Sun, Q. et al. Identification of Barkor as a mammalian autophagy-specific factor for Beclin 1 and class III phosphatidylinositol 3-kinase. Proc. Natl. Acad. Sci. USA 105, 19211-19216

Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 01/2009; 105(49):19211-6. DOI: 10.1073/pnas.0810452105
Source: PubMed


Autophagy mediates the cellular response to nutrient deprivation, protein aggregation, and pathogen invasion in human. Dysfunction of autophagy has been implicated in multiple human diseases including cancer. The identification of novel autophagy factors in mammalian cells will provide critical mechanistic insights into how this complicated cellular pathway responds to a broad range of challenges. Here, we report the cloning of an autophagy-specific protein that we called Barkor (Beclin 1-associated autophagy-related key regulator) through direct interaction with Beclin 1 in the human phosphatidylinositol 3-kinase class III complex. Barkor shares 18% sequence identity and 32% sequence similarity with yeast Atg14. Elimination of Barkor expression by RNA interference compromises starvation- and rapamycin-induced LC3 lipidation and autophagosome formation. Overexpression of Barkor leads to autophagy activation and increased number and enlarged volume of autophagosomes. Tellingly, Barkor is also required for suppression of the autophagy-mediated intracellular survival of Salmonella typhimurium in mammalian cells. Mechanistically, Barkor competes with UV radiation resistance associated gene product (UVRAG) for interaction with Beclin 1, and the complex formation of Barkor and Beclin1 is required for their localizations to autophagosomes. Therefore, we define a regulatory signaling pathway mediated by Barkor that positively controls autophagy through Beclin 1 and represents a potential target for drug development in the treatment of human diseases implicated in autophagic dysfunction.

