STIMULATION OF HEPARAN-SULFATE PROTEOGLYCAN SYNTHESIS AND SECRETION DURING G(1) PHASE INDUCED BY GROWTH-FACTORS AND PMA

Fetal calf serum (FCS) and PMA(phorbol 12-myristate-13-acetate) specif ically stimulate the synthesis of heparan sulfate proteoglycan in endo thelial cells. Staurosporine and n-butanol, kinase inhibitors, abolish the PMA effect. Forskolin and 8-bromo adenosine 3':5'-cyclic monophos phate, activators of, respectively, adenylate cyclase and protein kina se A cannot reproduce the PMA effect. The kinetics of cell entry into S phase of the endothelial cells was determined by DNA synthesis ([H-3 ]thymidine and Br-dU incorporation), and flow cytometry. The mitogenic effect of fetal calf serum is abolished by PMA. Also, PMA pre-treatme nt inhibits the enhanced synthesis of heparan sulfate proteoglycan aft er a second PMA exposure. Remarkably, the stimulation of heparan sulfa te proteoglycan synthesis by fetal calf serum and PMA seems to be main ly restricted to G(1) phase. Therefore fetal calf serum and PMA cause an enhanced synthesis of heparan sulfate proteoglycan, and PMA causes a cell cycle block at G(1) phase. J. Cell. Biochem. 70:563-572, 1998. (C) 1998 Wiley-Liss, Inc.