Heat shock protein 22 (Hsp22) regulates oxidative phosphorylation upon its mitochondrial translocation with the inducible nitric oxide synthase in mammalian heart.
OBJECTIVE
Stress-inducible heat shock protein 22 (Hsp22) confers protection against ischemia through induction of the inducible isoform of nitric oxide synthase (iNOS). Hsp22 overexpression in vivo stimulates cardiac mitochondrial respiration, whereas Hsp22 deletion in vivo significantly reduces respiration. We hypothesized that Hsp22-mediated regulation of mitochondrial function is dependent upon its mitochondrial translocation together with iNOS.


RESULTS
Adenoviruses harboring either the full coding sequence of Hsp22 (Ad-WT-Hsp22) or a mutant lacking a N-terminal 20 amino acid putative mitochondrial localization sequence (Ad-N20-Hsp22) were generated, and infected in rat neonatal cardiomyocytes. Compared to β-Gal control, WT-Hsp22 accumulated in mitochondria by 2.5 fold (P<0.05) and increased oxygen consumption rates by 2-fold (P<0.01). This latter effect was abolished upon addition of the selective iNOS inhibitor, 1400 W. Ad-WT-Hsp22 significantly increased global iNOS expression by about 2.5-fold (P<0.01), and also increased iNOS mitochondrial localization by 4.5 fold vs. β-gal (P<0.05). Upon comparable overexpression, the N20-Hsp22 mutant did not show significant mitochondrial translocation or stimulation of mitochondrial respiration. Moreover, although N20-Hsp22 did increase global iNOS expression by 4.6-fold, it did not promote iNOS mitochondrial translocation.


CONCLUSIONS
Translocation of both Hsp22 and iNOS to the mitochondria is necessary for Hsp22-mediated stimulation of oxidative phosphorylation.
Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States of America.
Eman
E
Rashed
Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States of America.
Paulo
P
Lizano
Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States of America.
Huacheng
H
Dai
Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States of America.
Andrew
A
Thomas
Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States of America.
Carolyn K
CK
Suzuki
Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States of America.
Christophe
C
Depre
Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States of America; Department of Basic Science, Division of Physiology, School of Medicine, Loma Linda University, Loma Linda, California, United States of America.
Hongyu
H
Qiu
D000818:Animals; D002478:Cells, Cultured; D050886:HSP20 Heat-Shock Proteins / Q000502:physiology*; D006360:Heat-Shock Proteins; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008929:Mitochondria, Heart / Q000201:enzymology / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D018832:Molecular Chaperones; D009124:Muscle Proteins / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley
D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C490206:Hspb8 protein, mouse; D018832:Molecular Chaperones; D009124:Muscle Proteins; D052247:Nitric Oxide Synthase Type II