Pc. Baciu et Pf. Goetinck, PROTEIN-KINASE-C REGULATES THE RECRUITMENT OF SYNDECAN-4 INTO FOCAL CONTACTS, Molecular biology of the cell, 6(11), 1995, pp. 1503-1513
Cell surface heparan sulfate proteoglycans have been implicated as co-
receptors facilitating cell adhesion and growth factor binding. Recent
studies on the role of a family of transmembrane heparan sulfate prot
eoglycans, syndecans, in cell adhesion has identified one member, synd
ecan-4, to be present within focal contacts. The current study investi
gates the mechanisms regulating the association of syndecan-4 with foc
al contacts based upon its immunolocalization with vinculin in quiesce
nt, serum-stimulated, and 12-O-tetradecanoylphorbol 13-acetate (TPA)-i
nduced cultures. In quiescent cells, syndecan-4 did not localize to fo
cal contacts. However, activation of protein kinase C by TPA or serum
induces the active recruitment of syndecan-4 into focal contacts. This
induction preferentially localizes syndecan-4 to focal contacts behin
d the leading lamella, the subnuclear region, and along the trailing e
dge of migratory cells. Focal contacts in either freshly adhered cells
or in the leading lamellae of migrating cells did not stain for synde
can-4. In addition to the observed subcellular distribution and recrui
tment, syndecan-4 was observed to co-localize with endogenously synthe
sized fibronectin fibrils within focal contacts as well as with fibril
s present in the matrix. These findings suggest that protein kinase C
activation results in syndecan-4 recruitment to focal contacts and its
association with sites of matrix deposition.