A FAK/Src chimera with gain‐of‐function properties promotes formation of large peripheral adhesions associated with dynamic actin assembly

Abstract

Formation of a complex between the tyrosine kinases FAK and Src is a key integrin-mediated signaling event implicated in cell motility, survival, and proliferation. Past studies indicate that FAK functions in the complex primarily as a "scaffold," acting to recruit and activate Src within cell/matrix adhesions. To study the cellular impact of FAK-associated Src signaling we developed a novel gainof-function approach that involves expressing a chimeric protein with the FAK kinase domain replaced by the Src kinase domain. This FAK/Src chimera is subject to adhesion-dependent activation and promotes tyrosine phosphorylation of p130Cas and paxillin to higher steady-state levels than is achieved by wild-type FAK. When expressed in FAK -/-mouse embryo fibroblasts, the FAK/Src chimera resulted in a striking cellular phenotype characterized by unusual large peripheral adhesions, enhanced adhesive strength, and greatly reduced motility. Live cell imaging of the chimeraexpressing FAK -/-cells provided evidence that the large peripheral adhesions are associated with a dynamic actin assembly process that is sensitive to a Src-selective inhibitor. These findings suggest that FAK-associated Src kinase activity has the capacity to promote adhesion integrity and actin assembly.

EGFR / FAK and c‐Src signalling pathways mediate the internalisation of Staphylococcus aureus by osteoblasts

“…Previous study has documented the critical role of actin microfilaments in the internalisation process of S. aureus (Ellington et al, 1999). Considering that FAK and Src family kinases are main signalling required to stabilise the actin microfilaments (Frame, 2004; Siesser et al, 2008), our study raises the possibility of FAK/Src/microfilaments system in initiating the internalisation of S. aureus by osteoblasts.…”

Nintedanib reduces ventilation‐augmented bleomycin‐induced epithelial–mesenchymal transition and lung fibrosis through suppression of the Src pathway

“…TGF‐β1 can induce the activation of Src by autophosphorylation of the tyrosine 416 . In the presence of active TGF‐β1, during a murine study of bleomycin‐induced lung fibrosis, epithelial integrin and focal adhesion kinases up‐regulated Src activity and Src inhibition attenuated EMT, which is a potential source of myofibroblasts accumulation in fibrotic lungs . Moreover, previous studies have demonstrated that oral administration of 60 and 100 mg/kg of nintedanib is sufficient to inhibit FGFRs, VEGFRs, Lck, Src and Flt‐3 in mice .…”

Focal adhesion kinase-Tyr 407 and -Tyr 397 exhibit antagonistic effects on blood–testis barrier dynamics in the rat

“…However, accumulating evidence suggests that a much more elaborate mechanism is required to fine-tune the activity of FAK because it is involved in multiple steps of the cell motility cycle (18), including adhesion assembly, actin remodeling, and adhesion turnover, which is why simple loss/gain-offunction studies often lead to seemingly contradictory results in the literature. For instance, an increase in FAK activity has been reported to reduce motility, stabilize adhesion, and promote stress fiber assembly (19), possibly via RhoA activation (20); however, on the other hand, FAK deficiency in a number of cell types also led to reduced motility, with impaired adhesion turnover and hyperactivated Rho-Rho associated coiled-coil containing protein kinase (Rho-ROCK) signaling (21,22). To ensure timely activation of a suitable downstream signaling pathway, it is likely that an efficient mechanism is in place to regulate this multifunctional molecule.…”