Grove B D, Vogl A W
Department of Anatomy, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
J Cell Sci. 1989 Jun;93 ( Pt 2):309-23. doi: 10.1242/jcs.93.2.309.
In this paper we provide evidence that ectoplasmic specializations are a form of intercellular adhesion junction. Ectoplasmic specializations, found at basal junctions between adjacent Sertoli cells and at sites of adhesion between Sertoli cells and germ cells, consist of actin filament bundles sandwiched between the plasma membrane and a cistern of endoplasmic reticulum. The actin filaments in each bundle are unipolar and are hexagonally packed. The bundles are coupled to the adjacent membranes and to each other. Because ectoplasmic specializations are associated with junctional sites, they may play a role in intercellular adhesion. In this study, we report a procedure for obtaining samples enriched for ectoplasmic specializations and identify polypeptides that may be associated with ectoplasmic specializations. On SDS-polyacrylamide gels, an 83K (K = 10(3) Mr) polypeptide is specific to the ectoplasmic specialization-enriched sample, suggesting that it may be a component of ectoplasmic specializations. Other polypeptides at 38, 53, 56 and 69K also may be associated with ectoplasmic specializations. Immunoblots further indicate that fimbrin and vinculin are present in the ectoplasmic specialization-enriched fraction. In addition, immunofluorescence indicates that vinculin is associated with spermatid-Sertoli cell and Sertoli-Sertoli cell junctions. We suspect that fimbrin, an actin-bundling protein, may be involved in cross-linking the hexagonally packed actin filaments in ectoplasmic specializations while vinculin may be associated with actin-membrane linkages. If so, ectoplasmic specializations may be a new class of actin-associated junctional site. Moreover, the presence of vinculin in testicular fractions enriched for ectoplasmic specializations and at junctional sites supports the view that these structures may play a role in intercellular adhesion, possibly by stabilizing an adhesive membrane domain.
在本文中，我们提供证据表明，外质特化是一种细胞间黏附连接形式。外质特化存在于相邻支持细胞之间的基底连接处以及支持细胞与生殖细胞的黏附部位，由夹在质膜和内质网池之间的肌动蛋白丝束组成。每个丝束中的肌动蛋白丝是单极的，呈六边形排列。这些丝束与相邻的膜以及彼此相连。由于外质特化与连接部位相关，它们可能在细胞间黏附中发挥作用。在本研究中，我们报告了一种获取富含外质特化样本的方法，并鉴定了可能与外质特化相关的多肽。在SDS-聚丙烯酰胺凝胶上，一种83K（K = 10³ Mr）多肽是富含外质特化样本所特有的，这表明它可能是外质特化的一个组成部分。其他38K、53K、56K和69K的多肽也可能与外质特化相关。免疫印迹进一步表明，丝束蛋白和纽蛋白存在于富含外质特化的组分中。此外，免疫荧光表明纽蛋白与精子细胞-支持细胞和支持细胞-支持细胞连接处相关。我们推测，作为一种肌动蛋白束蛋白，丝束蛋白可能参与在外质特化中交联六边形排列的肌动蛋白丝，而纽蛋白可能与肌动蛋白-膜连接相关。如果是这样，外质特化可能是一类新的与肌动蛋白相关的连接部位。此外，在富含外质特化的睾丸组分中以及连接部位存在纽蛋白，支持了这些结构可能在细胞间黏附中发挥作用的观点，可能是通过稳定黏附膜结构域来实现的。
