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A letter to the editor is presented which discusses a study of immunoglobulin G (IgG) anti-BP180 antibodies in patients with paraneoplastic pemphigus (PNP).

Paraneoplastic pemphigus (PNP) shows autoantibodies mainly to plakin and desmosomal cadherin family proteins. We have recently identified alpha-2-macroglobulin-like-1 (A2ML1), a broad range protease inhibitor, as a unique PNP antigen. In this study, we tested a large number of PNP sera by various methods. Forty (69.0%) of 58 PNP sera recognized A2ML1 recombinant protein expressed in COS7 cells by immunofluorescence (IF) and/or immunoprecipitation (IP)/immunoblotting (IB). IP/IB showed higher sensitivity than IF. In addition, 22 (37.9%) PNP sera reacted with A2ML1 by IB of cultured normal human keratinocytes (NHKs) under non-reducing conditions. Statistical analyses using various clinical and immunological data showed that the presence of anti-A2ML1 autoantibodies was associated with early disease onset and absence of ocular lesions. Next, to investigate the pathogenic role of anti-A2ML1 antibody, we performed additional functional studies. Addition of anti-A2ML1 polyclonal antibody to culture media decreased NHK cell adhesion examined by dissociation assay, and increased plasmin activity detected by casein zymography, suggesting that anti-A2ML1 antibody may decrease NHK cell adhesion through plasmin activation by inhibition of A2ML1. This study demonstrates that autoantibodies to A2ML1 are frequently and specifically detected and may have a pathogenic role in PNP. [ABSTRACT FROM AUTHOR]

Abstract: Background: Plectin, a member of the plakin family proteins, is a high molecular weight protein that is ubiquitously expressed. It acts as a cytolinker for the three major components of the cyotoskeleton, namely actin microfilaments, microtubules and intermediate filaments. Objective: The aim of our experiments was to identify new binding sites for intermediate filaments on plectin and to specify these sites. Methods: We introduced truncated forms of plectin into several cell lines and observe interaction between plectin and intermediate filaments. Results: We found that a linker region in the COOH-terminal end of plectin was required for the association of the protein with intermediate filaments. In addition, we also demonstrated that a serine residue at position 4645 of plectin may have a role on binding of plectin to intermediate filaments. Conclusion: A linker region in the COOH-terminal end and serine residue at position 4645 may be important for the binding of plectin to intermediate filaments. [Copyright &y& Elsevier]