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A cysteine-rich motif confers hypoxia sensitivity to mammalian large conductance voltage- and Ca-activated K (BK) channel alpha-subunits

McCartney, Claire E. and McClafferty, Heather and Huibant, Jean-Marc and Rowan, Edward.G. and Shipston, Michael J. and Rowe, Iain C.M. (2005) A cysteine-rich motif confers hypoxia sensitivity to mammalian large conductance voltage- and Ca-activated K (BK) channel alpha-subunits. Proceedings of the National Academy of Sciences, 102 (49). pp. 17870-17876. ISSN 0027-8424

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Abstract

Cellular responses to hypoxia are tissue-specific and dynamic. However, the mechanisms that underlie this differential sensitivity to hypoxia are unknown. Large conductance voltage- and Ca-activated K (BK) channels are important mediators of hypoxia responses in many systems. Although BK channels are ubiquitously expressed, alternative pre-mRNA splicing of the single gene encoding their pore-forming alpha-subunits provides a powerful mechanism for generating functional diversity. Here, we demonstrate that the hypoxia sensitivity of BK channel alpha-subunits is splice-variant-specific. Sensitivity to hypoxia is conferred by a highly conserved motif within an alternatively spliced cysteine-rich insert, the stress-regulated exon (STREX), within the intracellular C terminus of the channel. Hypoxic inhibition of the STREX variant is Ca-sensitive and reversible, and it rapidly follows the change in oxygen tension by means of a mechanism that is independent of redox or CO regulation. Hypoxia sensitivity was abolished by mutation of the serine (S24) residue within the STREX insert. Because STREX splice-variant expression is tissue-specific and dynamically controlled, alternative splicing of BK channels provides a mechanism to control the plasticity of cellular responses to hypoxia.