Detection and expression of a cDNA clone that encodes a polypeptide containing two inhibitory domains of human calpastatin and its recognition by rheumatoid arthritis sera.

Abstract

RA is the most frequent and most destructive inflammatory arthropathy. Rheumatoid factors, in spite of their lack of disease specificity, are important serological markers for RA and appear important in its immunopathogenesis as well. In search of more disease-specific autoimmune systems, we have screened a human placenta Xgtll cDNA expression library using selected sera from patients with classical erosive RA. We have identified one clone (RA-1) that is recognized by three of five screening sera. The 950-bp insert shows a complete nucleotide sequence homology to the cDNA encoding the two COOH-terminal domains of calpastatin. The deduced open reading frame of the RA-1 cDNA predicts a 284-amino acid protein, with a calculated mol wt of 35.9 kD. Calpastatin is the natural inhibitor of calpains, which are members of the cysteine proteinases recently implicated in joint destruction in rheumatic diseases. The two domains encoded by the RA-1 clone each contain the structural features associated with the inhibitory activity of human calpastatin. By Western blotting, 45.5% or 21/44 RA sera specifically recognized both the fusion and the cleaved recombinant protein. This is in contrast to 4.7% (2/43) in nonrheumatoid sera and 0/10 in normal sera. Anticalpastatin autoantibodies could represent a diseaseassociated marker in chronic erosive arthritis of the rheumatoid type and could hypothetically play a dual pathogenic role, directly via an immune interference and indirectly through an immune complex mechanism. (J. Clin. Invest. 1995Invest. . 95:1891

Cloning of novel soluble gp130 and detection of its neutralizing autoantibodies in rheumatoid arthritis

“…It is well documented that some autoantibodies are pathogenic, modifying or inhibiting the activities of their target molecules in autoimmune and malignant diseases, e.g., autoantibody to β2-glycoprotein-I in antiphospholipid syndrome, autoantibody to thyroid-stimulating hormone receptor in Graves disease, and autoantibody to acetylcholine receptor in myasthenia gravis. In RA, blocking autoantibody to calpastatin was reported to aid calpain activity in destructive joint inflammation (27,28). Autoantibody to follistatin-related protein, which we reported previously (3), is another candidate and under investigation.…”

Identification of novel molecular markers which correlate with HPV-induced tumor progression

“…For example, MN1 (Buijs et al, 1995;, FKHR (Barr, 1997;Galili et al, 1993;Scheidler et al, 1996) and FUS/TLS (Aman et al, 1996;Calvio et al, 1995;Zinszner et al, 1997) are frequently a ected by chromosomal translocations in malignancies. Others, such as Mi-2 (Seelig et al, 1995;Ge et al, 1995), desmoplakin and calpastatin (Despres et al, 1995) are autoantigenic. While others are involved in regulating intracellular calcium concentrations or are themselves regulated by Ca 2+ -ions.…”

“…mediates cell attachment to ECM as receptor for laminins in hemidesmosomes and focal adhesions, activation of intracellular signal transduction (focal adhesion kinase FAK) D18.10 human desmoplakin (DP) major component of intracellular desmosomal plaque, interaction with cytokeratins D47.6+D95.9 human cytokeratin 6 hyperproliferation-speci®c cytokeratin D68.5 human L-plastin (®mbrin) calcium-dependent, cytoskeleton-associated, actin-bundling protein (®mbrin) D85.5 novel, highly homologous to mouse+chicken collagen XII (member of FACIT subgroup of collagen multigene family) (Despres et al, 1995) Di erential display of mRNAs (RT ± PCR)…”

Autoantibodies in Connective Tissue Diseases. Clinical Significance and Analysis of Target Autoantigens.

“…Weas well as Canadian investigators described independently the presence of autoantibodies to calpastatin in patients with systemic rheumatic diseases (80,81). There have been several reports suggesting that calpain may be involved in activating inflammatory processes and pathogenic mechanisms of rheumatic disorders.…”