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Reciprocal regulation of the Ca2+ and H+ sensitivity in the SLO1 BK channel conferred by the RCK1 domain

Nature Structural & Molecular Biology volume 15, pages 403–410 (2008)Cite this article

Abstract

Increasing evidence suggests that intracellular H+ directly stimulates large-conductance Ca2+- and voltage-activated K+ (SLO1 BK) channels, thus providing a crucial link between membrane excitability and cell metabolism. Here we report that two histidine residues, His365 and His394, located in the intracellular regulator of conductance for K+ (RCK) 1 domain, serve as the H+ sensors of the SLO1 BK channel. Activation of the channel by H+ requires electrostatic interactions between the histidine residues and a nearby negatively charged residue involved in the channel's high-affinity Ca2+ sensitivity. Reciprocally, His365 and His394 also participate in the Ca2+-dependent activation of the channel, functioning as Ca2+ mimetics once they are protonated. Therefore, a common motif in the RCK1 domain mediates the stimulatory effects of both H+ and Ca2+, and provides a basis for the bidirectional coupling of cell metabolism and membrane electrical excitability.

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Figure 1: Low pHi enhances the native and recombinant BK channel activity.
Figure 2: Mutation of two histidine residues located in the RCK1 domain of human SLO1 abolishes the sensitivity to low pHi.
Figure 3: Mutation of His365 and His394.
Figure 4: High-ionic-strength solutions diminish ΔV0.5 caused by lowering pHi from 7.2 to 6.2 in the absence of Ca2+.
Figure 5: Mutation of Asp367 diminishes the pHi sensitivity.
Figure 6: Mutation of His365 and His394 disrupts the Ca2+-dependent activation of SLO1, but fails to alter its Mg2+-dependent activation.

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Acknowledgements

We thank M.L. Garcia, Merck Research Laboratories, New Jersey, for the original SLO1 construct and R. Latorre and S. Brauchi, Centro de Estudios Científicos, Valdivia, Chile, for the structural model. Supported in part by the US National Institutes of Health and SFB 604 (TP A4).

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  1. Department of Physiology, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia, 19104, Pennsylvania, USA

    Shangwei Hou, Rong Xu & Toshinori Hoshi

  2. Department of Biophysics, Center for Molecular Biomedicine, Friedrich Schiller University Jena, Hans-Knöll-St. 2, Jena, D-07745, Germany

    Stefan H Heinemann

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S.H., S.H.H. and T.H. designed the research; S.H., R.X. and T.H. performed the research; S.H., S.H.H., T.H. analyzed the data; S.H., S.H.H. and T.H. wrote the paper.

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Correspondence to Toshinori Hoshi.

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Hou, S., Xu, R., Heinemann, S. et al. Reciprocal regulation of the Ca2+ and H+ sensitivity in the SLO1 BK channel conferred by the RCK1 domain. Nat Struct Mol Biol 15, 403–410 (2008). https://doi.org/10.1038/nsmb.1398

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