Platelet-derived growth factor stimulated mechanisms of glucosamine incorporation

Platelet-derived growth factor (PDGF) treatment of density-arrested BALB/c-3T3 cells results in increased [3H]glucosamine (GlcN) incorporation into cellular material. The enhanced GlcN incorporation is not due to a preferential increase in proteoglycan synthesis as measured by [35S]H2SO4 incorporation. Approximately 50% of the GlcN incorporated in PDGF or platelet-poor plasma (PPP)-treated cultures enters N-linked glycoproteins. Addition of dolichol-phosphate (dolichol-P), a required intermediate in N-linked glycosylation, did not alter [3H]GlcN incorporation in PDGF-treated cells but did increase incorporation in PPP-treated cultures to a level comparable to that observed for PDGF-treated cultures. PDGF-treated cultures contained twofold greater quantities of [3H]GlcN dolichol intermediates and lipid-free glycoprotein. Over a 12-h time course 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA reductase) activity was similar in cultures treated with PDGF or PPP. Results of these studies reveal that enhanced protein glycosylation in response to PDGF treatment is not the result of a direct effect on HMG CoA reductase.