Integrins mediate the inhibitory effect of focal adhesion on angiotensin II-induced p44/42 mitogen-activated protein (MAP) kinase activity in human mesangial cells.

Previously, we reported that the formation of focal adhesion accelerated by accumulation of extracellular matrices may inhibit the angiotensin II-stimulated proliferation of human mesangial cells (HMCs). The process is regulated by p44/42 MAP kinase activity through the mediation of paxillin and GTPase activating proteins. In this report, we investigated the effect of integrin molecules on the angiotensin II-induced p44/42 MAP kinase activation in non-adherent HMCs. The results demonstrated that incubation of cells with both antibody to integrin beta(1) chain (K20) and GRGDS peptide induced integrin clustering, paxillin aggregation, and marked suppression of angiotensin II-induced p44/42 MAP kinase activation. On the other hand, incubation of cells with K20 alone induced integrin clustering without paxillin aggregation and the suppressive effect on angiotensin II-stimulated p44/42 MAP kinase activity. Our results strongly suggest the pivotal role of integrins in the inhibitory effect of focal adhesion on p44/42 MAP kinase activity, the checking system against angiotensin II-induced MAP kinase overactivation.