title: Down-regulation of the mitochondrial matrix peptidase ClpP in muscle cells causes mitochondrial dysfunction and decreases cell proliferation.
abstract: The caseinolytic peptidase P (ClpP) is the endopeptidase component of the mitochondrial matrix ATP-dependent ClpXP protease. ClpP degrades unfolded proteins to maintain mitochondrial protein homeostasis and is involved in the initiation of the mitochondrial unfolded protein response (UPR(mt)). Outside of an integral role in the UPR(mt), the cellular function of ClpP is not well characterized in mammalian cells. To investigate the role of ClpP in mitochondrial function, we generated C2C12 muscle cells that are deficient in ClpP using siRNA or stable knockdown using lentiviral transduction. Reduction of ClpP levels by ~70% in C2C12 muscle cells resulted in a number of mitochondrial alterations including reduced mitochondrial respiration and reduced oxygen consumption rate in response to electron transport chain (ETC) complex I and II substrates. The reduction in ClpP altered mitochondrial morphology, changed the expression level of mitochondrial fission protein Drp1 and blunted UPR(mt) induction. In addition, ClpP deficient cells showed increased generation of reactive oxygen species (ROS) and decreased membrane potential. At the cellular level, reduction of ClpP impaired myoblast differentiation, cell proliferation and elevated phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α) suggesting an inhibition of translation. Our study is the first to define the effects of ClpP deficiency on mitochondrial function in muscle cells in vitro. In addition, we have uncovered novel effects of ClpP on mitochondrial morphology, cell proliferation and protein translation pathways in muscle cells.
authors.affiliation: Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA. Electronic address: Deepa-Sathyaseelan@omrf.org.
authors.forename: Sathyaseelan S
authors.initials: SS
authors.lastname: Deepa
authors.affiliation: Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
authors.forename: Shylesh
authors.initials: S
authors.lastname: Bhaskaran
authors.affiliation: Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
authors.forename: Rojina
authors.initials: R
authors.lastname: Ranjit
authors.affiliation: Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
authors.forename: Rizwan
authors.initials: R
authors.lastname: Qaisar
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Binoj C
authors.initials: BC
authors.lastname: Nair
authors.affiliation: Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78245, USA.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78245, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Walsh
authors.affiliation: Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX 78245, USA.
authors.forename: Wilson C
authors.initials: WC
authors.lastname: Fok
authors.affiliation: Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA; Oklahoma City VA Medical Center, Oklahoma City, OK 73104, USA.
authors.forename: Holly
authors.initials: H
authors.lastname: Van Remmen
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D048430:Cell Shape; D015536:Down-Regulation; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism; D049071:Endopeptidase Clp / Q000378:metabolism*; D006019:Glycolysis; D006861:Hydrogen Peroxide / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008931:Mitochondria, Muscle / Q000201:enzymology* / Q000648:ultrastructure; D032446:Myoblasts / Q000502:physiology* / Q000648:ultrastructure; D014176:Protein Biosynthesis; D056811:Unfolded Protein Response
chemical_list: D045222:Electron Transport Chain Complex Proteins; D006861:Hydrogen Peroxide; C000589752:CLPP protein, mouse; D049071:Endopeptidase Clp
keywords: ClpP; ClpX; Mitochondrial fission/fusion; Mitochondrial unfolded protein response; Reactive oxygen species; Respiration