Objective: Ղig-h3 is an extracellular matrix protein, which is overexpressed in synovial tissues of rheumatoid arthritis (RA) similar to adhesive glycoproteins. We sought to evaluate the compensatory role of Ղig-h3 with adhesive glycoproteins in mediating the adhesion of fibroblast- like synoviocytes (FLS) and to confirm the inhibitory effect of YH18 peptide of the 2nd fas-1 domain in Ղig-h3-mediated adhesion. Methods: The adhesion of FLS isolated from synovial tissues of RA, was evaluated in 96 well microtiter plate coated with matrix proteins. Inhibitory effect of YH18 peptides from the 2nd and 4th fas-1 domains was estimated in Ղig-h3-mediated adhesion of FLS. Results: The adhesion of FLS on Ղig-h3 was weaker than that of fibronectin and vitronectin. The Ղig-h3-mediated adhesion was enhanced by the stimulation with phorbol myristate acetate (PMA), but not by cytokines and growth factors. Combination of fibronectin with Ղig-h3 synergistically enhanced the adhesion of FLS, in contrast to the additive effect of vitronectin combined with Ղig-h3. YH18 peptide of the 2nd fas-1 domain did not block the Ղig-h3-mediated adhesion of FLS. Conclusion: Our results reveal that Ղig-h3 may regulate the adhesion of FLS through the interaction with adhesive glycoproteins and confirm that the essential motifs mediating adhesion on Ղig-h3 are different according to the type of cells.

Keywords: Ղ,ig-h3, Fas-1 domain, YH motif, Fibroblast-like synoviocyte, Rheumatoid arthritis