FAK–Src signalling through paxillin, ERK and MLCK regulates adhesion disassembly

Abstract

Cell migration is a complex, highly regulated process that involves the continuous formation and disassembly of adhesions (adhesion turnover). Adhesion formation takes place at the leading edge of protrusions, whereas disassembly occurs both at the cell rear and at the base of protrusions. Despite the importance of these processes in migration, the mechanisms that regulate adhesion formation and disassembly remain largely unknown. Here we develop quantitative assays to measure the rate of incorporation of molecules into adhesions and the departure of these proteins from adhesions. Using these assays, we show that kinases and adaptor molecules, including focal adhesion kinase (FAK), Src, p130CAS, paxillin, extracellular signal-regulated kinase (ERK) and myosin light-chain kinase (MLCK) are critical for adhesion turnover at the cell front, a process central to migration.

The actin-associating protein Tm5NM1 blocks mesenchymal motility without transition to amoeboid motility

“…In 3D collagen gels, both control and Tm5NM1-expressing cells appear to be connected to the surrounding collagen as they pull on and deform the matrix (Supplementary Video 1), therefore, suggesting that these cells are adhered to the collagen matrix. Src kinase is a major regulator of focal adhesion stability (Fincham and Frame, 1998;Webb et al, 2004), and Src inhibition specifically blocks mesenchymal motility (Carragher et al, 2006). Related to this, we have previously shown that Src expression is suppressed in cells with elevated Tm5NM1 (Bach et al, 2009), and in the present study, we establish that Src activity is significantly suppressed in cells with elevated Tm5NM1.…”

“…As Src kinase is a major regulator of focal adhesion stability and mesenchymal motility (Fincham and Frame, 1998;Webb et al, 2004;Carragher et al, 2006), and we have demonstrated that total Src expression is decreased in cells with elevated Tm5NM1 (Bach et al, 2009), we next tested whether Src kinase activity is suppressed. Using antibodies to the activated form of Src kinase, we find significantly decreased activated Src, relative to total Src protein in cells with elevated Tm5NM1 (Figures 3g and h).…”

Scaffold mediated regulation of MAPK signaling and cytoskeletal dynamics: A perspective

“…This ordered assembly promotes sequential tyrosine phosphorylation at nascent complexes and regulates the maturation and life-time of adhesions [74,77,78]. However, it should be noted that focal adhesions do not mature solely by accumulating signaling molecules; there is also an ordered exit of molecules during maturation, as evidenced by the decreased content of FAK and zyxin in mature adhesions [74,79]. RhoA might play a role in focal adhesion disassembly by recruiting c-Src to focal adhesions through activation of mDia [80].…”

“…Thus, FAK null cells contain enlarged focal adhesions and "thicker" actin stress fibres and are severely impaired in migration [86]. These defects are in part due to misregulation of Rho-ROCK signaling [87,88] but might also involve MEK-ERK signaling [79] and microtubules (see below).…”

“…Indeed, considerable evidence indicates that the integration of Rho family GTPase and ERK signaling is important in the control of cell morphogenesis [96][97][98][99][100][101][102][103]. Integrin activation of MAPK requires c-Src and FAK, and ERK activity is required for FAK stimulated focal adhesion disassembly to promote cell migration [79,89]. Several studies have shown that FAK or v-Src can suppress the activities of Rho [48,87] and its effector, ROCK [88], and this pathway requires ERK signaling [79,104] to modulate actin and focal adhesion dynamics.…”