FERM Domain Interaction Promotes FAK Signaling

Abstract

From the results of deletion analyses, the FERM domain of FAK has been proposed to inhibit enzymatic activity and repress FAK signaling. We have identified a sequence in the FERM domain that is important for FAK signaling in vivo. Point mutations in this sequence had little effect upon catalytic activity in vitro. However, the mutant exhibits reduced tyrosine phosphorylation and dramatically reduced Src family kinase binding. Further, the abilities of the mutant to transduce biochemical signals and to promote cell migration were severely impaired. The results implicate a FERM domain interaction in cell adhesion-dependent activation of FAK and downstream signaling. We also show that the purified FERM domain of FAK interacts with full-length FAK in vitro, and mutation of this sequence disrupts the interaction. These findings are discussed in the context of models of FAK regulation by its FERM domain.The focal adhesion kinase, FAK, plays a major role in transducing signals downstream of integrins (40,47). Upon integrinmediated adhesion, FAK becomes tyrosine phosphorylated and activated. Additional signaling molecules, e.g., Src and phosphatidylinositol 3-kinase, are recruited into complexes with FAK, leading to the transduction of biochemical signals that control important biological processes. Integrin signaling via FAK regulates cell migration, proliferation, and survival. FAK-dependent regulation of one or more of these processes is essential, since fak Ϫ/Ϫ mice exhibit embryonic lethality (27). Conversely, enhanced FAK signaling may lead to aberrant cell proliferation, survival, or migration, which may have pathological consequences in humans. For example, aberrant FAK signaling may contribute to cancer development and progression to metastatic disease (40).FAK contains three major domains, an N-terminal domain, a central catalytic domain, and a C-terminal domain (40, 47). The C-terminal domain can be further subdivided into the focal adhesion targeting (FAT) sequence, comprising the Cterminal 140 amino acids of the protein, and the region between the catalytic domain and the FAT sequence. Focal adhesion-associated FAT sequence binding partners have been identified, and insight into the molecular basis of FAT sequence function was recently obtained from crystal and nuclear magnetic resonance structure analyses (3,14,23,26,31). The sequence between the catalytic domain and the FAT sequence contains docking sites for SH3 domain-containing proteins and thus serves as a scaffold for the recruitment of signaling proteins. Several sites of tyrosine phosphorylation play important regulatory roles in FAK. Within the catalytic domain, two tyrosine residues in the activation loop, tyrosines 576 and 577, regulate catalytic activity. The major site of autophosphorylation, tyrosine 397, lies just N terminal to the catalytic domain and serves as a binding site for Src family kinases. While details regarding the function of the catalytic and C-terminal domains have been elucidated, fewer studies have examined the function of ...

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

“…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). Truncation of the FERM domain increases FAK tyrosine phosphorylation and/or activity (Cooper et al, 2003;Dunty et al, 2004;Ja´camo and Rozengurt, 2005).…”

“…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). Truncation of the FERM domain increases FAK tyrosine phosphorylation and/or activity (Cooper et al, 2003;Dunty et al, 2004;Ja´camo and Rozengurt, 2005). Mutation of K38 within the FERM domain also leads to FAK activation (Cohen and Guan, 2005).…”

Distinct biophysical mechanisms of focal adhesion kinase mechanoactivation by different extracellular matrix proteins

“…In addition to the FAT domain function, the basic patch in the N-terminal protein 4.1/ezrin/redixin/moesin (FERM) F2 domain and its interaction with acidic molecules [e.g., phosphatidylinositol 4,5-biphosphate (PIP 2 )] have been suggested to regulate the FAK activation (40,41). In fact, mutations on the FERM basic patch, K216A/K218A/R221A/K222A (KAKTLRK), or PIP 2 inhibitor neomycin (42), inhibited the FAK activation on cell adhesion (Figs.…”

Clinical Implications of the Influence of Ehm2 on the Aggressiveness of Breast Cancer Cells through Regulation of Matrix Metalloproteinase-9 Expression

“…Regulation of this intramolecular interaction modulates FERM protein-mediated intermolecular interactions. The FERM domain of focal adhesion kinase interacts with the COOH terminal catalytic domain, and this interaction represses its catalytic activity (8).…”