p21-activated Kinase 4 Phosphorylation of Integrin β5 Ser-759 and Ser-762 Regulates Cell Migration

Abstract

Modulation of integrin ␣v␤5 regulates vascular permeability, angiogenesis, and tumor dissemination. In addition, we previously found a role for p21-activated kinase 4 (PAK4) in selective regulation of integrin ␣v␤5-mediated cell motility (Zhang, H., Li, Z., Viklund, E. K., and Strömblad, S. (2002) J. Cell Biol. 158, 1287-1297). This report focuses on the molecular mechanisms of this regulation. We here identified a unique PAK4-binding membrane-proximal integrin ␤5-SERS-motif involved in controlling cell attachment and migration. We also mapped the integrin ␤5-binding site within PAK4. We found that PAK4 binding to integrin ␤5 was not sufficient to promote cell migration, but that PAK4 kinase activity was required for PAK4 promotion of cell motility. Importantly, PAK4 specifically phosphorylated the integrin ␤5 subunit at Ser-759 and Ser-762 within the ␤5-SERS-motif. Point mutation of these two serine residues abolished the PAK4-induced cell migration, indicating a functional role for these phosphorylations in migration. Our results may give important leads to the functional regulation of integrin ␣v␤5, with implications for vascular permeability, angiogenesis, and cancer dissemination.Integrins are heterodimers composed of ␣ and ␤ subunits that contain a large extracellular domain with ligand binding capacity, a transmembrane domain, and a short cytoplasmic domain (2). Integrins mediate cell adhesion and thereby play a central role in cell migration. Integrins also participate in bidirectional signaling processes across the plasma membrane where ligand binding to the extracellular matrix generates intracellular signals (outside-in) and where signaling affecting integrin cytoplasmic tails can lead to regulation of the integrin extracellular binding capacity (inside-out) (3-6).The membrane-proximal regions of the cytoplasmic domains of the integrin heterodimer interact with each other via a salt bridge. Disruption of this salt bridge can change the integrin affinity state, indicating that the short cytoplasmic domains of integrins are essential for both inside-out and outside-in signaling (3, 7). One important mechanism whereby cellular signaling influences cellular behavior is through the interaction and/or phosphorylation of integrin cytoplasmic tails by intracellular proteins (8 -12). Interactions and/or phosphorylation of integrin cytoplasmic tails may also regulate the activation state of integrins, for example, ␤ integrin tyrosine phosphorylation can regulate talin-induced integrin activation (11,(13)(14)(15)(16).Integrin phosphorylation at tyrosine residues has been found in the cytoplasmic domains of ␣6A, ␤1, ␤3, and ␤4 (17-22). Also, serine/threonine phosphorylation of integrin cytoplasmic domains has been found in ␣4, ␤1, ␤2, ␤3, and ␤7 subunits (23-31). However, so far only a few protein kinases have been identified that phosphorylate integrin cytoplasmic domains. c-Src was found to be responsible for tyrosine phosphorylation, whereas protein kinase C and integrin-linked kinase may mediate serine/threon...

PAK signalling during the development and progression of cancer

“…3). It has also been suggested that PAK4 plays a role in angiogenesis through phosphorylation of the integrin αvβ5, which affects endothelial cell motility and permeability 84 .…”

Structure, biochemistry, and biology of PAK kinases

“…PAK4-Cdc42 interaction has also been shown to support redistribution of PAK4 to the Golgi compartment in porcine endothelial cells (Abo et al, 1998). In addition, PAK4 also signals through LIMK1 and stabilizes actin–myosin filaments (Dan et al, 2001), while PAK4 phosphorylation of integrin β5 on Ser759 and Ser762 promotes cell migration (Li et al, 2010b). Both PAK4 and PAK5 phosphorylate p120-catenin on Ser288 for cytoskeleton reorganization (Wong et al, 2010).…”

P21 activated kinases

“…PAK4 phosphorylates the cytoplasmic tail of β-5 integrin, which subsequently has important implications in cell adhesion and migration. 54 Phosphorylation of p120 and β-5 integrin by the group A Paks has not yet been reported. Group A Paks are also implicated in cell adhesion, however, and one important mediator is GIT1.…”