotubes and mouse and human muscle tissues. Changes in chromatin accessibility and/or expression of genes resulted in distinct clusters of temporal molecular changes including transient, persistent, and delayed responses during hyperammonemia in myotubes. Known responses to hyperammonemia, including mitochondrial and oxidative dysfunction, protein homeostasis disruption, and oxidative stress pathway activation were enriched in our datasets. During hyperammonemia, pathways that impact skeletal muscle structure and function that were consistently enriched were those that contribute to mitochondrial dysfunction, oxidative stress, and senescence. We made several novel observations, including an enrichment in antiapoptotic Bcl2 family protein expression, increased calcium flux, and increased protein glycosylation in myotubes and muscle tissue upon hyperammonemia. Critical molecules in these pathways were validated experimentally. Human skeletal muscle from patients with cirrhosis displayed similar responses, establishing translational relevance. These data can be used to identify complex molecular interactions during adaptive and maladaptive responses during the cellular stress response to hyperammonemia.
... Le régulateur Nuclear Respiratory Factor-1 (NRF-1) a été identifié en étudiant le promoteur du gène codant pour le cytochrome c (Evans and Scarpullas, 1989;Evans and Scarpulla, 1990). ...
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Dans la cellule, les fonctions cellulaires majeures, telles que la prolifération cellulaire, impliquent une consommation très importante d’énergie sous forme d’Adénosine Triphosphate (ATP). Pour répondre à l’augmentation de la demande énergétique, une production continuelle d’ATP est nécessaire. Dans ce contexte, les mitochondries sont les principaux producteurs d’ATP via le système des oxydations phosphorylantes (ou OXPHOS). Ce système couple l’activité de la chaine respiratoire (consommation d’oxygène) à celle de l’ATP synthase grâce au gradient électrochimique en protons de part et d’autre de la membrane interne mitochondriale. Ceci fait de la mitochondrie un élément central qui peut être régulé pour s’adapter aux demandes énergétiques de la cellule. En effet, une régulation cinétique de l’activité de la mitochondrie peut mener à une régulation plus globale du flux de production d’ATP tout comme une régulation du nombre de mitochondries au sein la cellule. Le réseau mitochondrial dans la cellule est géré par deux phénomènes : leur synthèse (biogénèse) et leur dégradation (ou mitophagie). Dans la souche de levure S. cerevisiae, la biogénèse mitochondriale est contrôlée par un hétérotétramère formé par les facteurs de transcription Hap2/3/4/5. L’activation du complexe dépend de la présence de la sous-unité régulatrice Hap4p, homologue fonctionnel de PGC1α. Ce complexe transcriptionel est responsable de l’activation de l’expression de nombreux gènes codant pour les enzymes du cycle de Krebs, les enzymes de biosynthèse de l’hème et les enzymes de la chaine respiratoire. Nous nous sommes intéressés aux différentes voies de régulation de la biogénèse mitochondriale et ce, par l’étude de la régulation de la protéine Hap4p. Nos résultats sont les premiers à clairement mettre en évidence une régulation de Hap4p par l’hème labile. Nous avons également étudié le rôle de la répression glucose sur la biogénèse mitochondriale et avons pu mettre en évidence un parallèle avec l’effet Warburg mis en place dans les cellules cancéreuses. Nos résultats ont notamment montré une décorrélation entre le remodelage métabolique dû à l’effet Warburg et l’augmentation de la vitesse de prolifération. Cette étude suggère également que l’augmentation du flux glycolytique n’a pas pour conséquence une augmentation de la production d’ATP dans les cellules. L’ensemble de ce travail permet un apport supplémentaire dans la compréhension de l’effet Warburg et dans l’étude de la régulation de la biogénèse mitochondriale chez S. cerevisiae.
... AUTS2 and NRF1 co-localize within chromatin and interact in the mouse brain To identify the factor(s) involved in the key process by which AUTS2 accesses chromatin, we first determined the motifs of transcription factors (TFs) enriched in AUTS2-bound sites in the mouse brain and identified an overrepresentation for that of NRF1 ( Figure 4A). NRF1 is a TF involved in mitochondrial biogenesis (Scarpulla, 2011), which binds to GC-rich DNA elements in the promoters of many mitochondrial biogenesisrelated genes (Evans and Scarpulla, 1990;Gleyzer et al., 2005). NRF1 is also associated with regulation of neurite outgrowth (Chang et al., 2005;Tong et al., 2013) and has essential roles in retinal development (Hsiao et al., 2013;Kiyama et al., 2018), but its function and regulation in the CNS are largely unknown. ...
Article
The heterogeneous family of complexes comprising Polycomb repressive complex 1 (PRC1) is instrumental for establishing facultative heterochromatin that is repressive to transcription. However, two PRC1 species, ncPRC1.3 and ncPRC1.5, are known to comprise novel components, AUTS2, P300, and CK2, that convert this repressive function to that of transcription activation. Here, we report that individuals harboring mutations in the HX repeat domain of AUTS2 exhibit defects in AUTS2 and P300 interaction as well as a developmental disorder reflective of Rubinstein-Taybi syndrome, which is mainly associated with a heterozygous pathogenic variant in CREBBP/EP300. Moreover, the absence of AUTS2 or mutation in its HX repeat domain gives rise to misregulation of a subset of developmental genes and curtails motor neuron differentiation of mouse embryonic stem cells. The transcription factor nuclear respiratory factor 1 (NRF1) has a novel and integral role in this neurodevelopmental process, being required for ncPRC1.3 recruitment to chromatin.
... PGC-1α and Nrf2 jointly enhance Nrf1 expression, which activates the transcription factor A, mitochondrial (TFAM) (Wu et al., 1999). TFAM is a mitochondrial transcription factor that is involved in recruiting mitochondrial RNA polymerase and transcription of genes involved in mitochondrial repair and synthesis (Evans and Scarpulla, 1990). Since four ARE sites were found in the promoter of PINK1, Nrf2 regulates its expression as well. ...
