A dual binding mode for RhoGTPases in plexin signalling.
A dual binding mode for RhoGTPases in plexin signalling.
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DOI：
10.1371/journal.pbio.1001134
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发表时间：
2011-08
期刊：
影响因子：
9.8
通讯作者：
Siebold C
中科院分区：
文献类型：
--
作者：
Bell CH;Aricescu AR;Jones EY;Siebold C
RhoGTP酶在丛状蛋白胞内区的一个新的结合位点诱导了对丛状蛋白功能至关重要的三聚体配体-受体排列。神经丛蛋白是细胞引导信号信号素家族的细胞表面受体。细胞质区域包括Ras GTP酶激活蛋白(GAP)结构域和RhoGTP酶结合结构域。胞外信号素和胞内RhoGTP酶结合触发GAP活性和信号转导。这种错综复杂的监管机制仍然难以捉摸。我们提出了人丛蛋白-B1细胞质区域的两种晶体结构，与具有结构性活性的RhoGTPase，rac1。截短的Plexin-B1-rac1复合体的结构不提供RhoGTPase和RAS结合位点的偶联机制。在包含膜旁螺旋的情况下，Plexin-B1-rac1复合体的三聚体结构被Ras位点附近的第二个新的RhoGTP酶结合位点稳定。定点突变与细胞和生物物理分析相结合，表明这个新的结合位点对于信号转导是必不可少的。我们的发现与细胞外和细胞内丛状蛋白聚集事件合并为单一信号输出的模型一致。轴突引导是中枢神经系统发育的基础。生长中的轴突被过多的细胞外信号引导到正确的位置。最重要的细胞外信号之一是信号素，它与轴突上的丛状受体结合。通常，这种细胞外配体结合足以将细胞外信号传递到细胞内空间，以触发细胞内的变化，如轴突生长。然而，丛状蛋白受体的激活需要“双重”的配基结合：细胞外侧的信号素和细胞内侧的RhoGTP酶。只有在两种配体都存在的情况下，信号转导才能发生。这种错综复杂的调控机制是如何组织的，以及伴随的配体结合如何整合到细胞内的单一信号输出中，目前仍不清楚。在这里，我们介绍了一个网络蛋白受体，网络蛋白-B1，在与细胞内RhoGTP酶配体(Rac1)的络合物中的晶体结构，并表明与rac1的结合将三个网络蛋白-B1分子结合在一起。在这种三聚体排列中，每个丛状蛋白分子与两个rac1配体分子相互作用。这导致了一个先前未知的Plexin-rac1配体接口，这对其功能至关重要。进一步的生物物理和细胞分析，结合以前对细胞外网织蛋白-信号素复合体的发现，使我们能够提出一个模型，说明配体诱导的细胞外和细胞内侧的聚集事件如何结合起来触发信号转导。
A novel binding site for RhoGTPases on the intracellular region of plexins induces a trimeric ligand—receptor arrangement that appears crucial for plexin function. Plexins are cell surface receptors for the semaphorin family of cell guidance cues. The cytoplasmic region comprises a Ras GTPase-activating protein (GAP) domain and a RhoGTPase binding domain. Concomitant binding of extracellular semaphorin and intracellular RhoGTPase triggers GAP activity and signal transduction. The mechanism of this intricate regulation remains elusive. We present two crystal structures of the human Plexin-B1 cytoplasmic region in complex with a constitutively active RhoGTPase, Rac1. The structure of truncated Plexin-B1-Rac1 complex provides no mechanism for coupling RhoGTPase and Ras binding sites. On inclusion of the juxtamembrane helix, a trimeric structure of Plexin-B1-Rac1 complexes is stabilised by a second, novel, RhoGTPase binding site adjacent to the Ras site. Site-directed mutagenesis combined with cellular and biophysical assays demonstrate that this new binding site is essential for signalling. Our findings are consistent with a model in which extracellular and intracellular plexin clustering events combine into a single signalling output. Axon guidance is fundamental to the development of the central nervous system. The growing axon is guided to its correct location by a plethora of extracellular signals. One of the most important extracellular signals is semaphorin, which binds to plexin receptors on the axon. Usually, this kind of extracellular ligand binding is sufficient to transmit the extracellular signal to the intracellular space to trigger changes in the cell, like axon growth. However, activation of plexin receptors requires a “dual” ligand binding: semaphorin on the extracellular side, and a RhoGTPase on the intracellular side. Signal transduction can only occur if both ligands are present. How this intricate regulation mechanism is organized and how concomitant ligand binding can be integrated into a single signalling output within the cell has remained largely unclear. Here, we present crystal structures of one plexin receptor, Plexin-B1, in complex with an intracellular RhoGTPase ligand (Rac1) and show that binding of Rac1 brings together three Plexin-B1 molecules. In this trimeric arrangement each plexin molecule interacts with two Rac1 ligand molecules. This leads to a previously unidentified plexin-Rac1 ligand interface that is crucial for its function. Further biophysical and cellular analysis in combination with previous findings on the extracellular plexin-semaphorin complex allow us to propose a model for how ligand-induced clustering events on the extra- as well as intracellular side are combined to trigger signal transduction.
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DOI：
10.1073/pnas.83.17.6258
发表时间：
1986-09-01
影响因子：
11.1
作者：
GRASBERGER, B;MINTON, AP;METZGER, H
通讯作者：
METZGER, H
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
DOI：
10.1107/s0907444904016427
发表时间：
2004-12-01
影响因子：
2.2
作者：
Blanc, E;Roversi, P;Bricogne, G
通讯作者：
Bricogne, G
DOI：
10.1038/nsb0297-147
发表时间：
1997-02-01
期刊：
NATURE STRUCTURAL BIOLOGY
影响因子：
--
作者：
Hirshberg, M;Stockley, RW;Webb, MR
通讯作者：
Webb, MR
影响因子：
14.9
作者：
Davis IW;Leaver-Fay A;Chen VB;Block JN;Kapral GJ;Wang X;Murray LW;Arendall WB 3rd;Snoeyink J;Richardson JS;Richardson DC
通讯作者：
Richardson DC