Envoplakin and periplakin are the paraneoplastic pemphigus antigens

Paraneoplastic pemphigus (PNP) sera have been reported to immunoprecipitate multiple proteins, including the 250 kDa and 210 kDa proteins believed to correspond to desmoplakins I/II, BP230, and two unidentified proteins of 190 kDa and 170 kDa. We have recently provided evidence that the presence of the 210 kDa and 190 kDa proteins is the most prominent feature of PNP, and have suggested that the major 210 kDa antigen may not correspond to desmoplakin II. Using immunoprecipitation and immunoblotting, we found that some PNP sera identified a doublet protein migrating at 210 kDa, with the larger protein corresponding to desmoplakin II, and the smaller protein corresponding to envoplakin, a recently described precursor of the keratinocyte cornified envelope. In contrast to desmoplakin II, envoplakin was detected by all PNP sera analyzed. Using immunoblotting and immunoprecipitation, we further showed that the 190 kDa PNP antigen is identical to periplakin, another recently identified envelope precursor that can form complexes with envoplakin. Like desmoplakin and BP230, envoplakin and periplakin belong to the plakin family of proteins.