Journal of Biological Chemistry
Volume 294, Issue 35, 30 August 2019, Pages 12921-12932
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Neurobiology
Large-conductance calcium-activated potassium channels mediate lipopolysaccharide-induced activation of murine microglia

https://doi.org/10.1074/jbc.RA118.006425Get rights and content
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Large-conductance calcium-activated potassium (BK) channels are ubiquitously expressed in most cell types where they regulate many cellular, organ, and organismal functions. Although BK currents have been recorded specifically in activated murine and human microglia, it is not yet clear whether and how the function of this channel is related to microglia activation. Here, using patch-clamping, Griess reaction, ELISA, immunocytochemistry, and immunoblotting approaches, we show that specific inhibition of the BK channel with paxilline (10 μm) or siRNA-mediated knockdown of its expression significantly suppresses lipopolysaccharide (LPS)-induced (100 ng/ml) BV-2 and primary mouse microglial cell activation. We found that membrane BK current is activated by LPS at a very early stage through Toll-like receptor 4 (TLR4), leading to nuclear translocation of NF-κB and to production of inflammatory cytokines. Furthermore, we noted that BK channels are also expressed intracellularly, and their nuclear expression significantly increases in late stages of LPS-mediated microglia activation, possibly contributing to production of nitric oxide, tumor necrosis factor-α, and interleukin-6. Of note, a specific TLR4 inhibitor suppressed BK channel expression, whereas an NF-κB inhibitor did not. Taken together, our findings indicate that BK channels participate in both the early and the late stages of LPS-stimulated murine microglia activation involving both membrane-associated and nuclear BK channels.

lipopolysaccharide (LPS)
microglia
neuroinflammation
NF-κB (NF-KB)
Toll-like receptor 4 (TLR4)
BK channel
cytokine
innate immunity

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This work was supported by National Natural Science Foundation of China Grants 31400924 (to X. S.) and 31401197 (to X. T.) and the Priority Academic Program Development of the Jiangsu Higher Education Institutes (PAPD). The authors declare that they have no conflicts of interest with the contents of this article.

This article contains Fig. S1.

1

Both authors contributed equally to this work.