Cargo sorting during endocytic recycling

细胞内循环对许多细胞事件至关重要，包括重要营养受体的循环， 如转铁蛋白受体和低密度脂蛋白受体，用于重复的几轮配体 摄取，以及整合素从细胞的回缩边缘到前缘的重新分布 调停他们的活动。尽管有这么多记载的重要作用，蛋白质是如何在 细胞内循环是一个关键地调节其功能的过程，但人们对此仍知之甚少。在……里面 初步研究，我们已经确定ACAP1在货物蛋白质的分类中起作用，这是例证 循环内体的结构性和受控循环，其磷酸化提供了一种 解释它如何能够参与这两个进程。此外，我们发现过度表达 ACAP1的表达诱导内吞体包被。因此，在目标1中，我们将为以下各项提供更明确的测试 ACAP1是否通过产生运输载体的重组系统作为外壳蛋白发挥功能 接下来的方法将证明ACAP1单独发挥作用 一种外壳蛋白，或它与其他蛋白质一起作为外壳复合体的一部分发挥作用。在目标2中， 因为受管制传输中的关键关系涉及与传输接口的信令过程 过程中，我们将确定预测直接磷酸化ACAP1K(S)。在目标3中，正如我们所做的 识别的分选信号由ACAP1识别用于成分回收，我们也将识别分选信号(S) 被ACAP1认可为规范回收，使用整合素Betal作为模型系统。这一发现将 从而使我们能够进一步阐明ACAP1是如何同时参与构成和调控的 回收利用。此外，整合素Betal中回收分选信号(S)的识别将使我们能够进行更多的测试 最终确定整合素循环是否在细胞迁移中发挥关键作用，从而证明 更好地理解细胞内循环对于理解其他细胞事件具有重要意义。

Endocytic recycling is critical for many cellular events, including the recycling of important nutrient receptors, such as the transferrin receptor and the low-density lipoprotein receptor, for reiterative rounds of ligand uptake, and also the redistribution of integrins from the retracting edges to the leading edge of cells to mediate their motility. Despite these many documented important roles, how proteins are sorted during endocytic recycling, a process that critically regulates their function, remains poorly understood. In preliminary studies, we have identified ACAP1 to function in the sorting of cargo proteins that exemplify constitutive and regulated recycling at the recycling endosome, with its phosphorylation providing an explanation for how it is able to participate in both processes. Moreover, we have found thatoverexpression of ACAP1 induces the coating of endosomes. Thus, in Aim 1, we will provide a more definitive test for whether ACAP1 functions as a coat protein using a reconstitution system that generates transport carriers from the recycling endosome, followed by approaches which will either prove that ACAP1 alone functions as a coat protein or that it functions in conjunction with other proteins as part of coat complex. In Aim 2, because the critical nexus in regulated transport involves the signaling process interfacing with the transport process, we will identify kinase(s) predicted to directly phosphorylate ACAP1. In Aim 3, as we have identified sorting signals recognized by ACAP1 for constitutive recycling, we will also identify sorting signal(s) recognized by ACAP1 for regulated recycling, using integrin betal as the model system. This finding will then enable us to further elucidate how ACAP1 is able to participate in both constitutive and regulated recycling. Moreover, the identification of recycling sorting signal(s) in integrin betal will allow us to test more definitively whether integrin recycling plays a critical role in cell migration, and thereby demonstrating that a better understanding of endocytic recycling has important implications to understanding other cellular events.