Mechanisms of membrane trafficking in endocytic and non-endocytic pathways

项目总结/摘要 受体的内化和再循环是所有真核细胞中的关键生物学过程。的 早期/分选内体是从质膜（PM）内化的受体的初始目的地。这 内体作为主要的分选站，受体从该分选站被分流到晚期内体， 溶酶体降解，或通过囊泡和溶酶体的短暂网络再循环回到PM。 管状再循环内体。而十年前，大多数研究人员认为，主动排序 蛋白质的降解途径，靶向回收途径被认为在很大程度上是一个被动的 默认情况下发生的过程。然而，最近的证据支持通过以下方式对回收途径进行主动分类： 特异性分选连接蛋白（SNX）和其他蛋白质，其结合受体的细胞质尾， 把它们作为回收目标。虽然回收是所有哺乳动物细胞的基本过程，但其复杂性 调节是知之甚少，包括内体膜上受体的分选，出芽和 囊泡和小管从内体分裂，以及受体转运回PM。所以我们的 对内体功能的认识大大落后于对受体内化机制的认识。一个关键 一组控制内体分选和运输的调节蛋白是逆转录复合物。 最初在从内体到高尔基复合体的生物合成货物的回收中鉴定，逆转录酶 最近被牵连在调节各种关键的细胞通路内外的 内吞运输的范围包括内吞再循环、线粒体稳态、中心体循环 和纤毛发生。逆转录复合物还与其他关键的内吞调节蛋白相互作用，包括 管状内体支架MICAL-L1;其相互作用伴侣和内体分裂调节剂，EH结构域 含有1（EHD 1）的蛋白质;以及介导内体货物分选的SNX蛋白质的宿主。该retromer还 通过WASH复合物连接到肌动蛋白细胞骨架。我们的实验室一直致力于 了解内吞调节蛋白在内吞途径中的作用机制， 和非内吞运输。我们的主要专长是生物化学和分子细胞生物学， 先进的光学显微镜，但我们认识到需要将体内成分纳入我们的 方法，并与其他小组正在进行合作，以检查整个生物体的这些过程， 包括斑马鱼和蠕虫。在我们的研究中，我们将解决重要的和尚未解决的生物学问题， 这些问题包括：1）内体分裂如何被调节并与分类和回收有关，2）关键是什么？ 内吞蛋白介导初级纤毛的生物发生。

PROJECT SUMMARY/ABSTRACT The internalization and recycling of receptors is a key biological process in all eukaryotic cells. The early/sorting endosome is the initial destination of receptors internalized from the plasma membrane (PM). This endosome serves as a major sorting station from which receptors are shunted to late endosomes and lysosomes for degradation, or are recycled back to the PM through a transitory network of vesicular and tubular recycling endosomes. Whereas a decade ago most researchers thought that active sorting directed proteins to the degradation pathways, targeting to the recycling pathway was thought to be largely a passive process that occurs by default. However, recent evidence supports active sorting to the recycling pathways by specific sorting nexin (SNX) and other proteins that bind to the cytoplasmic tails of receptors and specifically target them for recycling. Although recycling is an essential process for all mammalian cells, its complex regulation is poorly understood including the sorting of receptors on endosomal membranes, the budding and fission of vesicles and tubules from the endosome, and the transport of receptors back to the PM. As such, our knowledge of endosomal function lags substantially behind that of receptor internalization mechanisms. A key group of regulatory proteins that controls sorting and trafficking at the endosome is the retromer complex. Originally identified in the retrieval of biosynthetic cargo from endosomes to the Golgi complex, the retromer has recently been implicated in the regulation of a variety of key cellular pathways both within and beyond the scope of endocytic trafficking including endocytic recycling, mitochondrial homeostasis, the centrosome cycle and ciliogenesis. The retromer complex also interacts with other key endocytic regulatory proteins, including the tubular endosome scaffold MICAL-L1; its interaction partner and endosomal fission modulator, EH domain containing 1 (EHD1); and a host of SNX proteins that mediate endosomal cargo sorting. The retromer also links to the actin cytoskeleton via the WASH complex. Our laboratory has been focusing on an overall understanding of the mechanisms by which endocytic regulatory proteins function both in endocytic pathways and in non-endocytic trafficking. Our primary expertise is in biochemistry and molecular cell biology coupled with advanced light microscopy, but we recognize the need to incorporate in vivo components into our approach and have ongoing collaborations with other groups to examine these processes in whole organisms, including zebrafish and worms. In our studies, we will address significant and as-yet-unresolved biological problems such as: 1) how endosomal fission is regulated and linked to sorting and recycling and 2) how key endocytic proteins mediate the biogenesis of the primary cilium.