Abstract
L-type Ca2+ channels are up-modulated with phosphorylation mediated by protein kinase A (PKA). Consensus phosphorylation sites in the carboxyl-terminal tail of guinea-pig Cav1.2 channel, which are conserved in other species, are four (Ser1574, Ser1626, Ser1699, Ser1927). Ser1927 is reported as the functional phosphorylation site to up-modulate the channel. In this study, we investigated possible roles of other phosphorylation sites. Mutations from Ser to Ala in one of consensus phosphorylation sites or in combinations were introduced, and expressed channels were investigated for the effects of PKA activator (5 μM forskolin) using patch-clamp technique in BHK cells. Expressed wild-type (WT) channels responded to forskolin with 4-fold increase in channel activity. Responses of mutant channels (S[1574]A, S[1626]A, S[1927]A) are significantly suppressed compared with that of WT channels (1 to 2-fold). Combined mutants containing S[1574]A showed low sensitivity to forskolin. These results suggest not only Ser1927 but also Ser1574 and Ser1626 are functional sites for PKA phosphorylation. We will also discuss phosphorylation of channel fragments containing these consensus phosphorylation sites. [J Physiol Sci. 2008;58 Suppl:S72]
