Mechanisms of membrane trafficking in endocytic and non-endocytic pathways

项目摘要/摘要 受体的内化和再循环是所有真核细胞的关键生物学过程。提前/分拣 内体是从质膜(PM)内化的受体的初始目的地，并作为一种 主要分拣站，受体从该分流站分流到晚期内切酶体和溶酶体进行降解，或 通过囊泡和管状循环内小体的暂时性网络循环回PM。鉴于A 十年前，大多数研究人员认为，主动分选将蛋白质定向到降解途径，靶向 回收途径在很大程度上被认为是一个默认发生的被动过程。然而，最近 有证据支持通过特定的分类连接素(SNX)和其他蛋白质对循环途径进行主动分类 它结合到受体的细胞质尾巴上，并专门针对它们进行回收。尽管回收是一种 对于所有哺乳动物细胞来说，其调控的复杂性还知之甚少，包括 内体膜上受体的分选，小泡和小管的萌发和分裂 内体和受体的运输回PM因此，我们对内体功能的了解滞后 明显落后于受体内化机制。 控制内体分选和运输的一组关键调控蛋白是逆转录复合体。 最初在从内体到高尔基复合体的生物合成货物的回收过程中发现，逆转录聚体具有 最近参与了范围内外的各种关键细胞通路的调节 包括细胞内循环、线粒体动态平衡、中心体循环和 纤毛发生。该反转录复合体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，其相互作用伙伴和内体分裂调节剂，EPS15同源 结构域蛋白1(EHD1)，以及一系列介导内体货物分拣的Nexin SNX蛋白。 Retrmer还通过WASH复合体连接到肌动蛋白细胞骨架。我们的实验室一直专注于 全面了解内吞调节蛋白在内吞中的作用机制 途径和非内吞的贩运。特别是，我们将处理重大和尚未解决的问题 生物学问题，如：一)如何调节内体分裂并将其与分类和回收相联系；二) 关键的内吞蛋白如何参与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), and serves as a major sorting station from which receptors are shunted to late endosomes and lysosomes for degradation, or 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 largely to be 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, the complexities of its regulation are 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 significantly 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 outside 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, Eps15 Homology Domain protein 1 (EHD1), and a host of sorting nexin SNX proteins that mediate endosomal cargo sorting. 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. In particular, we will address significant and as-yet-unresolved biological problems such as: i) How endosomal fission is regulated and linked to sorting and recycling, and ii) How key endocytic proteins mediate the biogenesis of the primary cilium.