Phosphorylation of calponin mediated by protein kinase C in association with contraction in porcine coronary artery.

Calponin is an actin-associated regulatory protein in smooth muscle. We report that both endothelin-1 (ET-1) and phorbol 12, 13-dibutyrate (PDBu) caused a significant increase in phosphorylation of calponin during contraction of porcine coronary artery, while high levels of KCl were ineffective. This phosphorylation was predominantly catalyzed by activation of protein kinase C(PKC). In addition, the level of phosphorylation of calponin increased closely in association with the size of the contractile force induced by PDBu. Thus, the phosphorylation of calponin in vivo by PKC might modulate in part the contraction of smooth muscle that occurs in response to ET-1 or PDBu.