TY - JOUR

T1 - PKCbeta-dependent activation of RhoA by syndecan-4 during focal adhesion formation.

AU - Dovas, Athanassios

AU - Yoneda, Atsuko

AU - Couchman, John R

N1 - Keywords: Animals; Cell Proliferation; Cells, Cultured; Embryo, Mammalian; Focal Adhesions; Gene Expression; Gene Silencing; Isoenzymes; Lysophospholipids; Membrane Glycoproteins; Protein Kinase C-alpha; Protein Kinase C-delta; Protein Kinase C-epsilon; Protein Kinase Inhibitors; Proteoglycans; RNA, Small Interfering; Rats; Stress Fibers; Syndecan-4; rhoA GTP-Binding Protein

PY - 2006

Y1 - 2006

N2 - Syndecan-4 is a ubiquitously expressed transmembrane heparan sulphate proteoglycan acting in concert with integrins in the formation of focal adhesions and stress fibres. Signalling events studied thus far suggest the formation of a ternary complex between syndecan-4, phosphatidylinositol 4,5-bisphosphate and protein kinase C alpha (PKCalpha). Syndecan-4 clustering at the cell surface has also been associated with RhoA-dependent signalling, but the relationship between PKCalpha and RhoA has not been resolved. Here we present evidence that syndecan-4, PKCalpha and RhoA are in a linear pathway necessary for the formation and maintenance of stress fibres in primary rat embryo fibroblasts. Inhibition of PKCalpha activity through the use of specific pharmacological inhibitors, a dominant-negative construct, or siRNA downregulation of protein levels, attenuated focal adhesion formation and the maintenance of stress fibres. However, these effects could be bypassed through independent activation of RhoA with lysophosphatidic acid, but not by clustering of syndecan-4 with ligand. Furthermore, inhibition of PKCalpha could block the increase in the GTP levels of RhoA induced by clustering of syndecan-4 at the cell surface. All these data point to a mechanism whereby syndecan-4 signals to RhoA in a PKCalpha-dependent manner and PKCalpha directly influences RhoA activity.

AB - Syndecan-4 is a ubiquitously expressed transmembrane heparan sulphate proteoglycan acting in concert with integrins in the formation of focal adhesions and stress fibres. Signalling events studied thus far suggest the formation of a ternary complex between syndecan-4, phosphatidylinositol 4,5-bisphosphate and protein kinase C alpha (PKCalpha). Syndecan-4 clustering at the cell surface has also been associated with RhoA-dependent signalling, but the relationship between PKCalpha and RhoA has not been resolved. Here we present evidence that syndecan-4, PKCalpha and RhoA are in a linear pathway necessary for the formation and maintenance of stress fibres in primary rat embryo fibroblasts. Inhibition of PKCalpha activity through the use of specific pharmacological inhibitors, a dominant-negative construct, or siRNA downregulation of protein levels, attenuated focal adhesion formation and the maintenance of stress fibres. However, these effects could be bypassed through independent activation of RhoA with lysophosphatidic acid, but not by clustering of syndecan-4 with ligand. Furthermore, inhibition of PKCalpha could block the increase in the GTP levels of RhoA induced by clustering of syndecan-4 at the cell surface. All these data point to a mechanism whereby syndecan-4 signals to RhoA in a PKCalpha-dependent manner and PKCalpha directly influences RhoA activity.

U2 - 10.1242/jcs.03020

DO - 10.1242/jcs.03020

M3 - Journal article

C2 - 16787950

VL - 119

SP - 2837

EP - 2846

JO - Journal of Cell Science

JF - Journal of Cell Science

SN - 0021-9533

IS - Pt 13

ER -