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Expression and processing of the TMEM70 protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:144-9. [DOI: 10.1016/j.bbabio.2010.10.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 09/30/2010] [Accepted: 10/05/2010] [Indexed: 11/18/2022]
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Domańska G, Motz C, Meinecke M, Harsman A, Papatheodorou P, Reljic B, Dian-Lothrop EA, Galmiche A, Kepp O, Becker L, Günnewig K, Wagner R, Rassow J. Helicobacter pylori VacA toxin/subunit p34: targeting of an anion channel to the inner mitochondrial membrane. PLoS Pathog 2010; 6:e1000878. [PMID: 20442789 PMCID: PMC2861713 DOI: 10.1371/journal.ppat.1000878] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 03/25/2010] [Indexed: 12/13/2022] Open
Abstract
The vacuolating toxin VacA, released by Helicobacter pylori, is an important virulence factor in the pathogenesis of gastritis and gastroduodenal ulcers. VacA contains two subunits: The p58 subunit mediates entry into target cells, and the p34 subunit mediates targeting to mitochondria and is essential for toxicity. In this study we found that targeting to mitochondria is dependent on a unique signal sequence of 32 uncharged amino acid residues at the p34 N-terminus. Mitochondrial import of p34 is mediated by the import receptor Tom20 and the import channel of the outer membrane TOM complex, leading to insertion of p34 into the mitochondrial inner membrane. p34 assembles in homo-hexamers of extraordinary high stability. CD spectra of the purified protein indicate a content of >40% beta-strands, similar to pore-forming beta-barrel proteins. p34 forms an anion channel with a conductivity of about 12 pS in 1.5 M KCl buffer. Oligomerization and channel formation are independent both of the 32 uncharged N-terminal residues and of the p58 subunit of the toxin. The conductivity is efficiently blocked by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), a reagent known to inhibit VacA-mediated apoptosis. We conclude that p34 essentially acts as a small pore-forming toxin, targeted to the mitochondrial inner membrane by a special hydrophobic N-terminal signal.
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Affiliation(s)
- Grażyna Domańska
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | - Christian Motz
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | - Michael Meinecke
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Anke Harsman
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | | | - Boris Reljic
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | | | - Antoine Galmiche
- Laboratoire de Biochimie, INSERM ERI12, Hopital Nord, CHU Amiens Picardie, Amiens, France
| | - Oliver Kepp
- INSERM U848, Institute Gustave Roussy, Université Paris Sud, Villejuif, France
| | - Lars Becker
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Kathrin Günnewig
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
| | - Richard Wagner
- Institut für Biophysik, Universität Osnabrück, Osnabrück, Germany
| | - Joachim Rassow
- Institut für Physiologische Chemie, Ruhr-Universität Bochum, Bochum, Germany
- * E-mail:
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Cheung ECC, Joza N, Steenaart NAE, McClellan KA, Neuspiel M, McNamara S, MacLaurin JG, Rippstein P, Park DS, Shore GC, McBride HM, Penninger JM, Slack RS. Dissociating the dual roles of apoptosis-inducing factor in maintaining mitochondrial structure and apoptosis. EMBO J 2006; 25:4061-73. [PMID: 16917506 PMCID: PMC1560366 DOI: 10.1038/sj.emboj.7601276] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Accepted: 07/19/2006] [Indexed: 11/09/2022] Open
Abstract
The mitochondrial protein apoptosis-inducing factor (AIF) translocates to the nucleus and induces apoptosis. Recent studies, however, have indicated the importance of AIF for survival in mitochondria. In the absence of a means to dissociate these two functions, the precise roles of AIF remain unclear. Here, we dissociate these dual roles using mitochondrially anchored AIF that cannot be released during apoptosis. Forebrain-specific AIF null (tel. AifDelta) mice have defective cortical development and reduced neuronal survival due to defects in mitochondrial respiration. Mitochondria in AIF deficient neurons are fragmented with aberrant cristae, indicating a novel role of AIF in controlling mitochondrial structure. While tel. AifDelta Apaf1(-/-) neurons remain sensitive to DNA damage, mitochondrially anchored AIF expression in these cells significantly enhanced survival. AIF mutants that cannot translocate into nucleus failed to induce cell death. These results indicate that the proapoptotic role of AIF can be uncoupled from its physiological function. Cell death induced by AIF is through its proapoptotic activity once it is translocated to the nucleus, not due to the loss of AIF from the mitochondria.
