Proliferation-dependent changes of proteoglycan metabolism in arterial smooth muscle cells

Cultured arterial smooth muscle cells synthesize and secrete two types of sulfated proteoglycans designated as proteoglycan A and proteoglycan B. Proteoglycan A has been characterized as chondroitin sulfate-rich, whereas proteoglycan B was found to be dermatan sulfate-rich [Schmidt, A. & Buddecke, E. (1985) Eur. J. Biochem. 153, 260-273]. During the logarithmic growth phase, arterial smooth muscle cells incorporated about 3 times more [35S]sulfate into the total proteoglycans secreted into the culture medium than did non-dividing cells. When arterial smooth muscle cells stopped proliferating the ratio of [35S]proteoglycan A/B increased. No differences were detected in the respective molecular and chemical characteristics of purified proteoglycans A and B isolated from both proliferating and non-dividing cells. Regardless of the growth phase proteoglycan A had a molecular mass of about 280 kDa and contained 8-9 chondroitin sulfate-rich side chains. Proteoglycan B had a molecular mass of about 180 kDa and contained 6-7 dermatan sulfate-rich side chains. The [35S]methionine-labelled protein cores of proteoglycan A and B had a molecular mass of about 48 kDa, but were distinguishable by their specific reactions to monospecific antibodies. Proliferating cells endocytosed proteoglycan B at a rate up to 100% higher than that of non-dividing cells. In all growth phases proteoglycan A was endocytosed at a 10-fold lower rate than proteoglycan B.