Hopkinson S B, Baker S E, Jones J C
Northwestern University Medical School, Chicago, Illinois 60611, USA.
J Cell Biol. 1995 Jul;130(1):117-25. doi: 10.1083/jcb.130.1.117.
The 180-kD bullous pemphigoid autoantigen (BP180) is a component of the hemidesmosome, a cell-matrix connector. This protein is oriented in a type II fashion in the membrane of the hemidesmosome and is a hybrid collagen (classified as type XVII). We have analyzed the fate of various mutant BP180 molecules transfected into several different cell types. A protein, D1, lacking the collagen-like extracellular domains of BP180 polarizes normally in 804G epithelial cells and colocalizes with other hemidesmosomal components in the plane of the basal cell surface. However, deletion of a stretch of 36 amino acids located at the NH2 terminus of D1 induces an apical polarization of the protein (D1-36N) in the cell surface of 804G cells. Deletion of the 27-amino acid noncollagenous extracellular domain that is located immediately after the membrane spanning domain of BP180 results in a failure of D1-27C protein to codistribute with other hemidesmosomal components despite its basal localization in transfected 804G cells. In FG cells, which lack their own BP180, transfected D1 protein localizes with the alpha 6 beta 4 integrin heterodimer. In HT1080 cells, which do not possess BP180 or beta 4 integrin, D1 protein localizes with alpha 6 beta 1 integrin while both the D1-27C and D1-36N proteins do not. Moreover, D1 protein coprecipitates with alpha 6 integrin from extracts of HT1080 transfectants. Taken together, these results suggest that the NH2-terminal domain of BP180 determines polarization of BP180 while the noncollagenous extracellular domain of BP180 stabilizes its interactions with other hemidesmosomal components, such as alpha 6 integrin. Perturbation of this latter domain by human bullous pemphigoid autoantibodies may explain the loss of epidermal cell-dermis attachment that characterizes the BP disease.
180-kD大疱性类天疱疮自身抗原（BP180）是半桥粒的一个组成部分，半桥粒是一种细胞与基质的连接结构。该蛋白在半桥粒膜中呈II型定向，是一种杂合胶原蛋白（归类为XVII型）。我们分析了转染到几种不同细胞类型中的各种突变BP180分子的命运。一种缺失BP180胶原样细胞外结构域的蛋白D1，在804G上皮细胞中正常极化，并与基底细胞表面平面内的其他半桥粒成分共定位。然而，删除位于D1 NH2末端的一段36个氨基酸会导致该蛋白（D1-36N）在804G细胞表面发生顶端极化。删除紧接在BP180跨膜结构域之后的27个氨基酸的非胶原细胞外结构域，导致D1-27C蛋白尽管在转染的804G细胞中位于基底，但无法与其他半桥粒成分共分布。在缺乏自身BP180的FG细胞中，转染的D1蛋白与α6β4整合素异二聚体共定位。在不具有BP180或β4整合素的HT1080细胞中，D1蛋白与α6β1整合素共定位，而D1-27C和D1-36N蛋白则不然。此外，D1蛋白可从HT1080转染细胞的提取物中与α6整合素共沉淀。综上所述，这些结果表明BP180的NH2末端结构域决定了BP180的极化，而BP180的非胶原细胞外结构域稳定了其与其他半桥粒成分（如α6整合素）的相互作用。人源性大疱性类天疱疮自身抗体对后一结构域的干扰可能解释了BP疾病所特有的表皮细胞与真皮附着丧失的现象。
