Hopkinson S B, Jones J C
Northwestern University Medical School, Chicago, IL 60611.
Biochem J. 1994 Jun 15;300 ( Pt 3)(Pt 3):851-7. doi: 10.1042/bj3000851.
A 230 kDa polypeptide component of the hemidesmosome, an epithelial-cell-connective-tissue attachment device, is thought to be involved in cytoskeleton-cell-surface anchorage. This 230 kDa polypeptide is recognized by bullous pemphigoid auto-antibodies and for this reason is generally termed the bullous pemphigoid antigen (BPA). We have identified two distinct mRNA products of the single BPA gene by RACE (rapid amplification of cDNA ends)/PCR techniques. The first of these mRNAs encodes the 230 kDa protein component of the hemidesmosome. A second mRNA lacks over 1800 bases that encode the C-terminus of the 230 kDa protein. We have raised antibodies against a peptide specific to the predicted protein product of this second mRNA. To our surprise this antibody recognizes a protein that migrates at 280 kDa on SDS/PAGE of extracts of a variety of human epidermal cell lines that also express the 230 kDa BPA. Moreover, we have confirmed the co-expression of the 230 and 280 kDa polypeptides in these cells by immunoblotting analyses using a monoclonal antibody preparation directed against a polypeptide encoded by sequence common to both mRNAs transcribed from the BPA gene. Intriguingly, in one non-epidermal tumour line (a pancreatic cell line termed FG), the 280 kDa polypeptide appears to be the only product of the BPA gene. Furthermore, in FG cells the 280 kDa protein is found in association with the intermediate filament cytoskeleton. We discuss our results in relation to control of BPA gene expression and with regard to potential functions of the domains of the protein products of the BPA gene.
半桥粒是上皮细胞与结缔组织的附着装置，其一种230 kDa的多肽成分被认为参与细胞骨架与细胞表面的锚定。这种230 kDa的多肽可被大疱性类天疱疮自身抗体识别，因此通常被称为大疱性类天疱疮抗原（BPA）。我们通过RACE（cDNA末端快速扩增）/PCR技术鉴定出了单一BPA基因的两种不同mRNA产物。其中第一种mRNA编码半桥粒的230 kDa蛋白质成分。第二种mRNA缺失了超过1800个编码230 kDa蛋白质C末端的碱基。我们制备了针对这种第二种mRNA预测蛋白产物特异性肽段的抗体。令我们惊讶的是，这种抗体识别出一种在多种也表达230 kDa BPA的人表皮细胞系提取物的SDS/PAGE上迁移率为280 kDa的蛋白质。此外，我们通过使用针对由BPA基因转录的两种mRNA共同序列编码的多肽的单克隆抗体制备进行免疫印迹分析，证实了这些细胞中230 kDa和280 kDa多肽的共表达。有趣的是，在一种非表皮肿瘤细胞系（一种称为FG的胰腺细胞系）中，280 kDa多肽似乎是BPA基因的唯一产物。此外，在FG细胞中，280 kDa蛋白质与中间丝细胞骨架相关。我们结合BPA基因表达的调控以及BPA基因蛋白产物结构域的潜在功能来讨论我们的结果。
