ANG II-mediated inhibition of neuronal delayed rectifier K+ current: role of protein kinase C-alpha

It was previously determined that ANG II and phorbol esters inhibit Kv curr ent in neurons cultured from newborn rat hypothalamus and brain stem in a p rotein kinase C (PKC)- and Ca2+-dependent manner. Here, we have further def ined this signaling pathway by investigating the roles of "physiological" a ctivators of PKC and different PKC isozymes. The cell-permeable PKC activat ors, diacylglycerol (DAG) analogs 1,2-dioctanoyl-sn-glycerol (1 mu mol/l, n = 7) and 1-oleoyl-2-acetyl-sn-glycerol (1 mu mol/l, n = 6), mimicked the e ffect of ANG II and inhibited Kv current. These effects were abolished by t he PKC inhibitor chelerythrine (1 mu mol/l, n = 5) or by chelation of inter nal Ca2+ (n = 8). PKC antisense (AS) oligodeoxynucleotides (2 mu mol/l) aga inst Ca2+ dependent PKC isoforms were applied to the neurons to manipulate the endogenous levels of PKC. PKC-alpha -AS (n = 4) treatment abolished the inhibitory effects of ANG II and 1-oleoyl-2-acetyl-sn-glycerol on Kv curre nt, whereas PKC-gamma -AS (n 5 4) and PKC-alpha -AS (n 5 4) did not. These results suggest that the angiotensin type 1 receptor-mediated effects of AN G II on neuronal Kv current involve activation of PKC-alpha.