Molecular Biology of the Cell (MOL BIOL CELL )

Publisher: American Society for Cell Biology, American Society for Cell Biology

Description

Molecular Biology of the Cell, the journal owned and published by The American Society for Cell Biology, publishes papers that describe and interpret results of original research concerning the molecular aspects of cell structure and function. Studies whose scope bridges several areas of biology are particularly encouraged, for example cell biology and genetics. The aim of the Journal is to publish papers describing substantial research progress in full: papers should include all previously unpublished data and methods essential to support the conclusions drawn.

Impact factor 4.55

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    Impact factor
  • 5-year impact
    5.35
  • Cited half-life
    7.40
  • Immediacy index
    1.07
  • Eigenfactor
    0.10
  • Article influence
    2.58
  • Website
    Molecular Biology of the Cell website
  • Other titles
    Molecular biology of the cell, MBC
  • ISSN
    1059-1524
  • OCLC
    24486692
  • Material type
    Periodical, Internet resource
  • Document type
    Journal / Magazine / Newspaper, Internet Resource

Publisher details

American Society for Cell Biology

  • Pre-print
    • Author cannot archive a pre-print version
  • Post-print
    • Author cannot archive a post-print version
  • Conditions
    • On author's personal website or institutional repository
    • Publisher's version/PDF must be used
    • In Press version must not be used
    • Publisher copyright and source must be acknowledged with citation
    • Must link to publisher version
    • Creative Commons Attribution Non-Commerical Share Alike 3.0 License
    • Articles are placed in PubMed Central after 2 months by publisher
  • Classification
    ​ blue

Publications in this journal

  • Gonzalo Vilas, Devishree Krishnan, Sampath Kumar Loganathan, Darpan Malhotra, Lei Liu, Megan Rachele Beggs, Patrizia Gena, Giuseppe Calamita, Martin Jung, Richard Zimmermann, Grazia Tamma, Joseph Roman Casey, Robert Todd Alexander
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    ABSTRACT: Aquaporin-1 (AQP1) enables greatly enhanced water flux across plasma membranes. The cytosolic carboxy-terminus of AQP1 has two acidic motifs homologous to known carbonic anhydrase II (CAII) binding sequences. CAII colocalizes with AQP1 in the renal proximal tubule. Expression of AQP1 with CAII in Xenopus oocytes or mammalian cells increased water flux relative to AQP1 expression alone. This required the amino terminal sequence of CAII, a region that binds other transport proteins. Expression of catalytically-inactive CAII failed to increase water flux through AQP1. Proximity ligation assays revealed close association of CAII and AQP1, an effect requiring the second acidic cluster of AQP1. This motif was also necessary for CAII to increase AQP1-mediated water flux. Red blood cell ghosts resealed with CAII demonstrated increased osmotic water permeability compared with ghosts resealed with albumin. Water flux across renal cortical membrane vesicles, measured by stopped-flow light scattering, was reduced in CAII-deficient mice compared with wild-type mice. These data are consistent with CAII increasing water conductance through AQP1 by a physical interaction between the two proteins.
    Molecular Biology of the Cell 01/2015;
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    ABSTRACT: The receptor tyrosine kinase Axl has been described as an oncogene and its deregulation has been implicated in the progression of several human cancers. While the role of Axl in oesophageal adenocarcinoma has been addressed, there is no information about its role in oesophageal squamous cell carcinoma. In the current report, we identified, for the first time, deregulation of Axl expression in oesophageal squamous cell carcinoma (OSCC). Axl is consistently overexpressed in OSCC cell lines and human tumor samples, mainly in advanced stages of the disease. Blockage of Axl gene expression by small interfering RNA inhibits cell survival, proliferation, migration, and invasion in vitro and oesophageal tumor growth in vivo. Additionally, repression of Axl expression results in Akt-dependent inhibition of pivotal genes involved in the NF-κB pathway and in the induction of GSK3β activity, resulting in loss of mesenchymal and induction of epithelial markers. Furthermore, treatment of oesophageal cancer cells with the Akt inhibitor wortmannin inhibits NF-κB signaling, induces GSK3β activity and blocks OSCC cell proliferation in an Axl-dependent manner. Taken together, our results establish a clear role for Axl in OSCC tumorigenesis with potential therapeutic implications. © 2015 by The American Society for Cell Biology.
