Association of protein kinase C to the Ca_v1.2 Ca²⁺ channel improves muscarinic‐induced contraction of urinary bladder

Abstract

Muscarinic agonists like carbachol induce contraction of urinary bladder. This contraction is blocked by L‐type Ca2+ channel antagonists and is abolished in detrusor muscle from Cav1.2 deficient mice, demonstrating that this type of contraction depends on functional L‐type Ca2+ channels. However, it is unclear how muscarinic stimulation couples to the L‐type Ca2+ channel. In this study, we present several lines of evidence that protein kinase C is involved in this signalling pathway: (i) carbachol‐induced contraction was attenuated by the protein kinase C inhibitor Gö6850; (ii) contraction and (iii) intracellular Ca2+ signals induced by carbachol were increased after activation of protein kinase C with phorbol ester; (iv) these effects of phorbol ester were inhibited by Gö6850; (v) co‐immunoprecipitation using a Cav1.2 antibody and (vi) analysis of membrane preparations using blue native gelelectrophoresis revealed an association of protein kinase C to the Cav1.2 channel if the muscles had been stimulated by carbachol; (vi) phosphorylation of the Cav1.2 channel was increased in carbachol‐stimulated preparations and attenuated by Gö6850. These results suggest that association of protein kinase C to the Cav1.2 Ca2+ channel participates, at least partially, in the signalling pathway from the muscarinic receptor to the L‐type Ca2+ channel during micturition.