Article
Parkinson's disease (PD) is a progressive neurodegenerative disorder. PD is associated with the loss of dopaminergic neurons in the substantia nigra pars compacta region of the midbrain. Present therapies for PD provide only symptomatic relief by restoring the dopamine (DA) level. However, they are not disease modifying agents and so they do not delay the disease progression. Alpha-synuclein aggregation, oxidative stress, mitochondrial dysfunction and chronic inflammation are considered to be the major pathological mechanisms mediating neurodegeneration in PD. To resist oxidative stress, the human body has an antioxidant defence mechanism consisting of many antioxidants and cytoprotective genes. The expression of those genes are largely controlled by the Kelch-like ECH-associated protein 1/Nuclear factor - erythroid - 2 - related factor 2/Antioxidant response element (Keap1/Nrf2/ARE) signalling pathway. The transcription factor Nrf2 is activated in response to oxidative or electrophilic stress and protects the cells from oxidative stress and inflammation. Nrf2 has been widely considered as a therapeutic target for neurodegeneration and several drugs are now being tested in clinical trials. Regulation of the Keap1/Nrf2/ARE pathway by small molecules which can act as Nrf2 activators could be effective for treating oxidative stress and neuroinflammation in PD. In this review, we had discussed the principal molecular mechanisms behind the neuroprotective effects of Keap1/Nrf2/ARE pathway in PD. Additionally, we also discussed the small molecules and phytochemicals that could activate the Nrf2 mediated anti-oxidant pathway for neuroprotection in PD.
... We took advantage of ChIP-seq data for NRF1 from other cell lines and observed a large overlap with PPARGC1A binding regions ( Supplementary Fig. S6B). NRF1 has previously been implicated in controlling mitochondrial function and its metabolic activities [40][41][42] and consistent with this, two of the top GO terms for genes associated with PPARGC1A binding regions are "mitochondrial organisation" and "TCA cycle and respiratory electron transport" (Supplementary Fig. S6G). ...
Article
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Oesophageal adenocarcinoma (OAC) patients show poor survival rates and there are few targeted molecular therapies available. However, components of the receptor tyrosine kinase (RTK) driven pathways are commonly mutated in OAC, typified by high frequency amplifications of the RTK ERBB2. ERBB2 can be therapeutically targeted, but this has limited clinical benefit due to the acquisition of drug resistance. Here we examined how OAC cells adapt to ERBB2 inhibition as they transition to a drug resistant state. ERBB2 inhibition triggers widespread remodelling of the accessible chromatin landscape and the underlying gene regulatory networks. The transcriptional regulators HNF4A and PPARGC1A play a key role in this network rewiring. Initially, inhibition of cell cycle associated gene expression programmes is observed, with compensatory increases in the programmes driving changes in metabolic activity. Both PPARGC1A and HNF4A are required for the acquisition of resistance to ERBB2 inhibition and PPARGC1A is instrumental in promoting a switch to dependency on oxidative phosphorylation. Our work therefore reveals the molecular pathways that support the acquisition of a resistant state and points to potential new therapeutic strategies to combat cellular adaptation and ensuing drug resistance.
... A number of transcriptional regulators, including peroxisome proliferative activated receptor gamma coactivator 1 (PGC-1) family members, nuclear respiratory factor 1 (Nrf1), and nuclear respiratory factor 2 (Nrf2/GABP), have been identified as key regulators for mitochondria biogenesis in different contexts [7][8][9][10]. Among them, Nrf1 is identified as an evolutionarily conserved transcription activator that binds to GC-rich DNA elements in promoters of a host of nuclear genes encoding proteins involved in mitochondrial structure and functions [11][12][13][14][15]. Multiple studies using ChIP-seq analysis have identified distinct sets of Nrf1's target genes in different cell types, suggesting that Nrf1 acts in a context-dependent manner in regulating cell growth, differentiation, and mitochondrial biogenesis [16][17][18][19]. ...
Article
The retina, the accessible part of the central nervous system, has served as a model system to study the relationship between energy utilization and metabolite supply. When the metabolite supply cannot match the energy demand, retinal neurons are at risk of death. As the powerhouse of eukaryotic cells, mitochondria play a pivotal role in generating ATP, produce precursors for macromolecules, maintain the redox homeostasis, and function as waste management centers for various types of metabolic intermediates. Mitochondrial dysfunction has been implicated in the pathologies of a number of degenerative retinal diseases. It is well known that photoreceptors are particularly vulnerable to mutations affecting mitochondrial function due to their high energy demand and susceptibility to oxidative stress. However, it is unclear how defective mitochondria affect other retinal neurons. Nuclear respiratory factor 1 (Nrf1) is the major transcriptional regulator of mitochondrial biogenesis, and loss of Nrf1 leads to defective mitochondria biogenesis and eventually cell death. Here, we investigated how different retinal neurons respond to the loss of Nrf1. We provide in vivo evidence that the disruption of Nrf1-mediated mitochondrial biogenesis results in a slow, progressive degeneration of all retinal cell types examined, although they present different sensitivity to the deletion of Nrf1, which implicates differential energy demand and utilization, as well as tolerance to mitochondria defects in different neuronal cells. Furthermore, transcriptome analysis on rod-specific Nrf1 deletion uncovered a previously unknown role of Nrf1 in maintaining genome stability.
... PGC-1α initiates the expression of a wide range of coactivated genes involved in virtually all aspects of mitochondrial energy metabolism [26]. NRF-1, one of the most important coactivated targets of PGC-1α, remarkably activates the expression of the gene that encodes COX6c through binding to its promoter [27,28]. Moreover, NRF-1-binding sites are also identified in the promoter of mitochondrial transcription factor A (TFAM), which subsequently binds to mtDNA and exerts significant effects on mtDNA replication, transcription, and maintenance [26]. ...
Article
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Cytochrome c oxidase subunit VIc (COX6c) is one of the most important subunits of the terminal enzyme of the respiratory chain in mitochondria. Numerous studies have demonstrated that COX6c plays a critical role in the regulation of oxidative phosphorylation (OXPHOS) and energy production. The release of COX6c from the mitochondria may be a hallmark of the intrinsic apoptosis pathway. Moreover, The changes in COX6c expression are widespread in a variety of diseases and can be chosen as a potential biomarker for diagnosis and treatment. In light of its exclusive effects, we present the elaborate roles that COX6c plays in various diseases. In this review, we first introduced basic knowledge regarding COX6c and its functions in the OXPHOS and apoptosis pathways. Subsequently, we described the regulation of COX6c expression and activity in both positive and negative ways. Furthermore, we summarized the elaborate roles that COX6c plays in various diseases, including cardiovascular disease, kidney disease, brain injury, skeletal muscle injury, and tumors. This review highlights recent advances and provides a comprehensive summary of COX6c in the regulation of OXPHOS in multiple diseases and may be helpful for drug design and the prediction, diagnosis, treatment, and prognosis of diseases.
... NRF1 is a nuclear respiratory factor that regulates the expression of electron transfer chain subunits encoded by the nuclear genome. It also regulates the expression of TFAM, a DNA-binding protein that activates the transcription of the mitochondrial genome [59][60][61][62]. Our data also showed a decrease in TFAM expression after H 2 O 2 treatment. ...