    Molecular Biology of the Cell 01/2015;
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    ABSTRACT: Kindlins are integrin interacting proteins, essential for integrin mediated cell adhesiveness. In this study, we focused on the evolutionary origin and functional specialization of Kindlins as a part of evolutionary adaptation of cell adhesive machinery. The database searches revealed that many members of integrin machinery (including Talin and integrins) already existed prior to Kindlin emergence in evolution. Among the analyzed species, all metazoan lineages-but none of the premetazoans-had at least one Kindlin encoding gene, whereas Talin was present in several premetazoan lineages. Kindlin appears to originate from a duplication of the sequence encoding the N-terminal fragment of Talin (the Talin Head domain), with a subsequent insertion of the PH domain of a separate origin. Sequence analysis identified a member of the Actin Filament-associated Protein 1 (AFAP1) superfamily as the most likely origin of the Kindlin PH domain. The functional divergence between Kindlin paralogs was assessed using the sequence swap (chimera) approach. Comparison of Kindlin 2 (K2)/Kindlin 3 (K3) chimeras revealed that the F2 subdomain, in particular its C-terminal part, is crucial for the differential functional properties of K2 and K3. The presence of this segment enables K2 but not K3 to localize to focal adhesions. Sequence analysis of the C-terminal part of the F2 subdomain of K3 suggests that an insertion of a variable glycine-rich sequence in vertebrates contributed to the loss of constitutive K3 targeting to focal adhesions. Thus, emergence and subsequent functional specialization of Kindlins allowed multicellular organisms to develop additional tissue-specific adaptations of cell adhesiveness. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Cytohesin Arf-GEFs are conserved plasma membrane regulators. The sole Drosophila cytohesin, Steppke, restrains Rho1-dependent membrane cytoskeleton activity at the base of plasma membrane furrows of the syncytial embryo. By mass spectrometry, we identified a single major Steppke-interacting protein from syncytial embryos we named Stepping stone (Sstn). By sequence, Sstn seems to be a divergent homolog of the mammalian cytohesin adaptor FRMD4A. Our experiments supported this relationship. Specifically, heterophilic coiled-coil interactions linked Sstn and Steppke in vivo and in vitro, whereas a separate C-terminal region was required for Sstn localization to furrows. Sstn mutant and RNAi embryos displayed abnormal, Rho1-dependent membrane cytoskeleton expansion from the base of pseudocleavage and cellularization furrows, closely mimicking Steppke loss-of-function embryos. Elevating Sstn furrow levels had no effect on the steppke phenotype, but elevating Steppke furrow levels reversed the sstn phenotype, suggesting Steppke acts downstream of Sstn, and that additional mechanisms can recruit Steppke to furrows. Finally, the coiled-coil domain of Steppke was required for Sstn binding but additionally homo-dimerization, and its removal disrupted Steppke furrow localization and activity in vivo. Overall, we propose that Sstn acts as a cytohesin adaptor that promotes Steppke activity for localized membrane cytoskeleton restraint in the syncytial Drosophila embryo. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Seipin is necessary both for adipogenesis and lipid droplet organization in non-adipose tissues, however its molecular function is incompletely understood. Phenotypes in the seipin-null mutant of Saccharomyces cerevisiae include aberrant droplet morphology (ER-droplet clusters and size heterogeneity) and sensitivity of droplet size to changes in phospholipid synthesis. It has not been clear, however, whether seipin acts in initiation of droplet synthesis or a later step. Here we utilize a system of de novo droplet formation to show that the absence of seipin results in a delay in droplet appearance with concomitant accumulation of neutral lipid in membranes. We also demonstrate that seipin is required for vectorial budding of droplets toward the cytoplasm. Furthermore, we find that the normal rate of droplet initiation depends on 14 amino acids at the amino terminus of seipin, deletion of which results in fewer, larger droplets that are consistent with a delay in initiation but are otherwise normal in morphology. Importantly, other functions of seipin, namely vectorial budding and resistance to inositol, are retained in this mutant. We conclude that seipin has dissectible roles in both promoting early lipid droplet initiation and in regulating lipid droplet morphology, supporting an important role in lipid droplet biogenesis. