Tandem repeats are involved in G1 domain inhibition of versican expressionand secretion and the G3 domain enhances glycosaminoglycan modification and product secretion via the complement-binding protein-like motif

The large aggregating chondroitin sulfate proteoglycans, including aggrecan , versican (PG-M), neurocan, and brevican, are characterized by N-terminal and C-terminal globular (or selectin-like) domains known as the G1 and G3 d omains, respectively, For this study, we generated a series of expression c onstructs containing various combinations of chicken versican/PG-M domains and a leading peptide of link protein in order to examine the roles of the G1 and G3 domains in versican function, In transfection studies, we observe d that the presence of the G1 domain was sufficient to inhibit product secr etion, while the G3 domain enhanced this process, We also demonstrated that the G1 domain inhibited the attachment of glycosaminoglycan chains to the core proteins, while the G3 domain enhanced this process. Further studies r evealed that inhibition of secretion by G1 was mediated by its two tandem r epeats, while G3's promotion of glycosaminoglycan chain attachment was appa rently dependent on G3's complement-binding protein (CBP)-like motif, The m odulatory effects of these two molecular domains may contribute to versican 's biological activities.