Carvalho Cátia A, Tame Mihoko A, St Johnston Daniel
The Gurdon Institute and Department of Genetics, University of Cambridge, Tennis Court Rd, Cambridge CB2 1QN, UK.
J Cell Sci. 2025 Jul 1;138(13). doi: 10.1242/jcs.263644. Epub 2025 Jul 10.
Adherens junctions formed by E-cadherin adhesion complexes play central roles in the organisation and apical-basal polarisation of both mammalian and insect epithelia. Here, we investigate the function of the components of the E-cadherin adhesion complex in the Drosophila midgut epithelium, which establishes polarity by a different mechanism from other fly epithelia and has an inverted junctional arrangement in which the adherens junctions lie below the septate junctions. Unlike other epithelial tissues, loss of E-cadherin, Armadillo (β-catenin) or α-catenin has no effect on the polarity or organisation of the adult midgut epithelium. This is not due to redundancy with other cadherins, as enterocytes lacking E-cadherin, N-cadherin and CadN2 still polarise normally. However, E-cadherin (shg) and armadillo mutants have expanded septate junction domains and shorter lateral domains below the septate junctions, indicating that E-cadherin adhesion complexes limit the basal extent of the septate junctions. Thus, Cadherin-mediated adhesion is dispensable for apical-basal polarity and epithelial organisation in the Drosophila midgut, in contrast to all other epithelia that have been studied so far, but it is required to define the size of the septate junctions and cell height.
由E-钙黏蛋白黏附复合体形成的黏着连接在哺乳动物和昆虫上皮组织的组织构建以及顶-基极化过程中发挥着核心作用。在此，我们研究了E-钙黏蛋白黏附复合体的组成成分在果蝇中肠上皮组织中的功能，果蝇中肠上皮组织通过一种与其他果蝇上皮组织不同的机制建立极性，并且具有一种倒置的连接排列方式，即黏着连接位于紧密连接下方。与其他上皮组织不同，E-钙黏蛋白、犰狳蛋白（β-连环蛋白）或α-连环蛋白的缺失对成年中肠上皮组织的极性或组织结构没有影响。这并非是由于与其他钙黏蛋白存在冗余，因为缺乏E-钙黏蛋白、N-钙黏蛋白和CadN2的肠细胞仍能正常极化。然而，E-钙黏蛋白（shg）和犰狳蛋白突变体具有扩大的紧密连接结构域以及紧密连接下方更短的侧向结构域，这表明E-钙黏蛋白黏附复合体限制了紧密连接的基底范围。因此，与迄今为止研究过的所有其他上皮组织不同，钙黏蛋白介导的黏附对于果蝇中肠的顶-基极性和上皮组织构建是可有可无的，但它对于确定紧密连接的大小和细胞高度是必需的。
