title: HAX-1 regulates cyclophilin-D levels and mitochondria permeability transition pore in the heart.
abstract: The major underpinning of massive cell death associated with myocardial infarction involves opening of the mitochondrial permeability transition pore (mPTP), resulting in disruption of mitochondria membrane integrity and programmed necrosis. Studies in human lymphocytes suggested that the hematopoietic-substrate-1 associated protein X-1 (HAX-1) is linked to regulation of mitochondrial membrane function, but its role in controlling mPTP activity remains obscure. Herein we used models with altered HAX-1 expression levels in the heart and uncovered an unexpected role of HAX-1 in regulation of mPTP and cardiomyocyte survival. Cardiac-specific HAX-1 overexpression was associated with resistance against loss of mitochondrial membrane potential, induced by oxidative stress, whereas HAX-1 heterozygous deficiency exacerbated vulnerability. The protective effects of HAX-1 were attributed to specific down-regulation of cyclophilin-D levels leading to reduction in mPTP activation. Accordingly, cyclophilin-D and mPTP were increased in heterozygous hearts, but genetic ablation of cyclophilin-D in these hearts significantly alleviated their susceptibility to ischemia/reperfusion injury. Mechanistically, alterations in cyclophilin-D levels by HAX-1 were contributed by the ubiquitin-proteosomal degradation pathway. HAX-1 overexpression enhanced cyclophilin-D ubiquitination, whereas proteosomal inhibition restored cyclophilin-D levels. The regulatory effects of HAX-1 were mediated through interference of cyclophilin-D binding to heat shock protein-90 (Hsp90) in mitochondria, rendering it susceptible to degradation. Accordingly, enhanced Hsp90 expression in HAX-1 overexpressing cardiomyocytes increased cyclophilin-D levels, as well as mPTP activation upon oxidative stress. Taken together, our findings reveal the role of HAX-1 in regulating cyclophilin-D levels via an Hsp90-dependent mechanism, resulting in protection against activation of mPTP and subsequent cell death responses.
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575.
authors.forename: Chi Keung
authors.initials: CK
authors.lastname: Lam
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575.
authors.forename: Guan-Sheng
authors.initials: GS
authors.lastname: Liu
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575.
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Cai
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575.
authors.forename: George
authors.initials: G
authors.lastname: Gardner
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575.
authors.forename: George
authors.initials: G
authors.lastname: Adly
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575 litsa.kranias@uc.edu.
authors.forename: Evangelia G
authors.initials: EG
authors.lastname: Kranias
mesh_terms: D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D016923:Cell Death; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006579:Heterozygote; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism; D018384:Oxidative Stress; D011485:Protein Binding; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism*; D059748:Proteolysis; D017207:Rats, Sprague-Dawley; D054875:Ubiquitination
chemical_list: D000081406:Peptidyl-Prolyl Isomerase F; D018841:HSP90 Heat-Shock Proteins; C491295:Hs1bp1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; C000631446:PPIF protein, mouse; D011506:Proteins; D021983:Cyclophilins; D002118:Calcium
keywords: HAX-1; cyclophilin-D; heat shock protein-90; mitochondrial permeability transition; necrosis