Analysis of glycosaminoglycan chains from different proteoglycan populations in human embryonic skin fibroblasts

1. The structure of chondroitin/dermatan and heparan‐sulphate chains from various proteoglycan populations derived from cultured human skin fibroblasts have been examined. Confluent cell cultures were biosynthetically labelled with [ 3 H]‐glucosamine and 35 SO 4 2‐ , and proteoglycans were purified according to buoyant density, size and charge density [Schmidtchen, A., Carlstedt, I., Malmström, A. & Fransson, L.‐Å. (1990) Biochem. J. 265 , 289–300]. Some proteoglycan fractions were further fractionated according to hydrophobicity on octyl‐Sepharose in Triton X‐100 gradients. The glycosaminoglycan chains, intact or degraded by chemical or enzymic methods were then analysed by gel chromatography on Sepharose CL‐6B, Bio‐Gel P‐6, ion exchange HPLC and gel electrophoresis. 2. Three types of dermatan‐sulphate chains were identified on the basis of disaccharide composition and chain length. They were derived from the large proteoglycan, two small proteoglycans and a cell‐associated proteoglycan with core proteins of 90 kDa and 45 kDa. Intracellular, free dermatansulphate chains were very similar to those of the small proteoglycans. 3. Heparan‐sulphate chains from different proteoglycans had, in spite of small but distinct differences in size, strikingly similar compositional features. They contained similar amounts of d ‐glucuronate, l ‐iduronate (with or without sulphate) and N ‐sulphate groups. They all displayed heparin‐lyase‐resistant domains with average molecular mass of 10–15 kDa. The heparan‐sulphate chains from proteoglycans with 250‐kDa and 350‐kDa cores were the largest (> 50 kDa), containing an average of four or five domains, in contrast to heparan‐sulphate chains from the small heparan‐sulphate proteoglycans which had average molecular mass of 45 kDa and consisted of three or four such domains. Free, cell‐associated heparan‐sulphate chains were heterogeneous in size (5–45 kDa). 4. These results suggest that the core protein may have important regulatory functions with regard to dermatan‐sulphate synthesis. On the other hand, synthesis of heparan sulphate may be largely controlled by the cell that expresses a particular proteoglycan core protein.