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Bnip3 functions as a mitochondrial sensor of oxidative stress during myocardial ischemia and reperfusion
Journal article   Peer reviewed

Bnip3 functions as a mitochondrial sensor of oxidative stress during myocardial ischemia and reperfusion

Dieter A. Kubli, Melissa N. Quinsay, Chengqun Huang, Youngil Lee and Asa B. Gustafsson
American journal of physiology. Heart and circulatory physiology, Vol.295(5), pp.H2025-H2031
11/01/2008
DOI: https://doi.org/10.1152/ajpheart.00552.2008
PMID: 18790835
Web of Science ID: WOS:000260722600022

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Abstract

Bcl-2/adenovirus E1B 19-kDa protein-interacting protein 3 (Bnip3) is a member of the Bcl-2 homology domain 3-only subfamily of proapoptotic Bcl-2 proteins and is associated with cell death in the myocardium. In this study, we investigated the potential mechanism(s) by which Bnip3 activity is regulated. We found that Bnip3 forms a DTT-sensitive homodimer that increased after myocardial ischemia-reperfusion (I/R). The presence of the antioxidant N-acetylcysteine reduced I/R-induced homodimerization of Bnip3. Overexpression of Bnip3 in cells revealed that most of exogenous Bnip3 exists as a DTT-sensitive homodimer that correlated with increased cell death. In contrast, endogenous Bnip3 existed mainly as a monomer under normal conditions in the heart. Screening of the Bnip3 protein sequence revealed a single conserved cysteine residue at position 64. Mutation of this cysteine to alanine (Bnip3C64A) or deletion of the NH2-terminus (amino acids 1-64) resulted in reduced cell death activity of Bnip3. Moreover, mutation of a histidine residue in the COOH-terminal transmembrane domain to alanine (Bnip3H173A) almost completely inhibited the cell death activity of Bnip3. Bnip3C64A had a reduced ability to interact with Bnip3, whereas Bnip3H173A was completely unable to interact with Bnip3, suggesting that homodimerization is important for Bnip3 function. A consequence of I/R is the production of reactive oxygen species and oxidation of proteins, which promotes the formation of disulfide bonds between proteins. Thus, these experiments suggest that Bnip3 functions as a redox sensor where increased oxidative stress induces homodimerization and activation of Bnip3 via cooperation of the NH2-terminal cysteine residue and the COOH-terminal transmembrane domain.

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