Src Family Kinases Are Required for Integrin-mediated but Not for G Protein-coupled Receptor Stimulation of Focal Adhesion Kinase Autophosphorylation at Tyr-397

Abstract

A rapid increase in the tyrosine phosphorylation of the nonreceptor tyrosine kinase FAK 1 (1, 2), which localizes to focal adhesion plaques, has been identified as a prominent early event in cells stimulated by diverse signaling molecules that regulate cell proliferation, migration, and apoptosis (3-5). In particular, FAK is activated and tyrosine-phosphorylated in response to integrin clustering induced by cell adhesion or antibody cross-linking (1, 2, 6 -9). In addition, FAK is rapidly tyrosine-phosphorylated in cells stimulated by mitogenic neuropeptide agonists including bombesin (10 -16) and bioactive lipids including LPA (17-19) that act via heptahelical GPCRs, polypeptide growth factors (20 -24), bacterial toxins (25,26), and activated variants of pp60 Src (27,28). The importance of FAK-mediated signal transduction is underscored by experiments implicating this tyrosine kinase in embryonic development (29) and in the control of cell migration (30 -33), proliferation (30, 34), and apoptosis (35,36). In addition, there is increasing evidence linking overexpression of FAK to the invasive properties of cancer cells (37,38). It is increasingly recognized that the tyrosine phosphorylation and activation of FAK is an important point of convergence in the action of integrins, GPCR agonists, growth factors, and oncogenes (5, 39, 40). However, the molecular pathways leading to FAK tyrosine phosphorylation in response to multiple extracellular factors remain incompletely understood.Plating suspended cells onto fibronectin-coated dishes, a paradigm of integrin receptor activation (41), induces adhesion-dependent phosphorylation of FAK at multiple sites including tyrosines 397, 576, 577, 861, and 925 (32, 42-45). Tyr-397, the only apparent autophosphorylation site (46 -51), has emerged as a critical residue in FAK-mediated signaling (5). The autophosphorylation of FAK at Tyr-397 creates a high affinity binding site for the SH2 domain of Src family kinases including Src, Yes, and Fyn and leads to the formation of a signaling complex between FAK and Src family kinases (46, 47, 49 -52). A model has recently been proposed that envisages reciprocal catalytic activation of FAK and Src family kinases in response to adhesiondependent signals. Src family kinases associated with FAK are thought to phosphorylate FAK at additional sites including Tyr-576 and Tyr-577 that are located in the activation loop of the kinase catalytic domain of FAK (32, 42, 53), thereby promoting maximal FAK catalytic activation. Because phenylalanine mutation of Tyr-576 and Tyr-577 reduced adhesion-mediated FAK autophosphorylation (at Tyr-397), it has been proposed that activation loop phosphorylation of FAK by Src stimulates intermolecular phosphorylation at Tyr-397, thereby leading to signal amplification at sites of integrin-mediated cell adhesion (32). Therefore, in this model Src family kinases are thought to play a major role leading to autophosphorylation of FAK at Tyr-397 as part of an adhesion-dependent signaling response. Recently, we demons...

Characterization of Heparanase-induced Phosphatidylinositol 3-Kinase-AKT Activation and Its Integrin Dependence

“…Several growth factors have been reported to induce FAK and PYK2 activation (42,52,53) although their receptors have not been shown to interact with talin. In the case of EGF and PDFG, the activation was achieved through the bridging of FAK and PYK2 between the receptors and integrin-associated proteins (presumably the talin-paxillin complex) (52,54).…”

Tyrosine kinase inhibition in diffuse large B-cell lymphoma: molecular basis for antitumor activity and drug resistance of dasatinib

“…In contrast to imatinib, cell lines including K562, LY7, LY8, LY10, VAL and LY1 are inhibited by PP2 with low IC 50 values with respect to typical doses of B10 mM. [19][20][21] Inhibition of LY18 requires high concentrations of PP2, yet inhibition of LY3 requires even higher concentrations (Supplementary Table 1). The sensitivity profile of the DLBCL cell lines to PP2 is, therefore, similar to that of dasatinib but completely different from that of imatinib.…”

The protein-tyrosine phosphatase DEP-1 modulates growth factor-stimulated cell migration and cell–matrix adhesion

“…Src is a component of focal adhesion complexes and plays an important role in the inside-outside and outside-inside signaling pathways regulating cell-matrix adhesion (Salazar and Rozengurt, 2001;Frame et al, 2002). Positive effects of RPTPa and PTP-1B on cellmatrix adhesion have previously been associated with PTP-mediated Src activation (Harder et al, 1998;Cheng et al, 2001).…”