title: The E3 ligase PARC mediates the degradation of cytosolic cytochrome c to promote survival in neurons and cancer cells.
abstract: The ability to withstand mitochondrial damage is especially critical for the survival of postmitotic cells, such as neurons. Likewise, cancer cells can also survive mitochondrial stress. We found that cytochrome c (Cyt c), which induces apoptosis upon its release from damaged mitochondria, is targeted for proteasome-mediated degradation in mouse neurons, cardiomyocytes, and myotubes and in human glioma and neuroblastoma cells, but not in proliferating human fibroblasts. In mouse neurons, apoptotic protease-activating factor 1 (Apaf-1) prevented the proteasome-dependent degradation of Cyt c in response to induced mitochondrial stress. An RNA interference screen in U-87 MG glioma cells identified p53-associated Parkin-like cytoplasmic protein (PARC, also known as CUL9) as an E3 ligase that targets Cyt c for degradation. The abundance of PARC positively correlated with differentiation in mouse neurons, and overexpression of PARC reduced the abundance of mitochondrially-released cytosolic Cyt c in various cancer cell lines and in mouse embryonic fibroblasts. Conversely, neurons from Parc-deficient mice had increased sensitivity to mitochondrial damage, and neuroblastoma or glioma cells in which PARC or ubiquitin was knocked down had increased abundance of mitochondrially-released cytosolic Cyt c and decreased viability in response to stress. These findings suggest that PARC-mediated ubiquitination and degradation of Cyt c is a strategy engaged by both neurons and cancer cells to prevent apoptosis during conditions of mitochondrial stress.
authors.affiliation: Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Vivian
authors.initials: V
authors.lastname: Gama
authors.affiliation: Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Vijay
authors.initials: V
authors.lastname: Swahari
authors.affiliation: Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Johanna
authors.initials: J
authors.lastname: Schafer
authors.affiliation: Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Kole
authors.affiliation: Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Allyson
authors.initials: A
authors.lastname: Evans
authors.affiliation: Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Cliffe
authors.affiliation: UNC RNAi Screening Facility, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Golitz
authors.affiliation: UNC RNAi Screening Facility, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Noah
authors.initials: N
authors.lastname: Sciaky
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Xin-Hai
authors.initials: XH
authors.lastname: Pei
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Xiong
authors.affiliation: Neuroscience Center, University of North Carolina, Chapel Hill, NC 27599, USA. Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA. Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. mohanish@med.unc.edu.
authors.forename: Mohanish
authors.initials: M
authors.lastname: Deshmukh
mesh_terms: D000818:Animals; D053477:Apoptotic Protease-Activating Factor 1 / Q000378:metabolism; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D002470:Cell Survival / Q000502:physiology*; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D028361:Mitochondrial Diseases / Q000503:physiopathology*; D009369:Neoplasms / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology*; D059748:Proteolysis; D034622:RNA Interference; D014166:Transferases; D054875:Ubiquitination
chemical_list: C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D002352:Carrier Proteins; D045304:Cytochromes c; C400192:Cul9 protein, human; D014166:Transferases