K+ channels and the microglial respiratory burst.
Microglial activation following central nervous system damage or disease often culminates in a respiratory burst that is necessary for antimicrobial function, but, paradoxically, can damage bystander cells. We show that several K+ channels are expressed and play a role in the respiratory burst of cultured rat microglia. Three pharmacologically separable K+ currents had properties of Kv1.3 and the Ca2+/calmodulin-gated channels, SK2, SK3, and SK4. mRNA was detected for Kv1.3, Kv1.5, SK2, and/or SK3, and SK4. Protein was detected for Kv1.3, Kv1.5, and SK3 (selective SK2 and SK4 antibodies not available). No Kv1.5-like current was detected, and confocal immunofluorescence showed the protein to be subcellular, in contrast to the robust membrane localization of Kv1.3. To determine whether any of these channels play a role in microglial activation, a respiratory burst was stimulated with phorbol 12-myristate 13-acetate and measured using a single cell, fluorescence-based dihydrorhodamine 123 assay. The respiratory burst was markedly inhibited by blockers of SK2 (apamin) and SK4 channels (clotrimazole and charybdotoxin), and to a lesser extent, by the potent Kv1.3 blocker agitoxin-2.
Division of Cellular and Molecular Biology, Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada.
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D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D003022:Clotrimazole / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D006131:Growth Inhibitors / Q000494:pharmacology; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D015640:Ion Channel Gating / Q000502:physiology; D051664:Kv1.3 Potassium Channel; D051666:Kv1.5 Potassium Channel; D008564:Membrane Potentials / Q000502:physiology; D017628:Microglia / Q000166:cytology / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst / Q000502:physiology*; D012604:Scorpion Venoms / Q000494:pharmacology; D051640:Small-Conductance Calcium-Activated Potassium Channels
D006131:Growth Inhibitors; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496975:Kcna3 protein, rat; C496983:Kcna5 protein, rat; C496899:Kcnn2 protein, rat; C496901:Kcnn3 protein, rat; C491575:Kcnn4 protein, rat; D051664:Kv1.3 Potassium Channel; D051666:Kv1.5 Potassium Channel; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D017382:Reactive Oxygen Species; D012604:Scorpion Venoms; D051640:Small-Conductance Calcium-Activated Potassium Channels; D018999:Charybdotoxin; C087603:agitoxin 2; D001030:Apamin; D009249:NADP; D003022:Clotrimazole