Genetic ablation of zyxin causes Mena/VASP mislocalization, increased motility, and deficits in actin remodeling

Abstract

Focal adhesions are specialized regions of the cell surface where integrin receptors and associated proteins link the extracellular matrix to the actin cytoskeleton. To define the cellular role of the focal adhesion protein zyxin, we characterized the phenotype of fibroblasts in which the zyxin gene was deleted by homologous recombination. Zyxin-null fibroblasts display enhanced integrin-dependent adhesion and are more migratory than wild-type fibroblasts, displaying reduced dependence on extracellular matrix cues. We identified differences in the profiles of 75- and 80-kD tyrosine-phosphorylated proteins in the zyxin-null cells. Tandem array mass spectrometry identified both modified proteins as isoforms of the actomyosin regulator caldesmon, a protein known to influence contractility, stress fiber formation, and motility. Zyxin-null fibroblasts also show deficits in actin stress fiber remodeling and exhibit changes in the molecular composition of focal adhesions, most notably by severely reduced accumulation of Ena/VASP proteins. We postulate that zyxin cooperates with Ena/VASP proteins and caldesmon to influence integrin-dependent cell motility and actin stress fiber remodeling.

Overexpression of LASP-1 mediates migration and proliferation of human ovarian cancer cells and influences zyxin localisation

“…This is in agreement with previous findings using a nongenetic approach and injecting a peptide derived from the N-terminus of zyxin to displace zyxin from its normal subcellular location thus leading to reduced cell migration (Drees et al, 1999). On the other hand, the knock-down of zyxin in SKOV-3 cells had no influence on cell migration while genetically zyxin-deficient fibroblasts display enhanced migration (Hoffman et al, 2006). These contrary effects have not been fully elucidated yet.…”

“…This is concordant with the fact that genetically zyxin-deficient fibroblasts show even enhanced adhesion to surface and increased integrin expression (Hoffman et al, 2006). In synopsis, our LASP-1 and zyxin silencing studies have demonstrated that LASP-1 is necessary for recruiting zyxin to focal contacts.…”

“…Recent data show that in genetically zyxin-deficient fibroblasts, focal adhesions are depleted from Mena and VASP, and that cells lacking zyxin display deficits in actin cytoskeleton remodelling (Hoffman et al, 2006). In our immunflourescence experiments with LASP-1-deficient SKOV-3 cells, we observed a diffuse cytoplasmic localiation of zyxin without protein loss and without changes in neither vinculin distribution nor actin stress fibre organisation, emphasising the importance of LASP-1 for binding and recruiting zyxin to focal adhesions.…”

Identification ofPFTAIREprotein kinase 1, a novel cell division cycle-2 related gene, in the motile phenotype of hepatocellular carcinoma cells

“…The actin stress fiber formation is considered a characteristic feature for cell migration through the cytoskeletal architecture remodeling. 36,37 Our finding may thus suggest that PFTK1 translated protein, hPFTAIRE1, confers cellular motility on HCC cells via the modulation of filamentous actin dynamics. The effect of PFTK1 on WEE1, an inhibitory protein on the Cdc2/cyclin complex formation, was also investigated.…”

Retrograde Fluxes of Focal Adhesion Proteins in Response to Cell Migration and Mechanical Signals

“…An alternative function of the focal adhesion flux is to facilitate the transport of signals from focal adhesions in response to mechanical cues, as suggested by impaired responses of zyxin Ϫ/Ϫ cells to ECM anchorage and mechanical stimulations (Yoshigi et al, 2005;Hoffman et al, 2006). Although focal adhesions have been recognized as an important source of signals with multiple downstream effects such as activation of the mitogen-activated protein kinase pathway and eventually gene expression (Giancotti and Ruoslahti, 1999), how these signals propagate is unclear.…”