title: The mammalian homologue of yeast Afg1 ATPase (lactation elevated 1) mediates degradation of nuclear-encoded complex IV subunits.
abstract: Mitochondrial protein homeostasis is crucial for cellular function and integrity and is therefore maintained by several classes of proteins possessing chaperone and/or proteolytic activities. In the present study, we focused on characterization of LACE1 (lactation elevated 1) function in mitochondrial protein homeostasis. LACE1 is the human homologue of yeast mitochondrial Afg1 (ATPase family gene 1) ATPase, a member of the SEC18-NSF, PAS1, CDC48-VCP, TBP family. Yeast Afg1 was shown to mediate degradation of mitochondrially encoded complex IV subunits, and, on the basis of its similarity to CDC48 (p97/VCP), it was suggested to facilitate extraction of polytopic membrane proteins. We show that LACE1, which is a mitochondrial integral membrane protein, exists as part of three complexes of approximately 140, 400 and 500 kDa and is essential for maintenance of fused mitochondrial reticulum and lamellar cristae morphology. We demonstrate that LACE1 mediates degradation of nuclear-encoded complex IV subunits COX4 (cytochrome c oxidase 4), COX5A and COX6A, and is required for normal activity of complexes III and IV of the respiratory chain. Using affinity purification of LACE1-FLAG expressed in a LACE1-knockdown background, we show that the protein interacts physically with COX4 and COX5A subunits of complex IV and with mitochondrial inner-membrane protease YME1L. Finally, we demonstrate by ectopic expression of both K142A Walker A and E214Q Walker B mutants, that an intact ATPase domain is essential for LACE1-mediated degradation of nuclear-encoded complex IV subunits. Thus the present study establishes LACE1 as a novel factor with a crucial role in mitochondrial protein homeostasis.
authors.affiliation: Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Cesnekova
authors.affiliation: Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic.
authors.forename: Marie
authors.initials: M
authors.lastname: Rodinova
authors.affiliation: Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic.
authors.forename: Hana
authors.initials: H
authors.lastname: Hansikova
authors.affiliation: Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Houstek
authors.affiliation: Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic.
authors.forename: Jiri
authors.initials: J
authors.lastname: Zeman
authors.affiliation: Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic lstib@lf1.cuni.cz.
authors.forename: Lukas
authors.initials: L
authors.lastname: Stiburek
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D008928:Mitochondria / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010101:Oxygen Consumption; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D021122:Protein Subunits; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D024101:Mitochondrial Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; D011451:Prostaglandin-Endoperoxide Synthases; C000609587:AFG1L protein, human; D000251:Adenosine Triphosphatases; D020558:GTP Phosphohydrolases; C415198:OPA1 protein, human
keywords: LACE1; YME1L; complex IV; mitochondria; oxidative phosphorylation