250 INDUCTION OF COLLAGENASE SECRETION IN HUMAN FIBROBLAST CULTURES BY GROWTH PROMOTING FACTORS

Abstract

In human foreskin fibroblast (HF) cultures, two proteins with Mr 60,000 and 55,000 were found to be induced about 3.5−fold by EGF, PDGF and β−TGF. The induced proteins were identified as procollagenases by immunoprecipitation of induced medium with antibodies to purified human fibroblast collagenase. Collagenase enzyme activity in the medium from EGF-treated cultures was also induced at least 3-fold compared to control cultures. Induction of collagenase was dependent upon de novo protein and RNA synthesis and was observed in the medium 10 hours after addition of EGF. Although they interact with separate membrane receptors, these three growth factors induce the secretion of a common protein. As a result, our study suggests that collagenase may be an important mediator of cell mobilization, a process which is essential for mito-genesis.