Acidosis regulates the stability, hydrophobicity, and activity of the BH3-only protein Bnip3

Donna P. Frazier, Amber Wilson, Regina M Graham, John W. Thompson, Nanette Bishopric, Keith A Webster

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Bnip3 is a prodeath member of the so-called BH3-only subfamily of Bcl-2 proteins. A major function of this class of proteins is to regulate the permeability state of the outer mitochondrial membrane by forming homo- and hetero-oligomers inside the membrane. We reported previously that Bnip3 accumulates in cardiac myocytes during exposure to hypoxia, but coincident acidosis is required to activate the death program. Acidosis increased the rate of intracellular accumulation of Bnip3 and promoted a tighter association with mitochondria. Here we report that acidic pH mediates increased half-lives of Bnip3 dimers and monomers (>3×) as well as that of a faster-migrating fragment (>10×) and confers protection against degradation by protease. Hydrophobic partitioning experiments revealed that Bnip3 monomers and oligomers from hypoxia-acidic cell fractions associated significantly with the detergent layer, whereas protein from hypoxia-neutral myocytes did not. Acidosis promoted homodimerization of Bcl-xL but did not increase its association with detergent. Neutralization of the extracellular medium of cardiac myocyte cultures under hypoxia-acidosis resulted in rapid degradation of accumulated Bnip3 (half life, <2 h), coincident with cessation of the death program. Bnip3 monomers appear to be the active species because substitution of alanine for histidine at position 173 within the transmembrane (TM) domain prevented homodimerization but did not inhibit the death function. These results demonstrate a pH-sensitive shift in the stability and apparent hydrophobicity of Bnip3 monomers that correlates closely with membrane binding and function.

Original languageEnglish
Pages (from-to)1625-1634
Number of pages10
JournalAntioxidants and Redox Signaling
Volume8
Issue number9-10
DOIs
StatePublished - Sep 1 2006

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Hydrophobicity
Acidosis
Hydrophobic and Hydrophilic Interactions
Monomers
Oligomers
Membranes
Cardiac Myocytes
Detergents
Proteins
Association reactions
Cell Hypoxia
Degradation
Mitochondria
Mitochondrial Membranes
Histidine
Alanine
Dimers
Muscle Cells
Half-Life
Permeability

ASJC Scopus subject areas

  • Biochemistry

Cite this

Acidosis regulates the stability, hydrophobicity, and activity of the BH3-only protein Bnip3. / Frazier, Donna P.; Wilson, Amber; Graham, Regina M; Thompson, John W.; Bishopric, Nanette; Webster, Keith A.

In: Antioxidants and Redox Signaling, Vol. 8, No. 9-10, 01.09.2006, p. 1625-1634.

Research output: Contribution to journalArticle

Frazier, Donna P. ; Wilson, Amber ; Graham, Regina M ; Thompson, John W. ; Bishopric, Nanette ; Webster, Keith A. / Acidosis regulates the stability, hydrophobicity, and activity of the BH3-only protein Bnip3. In: Antioxidants and Redox Signaling. 2006 ; Vol. 8, No. 9-10. pp. 1625-1634.
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