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Available from: Weiliang Fan, Dec 22, 2014
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    • "; impaired bacteria clearance, unaffected obatoclax-induced toxicity, augmented genomic instability, aberrant cell apoptosis, and altered cell cycle, and cytoskeletal protein filamentous actin network in mouse embryonic fibroblasts Komatsu et al., 2005; Sun et al., 2008; McCoy et al., 2010; Lee et al., 2012; Zhuo et al., 2013 iUbc-Cre Perturbed glucose metabolism and inhibited progression of non-small cell lung cancer Karsli-Uzunbas et al., 2014 Liver Mx1-Cre Hepatomegaly with malformations of organelles and ubiquitin-positive protein aggregates Komatsu et al., 2005; Matsumoto et al., 2008 Alb-Cre Oxidative stress with increased total protein mass; excessive storage of triglyceride in lipid droplets during nutrient deprivation Matsumoto et al., 2008; Singh et al., 2009a GFAP-Cre Inhibited lipid release and fibrogenesis in hepatic stellate cells Hernandez-Gea et al., 2012 Pancreas RIP-Cre Impaired glucose tolerance; degenerated islets; decreased mitochondrial oxidation consumption and increased compensatory basal glycolytic rates and reactive oxygen species levels Ebato et al., 2008; Jung et al., 2008; Wu et al., 2009 Skeletal muscle MCK-Cre Decreased mitochondrial oxidation consumption and increased compensatory basal glycolytic rates and reactive oxygen species levels Wu et al., 2009 Endothelium VE-cadherin- Cre Impaired von Willebrand factor (VWF) release; susceptibility to bleomycin-induced pulmonary fibrosis Torisu et al., 2013; Singh et al., 2015 Vascular smooth muscle "
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    ABSTRACT: Macroautophagy is an evolutionarily conserved intracellular degradation system used by life ranging from yeasts to mammals. The core autophagic machinery is composed of ATG (autophagy-related) protein constituents. One particular member of the ATG protein family, Atg7, has been the focus of recent research. Atg7 acts as an E1-like activating enzyme facilitating both microtubule-associated protein light chain 3 (LC3)-phosphatidylethanolamine and ATG12 conjugation. Thus, Atg7 stands at the hub of these two ubiquitin-like systems involving LC3 and Atg12 in autophagic vesicle expansion. In this review, I focus on the pleiotropic function of Atg7 in development, maintenance of health, and alternations of such control in disease.
    Protein & Cell 09/2015; DOI:10.1007/s13238-015-0195-8 · 3.25 Impact Factor
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    • "Another key autophagy complex is the phosphatidylinositol 3-kinase (PI3K) complex. In the mammalian system, this complex is composed of ATG14L (also known as ATG14 and Barkor), BECN1 (Beclin 1, yeast Atg6 ortholog), hVPS34 (vacuolar protein sorting protein 34-VPS34-homolog), and hVPS15 (Figure 1) (Itakura et al., 2008; Sun et al., 2008; Zhong et al., 2009; Matsunaga et al., 2010). In the PI3K complex, hVPS34 is the kinase and its activity and localization is controlled by other components of the complex. "
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    ABSTRACT: Autophagy is an evolutionary conserved intracellular degradation and stress response mechanism that is mainly responsible for the breakdown and recycling of cytoplasmic materials, including long-lived proteins, protein aggregates, and damaged organelles. In this way, autophagy provides the cell with building blocks and allows the maintenance of homeostasis under stress conditions such as growth factor deficiency, nutrient deprivation, hypoxia, and toxins. Consequently, abnormalities of autophagy contribute to a number of pathologies ranging from neurodegenerative diseases to cancer. Autophagy was reported to have a dual role in cancer. Depending on cancer stage, autophagy seems to act as tumor suppressor or as a mechanism supporting tumor growth and spread. In this review, we provide a summary of the relevant literature and discuss the role of autophagy in cancer formation and chemotherapy responses.
    Turkish Journal of Biology 11/2014; 38(6):720-739. DOI:10.3906/biy-1408-16 · 1.34 Impact Factor
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    • "The autophagic and oncogenic phenotype of Beclin 1 might be attributed to its interaction with class III phosphatidylinositol 3-kinase (PI3KC3) complexes and other important cellular regulators, including mammalian target of rapamycin (mTOR) [39], Bim [40], Bcl-xL [41], c-Jun N-terminal kinase (JNK) [42], Ambra 1 [43], Bif-1 and Beclin 1-associated autophagy-related key regulator (Barkor) [44,45]. Under the nutrient-deprived stress, mesenchymal stem cells (MSCs) survived by activating Beclin 1 mediated autophagy, and facilitated breast cancer MCF-7 cells to invasiveness through upregulating histone deacetylases 6 (HDAC6) activity and increasing motility [45]. Here, we found that the cholangiocarcinoma patients with lymph node metastasis (N1 stage) had a lower level of Beclin 1 than that of N0 stage patients (IHC score: 3.45±2.82 "
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    ABSTRACT: Autophagy can be tumor suppressive as well as promotive in regulation of tumorigenesis and disease progression. Accordingly, the prognostic significance of autophagy key regulator Beclin 1 was varied among different tumors. Here, we detected the clinicopathological and prognostic effect of Beclin 1 in the subtypes of intrahepatic cholangiocarcinoma (ICC) and extrahepatic cholangiocarcinoma (ECC). Beclin 1 expression level was detected by immunohistochemistry staining in 106 ICC and 74 ECC patients. We found that Beclin 1 was lowly expressed in 126 (70%) cholangiocarcinoma patients, consist of 72 ICC and 54 ECC. Moreover, the cholangiocarcinoma patients with lymph node metastasis (N1) had a lower Beclin 1 level than that of N0 subgroup (P=0.012). However, we did not detect any correlations between Beclin 1 and other clinicopathological features, including tumor subtypes, vascular invasion, HBV infection, liver cirrhosis, cholecystolithiasis and TNM stage. Survival analysis showed that, compared with the high expression subset, Beclin 1 low expression was correlated with a poorer 3-year progression-free survival (PFS, 69.1% VS 46.8%, P=041) for cholangiocarcinoma. Importantly, our stratified univariate and multivariate analysis confirmed that Beclin 1 lowly expressed ICC had an inferior PFS as well as overall survival than ECC, particularly than that of Beclin 1 highly expressed ECC patients. Thus, our study demonstrated that Beclin 1low expression, correlated with lymph node metastasis, and might be a negative prognostic biomarker for cholangiocarcinoma. Combined Beclin 1 level with the anatomical location might lead to refined prognosis for the subtypes of ICC and ECC.
    PLoS ONE 11/2013; 8(11):e80317. DOI:10.1371/journal.pone.0080317 · 3.23 Impact Factor
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