Article
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Disuse muscle atrophy is characterized by a decrease in muscle mass and strength and an increase in glycolytic muscle fiber type. Although Schisandra chinensis extract has beneficial effects on muscle atrophy induced by various conditions (e.g., dexamethasone and aging), the effect of gomisin G, a lignan component of S. chinensis, on disuse muscle atrophy is unclear. Here, we induced disuse muscle atrophy through wire immobilization of the hind legs in mice followed by the oral administration of gomisin G. The cross-sectional area and muscle strength in disuse muscle atrophic mice were increased by gomisin G; however, the total muscle mass did not increase. Gomisin G decreased the expression of muscle atrophic factors (myostatin, atrogin-1, and MuRF1) but increased the expression of protein synthesis factors (mTOR and 4E-BP1). In H2O2-treated C2C12 myotubes, the level of puromycin incorporation (as a marker of protein synthesis) gradually increased in a dose-dependent manner by gomisin G. Furthermore, gomisin G induced a muscle fiber switch from fast-type glycolytic fibers (type 2B) to slow-type oxidative fibers (type I, 2A) in the gastrocnemius (GA) muscle as proved a decrease in the expression of TnI-FS and an increase in the expression of TnI-SS. Gomisin G increased mitochondrial DNA content and ATP levels in the GA muscle and COX activity in H2O2-treated C2C12 myotubes, improving mitochondrial function. Mechanistically, mitochondrial biogenesis is regulated by gomisin G via the Sirt 1/PGC-1α signaling pathway, targeting NRF1 and TFAM. These data suggest that gomisin G has a potential therapeutic effect on disuse muscle atrophy.
... By contrary, the CypD KO group displayed an increased level of PGC1-α compared both to the WT group and the preoperative state. However, the increase of PGC1-α was not followed by NRF1, which is a major transcriptional factor of mitochondrial respiratory complexes [23]. Therefore, it was also a compelling question whether the protein complexes of the OXPHOS system were affected by CypD depletion. ...
Article
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Aim Associating Liver Partition and Portal vein ligation for Staged hepatectomy (ALPPS) is a modification of two-stage hepatectomy profitable for patients with inoperable hepatic tumors by standard techniques. Unfortunately, initially poor postoperative outcome was associated with ALPPS, in which mitochondrial dysfunction played an essential role. Inhibition of cyclophilins has been already proposed to be efficient as a mitochondrial therapy in liver diseases. To investigate the effect of Cyclophilin D (CypD) depletion on mitochondrial function, biogenesis and liver regeneration following ALPPS a CypD knockout (KO) mice model was created. Methods Male wild type (WT) (n = 30) and CypD KO (n = 30) mice underwent ALPPS procedure. Animals were terminated pre-operatively and 24, 48, 72 or 168 h after the operation. Mitochondrial functional studies and proteomic analysis were performed. Regeneration rate and mitotic activity were assessed. Results The CypD KO group displayed improved mitochondrial function, as both ATP production (P < 0.001) and oxygen consumption (P < 0.05) were increased compared to the WT group. The level of mitochondrial biogenesis coordinator peroxisome proliferator-activated receptor γ co-activator 1-α (PGC1-α) was also elevated in the CypD KO group (P < 0.001), which resulted in the induction of the mitochondrial oxidative phosphorylation system. Liver growth increased in the CypD KO group compared to the WT group (P < 0.001). Conclusions Our study demonstrates the beneficial effect of CypD depletion on the mitochondrial vulnerability following ALPPS. Based on our results we propose that CypD inhibition should be further investigated as a possible mitochondrial therapy following ALPPS.
... Nrf1 also regulates certain aspects of the ETC [31]. Given our previous findings regarding the importance of the ETC in AML, we examined the effect of these compounds on the ETC in the MOLM-13 cells. ...
Article
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Acute myeloid leukemia (AML) is a heterogeneous group of aggressive hematological malignancies commonly associated with treatment resistance, high risk of relapse, and mitochondrial dysregulation. We identified six mitochondria-affecting compounds (PS compounds) that exhibit selective cytotoxicity against AML cells in vitro. Structure-activity relationship studies identified six analogs from two original scaffolds that had over an order of magnitude difference between LD50 in AML and healthy peripheral blood mononuclear cells. Mechanistically, all hit compounds reduced ATP and selectively impaired both basal and ATP-linked oxygen consumption in leukemic cells. Compounds derived from PS127 significantly upregulated production of reactive oxygen species (ROS) in AML cells and triggered ferroptotic, necroptotic, and/or apoptotic cell death in AML cell lines and refractory/relapsed AML primary samples. These compounds exhibited synergy with several anti-leukemia agents in AML, acute lymphoblastic leukemia (ALL), or chronic myelogenous leukemia (CML). Pilot in vivo efficacy studies indicate anti-leukemic efficacy in a MOLM14/GFP/LUC xenograft model, including extended survival in mice injected with leukemic cells pre-treated with PS127B or PS127E and in mice treated with PS127E at a dose of 5 mg/kg. These compounds are promising leads for development of future combinatorial therapeutic approaches for mitochondria-driven hematologic malignancies such as AML, ALL, and CML.
... Indeed, genes expressed in mitochondria work in concert with those expressed in the nucleus to regulate OXPHOS [27]. Nuclear-encoded genes that are important for adipose tissue metabolism and mitochondrial functions include mitochondrial transcription factor A (TFAM), that encodes for the protein primary driving the mtDNA packaging generating nucleoids [28,29], peroxisome proliferator-activated receptor γ (PPARG) and PPARγ coactivator 1α (PGC1α), regulating adipogenesis, insulin sensitivity and mitochondrial biogenesis [30] and the nuclear respiratory factor 1 (NRF1), that regulates mitochondrial biogenesis and binds to promoters of genes involved in mtDNA transcription such as TFAM [31,32]. In addition, mitochondria have a central role in the one carbon (1C) metabolism, that regulates bioavailability of methyl groups necessary for DNA methylation [33]. ...
