PTP1B promotes focal complex maturation, lamellar persistence and directional migration

Previous findings established that ER-bound PTP1B targets peripheral cell-matrix adhesions and positively regulates cell adhesion to fibronectin. Here we show that PTP1B enhances focal complex lifetime at the lamellipodium base, delaying their turnover and facilitating a-actinin incorporation. We demonstrate the presence of catalytic PTP1BD181A-alpha-actinin complexes at focal complexes. Kymograph analysis revealed that PTP1B contributes to lamellar protrusion persistence and directional cell migration. Pull-down and FRET analysis also showed that PTP1B is required for efficient integrin-dependent downregulation of RhoA and upregulation of Rac1 during spreading. A substrate trap strategy revealed that FAK/Src recruitment and Src activity are essential for the generation of PTP1B substrates in adhesions. PTP1B targets the negative regulatory site of Src (phosphotyrosine 529), paxillin and p130Cas at peripheral cell-matrix adhesions. We postulate that PTP1B modulates more than one pathway required for focal complex maturation and membrane protrusion, including alpha-actinin-mediated cytoskeletal anchorage, integrin-dependent activation of the FAK/Src signaling pathway, and RhoA and Rac1 GTPase activity. By doing so, PTP1B contributes to coordinated adhesion turnover, lamellar stability and directional cell migration.