Integrin alpha9beta1 promotes cell migration via Src kinase mediated nitric oxide synthesis

Abstract

Beta-1 integrins are important mediators of cell migration but may do so through different signaling mechanisms. However, c-src-activation seems to be a key signaling intermediate. Nitric oxide (NO) synthesis is another novel molecule that modulates cell migration, which may be utilized during integrin mediated cell migration. We used α9 expressing SW480 colon carcinoma cells, to explore a role for src and NO in α9β1 mediated-cell migration. We found that α9β1-ligation leads to c-Src phosphorylation (Tyr-416) and Erk MAP kinase phosphorylation; phospho-c-src was maximum at 5 min, and phospho-Erk maxima was at 20min. Pre-treated cells with src and Erk kinase inhibitors, PP1 and PD98059, inhibited α9-dependent cell motility. c-src appeared to signal upstream of Erk since inhibition of c-Src-kinase blocked Erk phosphorylation. Furthermore, α9β1-ligation enhanced NO synthesis through activation of inducible Nitric Oxide Synthase (iNOS), which was constitutively expressed in SW480 cells. Using the NO specific inhibitor L-NAME, α9β1-dependent cell migration was blocked. Also, enhanced iNOS phosphorylation and NO production were src kinase (but not Erk) dependent. These results suggest a novel signaling pathway for α9β1-induced cell migration through c-src kinase activation of iNOS and subsequent NO production.