In addition, it was recently reported that human Hsp60 and anti-Hsp60 antibodies are detectable even in sera of healthy individuals (Pockley et al 1999)

In addition, it was recently reported that human Hsp60 and anti-Hsp60 antibodies are detectable even in sera of healthy individuals (Pockley et al 1999). of the anti-Hsp60 IgG recognized CCT, anti-GroEL (or antimycobacterial Hsp65) IgG contained antibodies specific for GroEL (or mycobacterial Hsp65) in addition to antibodies cross-reactive with CCT and Hsp60. Results from immunoblot analyses, together with weak (15% to 20%) amino acid sequence identities between CCT and LY 2183240 the other Hsp60 family members, suggested that CCT-reactive autoantibodies recognize conformational epitopes that are conserved among CCT and other Hsp60 family members. == INTRODUCTION == Heat shock proteins (Hsps) play essential roles as molecular chaperones and are conserved across a wide evolutionary range from prokaryotes NR4A2 to eukaryotes. Members of the Hsp60 protein family are made up of subunits that have an approximate molecular mass of 60 kDa and assist in the folding of newly synthesized and denatured proteins (Ellis LY 2183240 and van der Vies 1991;Hartl et al 1992). The Hsp60 family (also called the chaperonin family) can be LY 2183240 divided into 2 groups (Kubota et al 1995a). Hsp60 of mitochondria, Hsp65 of mycobacteria (the homologue ofEscherichia coliis GroEL), and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) subunit binding protein of plastid fall into group 1, whereas cytosolic chaperonin containing t-complex polypeptide 1 (CCT, also called TRiC or c-cpn) of eukaryotes and chaperonins of archea are classified into group 2. CCT is a hetero-oligomeric molecular chaperone that assists in folding of cytosolic proteins (Kubota et al 1995a;Lewis et al 1996) and is known to LY 2183240 facilitate the folding of actin, tubulin, and certain other cytosolic proteins in the presence of adenosine triphosphate (ATP) (Tian et al 1995;Frydman and Hartl 1996;Farr et al 1997). Eight subunit species, , , , , , -1 (plus -2 in testis), , and , constitute the mammalian CCT complex and show approximately 30% amino acid sequence identity to each other (Kubota et al 1994,1995b). These subunits are assembled into a hexadecameric complex (Llorca et al 1999) similar to the GroEL tetradecameric complex. The relation between mycobacterial Hsp65 and rheumatic diseases has been the subject of much discussion, and the T-cell response to Hsp65 is thought to be involved in the generation of rheumatic diseases (Holoshitz et al 1986;van Eden et al 1998;Zgel and Kaufmann 1999). In terms of B-cell response, patients with rheumatoid arthritis (RA) showed higher levels of immunoglobulin G (IgG) and IgA against Hsp65 than healthy controls in a number of studies (Tsoulfa et al 1989a,1989b;McLean et al 1990;Winfield and Jarjour 1991a,1991b). In addition, high antibody titers againstE coliGroEL relative to those against mycobacterial Hsp65 have been reported in the sera of patients with RA (Hirata et LY 2183240 al 1997) and healthy adults (Handley et al 1996). Autoantibodies against mitochondrial Hsp60 are thought to be raised as a result of molecular mimicry by mycobacterial Hsp65 (orE coliGroEL), because there is a high amino acid sequence identity (approximately 50% to 60%) (Gupta 1990,1996). Although the T-cell epitopes of Hsp family proteins have been analyzed in detail (van Eden et al 1988;van der Zee et al 1998), the epitopes recognized by antimitochondrial Hsp60 autoantibodies remain obscure. Herein, we report that serum titers of CCT-reactive antibodies are significantly higher in patients with rheumatic autoimmune diseases than in healthy controls. The anti-CCT autoantibodies cross-reacted with mitochondrial Hsp60,E coliGroEL, and mycobacterial Hsp65 despite weak (15% to 20%) amino acid sequence identity between CCT and these group 1 chaperonins. The antibodies appeared to recognize conformational epitope(s) shared by these antigens. We discuss the characteristics of the anti-CCT autoantibodies and their role in rheumatic autoimmune diseases. == MATERIALS AND METHODS == == Sera == Sera were donated from 25 patients with RA (22 women and 3 men; mean SD age, 55.6 12.1 years; mean SD years affected, 6.7 5.0), 25 patients with systemic lupus erythematodes (SLE; 23 women and 2 men; mean SD age, 39.0 12.5 years; mean SD.