BINDING OF LOW-DENSITY LIPOPROTEINS BY PROTEOGLYCANS SYNTHESIZED BY PROLIFERATING AND QUIESCENT HUMAN ARTERIAL SMOOTH-MUSCLE CELLS

Chondroitin sulfate-rich proteoglycans secreted by arterial intima smo oth muscle cells appear involved in low density lipoprotein entrapment and modification. Hypothetically, such a process may contribute to at herogenesis. We compared composition and size of those proteoglycans s ynthesized by proliferating and resting human arterial smooth muscle c ells for which low density lipoprotein had affinity. Lipoprotein-bindi ng proteoglycans secreted by proliferating cells were larger than thos e of resting cells (M(r) = 1.1 x 10(6) versus 0.8 x 10(6)). This was p rimarily caused by increased M(r) of the chondroitin sulfate chains (6 x 10(4) versus 3.5 x 10(4)). The glycosaminoglycan chains of the prot eoglycans from both cells were made of more than 90% chondroitin 6-sul fate and chondroitin 4-sulfate in a 6:4 ratio. Affinity chromatography indicated that low density lipoprotein had a higher affinity with the proteoglycans synthesized by proliferating cells than those from rest ing cells. Measured with gel mobility shift assay, the apparent affini ty constant of low density lipoproteins for proteoglycans from prolife rating cells was 3-fold higher than that for proteoglycans from restin g cells. This increased affinity appeared related to the higher relati ve proportion of proteoglycans with longer glycosaminoglycan chains se creted by the proliferating cells than those secreted by the resting c ells.