Protein kinase C inhibits BK_Cachannel activity in pulmonary arterial smooth muscle

Abstract

Barman, Scott A., Shu Zhu, and Richard E. White. Protein kinase C inhibits BKCa channel activity in pulmonary arterial smooth muscle. Am J Physiol Lung Cell Mol Physiol 286: L149-L155, 2004. First published September 26, 2003 10.1152/ajplung.00207.2003Signaling mechanisms that elevate cyclic AMP (cAMP) activate large-conductance, calcium-and voltage-activated potassium (BKCa) channels in pulmonary vascular smooth muscle and cause pulmonary vasodilatation. BKCa channel modulation is important in the regulation of pulmonary arterial pressure, and inhibition (closing) of the BKCa channel has been implicated in the development of pulmonary vasoconstriction. Protein kinase C (PKC) causes pulmonary vasoconstriction, but little is known about the effect of PKC on BKCa channel activity. Accordingly, studies were done to determine the effect of PKC activation on cAMP-induced BKCa channel activity using patchclamp studies in pulmonary arterial smooth muscle cells (PASMC) of the fawn-hooded rat (FHR), a recognized animal model of pulmonary hypertension. Forskolin (10 M), a stimulator of adenylate cyclase and an activator of cAMP, opened BKCa channels in single FHR PASMC, which were blocked by the PKC activators phorbol 12-myristate 13-acetate (100 nM) and thymeleatoxin (100 nM). The inhibitory response by thymeleatoxin on forskolin-induced BKCa channel activity was blocked by Gö-6983, which selectively blocks the ␣, ␤, ␦, ␥, and PKC isozymes, and Gö-6976, which selectively inhibits PKC-␣, PKC-␤, and PKC-, but not by rottlerin, which selectively inhibits PKC-␦. Collectively, these results indicate that activation of specific PKC isozymes inhibits cAMP-induced activation of the BKCa channel in pulmonary arterial smooth muscle, which suggests a unique signaling pathway to modulate BKCa channels and subsequently cAMP-induced pulmonary vasodilatation.high-conductance calcium-and voltage-activated potassium channel; protein kinase C isozymes; forskolin; cyclic adenosine 5Ј-monophosphate IN THE PULMONARY VASCULATURE, protein kinase C (PKC) is a key regulatory enzyme involved in the signal transduction of several cellular functions, including vascular smooth muscle growth and contractility (4,8,16). PKC consists of a family of serine/threonine kinases with at least 12 members. On the basis of their structures, the PKC family can be divided into three major subclasses: 1) the classic group PKCs, comprising the ␣, ␤I and II, and ␥ isozymes that are Ca 2ϩ dependent and diacylglycerol (DAG) sensitive, 2) the novel group PKCs comprising the ␦, ⑀, , and isozymes that are Ca 2ϩ independent and DAG sensitive, and 3) the atypical group isozymes consisting of the , , , and isozymes that are Ca 2ϩ independent and DAG insensitive (25,38). Numerous PKC isozymes are expressed in vascular smooth muscle (␣, ␤, ⑀, , and ␦), which may be dependent on species, type of vessel, and age of the vessel (15,19,21,27).Although multiple classes of K ϩ channels are expressed at varying densities in different vascular beds, the large-conductance, calcium-and...

Dual role of protein kinase C on BK channel regulation

“…Similar to the results obtained with the mutant BK channel S 1151 A (Fig. 4B), PKC [19][20][21][22][23][24][25][26][27][28][29][30][31] prevented the stimulatory action of PKG in TSMCs and switched the responsiveness of the channel toward PKA. At a holding potential of 40 mV, NP o was not significantly changed by PKG (control NP o 0.44 ± 0.05; after PKG 0.37 ± 0.05, n = 6), whereas a 2.4-fold increase was induced by PKA (control NP o 0.47 ± 0.03; after PKA 1.19 ± 0.17, n = 6; Fig.…”

“…The inhibition of BK channels by phorbol esters and PKC c has been shown before in isolated smooth muscle cells from different arterial beds (30,31). In the present study, we used mouse TSMCs to prove that the regulation of BK channel activity by PKC in primary smooth muscle cells is identical to that observed in the recombinant channels.…”

“…Reduced G max could not be reversed by increasing voltage or Ca 2+ . The inhibitory PKC effect was abolished when inside-out patches were concurrently superfused for at least 5 min with PKC c and 5 μM of the PKC pseudosubstrate inhibitor peptide PKC [19][20][21][22][23][24][25][26][27][28][29][30][31] (Fig. 1A).…”

“…The broad-spectrum PKC inhibitor Ro-31-8220 inhibited the effects of CCh. Dephosphorylation of presumably Ser 1151 , by pretreating inside-out patches from TSMCs with ATP-free solution in the presence of the PKC pseudosubstrate inhibitor PKC [19][20][21][22][23][24][25][26][27][28][29][30][31] , resulted in a switch of channel regulation from PKG to PKA, resembling the switch in the S 1151 A mutant. The regulation of BK channels by closely associated phosphatases has been shown before (16)(17)(18).…”

“…To allow complete dephosphorylation of PKC sites, inside-out patches were first superfused for 5 min with ATP-free solution to which 5 μM PKC [19][20][21][22][23][24][25][26][27][28][29][30][31] had been added. This solution, which did not significantly alter NP o , was then changed for another 5 min to a solution containing ATP, PKC [19][20][21][22][23][24][25][26][27][28][29][30][31] , and either PKG or PKA. Similar to the results obtained with the mutant BK channel S 1151 A (Fig.…”