Molecular Structure of a New Member of the Plectin Family and Gene Expression

我们最近描述了一例在临床和病理上与大疱性类天疱疮相似的表皮下水泡病患者。免疫印迹分析显示，患者的血清不与230或180 kDa的大疱性类天疱疮抗原反应，但仅识别450 kDa的表皮多肽。为了阐明该抗原的分子结构，我们现在克隆并鉴定了编码该抗原一部分的cDNA。我们用最初由患者血清检测到的免疫反应克隆的探针，在筛选人角质形成细胞和HeLa细胞的cDNA文库时，鉴定了编码plectin和plectin样分子的cDNAs。表位定位结果表明，450 kDa的表皮自身抗原为凝集素样分子(序列G-F)。该分子命名为plectin 2。它有一个羧基末端结构域，包含三个高度同源的534个氨基酸重复序列，这与人和大鼠plectin不同。在桥粒蛋白中发现了类似的结构。在这一部分中，存在着另一种拼接变体。它也与人类大疱性类天疱疮抗原1几乎没有同源性。这些结构差异可能对生物学功能有重要影响。在检测到的许多潜在位点中的一个或多个位置上，类凝集素分子的磷酸化可能在调节蛋白质与细胞骨架或半染色体元件的相互作用中发挥重要作用。

We recently described an individual with subepidermal blistering disease that resembled bullous pemphigoid both clinically and pathologically. Immunoblot analysis revealed that the patient's serum did not react with the 230-or 180-kDa bullous pemphigoid antigens, but recognized exclusively a 450-kDa epidermal polypeptide. To elucidate the molecular structure of this antigen, we have now cloned and characterized the cDNAs encoding a portion of this antigen. We have identified cDNAs encoding plectin and a plectin-like molecule on screening human keratinocyte and HeLa cell cDNA libraries with a probe derived from the immunoreactive clone originally detected by the patient's serum. Epitope mapping showed that the 450-kDa epidermal autoantigen was found to be the plectin-like molecule (sequence G-F). This molecule was named plectin 2. It has a carboxyl terminal domain that contains three highly homologous repeats of 534 amino acids, which differ from human or rat plectin. Similar structure is found in desmoplakin. In this part, another splicig variant existed. It also shows little homology to human bullous pemphigoid antigen 1. These structural difference may have important consequences for biological function. Phosphorylation of the plectin-like molecule at one or more of the many potential sites detected might play an important role in modulating interaction of the protein with cytoskeletal or hemidesmosomal elements.