Key result
Protein kinase C activation significantly reduced the whole cell Ca-activated K current and single KCa channel activity in rat tail artery smooth muscle cells.
Protein kinase C directly attenuates the Ca-activated K current in rat tail artery smooth muscle cells independently of local Ca release events.
Should not alter clinical management; leaves open PKC-KCa interactions in human vascular physiology.
The hypothesis that protein kinase C (PKC) is able to regulate the whole cell Ca-activated K (KCa) current independently of PKC effects on local Ca release events was tested using the patch-clamp technique and freshly isolated rat tail artery smooth muscle cells dialyzed with a strongly buffered low-Ca solution. The active diacylglycerol analog 1,2-dioctanoyl-sn-glycerol (DOG) at 10 microM attenuated the current-voltage (I-V) relationship of the KCa current significantly and reduced the KCa current at +70 mV by 70 +/- 4% (n = 14). In contrast, 10 microM DOG after pretreatment of the cells with 1 microM calphostin C or 1 microM PKC inhibitor peptide, selective PKC inhibitors, and 10 microM 1,3-dioctanoyl-sn-glycerol, an inactive diacylglycerol analog, did not significantly alter the KCa current. Furthermore, the catalytic subunit of PKC (PKCC) at 0.1 U/ml attenuated the I-V relationship of the KCa current significantly, reduced the KCa current at +70 mV by 44 +/- 3% (n = 17), and inhibited the activity of single KCa channels at 0 mV by 79 +/- 9% (n = 6). In contrast, 0.1 U/ml heat-inactivated PKCC did not significantly alter the KCa current or the activity of single KCa channels. Thus these results suggest that PKC is able to considerably attenuate the KCa current of freshly isolated rat tail artery smooth muscle cells independently of effects of PKC on local Ca release events, most likely by a direct effect on the KCa channel.
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Schubert et al. (1999) studied this question. Protein kinase C (PKC) activation (via DOG or PKCC) vs. PKC inhibitors, inactive analog, or heat-inactivated PKCC was evaluated on KCa current at +70 mV and single KCa channel activity at 0 mV. Protein kinase C activation significantly reduced the whole cell Ca-activated K current and single KCa channel activity in rat tail artery smooth muscle cells.