BAR proteins linking membrane and cytoskeleton dynamics

项目摘要 肌动蛋白细胞骨架动力学和膜动力学通常是相互关联和紧密调控的。酒吧 含有结构域的蛋白质正在成为信号传导、细胞骨架和 膜。BAR结构域是一个二聚化的膜曲率传感/诱导模块， 在与其他结构域相关的模块蛋白中，包括肌动蛋白细胞骨架调节，自抑制， 和信令模块。 虽然BAR结构域蛋白的研究最近有所加强，但严重缺乏的是全面的 它们的膜结合，细胞因子调节， 和信号活动，这是本提案的目标。最初，重点将放在三种蛋白质上：PICK 1， IRSp 53和PInB。PICK 1已成为神经元细胞中AMPA受体运输的关键调节因子， 与突触可塑性、学习和记忆有关的过程。IRSp 53富含突触， 与神经棘和细胞突起如板状伪足和丝状伪足的形成有关。 PInB从未被表征过，但这里提出的初步研究表明，它可以稳定 上皮细胞刷状缘膜。IRSp 53和PInB共享中等序列同一性（24%），并且 将平行研究，因为预计这两种蛋白质具有相似的功能， 机制和有约束力的伙伴。 目的1将测试从初步研究中出现的假设，即PICK 1作为支架连接 膜囊泡和肌球蛋白马达用于神经元中的受体运输。另一个假设是， 将要测试的初步研究是PICK 1在静息状态下是内部自抑制的， 通过其各个结构域与受体尾、膜和肌球蛋白的协调相互作用而激活 电动机. 目的2将检验PInB代表一种全新类型的BAR结构域蛋白的假设， 参与上皮细胞中平面膜结构的形成。自我抑制的机制 并研究Rho家族GTP酶对IRSp 53和PInB的激活作用。SH 3的结合伴侣 将在细胞中鉴定PInB的结构域，并表征它们的相互作用。 大量的初步结果为这些研究奠定了基础。几乎所有的蛋白质结构都有 被表达和描述。全长PICK 1与结合的Ca 2+和GluR 2 AMPA一起结晶 受体尾PInB的BAR结构域的结构已接近完成。细胞研究合作， PICK 1和PInB已经产生了重要的结果，更重要的是， 细胞和结构/生物物理研究开始产生新的假设。

Project Summary Actin cytoskeleton dynamics and membrane dynamics are often interconnected and tightly regulated. BAR domain-containing proteins are emerging as a critical linkage between signaling, the cytoskeleton and membranes. The BAR domain is a dimerization, membrane-curvature sensing/inducing module that occurs in modular proteins in association with other domains, including actin cytoskeleton regulatory, auto-inhibitory, and signaling modules. While the study of BAR domain proteins has recently intensified, what is critically lacking is a comprehensive structure-function understanding of the interplay between their membrane-binding, cytoskeleton-regulatory and signaling activities, which is the goal of this proposal. Initially, the focus will be on three proteins: PICK1, IRSp53 and PInB. PICK1 has emerged as a key regulator of AMPA receptor trafficking in neuronal cells, a process linked to synaptic plasticity, learning, and memory. IRSp53 is enriched in synapses, and is implicated in the formation of neuronal spines and cellular protrusions such as lamellipodia and filopodia. PInB had never been characterized, but preliminary studies presented here suggest that it stabilizes the brush border membrane of epithelial cells. IRSp53 and PInB share moderate sequence identity (24%), and will be studied in parallel, because it is anticipated that these two proteins share similar functional mechanisms and binding partners. Aim 1 will test the hypothesis, emerging from preliminary studies, that PICK1 functions as a scaffold linking membrane vesicles and myosin motors for receptor trafficking in neurons. Another hypothesis suggested by the pilot studies that will be tested is that PICK1 is internally auto-inhibited in the resting state, and becomes activated by coordinated interactions of its various domains with receptor tails, membranes and myosin motors. Aim 2 will test the hypothesis that PInB represents a fundamentally new type of BAR domain protein, involved in the formation of planar membrane structures in epithelial cells. The mechanisms of auto-inhibition and activation by Rho-family GTPases of IRSp53 and PInB will be investigated. Binding partners of the SH3 domain of PInB will be identified in cells, and their interactions will be characterized. Extensive preliminary results lay the groundwork for these studies. Nearly all the protein constructs have been expressed and characterized. Full-length PICK1 was crystallized with bound Ca2+ and the GluR2 AMPA receptor tail. The structure of the BAR domain of PInB is nearly finished. Collaborative cellular studies on PICK1 and PInB have already produced important results and, more importantly, the feedback between the cellular and structural/biophysical studies is beginning to generate new hypotheses.