Involvement of protein kinase a in nitric oxide stimulating effect on a BKCa channel of human dermal fibroblasts

초록

We reported previously that a large-conductance Ca2+ -activated K+ (BKCa) channel constitutes a significant fraction of the K+ current in human dermal fibroblasts, and that nitric oxide ( NO) increases the open-channel probability (NPo) of BKCa channels via a soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) pathway. The purpose of this study was to investigate whether the adenylate cyclase (AC)/cAMP/protein kinase A (PKA) pathway may also be involved in NO action on BKCa channels in human dermal fibroblasts. Electrophysiological single-channel recordings were performed on fifth-passage cells of human penile skin cultures. KT5720 ( specific PKA inhibitor) blocked the stimulatory effect of sodium nitroprusside ( NO donor) on BKCa channels. By contrast, forskolin ( AC activator) or 8-bromo-cAMP (cell-permeable cAMP analog) did not increase the NPo of the channel. The PKA catalytic subunit (PKAcs) alone did not increase the NPo of the channel in cell-attached and inside-out patches, however, PKAcs with cGMP increased the NPo. In contrast, PKAcs with cGMP did not increase the NPo of BKCa channels with 1H-[1,2,4]oxadiazolo[ 4,3-a] quinoxalin-1-one pretreatment, and KT5720 pretreatment also blocked the stimulatory effect of 8-Br-cGMP. In conclusion, the present data suggest the involvement of PKA in the stimulatory effect of NO on the BKCa channel in human dermal fibroblasts through cGMP.

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