Phosphoinositide Signaling at the Synapse

兴奋性突触的磷酸肌苷信号产生Ca2+信号，改变突触的功能，并传播到细胞核，在那里它们导致转录反应。Snyder/Worley项目将研究突触信号转导的三个关键阶段。第1组代谢受体（mGluR）刺激磷脂酶C产生IP3，引起细胞内钙池的释放。最近的研究表明，mGluR5对可卡因的行为反应至关重要。Worley实验室研究了mGluRs及其由直接早期基因Homer调控的功能。在正在进行的研究中，他们发现荷马2基因缺失的老鼠对可卡因的反应增强。这些观察结果集中在荷马在药物成瘾模型中调节mGluR功能的作用上。Aim 1将产生具有mGluR突变的小鼠遗传模型，该突变会破坏与Homer和Shank的特定相互作用。目的2将研究一种新的mGluR信号/支架蛋白。一个被称为Hopi的蛋白质家族，是基于它们与Homer相互作用与mGluR的偶联而被鉴定出来的。初步研究表明，Hopi将1 mGluR组与p21活化激酶（Pak）和CDK5的激活联系起来。研究将包括条件Hopi基因敲除小鼠的产生和分析，以及信号传导的分子研究。目的3将研究IP3受体靶向兴奋性突触的分子机制。Snyder实验室对肌醇三磷酸脑受体（IP3R）有着长期的兴趣，并确定了其信号转导中涉及的重要相互作用。该方法利用了最近的一项观察，即Shank诱导了包含IP3R的棘的形成。为了确定IP3R在脊柱中积累所必需的区域，IP3R缺失突变体将与Shank在神经元中共表达。关键的发现将在切片培养中得到证实。平行的生化研究将确定与IP3R结构域相互作用的蛋白质，这对其脊柱定位和功能至关重要。这些研究将为mGluR5/IP3R信号复合物如何在突触上组装以及扰动如何导致精神疾病提供重要的新见解。

Phosphoinositide signaling at the excitatory synapse generates Ca2+ signals that modify the function of the synapse, and propagate to the nucleus where they result in transcriptional responses. The Snyder/Worley project will examine three critical stages in signal transduction at the synapse. Group 1 metabotropic receptors (mGluR) stimulate phospholipase C to generate IP3, which evokes release of calcium from intracellular pools. Recent studies indicate that mGluR5 is essential for behavioral responses to cocaine. The Worley laboratory has studied mGluRs and their functional modulation by the immediate early gene Homer. In ongoing studies, they find that mice with a genetic deletion of Homer 2 exhibit enhanced responses to cocaine . These observations focus attention on the role of Homer in regulating mGluR function in models of drug addiction. Aim 1 will generate mouse genetic models with mutations of mGluR that disrupt specific interactions with Homer and Shank. Aim 2 will examine a novel signaling/scaffold protein for mGluR. A family of proteins, termed Hopi, was identified based on their coupling to mGluR by interacting with Homer. Preliminary studies indicate that Hopi couples group 1 mGluR to activation of p21-activated kinase (Pak) and perhaps CDK5. Studies will include generation and analysis of conditional Hopi knockout mice, and as well as molecular studies of signaling. Aim 3 will examine molecular mechanisms that target IP3 receptors to the excitatory synapse. The Snyder laboratory has a long-standing interest in the brain receptor for inositol trisphosphate (IP3R) and has defined important interactions involved in its signal transduction. The approach exploits a recent observation that Shank induces the formation of spines that include IP3R. In order to define regions of the IP3R that are essential for accumulation in spines, IP3R deletion mutants will be co-expressed with Shank in neurons. Critical finding will be confirmed in slice cultures. Parallel biochemical studies will identify proteins that interact with the domain of the IP3R that is essential in its spine localization and function. These studies will provide important new insights into how the mGluR5/IP3R signaling complex is assembled at the synapse, and how perturbations contribute to mental illness.