Characterization and binding activity of the chondroitin / dermatan sulphate chain from Endocan, a soluble endothelial Proteoglycan.

International audienceEndocan is a recently identified soluble chondroitin/dermatan sulphate (CS/DS) proteoglycan. Synthesized by endothelial cells, it has been found to be over-expressed in the vasculature surrounding a number of tumours, and by promoting growth factor mitogenic activities, HGF/SF in particular, it supports cellular proliferation. In this work we characterized the GAG chain of Endocan, purified either from the naturally-producing human umbilical vein endothelial cells, or from a recombinant over-expression system in Human Embryonic Kidney cells. Compositional analysis using different chondroitinases as well as NMR studies revealed that the GAG chains from both sources share many characteristics, with the exception of size length (15 and 40 kDa, respectively, for HUVEC or HEK-293 cells). The DS-specific, IdoA-containing disaccharides contribute 30 % of the chain (15 % of which are 2-O-sulphated) and are mostly clustered in tetra (35%)-, hexa (12%)- and octa (5%)- saccharide domains. Highly sulphated big up tri, openD, big up tri, openE and big up tri, openB disaccharide units ( big up tri, openHexA2S-GalNAc6S, big up tri, openHexA-GalNAc4S6S and big up tri, openHexA2S-GalNAc4S) were also detected in significant amounts in both chains and may account for the HGF/SF-binding activity of the CS/DS. This work establishes that HEK-293 cells can be engineered to provide a valuable source of Endocan with authentic CS/DS chains, enabling the purification of sufficient amounts for structural and/or binding analysis, and providing a possible model of Endocan CS/DS chain organisation