Loyer Nicolas, Kolotuev Irina, Pinot Mathieu, Le Borgne Roland
CNRS, UMR 6290, F-35000 Rennes, France; Institut de Génétique et Développement de Rennes, Université Rennes 1, F-35000 Rennes, France; Equipe Labellisée Ligue Nationale Contre le Cancer, F-35000 Rennes, France;
CNRS, UMR 6290, F-35000 Rennes, France; Institut de Génétique et Développement de Rennes, Université Rennes 1, F-35000 Rennes, France; Equipe Labellisée Ligue Nationale Contre le Cancer, F-35000 Rennes, France; CNRS, Structure Fédérative de Recherche BIOSIT, Microscopy Rennes Imaging Center-Electron Microscopy Facility, F-35000 Rennes, France.
Proc Natl Acad Sci U S A. 2015 Oct 13;112(41):12717-22. doi: 10.1073/pnas.1504455112. Epub 2015 Sep 30.
Intercellular bridges called "ring canals" (RCs) resulting from incomplete cytokinesis play an essential role in intercellular communication in somatic and germinal tissues. During Drosophila oogenesis, RCs connect the maturing oocyte to nurse cells supporting its growth. Despite numerous genetic screens aimed at identifying genes involved in RC biogenesis and maturation, how RCs anchor to the plasma membrane (PM) throughout development remains unexplained. In this study, we report that the clathrin adaptor protein 1 (AP-1) complex, although dispensable for the biogenesis of RCs, is required for the maintenance of the anchorage of RCs to the PM to withstand the increased membrane tension associated with the exponential tissue growth at the onset of vitellogenesis. Here we unravel the mechanisms by which AP-1 enables the maintenance of RCs' anchoring to the PM during size expansion. We show that AP-1 regulates the localization of the intercellular adhesion molecule E-cadherin and that loss of AP-1 causes the disappearance of the E-cadherin-containing adhesive clusters surrounding the RCs. E-cadherin itself is shown to be required for the maintenance of the RCs' anchorage, a function previously unrecognized because of functional compensation by N-cadherin. Scanning block-face EM combined with transmission EM analyses reveals the presence of interdigitated, actin- and Moesin-positive, microvilli-like structures wrapping the RCs. Thus, by modulating E-cadherin trafficking, we show that the sustained E-cadherin-dependent adhesion organizes the microvilli meshwork and ensures the proper attachment of RCs to the PM, thereby counteracting the increasing membrane tension induced by exponential tissue growth.
由不完全胞质分裂产生的称为“环管”（RCs）的细胞间桥在体细胞和生殖组织的细胞间通讯中起着至关重要的作用。在果蝇卵子发生过程中，环管将成熟的卵母细胞与支持其生长的滋养细胞连接起来。尽管进行了大量旨在鉴定参与环管生物发生和成熟的基因的遗传筛选，但环管在整个发育过程中如何锚定到质膜（PM）上仍未得到解释。在这项研究中，我们报告网格蛋白衔接蛋白1（AP - 1）复合物虽然对于环管的生物发生是可有可无的，但对于维持环管与质膜的锚定以承受卵黄发生开始时与指数级组织生长相关的增加的膜张力是必需的。在这里，我们揭示了AP - 1在大小扩张期间使环管维持与质膜锚定的机制。我们表明AP - 1调节细胞间粘附分子E - 钙粘蛋白的定位，并且AP - 1的缺失导致环管周围含E - 钙粘蛋白的粘附簇消失。E - 钙粘蛋白本身被证明是维持环管锚定所必需的，由于N - 钙粘蛋白的功能补偿，这一功能以前未被认识到。扫描块面电子显微镜与透射电子显微镜分析相结合揭示了包裹环管的相互交错的、肌动蛋白和膜突蛋白阳性的微绒毛样结构的存在。因此，通过调节E - 钙粘蛋白的运输，我们表明持续的E - 钙粘蛋白依赖性粘附组织了微绒毛网络，并确保环管与质膜的正确附着从而抵消由指数级组织生长引起的增加的膜张力。