Article
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Background: Peripheral alterations of mitochondrial DNA copy number (mtDNAcn) in obesity and associated co-morbidities have been previously shown. Furthermore, the possibility that methylation could occur in the mtDNA (in particular in the displacement loop, D-Loop) and regulate its functions has been raised. However, limited data about mtDNA methylation in adipose tissue are currently available. Since a strict crosstalk between the nucleus and mitochondria exists, especially in terms of the one-carbon cycle (that supports methylation reactions in the cell), we investigated methylation in selected areas of the mitochondrial and nuclear DNA and their expression in visceral adipose tissue (VAT) samples of patients with severe obesity. Methods: VAT biopsies were collected from surgery patients to isolate DNA and RNA. Gene expression and mtDNAcn were assessed through qPCR. DNA methylation in both nuclear and mitochondrial areas were determined through bisulfite pyrosequencing. Results: Methylation levels of the mtDNA were only marginally associated with the obesity degree (higher D-Loop methylation in severe obesity) and were not correlated with mtDNAcn. A significant correlation between D-Loop methylation and LINE-1 methylation was observed in VAT samples, and this was independent from the obesity degree. A progressive reduction of mtDNAcn and increase in NRF1 expression levels were measured in VAT in severe obesity. NRF1 expression was directly correlated with PPARG and MTHFR expression levels, while mtDNAcn was associated to TFAM expression. The correlation between mtDNAcn and TFAM expression was affected by the obesity status. Conclusions: This evidence supports the hypothesis that mtDNA alterations occur in obesity and a complex dynamic correlation between mitochondrial and nuclear DNA methylation exists, highlighting the need for further investigations.
... Nevertheless, as mtDNA J o u r n a l P r e -p r o o f transcriptional regulation require a core set of dedicated transcription factors, it is not surprising that a set of transcription factors preferentially regulate nDNA-encoded mitochondrial genes. Indeed, nuclear respiratory factors 1 and 2 (NRF1,2) [59,68,69], YY1 [59,70] and PGC1 alpha [71] have been suggested to preferentially regulate the transcription of nDNA-encoded oxidative phosphorylation subunits, as well as nDNA- [72]. Although very initial, these results provide reasons to believe that transcriptional regulatory coordination of the nucleus and the mitochondria can be mediated by double nuclear-mitochondrial localization of certain transcriptional factors, an argument that should be further evaluated in the future. ...
Article
Mitochondrial dysfunction has been reported in monogenic phenotypes, but also as part of common complex disorders. Explanations for the underlying mechanism of both disease types mostly focused on mutations in the open reading frames of proteins encoded by either the mitochondrial or nuclear genomes, as well as in tRNA or ribosomal RNA genes in the mitochondrial DNA (mtDNA). Although disease-causing mutations have been identified in regulatory proteins of mtDNA replication and maintenance, coordination between the regulation of mitochondrial and nuclear gene expression was only rarely considered as an explanation for mitochondrial dysfunction in diseases. Here, we review evidence suggesting that compromised coordination of mito-nuclear regulation of gene expression constitute an attractive mechanism to explain the involvement of mitochondrial dysfunction in a variety of disorders and in evolutionary processes. We discuss candidate mechanisms for coordination of mito-nuclear gene expression and future avenues for their identification, with emphasis on functional genomics techniques.
... Active transcription of the mitochondrial genome has been demonstrated to initiate at various developmental stages, depending on the species [22]. Reports from many studies suggested that gene-specific transcription factors directly affect gene transcription in mitochondria [23]. ...
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In some cases of infertility in women, human oocytes fail to mature when they reach the metaphase II (MII) stage. Mitochondria plays an important role in oocyte maturation. A large number of mitochon-drial DNA (mtDNA), copied in oocytes, is essential for providing adenosine triphosphate (ATP) during oocyte maturation. The purpose of this study was to identify the relationship between transcript expression levels of the mitochondrial encoded gene (MT-CO1) and two nuclear encoded genes, nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) in various stages of human oocyte maturation. Nine consenting patients, age 21-35 years old, with male factors were selected for ovarian stimulation and intracytoplasmic sperm injection (ICSI) procedures. mRNA levels of mito-chondrial-related genes were performed by single-cell TaqMan® quantitative real-time polymerase chain reaction (qRT-PCR). There was no significant relationship between the relative expression levels in germinal vesicle (GV) stage oocytes (p = 0.62). On the contrary, a significant relationship was seen between the relative expression levels of TFAM and NRF1 and the MT-CO1 genes at the stages of meta-phase I (MI) and MII (p = 0.03 and p = 0.002). A relationship exists between the transcript expression levels of TFAM and NRF1, and MT-CO1 genes in various stages of human oocyte maturation.
... Similar to PGC-1α, the nuclear DNA-encoded gene NF-E2-related factor 2 (NRF2) is an important transcription factor for regulating nuclear and mitochondrial gene expression, which are involved in the electron transfer chain (ETC) reaction [58][59][60]. Under normal physiological conditions, NRF2 is regulated by the proteasome degradation pathway via the Kelch-like ECH-associated protein 1 (Keap1)-Cul3 E3 ligase. ...
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Mitochondrial DNA (mtDNA) has been identified as a significant genetic biomarker in disease, cancer and evolution. Mitochondria function as modulators for regulating cellular metabolism. In the clinic, mtDNA variations (mutations/single nucleotide polymorphisms) and dysregulation of mitochondria-encoded genes are associated with survival outcomes among cancer patients. On the other hand, nuclear-encoded genes have been found to regulate mitochondria-encoded gene expression, in turn regulating mitochondrial homeostasis. These observations suggest that the crosstalk between the nuclear genome and mitochondrial genome is important for cellular function. Therefore, this review summarizes the significant mechanisms and functional roles of mtDNA variations (DNA level) and mtDNA-encoded genes (RNA and protein levels) in cancers and discusses new mechanisms of crosstalk between mtDNA and the nuclear genome.
... PGC-1α regulates mitochondrial biogenesis through a number of mechanisms and molecular targets. Briefly, PGC-1α regulates the expression of nuclear respiratory factors (NRF1/2) (Gleyzer et al. 2005;Scarpulla, 2002Scarpulla, , 2011, and mitochondrial transcription factor A (TFAM) (Evans andScarpulla 1990, 2002;Virbasius and Scarpulla 1994), which regulates the production of respiratory components, and ultimately regulates oxidative metabolism. ...
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Glutamine is an amino acid previously linked with improved skeletal muscle metabolism and insulin signaling, however, past observations often use cell culture models with only supraphysiological concentrations. Additionally, past reports have yet to simultaneously investigate both metabolic outcomes and insulin signaling. The present report utilized cell culture experiments and measured the effects of both physiological and supraphysiological levels of glutamine on myotube metabolism and insulin signaling/resistance. It was hypothesized the addition of glutamine at any level would increase cell metabolism and related gene expression, as well as improve insulin signaling versus respective control cells. C2C12 myotubes were treated with glutamine ranging from 0.25 mM-4 mM (or media control) for 24 h to capture a range of physiological and supraphysiological concentrations. qRT-PCR was used to measure metabolic gene expression. Mitochondrial and glycolytic metabolism were measured via oxygen consumption and extracellular acidification rate, respectively. Insulin sensitivity (indicated by pAkt:Akt) and metabolism following glucose/insulin infusion were also assessed. Glutamine treatment consistently increased mitochondrial and glycolytic metabolism versus true controls (cells treated with media void of glutamine), however, supraphysiological glutamine did not enhance metabolism beyond that of cells with physiological levels of glutamine. Neither physiological nor supraphysiological levels of glutamine altered insulin signaling regardless of insulin stimulation or insulin resistance when compared with respective controls. These data demonstrate excess glutamine does not appear to alter myotube metabolism or glucose disposal when base levels of glutamine are present. Moreover, glutamine does not appear to alter insulin sensitivity regardless of level of insulin resistance or presence of insulin stimulation.
