Figure 1.

Signaling mechanisms of integrin α9β1. (A) Selective ligation of integrin α9β1 activates proximal tyrosine kinase Src. Src coordinates subsequent signaling pathways; first through activation of FAK, tyrosine phosphorylation of the adaptor protein p130Cas and ultimately co-ordinates activation of small GTPase rac1, which translocates to the cell membrane and causes lamellipodial protrusion; second, Src activates iNOS resulting in increased NO production, activation of cGMP and protein kinase G signaling cascades to enhance cell migration (as reported by Gupta et al.¹⁶). (B) Integrin α9β1 can regionally recruit SSAT, an enzyme involved in the catabolism of higher order polyamines spermidine and spermine, which are potent blockers of inward rectifier K⁺ (Kir) channels. SSAT (along with PAO, polyamine oxidase) facilitates localized enzymatic processing of spermidine and spermine in to the smaller polyamine, putrescine and thus relieving outward efflux of K⁺ to co-ordinate cell migration (as reported by deHart et al.³⁷).