ISOLATION AND CHARACTERIZATION OF A RHEUMATOID ARTHRITIS-SPECIFIC ANTIGEN (RA-A47) FROM A HUMAN CHONDROCYTIC CELL-LINE (HCS-2 8)/

Two types of 47 kDa antigen specifically recognized by sera from rheum atoid arthritis (RA) patients were isolated from the membrane fraction of a human chondrosarcoma-derived chondrocytic cell line (HCS-2/8) by a 2-step procedure: preparative SDS-PAGE and reverse-phase HPLC. An N -terminal amino acid sequence in one of the 47 kDa antigens, named RA- A47, had 81% homology to that deduced from the DNA sequence of the col ligin gene which is reported as human hsp47 gene, and 100% homology to that deduced from the DNA sequence of colligin-2 gene, a homologue of colligin. The RA-A47 cross-reacted with a monoclonal antibody raised against chick heat shock protein (Hsp) 47 and bound to gelatin. The ex pression of the ra-a47 gene was enhanced by heat shock treatment and T GF-beta stimulation. These findings suggest that RA-A47 is a Hsp47-lik e protein, presumably the product of the colligin-2 gene, and that a c ollagen-specific molecular chaperone(s) such as Hsp47 and/or RA-A47 is involved in cartilage destruction in RA. (C) 1998 Academic Press.