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that binds and transmits signals from various collagens in epithelial cells. However, how DDR1-dependent signaling is regulated has not been understood. Here we report that collagen binding induces ADAM10-dependent ectodomain shedding of DDR1. DDR1 shedding is not a result of an activation of its signaling pathway since DDR1 mutants defective in signaling were shed in an efficient manner. DDR1 and ADAM10 were found to be in a complex on the cell surface, but shedding did not occur unless collagen bound to DDR1. Using a shedding resistant DDR1 mutant, we found that ADAM10-dependent DDR1 shedding regulates the half-life of collagen-induced phosphorylation of the receptor. Our data also revealed that ADAM10 plays an important role in regulating DDR1 mediated cell adhesion to achieve efficient cell migration on collagen matrices. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Chromatin and nuclear pore complexes (NPCs) undergo dramatic changes during mitosis which in vertebrates and Aspergillus nidulans involves movement of Nup2 from NPCs to the chromatin region to fulfill unknown functions. This transition is shown to require the Cdk1 mitotic kinase and to be promoted prematurely by ectopic expression of the NIMA kinase. Nup2 localizes with a copurifying partner termed NupA, a highly divergent yet essential NPC protein. NupA and Nup2 locate throughout the chromatin region during prophase but during anaphase move to surround segregating DNA. NupA function is shown to involve targeting Nup2 to its interphase and mitotic locations. Deletion of either Nup2 or NupA causes identical mitotic defects that initiate a spindle assembly checkpoint (SAC) dependent mitotic delay and also cause defects in karyokinesis. These mitotic problems are not caused either by overall defects in mitotic NPC disassembly-reassembly or general nuclear import. However, without Nup2 or NupA, although the SAC protein Mad1 locates to its mitotic locations it fails to locate to NPCs normally in G1 after mitosis. Collectively the study provides new insight to the roles of Nup2 and NupA during mitosis and in a surveillance mechanism that regulates nucleokinesis when mitotic defects occur after SAC fulfillment. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: The anaphase-promoting complex/cyclosome (APC/C) controls a variety of cellular processes through its ability to target numerous protein substrates for timely degradation. Substrate selection by this ubiquitin ligase depends on related activator proteins, Cdc20 and Cdh1, which bind and activate the APC/C at distinct cell cycle stages. Biochemical and structural studies revealed that Cdc20 and Cdh1 carry conserved receptor domains to recognize specific sequence motifs in substrates, such as d- and KEN-boxes. The mechanisms for ordered degradation of APC/C substrates, however, remain incompletely understood. Here, we describe minimal degradation sequences (degrons) sufficient for rapid APC/C-Cdh1-specific in vivo degradation. The polo kinase Cdc5-derived degron contained an essential KEN motif, while a single RxxL-type d-box was the relevant signal in the Cdc20-derived degradation domain, indicating that either motif may support specific recognition by Cdh1. In both degrons, the APC/C recognition motif was flanked by a nuclear localization sequence. Forced localization of the degron constructs revealed that proteolysis mediated by APC/C-Cdh1 is restricted to the nucleus and maximally active in the nucleoplasm. Levels of Iqg1, a cytoplasmic Cdh1 substrate, decreased detectably later than the nuclear-localized Cdh1 substrate Ase1, indicating that confinement to the nucleus may allow for temporal control of APC/C-Cdh1-mediated proteolysis. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: DIF-1 is a polyketide that induces Dictyoselium amoebae to differentiate as prestalk cells. We performed a global quantitative screen for phosphorylation changes that occur within the first minutes after addition of DIF-1 using a triple-label SILAC approach. This revealed a new world of DIF-1 controlled signaling: with changes in components of the MAPK and protein kinase-B signaling pathways, components of the actinomyosin cytoskeletal signaling networks and in a broad range of small GTPases and their regulators. The results also provide evidence that the Ca(2+)/calmodulin dependent phosphatase calcineurin plays a role in DIF-1 signaling to the DimB prestalk transcription factor. At the global level DIF-1 causes a major shift in the phosphorylation/dephosphorylation equilibrium toward net dephosphorylation. Interestingly, many of the sites that are dephosphorylated in response to DIF-1 are phosphorylated in response to extracellular cAMP signaling. This accords with studies that suggest an antagonism between the two inducers and also with the rapid dephosphorylation of the cAMP receptor that we observe in response to DIF-1 and with the known inhibitory effect of DIF-1 on chemotaxis to cAMP. All MS data are available via ProteomeXchange with identifier PXD001555. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Transcriptional stochasticity can be measured by counting the number of mRNA molecules per cell. Cell-to-cell variability is best captured in terms of concentrations rather than molecule counts, because reaction rates depend on concentrations. We combined single-molecule mRNA counting with single-cell volume measurements to quantify the statistics of both transcript numbers and concentrations in human cells. We compare three cell clones that differ only in the genomic integration site of an identical constitutively expressed reporter gene. The transcript numbers per cell varied proportional with cell volume in all three clones, indicating concentration homeostasis. We find that the cell-to-cell variability in the mRNA concentration is almost exclusively due to cell-to-cell variation in gene expression activity, whereas the cell-to-cell variation in mRNA number is larger, due to a significant contribution of cell-volume variability. We conclude that the precise relationship between transcript numbers and cell volume sets the biological stochasticity of living cells. This study highlights the importance of the quantitative measurement of transcript concentrations in studies of cell-to-cell variability in biology. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Apolipoprotein (apo) B is an obligatory component of very low-density lipoprotein (VLDL), whose co- and posttranslational modifications are important in VLDL synthesis, secretion and hepatic lipid homeostasis. ApoB100 contains 25 cysteine residues and 8 disulfide bonds. Although these disulfide bonds were suggested to be important in maintaining apoB100 function, neither the specific oxidoreductase involved nor the direct role of these disulfide bonds in apoB100-lipidation are known. Herein, we used RNA knockdown to evaluate both MTP-dependent and -independent roles of PDI1 in apoB100 synthesis and lipidation in McA-RH7777 cells. Pdi1-knockdown did not elicit any discernible detrimental effect under normal, unstressed conditions. However, it decreased apoB100 synthesis with attenuated MTP activity, delayed apoB100 oxidative folding and reduced apoB100 lipidation, leading to defective VLDL secretion. The oxidative folding-impaired apoB100 was secreted mainly associated with LDL instead of VLDL particles from PDI1-deficient cells, a phenotype which was fully rescued by overexpression of wildtype but not a catalytically inactive PDI1 that fully restored MTP activity. Further, we demonstrate that PDI1 directly interacts with apoB100 via its redox-active CXXC motifs and assist in the oxidative folding of apoB100. Taken together, these findings reveal an unsuspected, yet, key role for PDI1 in oxidative folding of apoB100 and VLDL assembly. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Increased levels of hepatocyte growth factor (HGF) in the injured lungs may reflect compensatory response to diminish acute lung injury (ALI). HGF-induced activation of Rac1 GTPase stimulates endothelial barrier protective mechanisms. This study tested the involvement of Rac-specific guanine nucleotide exchange factor Asef in the HGF-induced endothelial cell (EC) cytoskeletal dynamics and barrier protection in vitro and in a two-hit model of ALI. HGF induced membrane translocation of Asef and stimulated Asef Rac1-specific nucleotide exchange activity. Expression of constitutively activated Asef mutant mimicked HGF-induced peripheral actin cytoskeleton enhancement. In contrast, siRNA-induced Asef