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Affiliation(s)
- Eric C C Cheung
- Ottawa Health Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Nicholas Joza
- IMBA, Institute of Molecular Biotechnology of the Austria Academy of Sciences, Vienna, Austria
| | | | - Kelly A McClellan
- Ottawa Health Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Margaret Neuspiel
- Ottawa Heart Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Stephen McNamara
- Ottawa Health Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Jason G MacLaurin
- Ottawa Health Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Peter Rippstein
- Ottawa Heart Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - David S Park
- Ottawa Health Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Gordon C Shore
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Heidi M McBride
- Ottawa Heart Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Josef M Penninger
- IMBA, Institute of Molecular Biotechnology of the Austria Academy of Sciences, Vienna, Austria
| | - Ruth S Slack
- Ottawa Health Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
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Huh KW, Siddiqui A. Hepatitis B virus X protein: a multifunctional viral regulator. J Gastroenterol 2001; 1:349-59. [PMID: 16120289 DOI: 10.1016/s1567-7249(01)00040-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2001] [Revised: 11/01/2001] [Accepted: 11/05/2001] [Indexed: 01/27/2023]
Abstract
Hepatitis B Virus (HBV) infection is one of the major causes of hepatocellular carcinoma (HCC). X protein (HBx) has been suspected to be oncogenic, although the precise role(s) remain uncertain. HBx is a multifunctional viral regulator that modulates transcription, cell responses to genotoxic stress, protein degradation, and signaling pathways. These modulations affect viral replication and viral proliferation, directly or indirectly. HBx also affects cell cycle checkpoints, cell death, and carcinogenesis. This article presents an overview of the progress in HBx research over the past several years.
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Affiliation(s)
- Kyung-Won Huh
- Department of Microbiology, University of Colorado Health Sciences Center, Denver, Colorado, OH, USA
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Cohen I, Guillerault F, Girard J, Prip-Buus C. The N-terminal domain of rat liver carnitine palmitoyltransferase 1 contains an internal mitochondrial import signal and residues essential for folding of its C-terminal catalytic domain. J Biol Chem 2001; 276:5403-11. [PMID: 11087756 DOI: 10.1074/jbc.m009555200] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously shown that the first 147 N-terminal residues of the rat liver carnitine palmitoyltransferase 1 (CPT1), encompassing its two transmembrane (TM) segments, specify both mitochondrial targeting and anchorage at the outer mitochondrial membrane (OMM). In the present study, we have identified the precise import sequence in this polytopic OMM protein. In vitro import studies with fusion and deletion CPT1 proteins demonstrated that none of its TM segments behave as a signal anchor sequence. Analysis of the regions flanking the TM segments revealed that residues 123-147, located immediately downstream of TM2, function as a noncleavable, matrix-targeting signal. They specify mitochondrial targeting, whereas the hydrophobic TM segment(s) acts as a stop-transfer sequence that stops and anchors the translocating CPT1 into the OMM. Heterologous expression in Saccharomyces cerevisiae of several deleted CPT1 proteins not only confirms the validity of the "stop-transfer" import model but also indicates that residues 1-82 of CPT1 contain a putative microsomal targeting signal whose cellular significance awaits further investigation. Finally, we identified a highly folded core within the C-terminal domain of CPT1 that is hidden in the entire protein by its cytosolic N-terminal residues. Functional analysis of the deleted CPT1 proteins indicates that this folded C-terminal core, which may belong to the catalytic domain of CPT1, requires TM2 for its correct folding achievement and is in close proximity to residues 1-47.
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Affiliation(s)
- I Cohen
- Endocrinologie, Métabolisme et Développement, CNRS-UPR 1524, 9 Rue J. Hetzel, 92190 Meudon, France
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Nakai K. Protein sorting signals and prediction of subcellular localization. ADVANCES IN PROTEIN CHEMISTRY 2000; 54:277-344. [PMID: 10829231 DOI: 10.1016/s0065-3233(00)54009-1] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- K Nakai
- Human Genome Center, Institute of Medical Science, University of Tokyo, Japan
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Cohen I, Girard J, Prip-Buus C. Biogenesis of the rat liver mitochondrial carnitine palmitoyltransferase I. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 466:1-16. [PMID: 10709623 DOI: 10.1007/0-306-46818-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- I Cohen
- Endocrinologie, Métabolisme et Développement CNRS UPR1524, Meudon, France
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Schleiff E. Signals and receptors--the translocation machinery on the mitochondrial surface. J Bioenerg Biomembr 2000; 32:55-66. [PMID: 11768763 DOI: 10.1023/a:1005512412404] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Most proteins involved in mitochondrial biogenesis are encoded by the genome of the nucleus. They are synthesized in the cytosol and have to be transported toward and, subsequently, imported into the organelle. This targeting and import process is initiated by the specific mitochondrial targeting signal, which differs pending on the final localization of the protein. The preprotein will be recognized by cytosolic proteins, which function in transport toward the mitochondria and in maintaining the import competent state of the preprotein. The precursor will be transferred onto a multicomponent complex on the outer mitochondrial membrane, formed by receptor proteins and the general insertion pore (GIP). Some proteins are directly sorted into the outer membrane whereas the majority will be transported over the outer membrane through the import channel followed by further distribution of those proteins.
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Affiliation(s)
- E Schleiff
- Department of Biochemistry, McGill University, Montreal, Canada.