... AUTS2 and NRF1 co-localize within chromatin and interact in the mouse brain To identify the factor(s) involved in the key process by which AUTS2 accesses chromatin, we first determined the motifs of transcription factors (TFs) enriched in AUTS2-bound sites in the mouse brain and identified an overrepresentation for that of NRF1 ( Figure 4A). NRF1 is a TF involved in mitochondrial biogenesis (Scarpulla, 2011), which binds to GC-rich DNA elements in the promoters of many mitochondrial biogenesisrelated genes (Evans and Scarpulla, 1990;Gleyzer et al., 2005). NRF1 is also associated with regulation of neurite outgrowth (Chang et al., 2005;Tong et al., 2013) and has essential roles in retinal development (Hsiao et al., 2013;Kiyama et al., 2018), but its function and regulation in the CNS are largely unknown. ...
Article
Erratum for NRF1 association with AUTS2-Polycomb mediates specific gene activation in the brain. (Molecular Cell 81, 4663–4676.e1–e8; November 18, 2021) In the originally published version of this article, three authors—James M. Stafford, Nicolas Descostes, and Pedro Lee—were mistakenly omitted from the author list. Their contributions have been added, and the authors also acknowledge funding support from the Simons Foundation and the NIH. The article has been corrected online and the correct version appears in print. The authors regret the error.
... PGC-1α is a positive regulator of mitochondrial biogenesis and respiration [53,54] and is also reported to play a central role in the detoxification of ROS by governing their removal through the regulation of the expressions of ROS-detoxifying enzymes [55]. NRF1, besides to regulating the expression of the electron transfer chain subunits encoded by the nuclear genome [56], also binds to specific promoter sites and thereby regulates the expression of TFAM [57]. NRF1 is, in turn, regulated by various transcription coactivators, as PGC-1α [58,59]. ...
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D-Aspartate (D-Asp) and its methylated form N-methyl-d-aspartate (NMDA) promote spermatogenesis by stimulating the biosynthesis of sex steroid hormones. d-Asp also induces spermatogonia proliferation directly by activating the ERK/Aurora B pathway. In the present study, a mouse spermatocyte-derived cell line (GC-2) which represents a stage between preleptotene spermatocyte and round spermatids was exposed to 200 μM d-Asp or 50 μM NMDA for 30 min, 2 h, and 4 h to explore the influence of these amino acids on cell proliferation and mitochondrial activities occurring during this process. By Western blotting analyses, the expressions of AMPAR (GluA1-GluA2/3 subunits), cell proliferation as well as mitochondria functionality markers were determined at different incubation times. The results revealed that d-Asp or NMDA stimulate proliferation and meiosis in the GC-2 cells via the AMPAR/ERK/Akt pathway, which led to increased levels of the PCNA, p-H3, and SYCP3 proteins. The effects of d-Asp and NMDA on the mitochondrial functionality of the GC-2 cells strongly suggested an active role of these amino acids in germ cell maturation. In both d-Asp- and NMDA-treated GC-2 cells mitochondrial biogenesis as well as mitochondrial fusion are increased while mitochondria fission is inhibited. Finally, the findings showed that NMDA significantly increased the expressions of the CII, CIII, CIV, and CV complexes of oxidative phosphorylation system (OXPHOS), whereas d-Asp induced a significant increase in the expressions only of the CIV and CV complexes. The present study provides novel insights into the mechanisms underlying the role of d-Asp and NMDA in promoting spermatogenesis.
... Leucine appears to induce mitochondrial biogenesis through several mechanisms including the activation or induction of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) [10][11][12][13][14][15][23][24][25][26]. PGC-1α regulates mitochondrial biogenesis through a number of factors including nuclear respiratory factors (NRF1/2) [27][28][29][30], mitochondrial transcription factor A (TFAM) [31][32][33], and the sirtuins (SIRT1 and SIRT3) [34][35][36][37]. Like upregulation of PGC-1α [10][11][12][13][14][15][23][24][25][26], leucine has also been shown to upregulate sirtuins [10,12,13], as well as peroxisome proliferatoractivated receptor alpha (PPARα) [38] and PPARβ/δ [11,16]. ...
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PurposeBranched-chain amino acids (BCAA) have been shown to enhance several cellular signaling pathways including protein synthesis and mitochondrial biogenesis, yet population data demonstrate a correlation between circulating BCAA and severity of insulin resistance which has been hypothesized to be, in part, a byproduct of BCAA inhibition of mitochondrial function. The purpose of this study is to examine the effect of a BCAA mixture on muscle metabolism and related gene expression in vitro.MethodsC2C12 myotubes were treated with a BCAA mixture containing leucine:isoleucine:valine at a ratio of 2:1:1 at 0.2, 2, or 20 mM (based on leucine content) for 6 days. qRT-PCR was used to measure metabolic gene expression. Oxygen consumption and extracellular acidification were used to assess mitochondrial and glycolytic metabolism, respectively. Mitochondrial content was determined via mitochondrial-specific staining.ResultsDespite significantly elevated mitochondrial staining, 6-day BCAA treatment reduced basal mitochondrial metabolism at a supraphysiological concentration (20 mM) in both insulin sensitive and resistant cells. Peak mitochondrial capacity was also reduced in insulin-resistant (but not insulin sensitive) cells. Conversely, basal glycolytic metabolism was elevated following 20 mM BCAA treatment, regardless of insulin resistance. In addition, insulin-resistant cells treated with 20 mM BCAA exhibited reduced gene expression of Ppargc1a, Cytc, Atp5b, Glut4, and several glycolytic enzymes versus insulin sensitive cells treated with 20 mM BCAA.Conclusions Collectively, these findings suggest BCAA at supraphysiologically high levels may negatively alter mitochondrial metabolism, and concurrent insulin resistance may also diminish peak mitochondrial capacity, as well as impede molecular adaptations that support a transition to a glycolytic preference/compensation.
