부산대학교 도서관

The contraction of gastrointestinal (GI) smooth muscles isregulated by both Ca2+-dependent and Ca2+ sensitizationmechanisms. Proline-rich tyrosine kinase 2 (Pyk2) is involved inthe depolarization-induced contraction of vascular smooth musclevia a Ca2+ sensitization pathway. However, the role of Pyk2in GI smooth muscle contraction is unclear. The spontaneouscontraction of colonic smooth muscle was measured by usingisometric force transducers. Protein and phosphorylation levelswere determined by using western blotting. Pyk2 protein wasexpressed in colonic tissue, and spontaneous colonic contractionswere inhibited by PF-431396, a Pyk2 inhibitor, in the presence oftetrodotoxin (TTX). In cultured colonic smooth muscle cells(CSMCs), PF-431396 decreased the levels of myosin light chain(MLC20) phosphorylated at Ser19 and ROCK2 protein expression,but myosin light chain kinase (MLCK) expression was not altered.However, Y-27632, a Rho kinase inhibitor, increasedphosphorylation of Pyk2 at Tyr402 and concomitantly decreasedROCK2 levels; the expression of MLCK in CSMCs did not change.The expression of P(Tyr402)-Pyk2 and ROCK2 was increasedwhen CSMCs were treated with Ach. Pyk2 is involved in theprocess of colonic smooth muscle contraction through theRhoA/ROCK pathway. These pathways may provide veryimportant targets for investigating GI motility disorders.