Regulation of ADP-ribosylation factor

协调的膜和肌动蛋白重塑是许多细胞功能的组成部分，包括（i）细胞运动，（ii）内吞作用和胞吐作用，以及（iii）有丝分裂，并且是病理过程如肿瘤细胞侵袭和转移的中心。许多控制膜和肌动蛋白重塑之一或两者的信号分子包括磷酸肌醇、Arf家族GTP结合蛋白和Rho家族GTP结合蛋白。本实验室工作的主要目的是阐明调节Arf家族蛋白介导的信号的机制。这项工作已经导致了一个家庭的Arf GTP酶激活蛋白，AZAP，可能整合至少四个信号通路，提供协调的反应，在膜和肌动蛋白必要的复杂的细胞行为的鉴定。AZAP由四个亚家族组成：ASAP 1/2/3，ACAP 1/2/3，AGAP 1/2/3和ARAP 1/2/3。目前正在进行有两个总目标的研究。本实验室的一个重点是研究Arf GAP与Arf相互作用并调节Arf功能的特定分子机制。在这些研究中，我们将确定（i）Arfs和GAP之间的界面;（ii）Arfs和外壳蛋白之间的界面;（iii）导致GTP水解的催化机制;（iv）调节GAP活性的机制;以及（v）Arfs、GAP和Arf效应物（包括外壳蛋白）之间的功能相互作用。迄今为止的研究使我们提出了（i）Arf调节货物分选和膜运输的分子机制的新范式，以及（ii）AZAP家族的Arf GAP的效应子功能。正在进行的研究包括测试这些假设和检查Arf GAP作为通过酪氨酸激酶和磷酸肌醇信号转导的靶点。实验室的第二个重点是检查AZAP家族成员的特定细胞作用部位。这一目标与第一个目标密切相关。使用几种策略，我们已经确定了代表性的Arf GAP的作用部位。我们已经发现了特定的膜运输隔间调节一些Arf GAP。例如，AGAP 1调节AP-3内体。我们还发现，特定的细胞骨架结构受到其他Arf GAP的调控。例如，ASAP 1调节局灶性粘连。目前，我们正在研究的具体机制，维护和调节Arf GAP在特定的网站，并探讨如何膜运输网站可能与细胞骨架网站的假设。我们目前正在测试的最新假设是（i）Arf GAP在Rho家族信号通路中，一些Arf GAP起Rho效应物的作用，以及（ii）Arf GAP是Src的靶点，Src对podosomes及其病理类似物invadopia的形成至关重要。

Coordinated membrane and actin remodeling are integral to a number of cellular functions, including (i) cell movement, (ii) endocytosis and exocytosis, and (iii) mitosis and are central to pathological processes such as tumor cell invasion and metastasis. A number of signaling molecules that control either or both membrane and actin remodeling include phosphoinositides, Arf family GTP-binding proteins and Rho family GTP-binding proteins. The main objective of the work in our laboratory is to elucidate the mechanisms that regulate signals mediated by Arf family proteins. The work has led to the identification of a family of Arf GTPase-activating proteins, the AZAPs, that may integrate at least four signaling pathways, providing coordinated responses in membranes and actin necessary for complex cellular behaviors. The AZAPs are comprised of four subfamilies: ASAP1/2/3, ACAP1/2/3, AGAP1/2/3 and ARAP1/2/3. Studies with two general goals are being conducted. One emphasis of the laboratory is to examine specific molecular mechanisms by which Arf GAPs interact with Arf and regulate Arf function. In these studies, we will determine (i) the interfaces between Arfs and GAPs; (ii) the interfaces between Arfs and coat proteins; (iii) the catalytic mechanism leading to GTP hydrolysis; (iv) mechanisms regulating GAP activity; and (v) functional interactions among Arfs, GAPs and Arf effectors including coat proteins. Studies to date have led us to propose (i) a new paradigm for the molecular mechanism by which Arf regulates cargo sorting and membrane trafficking, and (ii) an effector function for Arf GAPs of the AZAP family. Ongoing studies include testing these hypotheses and examining Arf GAPs as targets of signaling through tyrosine kinases and phosphoinositides. A second emphasis of the laboratory is an examination of the specific cellular sites of action of AZAP family members. This aim is closely related to the first. Using several strategies we have been determining the site of action for representative Arf GAPs. We have found specific membrane trafficking compartments regulated by some Arf GAPs. For instance, AGAP1 regulates AP-3 endosomes. We have also found that specific cytoskeletal structures are regulated by other Arf GAPs. For instance, ASAP1 regulates focal adhesions. We are currently examining the specific mechanisms that maintain and regulate Arf GAPs at specific sites, and exploring hypotheses about how the membrane trafficking sites may be related to the cytoskeletal sites. The most recent hypotheses that we are currently testing are (i) that Arf GAPs are in the Rho family signaling pathway with some Arf GAPs functioning as Rho effectors and (ii) Arf GAPs are targets of Src that are of crucial importance for the formation of podosomes and their pathologic analogs invadopia.