INHIBITION OF BASIC FIBROBLAST GROWTH FACTOR-INDUCED GROWTH PROMOTIONBY OVEREXPRESSION OF SYNDECAN-1

The expression of syndecan-1, the prototype member of the cell surface proteoglycan family, follows morphogenetic rather than histological b oundaries during organ formation. As a heparan sulfate-containing cell surface molecule, syndecan-1 can simultaneously bind various componen ts of the extracellular matrix and members of the heparin-binding grow th factors. Indeed, syndecan-1 may act as a co-receptor for basic fibr oblast growth factor (bFGF) (Salmivirta, M., Heino, J., and Jalkanen, M. (1992) J. Biol. Chem. 267, 17606-17610), allowing the growth factor to bind the tyrosine kinase bFGF receptor. We have studied the role o f syndecan-1 in growth factor response by growing 3T3 cells transfecte d with syndecan-1 in the presence of bFGF. The enhanced expression of syndecan-1 caused down-regulation of bFGF-induced cell proliferation a nd, at the same time, enhancement of cell matrix interactions. Thus, t he induced expression of the heparan sulfate co-receptor (syndecan-1) may provide a mechanism to restrict FGF action and modulate cell-matri x interactions to maintain co-ordinated growth of cells during organ f ormation.