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Most of the genetic information has been lost or transferred to the nucleus during the evolution of mitochondria. Neverthelss, mitochondria have retained their own genome that is essential for oxidative phosphorylation (OXPHOS). In mammals, a gene‐dense circular mitochondrial DNA (mtDNA) of about 16.5kb encodes 13 proteins, which constitute only 1% of the mitochondrial proteome. Mammalian mtDNA is present in thousands of copies per cell and mutations often affect only a fraction of them. Most pathogenic human mtDNA mutations are recessive and only cause OXPHOS defects if present above a certain critical threshold. However, emerging evidence strongly suggests that the proportion of mutated mtDNA copies is not the only determinant of disease but that also the absolute copy number matters. In this review, we critically discuss current knowledge of the role of mtDNA copy number regulation in various types of human diseases, including mitochondrial disorders, neurodegenerative disorders, and cancer, and during ageing. We also provide an overview of new exciting therapeutic strategies to directly manipulate mtDNA to restore OXPHOS in mitochondrial diseases.
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Hypoxia‐induced cardiomyocyte apoptosis is one of the leading causes of heart failure. Nuclear respiratory factor 1 (NRF‐1) was suggested as a protector against cell apoptosis. however, the mechanism is not clear. Therefore, the aim of this study was to elucidate the role of NRF‐1 in hypoxia‐induced H9C2 cardiomyocyte apoptosis, and to explore its effect on regulating the death receptor pathway and mitochondrial pathways. NRF‐1 was overexpressed or knocked‐down in H9C2 cells, which were then exposed to a hypoxia condition for 0, 3, 6, 12, and 24 h. Changes in cell proliferation, cell viability, reactive oxygen species (ROS) generation, and mitochondrial membrane potential (MMP) were investigated. The activities of caspase‐3, ‐8, and ‐9, apoptosis rate, and the gene and protein expression levels of the death receptor pathway and mitochondrial pathway were analyzed. Under hypoxia exposure, NRF‐1 overexpression improved the proliferation and viability of H9C2 cells, and decreased ROS generation, MMP loss, caspase activities, and the apoptosis rate. However, the NRF‐1 knockdown group showed the opposite results. Additionally, NRF‐1 upregulated the expression of anti‐apoptotic molecules involved in the death receptor and mitochondrial pathways, such as CASP8 and FADD‐like apoptosis regulator, B‐cell lymphoma 2, B‐cell lymphoma‐extra‐large, and cytochrome‐C. Conversely, the expression of pro‐apoptotic molecules such as caspase‐8, BH3‐interacting domain death agonist, Bcl‐2‐associated X protein, caspase‐9, and caspase‐3 was down‐regulated by NRF‐1 overexpression in hypoxia‐induced H9C2 cells. These results suggest that NRF‐1 functions as an anti‐apoptotic factor in the death receptor and mitochondrial pathways to mitigate hypoxia‐induced apoptosis in H9C2 cardiomyocytes. This article is protected by copyright. All rights reserved.
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Previous studies have shown various metabolic stressors such as saturated fatty acids (SFA) and excess insulin promote insulin resistance in metabolically meaningful cell types (such as skeletal muscle). Additionally, these stressors have been linked with suppressed mitochondrial metabolism, which is also a common characteristic of skeletal muscle of diabetics. This study characterized the individual and combined effects of excess lipid and excess insulin on myotube metabolism and related metabolic gene and protein expression. C2C12 myotubes were treated with either 500 μM palmitate (PAM), 100 nM insulin (IR), or both (PAM‐IR). qRT‐PCR and western blot were used to measure metabolic gene and protein expression, respectively. Oxygen consumption was used to measure mitochondrial metabolism. Glycolytic metabolism and insulin‐mediated glucose uptake were measured via extracellular acidification rate. Cellular lipid and mitochondrial content were measured using Nile Red and NAO staining, respectively. IR and PAM‐IR treatments led to reductions in p‐Akt expression. IR treatment reduced insulin mediated glucose metabolism while PAM and PAM‐IR treatment showed increases with concurrent reductions in mitochondrial metabolism. All three treatments showed suppression in mitochondrial metabolism. PAM and PAM‐IR also showed increases in glycolytic metabolism. While PAM and PAM‐IR significantly increased lipid content, expression of inflammatory and lipogenic proteins were unaltered. Lastly, PAM‐IR reduced BCAT2 protein expression, a regulator of BCAA metabolism. Both stressors independently reduced insulin signaling, mitochondrial function, and cell metabolism, however, only PAM‐IR co‐treatment significantly reduced the expression of regulators of metabolism not seen with individual stressors, suggesting an additive effect of stressors on metabolic programming.
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Substantial evidence indicates that mitochondrial impairment contributes to neuronal dysfunction and vulnerability in disease states, leading investigators to propose that the enhancement of mitochondrial function should be considered a strategy for neuroprotection. However, multiple attempts to improve mitochondrial function have failed to impact disease progression, suggesting that the biology underlying the normal regulation of mitochondrial pathways in neurons, and its dysfunction in disease, is more complex than initially thought. Here, we present the proteins and associated pathways involved in the transcriptional regulation of nuclear-encoded genes for mitochondrial function, with a focus on the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1α). We highlight PGC-1α’s roles in neuronal and non-neuronal cell types and discuss evidence for the dysregulation of PGC-1α-dependent pathways in Huntington’s Disease, Parkinson’s Disease, and developmental disorders, emphasizing the relationship between disease-specific cellular vulnerability and cell-type-specific patterns of PGC-1α expression. Finally, we discuss the challenges inherent to therapeutic targeting of PGC-1α-related transcriptional programs, considering the roles for neuron-enriched transcriptional coactivators in co-regulating mitochondrial and synaptic genes. This information will provide novel insights into the unique aspects of transcriptional regulation of mitochondrial function in neurons and the opportunities for therapeutic targeting of transcriptional pathways for neuroprotection.
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A mutational analysis of the rat cytochrome c oxidase subunit IV (RCO4) promoter region revealed the presence of a major control element consisting of a tandemly repeated pair of binding sites for a nuclear factor from HeLa cells. This factor was designated NRF-2 (nuclear respiratory factor 2) because a functional recognition site was also found in the human ATP synthase beta-subunit gene. Deletion or site-directed point mutations of the NRF-2 binding sites in the RCO4 promoter resulted in substantial loss of transcriptional activity, and synthetic oligomers of the NRF-2 binding sites from both genes stimulated a heterologous promoter when cloned in cis. NRF-2 binding and transcriptional activation required a purine-rich core sequence, GGAA. This motif is characteristic of the recognition site for a family of activators referred to as ETS domain proteins because of the similarity within their DNA-binding domains to the ets-1 proto-oncogene product. NRF-2 recognized an authentic Ets-1 site within the Moloney murine sarcoma virus long terminal repeat, and this site was able to compete for NRF-2 binding to the RCO4 promoter sequence. In addition, a single polypeptide of 55 kDa was detected following cross-linking of a partially purified NRF-2 fraction to RCO4, the human ATP synthase beta subunit, or Moloney murine sarcoma virus binding sites. However, in contrast to Ets-1, which appears to be exclusive to lymphoid tissues, NRF-2 has the broad tissue distribution expected of a regulator of respiratory chain expression.
