Activation of Cell Adhesion Kinase β by Mechanical Stretch in Vascular Smooth Muscle Cells

We have studied whether activation of cell adhesion kinase beta (CAKbeta) is involved in stretch-induced signaling pathway in cultured rat vascular smooth muscle cells. Cyclic stretch (1 Hz) induced a rapid (within 1 min) phosphorylation of CAKbeta, whose effect was time and strength dependent. Both Ca(2+) and Na(+) ionophores (A23187 and monensin) stimulated phosphorylation of CAKbeta in a similar fashion to mechanical stretch. The stretch-induced phosphorylation of CAKbeta was inhibited completely by an intracellular Ca(2+) chelator [1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester)] and largely by gadolinium, but only partially by an extracellular Ca(2+) chelator (EGTA). An angiotensin type 1 receptor antagonist (CV11974) abolished the phosphorylation of CAKbeta stimulated by angiotensin II, but not by mechanical stretch. Mechanical stretch rapidly (within 1 min) increased the association of CAKbeta with c-Src, but not pp125(focal adhesion kinase). Stretch-induced phosphorylation of ERK1/2 was inhibited by EGTA and an inhibitor of the Src kinase family [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine], but not by cytochalasin D, to disrupt actin polymerization. 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine or cytochalasin D did not affect stretch-induced phosphorylation of CAKbeta. These data suggest that mechanical stretch stimulates activation of CAKbeta, followed by its association with c-Src, which requires ion influx mainly via stretch-activated nonselective ion channels, thereby leading to activation of the p21(Ras)/ERK1/2 cascade in vascular smooth muscle cells.