Regulation of ADP-ribosylation factor

协调的膜和肌动蛋白重塑是许多细胞功能所必需的，包括(I)细胞运动，(Ii)内吞和胞吐，以及(Iii)有丝分裂。许多控制膜和肌动蛋白重塑的信号分子包括磷脂酰肌醇、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Arf家族蛋白调节信号的机制。这项工作导致了一个Arf GTPase激活蛋白家族的鉴定，AZAPs可能整合了至少四条信号通路，在膜和肌动蛋白中提供复杂细胞行为所需的协调反应。AZAP由ASAP1/2/3、ACAP1/2/3、AGAP1/2/3和ARAP1/2/3四个亚家族组成。 该实验室的重点之一是研究Arf间隙与Arf相互作用并影响Arf活性的特定分子机制。在这些研究中，我们将确定(1)ARF和GAP之间的界面；(2)ARF和外壳蛋白之间的界面；(3)导致GTP水解的催化机制；(4)调节GAP活性的机制；以及(5)ARF、GAP和包括外壳蛋白在内的ArF效应器之间的功能相互作用。到目前为止的研究已经引导我们提出了(I)Arf调节货物分拣和膜运输的分子机制的新范式，以及(Ii)AZAP家族Arf间隙的效应函数。正在进行的研究包括验证这些假说，并检查Arf间隙作为酪氨酸激酶和磷酸肌醇信号转导的靶标。 该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，我们一直在确定有代表性的ARF差距的行动地点。我们已经发现了受一些Arf间隙调控的特定的膜转运间隔。例如，AGAP1调节AP-3内含体。我们还发现，特定的细胞骨架结构受其他Arf间隙的调节。例如，ASAP1调节局部粘连。我们目前正在研究在特定部位维持和调节Arf间隙的具体机制，并探索膜转运部位如何与细胞骨架部位相关的假说，包括Arf间隙具有间隙独立功能的可能性。

Coordinated membrane and actin remodeling are integral to a number of cellular functions, including (i) cell movement, (ii) endocytosis and exocytosis, and (iii) mitosis. 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 impact Arf activities. 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, including the possibility that the Arf GAPs have GAP-independent functions.