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Early treatment can prevent the occurrence of diabetes; however, there are few pharmacological treatment strategies to date. The liver is a major metabolic organ, and hepatic glucose homeostasis is dysregulated in type 1 and type 2 diabetes mellitus. However, the potential of specifically targeting the liver to prevent diabetes has not been fully exploited. In this study, we found that compartmentally inhibiting hepatic oxidants by nano-MitoPBN, a liver mitochondrial-targeting ROS scavenger, could effectively prevent diabetes. Our results demonstrated that nano-MitoPBN reversed the downregulation of PGC-1α and the enhanced gluconeogenesis in the livers of diabetic mice. PGC-1α, through an AMPK- and SIRT3-mediated mechanism, promoted mitochondrial biogenesis, increased the number of mitochondria, and enhanced the rate of aerobic oxidation, leading to decreased glucose levels in the blood by increasing glucose uptake and catabolism in the liver. Moreover, the increase in PGC-1α activity did not promote the activation of gluconeogenesis. Our study demonstrated that by regulating the redox balance of liver mitochondria in the early stage of diabetes, PGC-1α could selectively inhibit gluconeogenesis in the liver and promote hepatic mitochondrial function, which accelerated the catabolism of hepatic glucose and reduced blood glucose. Thus, glucose tolerance can be normalized through only three weeks of intervention. Our results showed that nano-MitoPBN could effectively prevent diabetes in a short period of time, highlighting the effectiveness and importance of early intervention for diabetes and suggesting the potential advantages of hepatic mitochondrial targeting oxidants nano-inhibitors in the prevention and early treatment of diabetes.
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Type 2 diabetes is characterized by reduced insulin sensitivity, elevated blood metabolites, and reduced mitochondrial metabolism. Insulin resistant populations often exhibit reduced expression of genes governing mitochondrial metabolism such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Interestingly, PGC-1α regulates the expression of branched-chain amino acid (BCAA) metabolism, and thus, the consistently observed increased circulating levels of BCAA in diabetics may be partially explained by reduced PGC-1α expression. Conversely, PGC-1α upregulation appears to increase BCAA catabolism. PGC-1α activity is regulated by 5′-AMP-activated protein kinase (AMPK), however, only limited experimental data exists on the effect of AMPK activation in the regulation of BCAA catabolism. The present report examined the effects of the commonly used AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) on the metabolism and expression of several related targets (including BCAA catabolic enzymes) of cultured myotubes. C2C12 myotubes were treated with AICAR at 1 mM for up to 24 h. Mitochondrial and glycolytic metabolism were measured via oxygen consumption and extracellular acidification rate, respectively. Metabolic gene and protein expression were assessed via qRT-PCR and western blot, respectively. AICAR treatment significantly increased mitochondrial content and peak mitochondrial capacity. AICAR treatment also increased AMPK activation and mRNA expression of several regulators of mitochondrial biogenesis but reduced glycolytic metabolism and mRNA expression of several glycolytic enzymes. Interestingly, branched-chain alpha-keto acid dehydrogenase a (BCKDHa) protein was significantly increased following AICAR-treatment suggesting increased overall BCAA catabolic capacity in AICAR-treated cells. Together, these experiments demonstrate AICAR/AMPK activation can upregulate BCAA catabolic machinery in a model of skeletal muscle.
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Elevated circulating branched-chain amino acids (BCAA) such as leucine have been consistently correlated with increasing severity of insulin resistance across numerous populations. BCAA may promote insulin resistance through either mTOR-mediated suppression of insulin receptor substrate-1 or through the accumulation of toxic BCAA catabolites. Although the link between circulating BCAA and insulin resistance has been consistent, it has yet to be concluded if BCAA causally contribute to the development or worsening of insulin resistance. This work investigated the effect of leucine both with and without varying levels of insulin resistance on metabolism, metabolic gene expression, and insulin signaling. C2C12 myotubes were treated with and without varied concentrations of leucine up to 2mM for 24 hours both with and without varied levels of insulin resistance. Gene and protein expression were measured via qRT-PCR and western blot, respectively. Mitochondrial metabolism was measured via O2 consumption. Leucine at 2mM increased oxidative metabolism as well as gene expression of mitochondrial biogenesis, which was associated with increased cellular lipid content. Despite increased lipid content of leucine-treated cells, neither acute nor chronic leucine treatment at 2mM affected insulin signaling in insulin sensitive, mildly insulin resistant, or severely insulin resistant cells. Similarly, leucine at lower concentrations (0.25mM, 0.5mM, and 1mM) did not alter insulin signaling either, regardless of insulin resistance. Leucine appears to improve myotube oxidative metabolism and related metabolic gene expression. And despite increased lipid content of leucine-treated cells, leucine does not appear to alter insulin sensitivity either acutely or chronically, regardless of level of insulin resistance.
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The Harderian gland (HG) of Rattus norvegicus is an orbital gland secreting lipids that accumulate in excess under condition of increased lipid metabolism. To study the response elicitated by lipid overload in rat HG, we housed the animals in thermoneutral conditions (28−30°C) in association to high fat diet (HFD). In HFD rats alterated blood lipid levels result in lipid accumulation in HG as demonstrated by the increased gland weight and histochemical/ultrastructural analyses. The HFD‐caused oxidative stress forces the gland to trigger antioxidant defense mechanisms and autophagic process, such as lipophagy and mitophagy. Induction of mitochondrial DNA (mtDNA) damage and repair was stronger in HFD‐rat HGs. An increase in marker expression levels of mitochondrial biogenesis, fission, and fusion occurred to counteract mtDNA copy number reduction and mitophagy. Therefore, the results demonstrate that rat HG activates autophagy as survival strategy under conditions of increased lipid metabolism and suggest a key role for mitophagy and membrane dynamics in the mitochondrial adaptive response to HFD. Autophagy increases in high fat diet (HFD) rat Harderian gland (HG) as survival strategy to overloap lipids. HFD induces mitochondrial DNA (mtDNA) damage/repair in rat HG. Mitochondrial biogenesis, fission, and fusion increase in HFD rat HG to counteract mtDNA copy number reduction and mitophagy.
