p53 is a major cellular tumor suppressor that in addition to its nuclear, transcription-dependent activity is also known to function extranuclearly. Cellular stressors such as reactive oxygen species can promote translocation of p53 into mitochondria where it acts to protect mitochondrial genome or trigger cell death via transcription-independent manner. Here we report that the mammalian homologue of yeast mitochondrial Afg1 ATPase (LACE1) promotes translocation of p53 into mitochondria. We further show that LACE1 exhibits significant pro-apoptotic activity, which is dependent on p53, and that the protein is required for normal mitochondrial respiratory function. LACE1 physically interacts with p53 and is necessary for mitomycin c-induced translocation of p53 into mitochondria. Conversely, increased expression of LACE1 partitions p53 to mitochondria, causes reduction in nuclear p53 content and induces apoptosis. Thus, LACE1 mediates mitochondrial translocation of p53 and its transcription-independent apoptosis.
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.
- MeSH
- Adenosine Triphosphatases genetics metabolism MeSH
- Prostaglandin-Endoperoxide Synthases genetics metabolism MeSH
- GTP Phosphohydrolases genetics metabolism MeSH
- HEK293 Cells MeSH
- Protein Conformation MeSH
- Humans MeSH
- RNA, Messenger genetics metabolism MeSH
- Mitochondrial Proteins genetics metabolism MeSH
- Mitochondria ultrastructure MeSH
- Mutation MeSH
- Protein Subunits MeSH
- Gene Expression Regulation, Enzymologic physiology MeSH
- RNA Interference MeSH
- Oxygen Consumption MeSH
- Electron Transport physiology MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Keywords
- ATPáza, mitochondriální proteázy,
- MeSH
- Adenosine Triphosphatases metabolism MeSH
- Microscopy, Electron utilization MeSH
- Humans MeSH
- Mitochondrial Membranes * enzymology MeSH
- Mitochondrial Proteins * secretion MeSH
- Mitochondrial Proton-Translocating ATPases deficiency secretion MeSH
- Mitochondria physiology MeSH
- Tumor Suppressor Protein p53 MeSH
- Oxidative Phosphorylation MeSH
- Saccharomyces cerevisiae MeSH
- Check Tag
- Humans MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
