Glucosamine inhibits the synthesis of glycosaminoglycan chains on vascular smooth muscle cell proteoglycans by depletion of ATP

Glucosamine via GlcNAc is a precursor for the synthesis of glycosaminoglycan (GAG) chains on proteoglycans. We previously found that proteoglycans synthesized and secreted by vascular smooth muscle cells (VSMC) in the presence of supplementary glucosamine had GAG of decreased not increased size. We investigated the possibility that the inhibition of GAG chains synthesis on proteoglycans might be related to cellular ATP depletion. Confluent primate VSMCs were exposed to glucosamine, azide, or 2-deoxyglucose (2-DG). Each of these agents depleted cell ATP content by 25-30%. All agents decreased 35S-SO4 incorporation and reduced the size of the proteoglycans, decorin and biglycan as assessed by SDS-PAGE. On withdrawal of the glucosamine, azide or 2-DG ATP levels and proteoglycan synthesis returned towards baseline values. Glucosamine decreased glucose uptake and consumption suggesting that ATP depletion was due preferential phosphorylation of glucosamine over glucose. Thus, glucosamine inhibition of proteoglycan synthesis is due, at least in part, to depletion of cellular ATP content.