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Yao J, Shoubridge EA. Expression and functional analysis of SURF1 in Leigh syndrome patients with cytochrome c oxidase deficiency. Hum Mol Genet 1999; 8:2541-9. [PMID: 10556303 DOI: 10.1093/hmg/8.13.2541] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Leigh syndrome (LS) associated with cytochrome c oxidase (COX) deficiency is an autosomal recessive neurodegenerative disorder caused by mutations in SURF1. Although SURF1 is ubiquitously expressed, its expression is lower in brain than in other highly aerobic tissues. All reported SURF1 mutations are loss of function, predicting a truncated protein (hSurf1) product. Western blot analysis with anti-hSurf1 antibodies demonstrated a specific 30 kDa protein in control fibroblasts, but no protein in LS patient cells. Steady-state levels of both nuclear- and mitochondrial-encoded COX subunits were also markedly reduced in patient cells, consistent with a failure to assemble or maintain a normal amount of the enzyme complex. An epitope (FLAG)-tagged hSurf1 was targeted to mitochondria in COS7 cells and a mitochondrial import assay showed that the hSurf1 precursor protein (35 kDa) was imported and processed to its mature form (30 kDa) in a membrane potential-dependent fashion. The protein was resistant to alkaline carbonate extraction and susceptible to proteinase K digestion in mitoplasts. Mutant proteins in which the N-terminal transmembrane domain or central loop were deleted, or the C-terminal transmembrane domain disrupted, did not accumulate and could not rescue COX activity in patient cells. Co-expression of the N- and C-terminal transmembrane domains as independent entities also failed to rescue the enzyme deficiency. These data demonstrate that hSurf1 is an integral inner membrane protein with an essential role in the assembly or maintenance of the COX complex and that insertion of both transmembrane domains in the intact protein is necessary for function.
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Affiliation(s)
- J Yao
- Montreal Neurological Institute and Department of Human Genetics, McGill University, 3801 University Street, Montreal H3A 2B4, Canada
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Cohen I, Kohl C, McGarry JD, Girard J, Prip-Buus C. The N-terminal domain of rat liver carnitine palmitoyltransferase 1 mediates import into the outer mitochondrial membrane and is essential for activity and malonyl-CoA sensitivity. J Biol Chem 1998; 273:29896-904. [PMID: 9792707 DOI: 10.1074/jbc.273.45.29896] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The rat liver carnitine palmitoyltransferase 1 (L-CPT1), an integral outer mitochondrial membrane (OMM) protein, is the key regulatory enzyme of fatty acid oxidation and is inhibited by malonyl-CoA. In vitro import of L-CPT1 into the OMM requires the presence of mitochondrial receptors and is stimulated by ATP but is membrane potential-independent. Its N-terminal domain (residues 1-150), which contains two transmembrane segments, possesses all of the information for mitochondrial targeting and OMM insertion. Deletion of this domain abrogates protein targeting, whereas its fusion to non-OMM-related proteins results in their mitochondrial targeting and OMM insertion in a manner similar to L-CPT1. Functional analysis of chimeric CPTs expressed in Saccharomyces cerevisiae shows that this domain also mediates in vivo protein insertion into the OMM. When the malonyl-CoA-insensitive CPT2 was anchored at the OMM either by a specific OMM signal anchor sequence (pOM29) or by the N-terminal domain of L-CPT1, its activity remains insensitive to malonyl-CoA inhibition. This indicates that malonyl-CoA sensitivity is an intrinsic property of L-CPT1 and that its N-terminal domain cannot confer malonyl-CoA sensitivity to CPT2. Replacement of the N-terminal domain by pOM29 results in a less folded and less active protein, which is also malonyl-CoA-insensitive. Thus, in addition to its role in mitochondrial targeting and OMM insertion, the N-terminal domain of L-CPT1 is essential to maintain an optimal conformation for both catalytic function and malonyl-CoA sensitivity.
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Affiliation(s)
- I Cohen
- Endocrinologie, Métabolisme, et Développement, CNRS-UPR 1524, 9 Rue J. Hetzel, 92190 Meudon, France
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Steenaart NA, Shore GC. Mitochondrial cytochrome c oxidase subunit IV is phosphorylated by an endogenous kinase. FEBS Lett 1997; 415:294-8. [PMID: 9357986 DOI: 10.1016/s0014-5793(97)01145-9] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This study was undertaken to identify novel mitochondrial membrane proteins that are potential targets for phosphorylation. Mitochondrial membranes were incubated in the presence of [gamma-32P]ATP and the Triton X-114 extractable protein was subjected to ion-exchange and polyacrylamide gel chromatography to purify a major phosphorylated protein of approximately 17000 Da. The determined peptide sequence of the purified phosphoprotein corresponded to a segment of cytochrome c oxidase subunit IV, an inner membrane protein of 17160 Da. The identity of the phosphoprotein was confirmed by two-dimensional electrophoresis and Western blotting. The results identify mitochondrial cytochrome c oxidase subunit IV as a protein which is phosphorylated by an endogenous kinase.
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Affiliation(s)
- N A Steenaart
- Department of Biochemistry, McGill University, Montreal, Que., Canada
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