The large-conductance Ca2+-activated K+ channel is essential for innate immunity

  • A Retraction to this article was published on 03 November 2010

Abstract

Neutrophil leukocytes have a pivotal function in innate immunity. Dogma dictates that the lethal blow is delivered to microbes by reactive oxygen species (ROS) and halogens1,2, products of the NADPH oxidase, whose impairment causes immunodeficiency. However, recent evidence indicates that the microbes might be killed by proteases, activated by the oxidase through the generation of a hypertonic, K+-rich and alkaline environment in the phagocytic vacuole3. Here we show that K+ crosses the membrane through large-conductance Ca2+-activated K+ (BKCa) channels. Specific inhibitors of these channels, iberiotoxin and paxilline, blocked oxidase-induced 86Rb+ fluxes and alkalinization of the phagocytic vacuole, whereas NS1619, a BKCa channel opener, enhanced both. Characteristic outwardly rectifying K+ currents, reversibly inhibited by iberiotoxin, were demonstrated in neutrophils and eosinophils and the expression of the α-subunit of the BK channel was confirmed by western blotting. The channels were opened by the combination of membrane depolarization and elevated Ca2+ concentration, both consequences of oxidase activity. Remarkably, microbial killing and digestion were abolished when the BKCa channel was blocked, revealing an essential and unexpected function for this K+ channel in the microbicidal process.

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Figure 1: BKCa channels influence the pH within the phagocytic vacuole and 86Rb+ efflux from neutrophils and eosinophils.
Figure 2: BKCa currents in granulocytes.
Figure 3: Ca2+ and membrane depolarization open BKCa channels.
Figure 4: Inhibitors of BKCa channels abolish microbial killing and digestion.

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Acknowledgements

We thank P. Rich for helpful discussions, S. Ranasinghe for technical help with the FLIPR, and A. Scott for the illustrations. Financial support was provided by the Wellcome Trust and Medical Research Council.

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Correspondence to Anthony W. Segal.

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Ahluwalia, J., Tinker, A., Clapp, L. et al. The large-conductance Ca2+-activated K+ channel is essential for innate immunity. Nature 427, 853–858 (2004). https://doi.org/10.1038/nature02356

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