title: Myocyte protection by 10 kD heat shock protein (Hsp10) involves the mobile loop and attenuation of the Ras GTP-ase pathway.
abstract: Heat shock proteins (hsp), hsp60 and hsp10, are involved in the folding of imported mitochondrial proteins and the refolding of denatured proteins after stress. We examined whether hsp10 can reduce myocyte death by its mitochondrial function or by interacting with cytoplasmic signaling pathways. Overexpression of hsp10 by adenoviral infection decreased myocyte death induced by hydrogen peroxide, sodium cyanide, and simulated ischemia and reoxygenation (SI/RO). We generated an adenoviral vector coding for a temperature-sensitive mutant hsp10 protein (P34H), incapable of cooperatively refolding denatured malate dehydrogenase with hsp60. Overexpression of the hsp10 mutant potentiated SI/RO-induced myocyte death. Analysis of electron transport chain function revealed increased Complex I capacity with hsp10 overexpression, whereas hsp10(P34H) overexpression decreased Complex II capacity. Hsp10 overexpression preserved both Complex I and II function after SI/RO. Examination of the Ras GTP-ase signaling pathway indicated that inhibition of Ras was required for protection by hsp10. Constitutive activation of Ras abolished the effects afforded by hsp10 and hsp10(P34H). Hsp10 overexpression inactivated Raf, ERK, and p90Ribosomal kinase (p90RSK) before and after SI/RO. Our results suggest that complex mechanisms are involved in the protection by hsp10 against SI/RO-induced myocyte death. This mechanism may involve the hsp10 mobile loop and attenuation of the Ras GTP-ase signaling pathway.
authors.affiliation: Division of Medical Engineering Research, National Health Research Institutes, Taipei, Taiwan.
authors.forename: Kurt M
authors.initials: KM
authors.lastname: Lin
authors.forename: John M
authors.initials: JM
authors.lastname: Hollander
authors.forename: Vivia Y
authors.initials: VY
authors.lastname: Kao
authors.forename: Brian
authors.initials: B
authors.lastname: Lin
authors.forename: Lindsey
authors.initials: L
authors.lastname: Macpherson
authors.forename: Wolfgang H
authors.initials: WH
authors.lastname: Dillmann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D018835:Chaperonin 10 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D032342:Muscle Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D009154:Mutation / Q000235:genetics; D015428:Myocardial Reperfusion Injury / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D017510:Protein Folding; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015398:Signal Transduction; D012966:Sodium Cyanide / Q000494:pharmacology; D013696:Temperature; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018835:Chaperonin 10; D006861:Hydrogen Peroxide; D007770:L-Lactate Dehydrogenase; D008291:Malate Dehydrogenase; D019908:Proto-Oncogene Proteins c-raf; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins; D012966:Sodium Cyanide