title: PARL mediates Smac proteolytic maturation in mitochondria to promote apoptosis.
abstract: Mitochondria drive apoptosis by releasing pro-apoptotic proteins that promote caspase activation in the cytosol. The rhomboid protease PARL, an intramembrane cleaving peptidase in the inner membrane, regulates mitophagy and plays an ill-defined role in apoptosis. Here, we employed PARL-based proteomics to define its substrate spectrum. Our data identified the mitochondrial pro-apoptotic protein Smac (also known as DIABLO) as a PARL substrate. In apoptotic cells, Smac is released into the cytosol and promotes caspase activity by inhibiting inhibitors of apoptosis (IAPs). Intramembrane cleavage of Smac by PARL generates an amino-terminal IAP-binding motif, which is required for its apoptotic activity. Loss of PARL impairs proteolytic maturation of Smac, which fails to bind XIAP. Smac peptidomimetics, downregulation of XIAP or cytosolic expression of cleaved Smac restores apoptosis in PARL-deficient cells. Our results reveal a pro-apoptotic function of PARL and identify PARL-mediated Smac processing and cytochrome c release facilitated by OPA1-dependent cristae remodelling as two independent pro-apoptotic pathways in mitochondria.
authors.affiliation: Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany.
authors.forename: Shotaro
authors.initials: S
authors.lastname: Saita
authors.affiliation: Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Nolte
authors.affiliation: Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany.
authors.forename: Kai Uwe
authors.initials: KU
authors.lastname: Fiedler
authors.affiliation: Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany.|Center for Molecular Medicine (CMMC), University of Cologne, Cologne 50931, Germany.|Institute for Medical Microbiology, Immunology and Hygiene (IMMIH), University of Cologne, Cologne 50931, Germany.
authors.forename: Hamid
authors.initials: H
authors.lastname: Kashkar
authors.affiliation: Leibniz Institute for Analytical Sciences (ISAS), Dortmund 44227, Germany.
authors.forename: A Saskia
authors.initials: AS
authors.lastname: Venne
authors.affiliation: Leibniz Institute for Analytical Sciences (ISAS), Dortmund 44227, Germany.
authors.forename: René P
authors.initials: RP
authors.lastname: Zahedi
authors.affiliation: Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany.|Center for Molecular Medicine (CMMC), University of Cologne, Cologne 50931, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Krüger
authors.affiliation: Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany.|Center for Molecular Medicine (CMMC), University of Cologne, Cologne 50931, Germany.
authors.forename: Thomas
authors.identifier: 0000-0003-1250-1462
authors.initials: T
authors.lastname: Langer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D045325:HCT116 Cells; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D045726:Metalloproteases / Q000172:deficiency / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011485:Protein Binding; D059748:Proteolysis; D040901:Proteomics; D013379:Substrate Specificity; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D045304:Cytochromes c; C529563:PGAM5 protein, human; D010749:Phosphoprotein Phosphatases; D045726:Metalloproteases; C485223:PARL protein, human