Focal Adhesion Kinase Facilitates Platelet-derived Growth Factor-BB-stimulated ERK2 Activation Required for Chemotaxis Migration of Vascular Smooth Muscle Cells

Abstract

Several vascular diseases result from neointima formation, a process that is characterized by the accumulation of vascular smooth muscle cells (SMCs) 1 and extracellular matrix (ECM) proteins in the intima of blood vessels (1). Neointima formation is triggered upon damage to the endothelial lining by the local release of chemotactic cytokines or growth factors (2) and by increased production of ECM proteins (3). Because combinations of these factors can stimulate cell division, it was originally hypothesized that neointimal hyperplasia resulted from enhanced SMC proliferation (4). However, further studies have shown that SMC migration also plays a significant role in neointima formation (5). Growth factors acting as chemotactic agents (6) and ECM molecules acting as haptotactic factors (7) can independently stimulate SMC migration. Therefore, a common signaling component that coordinates both chemotactic and haptotactic cell migration events would be a promising target for intervention strategies.Investigations of the molecular regulation of cell migration have demonstrated an important role for the focal adhesion kinase (FAK), a protein-tyrosine kinase (PTK) that localizes to cell-substratum contact sites also known as focal adhesions (for a review see Ref. 8). Genetic support for FAK in promoting cell motility comes from studies using FAK-null fibroblasts that exhibit refractory responses to normal motility-promoting stimuli (9). Importantly, these defects are rescued by stable re-expression of FAK in FAK-null cells (10, 11). Work from a number of laboratories using a variety of cell types has provided evidence that FAK promotes cell migration potentially through the activation of multiple downstream targets such as Src family PTKs (10,14), by the increased phosphorylation of p130 Cas (15,16) or paxillin adaptor proteins (17), or through the association with other signaling proteins such as Grb7 (18) and . Although no clear consensus has emerged on the molecular mechanism(s) of how FAK promotes cell migration, studies with FAK-null cells have shown that FAK is required for both integrin-and growth factor-stimulated cell motility (10, 12).FAK activity is regulated by protein-tyrosine phosphatase action (16) and inhibited by the overexpression of the FAK C-terminal domain termed FRNK (FAK-related non-kinase) (22)(23)(24). Importantly, the regulated and autonomous expression of FRNK during embryonic development is under the control of alternative intronic promoter region and therefore may function as an endogenous inhibitor of FAK in vivo (22,25) In this study, we employed the transient and stable overexpression of hemagglutinin (HA)-tagged FRNK to investigate the role of endogenous FAK in promoting platelet-derived

Signaling Pathways Transduced through the Elastin Receptor Facilitate Proliferation of Arterial Smooth Muscle Cells

“…We therefore, speculate that FAK may also be an upstream factor responsible for phosphorylation of cytoskeletal components after SMC exposure to elastin peptides. It has also been shown that FAK facilitates ERK2 activation in vascular smooth muscle cells stimulated by PDGF-BB (85) and that ERK2 activation can be connected to an increased activityofmyosinlightchainkinase (79).Becauseelastinpeptidedependent tyrosine phosphorylation of FAK was also abolished in cells preincubated with lactose, pertussis toxin, and nisoldipine, we conclude that its activation comprises a downstream event of the EBP-dependent stimulation of G protein and may require influx of Ca 2ϩ . Because an up-to-date specific inhibitor of FAK has not been described and we did not attempt the FAK knock-out transfection of arterial SMC, we can only guess (Fig.…”

Anthocyanidins inhibit migration of glioblastoma cells: Structure‐activity relationship and involvement of the plasminolytic system

“…Phosphorylation State of ERK-1/2 Induced by S1P and SF/HGF Since ERK-1/2 plays an important role in regulating cell motility [Howe et al, 2002], and recent evidence supports a role for anchoragedependent activation of ERK by growth factors in regulating chemotactic migration [Cho and Klemke, 2000;Hauck et al, 2000], we examined whether Dp could have an effect on the induction of ERK-1/2 phosphorylation by the two most potent stimulators of glioblastoma cell migration, S1P and SF/HGF. Quiescent U-87 cells were incubated in serum-free medium in the presence or absence of Dp for 24 h and cells were then stimulated with 1 mM S1P or 50 ng/ml SF/HGF.…”

Thrombospondin Induces RhoA Inactivation through FAK-dependent Signaling to Stimulate Focal Adhesion Disassembly

“…Constructs encoding for a dominant negative truncated form of FAK, termed FRNK, and an inactive FRNK (FRNK L1034S) deficient in focal adhesion localization were transfected into BAE cells (50,51). In addition, a FAK construct containing a mutated Tyr 397 residue, which can incorporate into focal adhesions but not become activated, was also employed.…”