A Stress-Responsive System for Mitochondrial Protein Degradation

Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
Molecular cell (Impact Factor: 14.02). 11/2010; 40(3):465-80. DOI: 10.1016/j.molcel.2010.10.021
Source: PubMed

ABSTRACT We show that Ydr049 (renamed VCP/Cdc48-associated mitochondrial stress-responsive--Vms1), a member of an unstudied pan-eukaryotic protein family, translocates from the cytosol to mitochondria upon mitochondrial stress. Cells lacking Vms1 show progressive mitochondrial failure, hypersensitivity to oxidative stress, and decreased chronological life span. Both yeast and mammalian Vms1 stably interact with Cdc48/VCP/p97, a component of the ubiquitin/proteasome system with a well-defined role in endoplasmic reticulum-associated protein degradation (ERAD), wherein misfolded ER proteins are degraded in the cytosol. We show that oxidative stress triggers mitochondrial localization of Cdc48 and this is dependent on Vms1. When this system is impaired by mutation of Vms1, ubiquitin-dependent mitochondrial protein degradation, mitochondrial respiratory function, and cell viability are compromised. We demonstrate that Vms1 is a required component of an evolutionarily conserved system for mitochondrial protein degradation, which is necessary to maintain mitochondrial, cellular, and organismal viability.

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Available from: Frank Madeo, Sep 29, 2015
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    • "Accumulating lines of evidence also indicate that the ubiquitin-proteasome system is critical for regulation of mitochondrial quality control [117, 118]. Inhibition of this system results in the accumulation of damaged and dysfunctional mitochondria [119]. In addition, defects of the ubiquitin-proteasome system result in cardiac hypertrophy and dysfunction and defective cardiac responses to stress [120, 121]. "
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    ABSTRACT: The heart is highly sensitive to the aging process. In the elderly, the heart tends to become hypertrophic and fibrotic. Stiffness increases with ensuing systolic and diastolic dysfunction. Aging also affects the cardiac response to stress. At the molecular level, the aging process is associated with accumulation of damaged proteins and organelles, partially due to defects in protein quality control systems. The accumulation of dysfunctional and abnormal mitochondria is an important pathophysiological feature of the aging process, which is associated with excessive production of reactive oxygen species. Mitochondrial fusion and fission and mitochondrial autophagy are crucial mechanisms for maintaining mitochondrial function and preserving energy production. In particular, mitochondrial fission allows for selective segregation of damaged mitochondria, which are afterward eliminated by autophagy. Unfortunately, recent evidence indicates that mitochondrial dynamics and autophagy are progressively impaired over time, contributing to the aging process. This suggests that restoration of these mechanisms could delay organ senescence and prevent age-associated cardiac diseases. Here, we discuss the current understanding of the close relationship between mitochondrial dynamics, mitophagy, oxidative stress, and aging, with a particular focus on the heart.
    Oxidative medicine and cellular longevity 07/2014; 2014:210934. DOI:10.1155/2014/210934 · 3.36 Impact Factor
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    • "The diverse cellular functions are directed by various cofactors and/or adaptors that bind to either or both the N-terminal and the C-terminal regulatory regions of Cdc48p (Meyer et al., 2000; Madsen et al., 2009). It has recently been shown that Cdc48p is also involved in degradation of proteins of the mitochondrial outer membrane (MOM), such as Mcl1, an anti-apoptotic protein of the Bcl2 family, and Fzo1p/mitofusin, which is required for mitochondrial tethering before mitochondrial fusion (Heo et al., 2010; Tanaka et al., 2010; Xu et al., 2011; Esaki and Ogura, 2012). In particular, mutations that inhibit ATP hydrolysis by the D2 domain of Cdc48p (Cdc48p E588Q mutant) or eliminate the positive cooperativity of the D2 ATPase activity (Cdc48p E315Q mutant) affect the turnover of proteins involved in the mitochondrial fusion events, and thereby induced aggregation of the mitochondria (Esaki and Ogura, 2012). "
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    ABSTRACT: Cdc48p is a highly conserved cytosolic AAA chaperone that is involved in a wide range of cellular processes. It consists of two ATPase domains (D1 and D2), with regulatory regions at the N- and C-terminals. We have recently shown that Cdc48p regulates mitochondrial morphology, in that a loss of the ATPase activity or positive cooperativity in the D2 domain leads to severe fragmentations and aggregations of mitochondria in the cytoplasm. We have now used serial block-face scanning electron microscopy (SBF-SEM), an advanced three-dimensional (3D) electron microscopic technique to examine the structures and morphological changes of mitochondria in the yeast Saccharomyces cerevisiae We found that mutants lacking ATPase activity of Cdc48p showed mitochondrial fragmentations and aggregations, without fusion of the outer membrane. This suggests that the ATPase activity of Cdc48p is necessary for fusion of the outer membranes of mitochondria. Our results also show that SBF-SEM has considerable advantages in morphological and quantitative studies on organelles and intracellular structures in entire cells.
    Journal of Structural Biology 05/2014; 187(2). DOI:10.1016/j.jsb.2014.05.010 · 3.23 Impact Factor
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    • "Fragmented, malfunctioning, or damaged mitochondria can be removed by mitophagy (Green et al., 2011; Rambold et al., 2011), and degradation of specific mitochondrial outer membrane (MOM) proteins by the UPS can promote proper mitochondrial function and morphology (Livnat-Levanon and Glickman, 2011; Taylor and Rutter, 2011). A UPS-driven, mitochondria-associated degradation (MAD) pathway, like the endoplasmic-reticulum-associated degradation [ERAD] pathway), has been postulated (Cohen et al., 2008; Heo et al., 2010). A UPS-dependent proteolytic event commences with polyubiquitination of a target, followed by recognition of the conjugate by the 26S proteasome. "
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    ABSTRACT: In eukaryotic cells, proteasomes exist primarily as 26S holoenzymes, the most efficient configuration for ubiquitinated protein degradation. Here, we show that acute oxidative stress caused by environmental insults or mitochondrial defects results in rapid disassembly of 26S proteasomes into intact 20S core and 19S regulatory particles. Consequently, polyubiquitinated substrates accumulate, mitochondrial networks fragment, and cellular reactive oxygen species (ROS) levels increase. Oxidation of cysteine residues is sufficient to induce proteasome disassembly, and spontaneous reassembly from existing components is observed both in vivo and in vitro upon reduction. Ubiquitin-dependent substrate turnover also resumes after treatment with antioxidants. Reversible attenuation of 26S proteasome activity induced by acute mitochondrial or oxidative stress may be a short-term response distinct from adaptation to long-term ROS exposure or changes during aging.
    Cell Reports 05/2014; 7(5). DOI:10.1016/j.celrep.2014.04.030 · 8.36 Impact Factor
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