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Branched‐chain amino acids (BCAA) are essential in the diet and promote several vital cell responses which may have benefits for health and athletic performance, as well as disease prevention. While BCAA are well‐known for their ability to stimulate muscle protein synthesis, their effects on cell energetics are also becoming well‐documented, but these receive less attention. In this review, we highlight much of the current evidence demonstrating BCAA ability (as individual amino acids or as part of dietary mixtures) to alter regulators of cellular energetics with an emphasis on mitochondrial biogenesis and related signaling. Several studies have shown, both in vitro and in vivo, that BCAA (either individual or as a mixture) may promote signaling associated with increased mitochondrial biogenesis including the upregulation of master regulator of mitochondrial biogenesis peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha (PGC‐1α), as well as numerous downstream targets and related function. However, sparse data in humans and the difficulty of controlling variables associated with feeding studies leaves the physiological relevance of these findings unclear. Future well‐controlled diet studies will be needed to assess if BCAA consumption is associated with increased mitochondrial biogenesis and improved metabolic outcomes in healthy and/or diseased human populations. This article is protected by copyright. All rights reserved
Chapter
Mitochondria control a myriad of intracellular processes including ATP synthesis, redox balance, ion homeostasis and metabolism of amino acids and lipids. Maintaining a healthy and demand-matched pool of mitochondria is critical for supporting the immune system. Changes in mitochondrial mass, size, number, morphology, connectiveness and distribution occur in a dynamic process mainly driven by oscillations in energy demand and supply in health and disease. Therefore, disruption of mitochondrial biogenesis and dynamics likely results in mitochondrial dysfunction-associated diseases. This chapter reviews the molecular mechanisms that regulate mitochondrial content, number and morphology. It also highlights the clinical implications of defective mitochondrial biogenesis and dynamics.
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The rat somatic cytochrome c promoter is resolved into a mosaic of cis-acting upstream and intron elements required for maximal activity. Mutations in each diminished cytochrome c promoter activity and eliminated the specific binding of cognate nuclear factors. Among these is the recognition sequence for a nuclear factor designated NRF-1 (nuclear respiratory factor 1) also found in the upstream regions of several other nuclear genes whose products function in the mitochondria. The NRF-1 site was tightly coupled to a second functionally independent element (region I), and together these sites constitute a major determinant of cytochrome c expression. In addition to these novel sequence elements, the promoter also contained recognition sites for the common transcriptional activators ATF and Sp1. A potent promoter element within the first intron consisted of two adjacent Sp1 binding sites. Point mutations in the first site eliminated the promoter activity of the element as well as Sp1 binding to both sites. An ATF recognition sequence in the upstream promoter was identical to an authentic cyclic AMP (cAMP) responsive element in stimulating promoter activity and in conferring a cAMP response upon a heterologous promoter. These promoter elements and their cognate nuclear factors likely contribute to the housekeeping function of cytochrome c and to the coordinate modulation of respiratory gene expression according to cellular energy demands.
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7-2 RNA (also termed RNA M and 7SM RNA) is a noncapped small RNA present in small ribonucleoprotein particles; these particles are present in the granular compartment of the nucleolus. Some sera from patients with scleroderma specifically immunoprecipitate 7-2 RNA-containing particles (Hashimoto, C., and Steitz, J. A. (1983) J. Biol. Chem. 258, 1379–1382; Reddy, R., Tan, E. M., Henning, D., Nohga, K., and Busch, H. (1983) J. Biol. Chem. 258, 1383–1386; Reimer, G., Raska, I., Scheer, U., and Tan, E.M. (1988) Exp. Cell Res. 176, 117–128). In this study, the primary sequence of Novikoff hepatoma 7-2 RNA was determined and a possible secondary structure is presented. The Novikoff hepatoma 7-2 RNA is 94% homologous to the recently described mouse mitochondrial RNase MRP RNA, suggesting that Novikoff hepatoma 7-2 RNA may be the homologue of mouse MRP RNA. The presence of 7-2 RNA in nucleoli and in mitochondria suggests that 7-2 ribonucleoproteins, in addition to being essential components of mitochondrial RNase, may also be functional in nucleolar RNA processing and ribosome biogenesis.
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The structural organization of the entire human nuclear encoded gene for mitochondrial cytochrome c1 was determined by analyzing a clone obtained from an EMBL3 genomic DNA library. The gene spans 2.4-kilobase pairs and contains seven exons interrupted by six introns of relatively small sizes. All intron/exon splice junctions follow the GT/AG rule. The 5'-flanking region of the gene lacks typical transcriptional regulatory sequence elements such as TATA and CAAT boxes but contains seven putative GC boxes (Sp1 binding sites) and several sequences that resemble another type of the Sp1 responsive element, the enhancer core consensus sequence, the AP-1 responsive element, and the cAMP- and phorbol ester-inducible element. The region also contains a 15-nucleotide sequence highly homologous to the AP-4 consensus sequence and to those in the 5'-flanking regions of the genes for two enzymes associated with respiratory function, the beta subunit of human ATP synthase and chicken 5-aminolevulinate synthase. The presequence, which is essential for the transport of the cytochrome c1 precursor into mitochondria, is encoded in both the first and second exons, and the nucleotide sequence corresponding to the presequence is separated by the first intron. This is the first example of a leader sequence coding for a presequence clearly separated into two parts by an intron.
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We have analysed various adult organs and different developmental stages of mouse embryos for the presence of octamer-binding proteins. A variety of new octamer-binding proteins were identified in addition to the previously described Oct1 and Oct2. Oct1 is ubiquitously present in murine tissues, in agreement with cell culture data. Although Oct2 has been described as a B-cell-specific protein, similar complexes were also found with extracts from brain, kidney, embryo and sperm. In embryo and brain at least two other proteins, Oct3 and Oct7, are present. A new microextraction procedure allowed the detection of two maternally expressed octamer-binding proteins, Oct4 and Oct5. Both proteins are present in unfertilized oocytes and embryonic stem cells, the latter containing an additional protein, Oct6. Whereas Oct4 was not found in sperm or testis, it is expressed in male and female primordial germ cells. Therefore Oct4 expression is specific for the female germline at later stages of germ cell development. Our results indicate that a family of octamer-binding proteins is present during mouse development and is differentially expressed during early embryogenesis. Protease clipping experiments of Oct4 and Oct1 suggest that both proteins contain similar DNA-binding domains.
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