knockdown or expression of dominant negative Asef attenuated HGF-induced Rac1 activation evaluated by Rac-GTP pulldown and FRET assay with Rac1 biosensor. Molecular inhibition of Asef attenuated HGF-induced peripheral accumulation of cortactin, formation of lamellipodia-like structures, enhancement of VE-cadherin adherens junctions and compromised HGF protective effect against thrombin-induced RhoA GTPase activation, Rho-dependent cytoskeleton remodeling and EC permeability. Intravenous HGF injection attenuated lung inflammation and vascular leak in the two-hit model of ALI induced by excessive mechanical ventilation and thrombin signaling peptide TRAP6. This effect was lost in Asef-/- mice. This study shows for the first time the role of Asef in HGF-mediated protection against endothelial hyperpermeability and lung injury. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: T-cells are critical for the adaptive immune response in the body. The binding of the T-cell receptor (TCR) with antigen on the surface of antigen presenting cells leads to cell spreading and signaling activation. The underlying mechanism of signaling activation is not completely understood. While cytoskeletal forces have been implicated in this process, the contribution of different cytoskeletal components and their spatial organization is unknown. Here, we use traction force microscopy to measure the forces exerted by Jurkat T-cells during TCR activation. Perturbation experiments reveal that these forces are largely due to actin assembly and dynamics with myosin contractility contributing to the development of force but not its maintenance. We find that Jurkat T-cells are mechanosensitive, with cytoskeletal forces and signaling dynamics both sensitive to the stiffness of the substrate. Our results delineate the cytoskeletal contributions to interfacial forces exerted by T-cells during activation. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Cell death in the model organism Dictyostelium, as studied in monolayers in vitro, can be induced by the polyketide DIF-1 or by the cyclical dinucleotide c-di-GMP. c-di-GMP, a universal bacterial second messenger, can trigger innate immunity in bacterially-infected animal cells, and is involved in developmental cell death in Dictyostelium. We show here that c-di-GMP was not sufficient to induce cell death in Dictyostelium cell monolayers. Unexpectedly, it also required the DIF-1 polyketide. The latter could be exogenous, as revealed by a telling synergy between c-di-GMP and DIF-1. The required DIF-1 polyketide could also be endogenous, as shown by the inability of c-di-GMP to induce cell death in Dictyostelium HMX44A cells and DH1 cells upon pharmacological or genetic inhibition of DIF-1 biosynthesis. In these cases c-di-GMP-induced cell death was rescued by complementation with exogenous DIF-1. Altogether, these results demonstrated that c-di-GMP could trigger cell death in Dictyostelium only in the presence of the DIF-1 polyketide or its metabolites. This identified another element of control to this cell death and perhaps also to c-di-GMP effects in other situations and organisms. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: The organization of the Golgi apparatus is essential for cell polarization and its maintenance. The polarity regulator PAR complex (PAR3, PAR6 and aPKC) plays critical roles in several processes of cell polarization. However, how the PAR complex participates in regulating the organization of the Golgi remains largely unknown. Here, we demonstrate the functional crosstalk of the PAR complex with CLASP2, which is a microtubule plus-end tracking protein and is involved in organizing the Golgi ribbon. CLASP2 directly interacted with PAR3 and was phosphorylated by aPKC. In epithelial cells, knockdown of either PAR3 or aPKC induced the aberrant accumulation of CLASP2 at the trans-Golgi network (TGN) concomitantly with disruption of the Golgi ribbon organization. The expression of a CLASP2 mutant that inhibited the PAR3-CLASP2 interaction disrupted the organization of the Golgi ribbon. CLASP2 is known to localize to the TGN through its interaction with the TGN protein GCC185. This interaction was inhibited by the aPKC-mediated phosphorylation of CLASP2. Furthermore, the non-phosphorylatable mutant enhanced the colocalization of CLASP2 with GCC185, thereby perturbing the Golgi organization. Based on these observations, we propose that PAR3 and aPKC control the organization of the Golgi through CLASP2 phosphorylation. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: How myosin II localizes to the cleavage furrow in Dictyostelium and metazoan cells remains largely unknown despite significant advances in understanding its regulation. We designed a genetic selection using cDNA library suppression of 3xAsp myosin II to identify factors involved in myosin cleavage furrow accumulation. The 3xAsp mutant is deficient in bipolar thick filament assembly, fails to accumulate at the cleavage furrow, cannot rescue myoII-null cytokinesis, and has impaired mechanosensitive accumulation. Eleven genes suppressed this dominant cytokinesis deficiency when 3xAsp was expressed in WT cells. 3xAsp myosin II's localization to the cleavage furrow was rescued by constructs encoding rcdBB, mmsdh, RMD1, actin, one novel protein, and a 14-3-3 hairpin. Further characterization showed that RMD1 is required for myosin II cleavage furrow accumulation, acting parallel with mechanical stress. Analysis of several mutant strains revealed that different thresholds of myosin II activity are required for daughter cell symmetry than for furrow ingression dynamics. Finally, an engineered myosin II with a longer lever arm (2xELC), producing a highly mechanosensitive motor, could also partially suppress the intragenic 3xAsp. Overall, myosin II accumulation is the result of multiple parallel and partially redundant pathways that comprise a cellular contractility control system.
    Molecular Biology of the Cell 12/2014; 25(25):4150-4165.
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    ABSTRACT: STARD9 is a largely uncharacterized mitotic kinesin and putative cancer target that is critical for regulating pericentriolar material cohesion during bipolar spindle assembly. To begin to understand the mechanisms regulating STARD9 function and their importance to cell division, we have taken a multidisciplinary approach to define the cis and trans factors that regulate the stability of the STARD9 motor domain. We show that unlike the other ∼50 mammalian kinesins, STARD9 contains an insertion in loop 12 of its motor domain (MD). Working with the STARD9-MD, we show that it is phosphorylated in mitosis by mitotic kinases that include Plk1. These phosphorylation events are important for targeting a pool of STARD9-MD for ubiquitination by the SCFbeta-TrCP ubiquitin ligase and proteasome-dependent degradation. Interestingly, overexpression of non-phosphorylatable/non-degradable STARD9-MD mutants leads to spindle assembly defects. Our results with STARD9-MD imply that in vivo the protein levels of full length STARD9 could be regulated by Plk1 and SCFbeta-TrCP to promote proper mitotic spindle assembly. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;
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    ABSTRACT: Various human diseases are associated with mitochondrial DNA (mtDNA) mutations, but heteroplasmy-the coexistence of mutant and wild-type mtDNA-complicates their study. We previously isolated a temperature lethal mtDNA mutation in Drosophila, mt:CoI(T300I) affecting the cytochrome c oxidase subunit I (CoI) locus. In the current study, we found that the decrease in cytochrome c oxidase (COX) activity was ascribable to a temperature dependent destabilization of cytochrome a heme. Consistently, the viability of homoplasmic flies at 29°C was fully restored by expressing an alternative oxidase, which specifically bypasses the cytochrome chains. Heteroplasmic flies are fully viable and were used to explore the age-related and tissue-specific phenotypes of mt:CoI(T300I). The proportion of mt:CoI(T300I) genome remained constant in somatic tissues along the aging process, suggesting a lack of quality control mechanism to remove defective mitochondria containing a deleterious mtDNA mutation. Using a genetic scheme that expresses a mitochondrially targeted restriction enzyme to induce tissue-specific homoplasmy in heteroplasmic flies, we found that mt:CoI(T300I) homoplasmy in the eye caused severe neurodegeneration at 29°C. Degeneration was suppressed by improving mitochondrial Ca(2+) uptake, suggesting that Ca(2+) mishandling contributed to mt:CoI(T300I) pathogenesis. Our results demonstrate a novel approach for Drosophila mtDNA genetics, and its application in modeling mtDNA diseases. © 2014 by The American Society for Cell Biology.
    Molecular Biology of the Cell 12/2014;