Focal adhesion kinase controls actin assembly via a FERM-mediated interaction with the Arp2/3 complex

Abstract

Networks of actin filaments, controlled by the Arp2/3 complex, drive membrane protrusion during cell migration. How integrins signal to the Arp2/3 complex is not well understood. Here, we show that focal adhesion kinase (FAK) and the Arp2/3 complex associate and colocalize at transient structures formed early after adhesion. Nascent lamellipodia, which originate at these structures, do not form in FAK-deficient cells, or in cells in which FAK mutants cannot be autophosphorylated after integrin engagement. The FERM domain of FAK binds directly to Arp3 and can enhance Arp2/3-dependent actin polymerization. Critically, Arp2/3 is not bound when FAK is phosphorylated on Tyr 397. Interfering peptides and FERM-domain point mutants show that FAK binding to Arp2/3 controls protrusive lamellipodia formation and cell spreading. This establishes a new function for the FAK FERM domain in forming a phosphorylation-regulated complex with Arp2/3, linking integrin signalling directly with the actin polymerization machinery.

Phosphorylation of focal adhesion kinase on tyrosine 194 by Met leads to its activation through relief of autoinhibition

“…Thus, it is possible that Met, EGFR and PDGFR may have distinct preference for Y5 and Y194 of FAK. However, it is not clear whether the phosphorylation of Y5 and/or Y194 affect interactions of FAK with other cellular proteins, in particular, those known to interact with the FERM domain of FAK such as the Arp2/3 complex (Serrels et al, 2007). In addition, it remains possible that phosphorylated Y5 and/or Y194 may serve as binding sites for other Srchomology 2 domain-containing proteins.…”

“…The NH2-terminus contains a region of sequence homology with FERM domain (band 4.1 and ezrin/radixin/moesin proteins). The FERM domain of FAK has been described to involve in interactions with other proteins including the cytoplasmic region of integrins (Schaller et al, 1995;Chen et al, 2000), the FERM domain of ezrin (Poullet et al, 2001), the pleckstrin homology domain of the Tec-family kinase Etk (Chen et al, 2001), the Arp2/3 complex (Serrels et al, 2007) and receptor tyrosine kinases (RTKs), including platelet-derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR) and hepatocyte growth factor (HGF) receptor (Sieg et al, 2000;Chen and Chen, 2006). It has been proposed that an intramolecular inhibitory interaction between the FERM and kinase domains of FAK suppresses its catalytic activity (Cooper et al, 2003;Dunty et al, 2004).…”

FAK transduces extracellular forces that orient the mitotic spindle and control tissue morphogenesis

“…3a). We went on to examine a possible role of the FERM (4.1 protein, ezrin, radixin, moesin) domain, which has been shown to interact with several proteins involved in spindle orientation, such as the Arp2/3 complex and integrins 30,31 . FAK-nulls were transfected with a kinase-dead mutant of FAK that lacks the FERM domain (DFERM/K454R).…”

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

“…In short, FAK harnesses multiple levels of control over actin polymerization. Interestingly, FAK/Arp3 interaction is negatively regulated by the phosphorylation of FAK-Tyr 397 , which is the major autophosphorylation site induced by integrin signaling (13). However, additional regulation by yet to be defined phosphorylation events is clearly at play, because Arp3 binding to FAK Y397F (nonphosphorylatable mutant) was further enhanced in suspended cells vs. adhered cells (13).…”

“…Interestingly, FAK/Arp3 interaction is negatively regulated by the phosphorylation of FAK-Tyr 397 , which is the major autophosphorylation site induced by integrin signaling (13). However, additional regulation by yet to be defined phosphorylation events is clearly at play, because Arp3 binding to FAK Y397F (nonphosphorylatable mutant) was further enhanced in suspended cells vs. adhered cells (13). In an effort to understand the possible involvement of other FAK phosphorylation sites in actin dynamics better, we found that p-FAK-Tyr 407 was recruited to actin-rich ultrastructures: the basal ES and the apical ES.…”