Schmelz M, Way D L, Borgs P, Peitsch W K, Schmidt H, Witte M H, Witte C L, Franke W W, Moll R
Department of Pathology, Martin Luther University Halle-Wittenberg, Magdeburgerstr. 14, D-06097 Halle (Saale), Germany.
Cell Tissue Res. 1998 Oct;294(1):11-25. doi: 10.1007/s004410051152.
Two major types of plaque-bearing adhering junctions are commonly distinguished: the actin microfilament-anchoring adhaerens junctions (AJs) and the desmosomes anchoring intermediate-sized filaments (IFs). Both types of junction usually possess the common plaque protein, plakoglobin, whereas the other plaque proteins and the transmembrane cadherins are mutually exclusive. For example, AJs contain E-, N-, or P-cadherin in combination with alpha- and beta-catenin, vinculin and alpha-actinin, whereas in desmosomes, desmogleins and desmocollins are associated with desmoplakin and one or several of the plakophilins (PP1-3). Here we describe a novel type of adhering junction comprising proteins of both AJs and desmosomes and the tight junction (TJ) plaque protein, ZO-1, in a newly established, liver-derived tumorigenic rat cell line (RMEC-1). By immunofluorescence microscopy, cell-cell contacts are characterized by mostly continuous-appearing lines which are usually resolved by electron microscopy as extended arrays of closely spaced small plaque subunits. These plaque-covered regions are positive for plakoglobin, alpha- and beta-catenin, the arm-repeat protein p120, vinculin, desmoplakin and protein ZO-1. They are positive for E-cadherin in cultures early on in passaging, but tend to turn negative for all known cadherins in densely grown cultures. On immunoblotting SDS-PAGE-separated proteins from dense-grown cell monolayers, "pan-cadherin" antibodies have reacted with a band at approximately 140 kDa, identified as N-cadherin by peptide fingerprinting of the immunoprecipitated protein, which for reasons not yet clear is modified or masked in immunolocalization experiments. The exact histological derivation of RMEC-1 cells is not known. However, the observations of several endothelial markers and the fact that all cells are rich in IFs containing vimentin and/or desmin, while only subpopulations also reveal IFs containing CKs 8 and 18, is suggestive of a mesenchymal, probably endothelial origin. We discuss the molecular relationship of this novel type of extended junction with other types of adhering junctions.
肌动蛋白微丝锚定的黏着连接（AJs）和锚定中间丝（IFs）的桥粒。这两种连接通常都含有共同的斑块蛋白——桥粒斑珠蛋白，而其他斑块蛋白和跨膜钙黏蛋白则相互排斥。例如，AJs含有E -、N -或P -钙黏蛋白，与α -和β -连环蛋白、纽蛋白和α -辅肌动蛋白结合，而在桥粒中，桥粒芯糖蛋白和桥粒胶蛋白与桥粒斑蛋白以及一种或几种桥粒斑菲素蛋白（PP1 - 3）相关联。在此，我们在一种新建立的、源自肝脏的致瘤大鼠细胞系（RMEC - 1）中描述了一种新型黏附连接，它包含AJs和桥粒的蛋白以及紧密连接（TJ）斑块蛋白ZO - 1。通过免疫荧光显微镜观察，细胞间接触的特征是大多呈现连续的线条，通过电子显微镜观察，这些线条通常解析为紧密排列的小斑块亚单位的延伸阵列。这些被斑块覆盖的区域对桥粒斑珠蛋白、α -和β -连环蛋白、臂重复蛋白p120、纽蛋白、桥粒斑蛋白和ZO - 1蛋白呈阳性。在传代早期培养物中它们对E -钙黏蛋白呈阳性，但在密集生长的培养物中对所有已知钙黏蛋白往往变为阴性。在用SDS - PAGE分离密集生长的细胞单层中的蛋白质进行免疫印迹时，“泛钙黏蛋白”抗体与一条约140 kDa的条带发生反应，通过对免疫沉淀蛋白进行肽指纹图谱分析鉴定为N -钙黏蛋白，其在免疫定位实验中因尚不清楚的原因被修饰或掩盖。RMEC - 1细胞的确切组织学来源尚不清楚。然而，对几种内皮标志物的观察以及所有细胞富含含有波形蛋白和/或结蛋白的中间丝，而只有亚群还显示含有细胞角蛋白8和18的中间丝这一事实，提示其起源于间充质，可能是内皮。我们讨论了这种新型延伸连接与其他类型黏附连接的分子关系。
