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J Cell Biol. 2011 Oct 17;195(2):263-76. doi: 10.1083/jcb.201108059. Epub 2011 Oct 10.

Bcl-xL regulates mitochondrial energetics by stabilizing the inner membrane potential.

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  • 1Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.

Abstract

Mammalian Bcl-x(L) protein localizes to the outer mitochondrial membrane, where it inhibits apoptosis by binding Bax and inhibiting Bax-induced outer membrane permeabilization. Contrary to expectation, we found by electron microscopy and biochemical approaches that endogenous Bcl-x(L) also localized to inner mitochondrial cristae. Two-photon microscopy of cultured neurons revealed large fluctuations in inner mitochondrial membrane potential when Bcl-x(L) was genetically deleted or pharmacologically inhibited, indicating increased total ion flux into and out of mitochondria. Computational, biochemical, and genetic evidence indicated that Bcl-x(L) reduces futile ion flux across the inner mitochondrial membrane to prevent a wasteful drain on cellular resources, thereby preventing an energetic crisis during stress. Given that F(1)F(O)-ATP synthase directly affects mitochondrial membrane potential and having identified the mitochondrial ATP synthase β subunit in a screen for Bcl-x(L)-binding partners, we tested and found that Bcl-x(L) failed to protect β subunit-deficient yeast. Thus, by bolstering mitochondrial energetic capacity, Bcl-x(L) may contribute importantly to cell survival independently of other Bcl-2 family proteins.

PMID:
21987637
[PubMed - indexed for MEDLINE]
PMCID:
PMC3198165
Free PMC Article
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