Tuning of CaV channel dynamics by stac proteins

黑质致密部多巴胺能神经元的选择性变性 是帕金森氏症发展过程中的一个关键事件。这些神经元很脆弱，因为它们 通过CaV1.3通道进行自主起搏，不寻常地依赖钙离子内流。 与在PD发病过程中保持相对保护的其他起搏神经元不同，SNC 神经元有较大的钝化失活的钙电流，因此加剧了 钙离子--过载。鉴于它的核心作用，识别调节钙通道的调节蛋白 SNC神经元的功能是至关重要的。一个有吸引力的监管候选人是SH3和富含半胱氨酸的 结构域(STAC)蛋白，一种肌肉和神经元特有的蛋白质，已成为 骨骼肌兴奋-收缩机制的组成部分，作为先天性疾病的一个部位 肌病。即便如此，STAc的神经功能仍不明确，尽管STAc-2- 突变与儿童期精神分裂症有关。受初步数据激励 显示SNC神经元中STAC的存在及其选择性减弱的功能 钙/钙调素依赖的失活(CDI)在异源体系中，我们在这里解剖分子 STAC的功能、潜在机制和在调节SNC起搏方面的潜在作用 一大堆分子工具和定量的光学和电生理方法。这 该项目将通过三个具体目标开启一个令人兴奋的发现时代。(1)堆积亚型是如何形成的 调整CAV函数？我们寻求开发一个统一的机制方案来管理堆叠 CaV1.3，通过结合选择性剪接和RNA编辑的效果，并通过严格的 量化STAC对CDI、基线通道活动性(PO)和表面膜的影响 贩运(NMEM)。(2)支持和提炼的分子决定因素和机制是什么？ CaV1堆积调控？根据我们先前的机械论研究，我们试图阐明 CaV1.3 PO和NMeM的堆积调节的分子基础以及生理或 病理生理过程可能会微调STAC的调节。(3)多管齐下如何- SNC起搏和钙信号对CaV1的调制？在这里，我们阐明是否 下调或上调STA2调频导致内源性CaV1改变 黑质核神经元的起搏和动作电位形态。这个项目承诺 在阐明CaV1和And的STAC调控的多方面机制方面取得了前所未有的进展 钙离子通道生理学的新兴前沿。此外，这项工作可能会为我们提供新的见解 钙离子通过CaV1.3流入黑质神经元的调控过程，这是一个重要的脆弱性 为帕金森病的发病机制和潜在的治疗靶点。

Selective degeneration of dopaminergic (DA) neurons of substantia nigra pars compacta (SNc) is a critical event in the progression of Parkinson’s disease. These neurons are vulnerable as they undergo autonomous pacemaking with an unusual reliance on Ca2+-influx via CaV1.3 channels. Unlike other pacemaking neurons that remain relatively protected during PD pathogenesis, SNc neurons have larger Ca2+-currents with blunted inactivation, thus aggravating the propensity for Ca2+-overload. Given its central role, identifying regulatory proteins that tune Ca2+-channel function in SNc neurons is critical. One attractive regulatory candidate is SH3 and cysteine rich domain (stac) protein, a muscle and neuron specific protein that has emerged as a requisite component of skeletal muscle excitation-contraction machinery and as a locus for congenital myopathies. Even so, the neuronal functions of stac remains poorly defined, although stac2- mutations have been linked to childhood-onset schizophrenia. Motivated by preliminary data showing both the presence of stac in SNc neurons, and its functional role to selectively diminish Ca2+/CaM-dependent inactivation (CDI) in heterologous systems, we here dissect the molecular functions of stac, underlying mechanisms, and potential role in tuning SNc pacemaking, utilizing a bevy of molecular tools and quantitative optical and electrophysiological approaches. This project will usher in an exciting era of discovery via three specific aims. (1) How do stac isoforms tune CaV function? We seek to develop a unified mechanistic scheme for stac regulation of CaV1.3, by incorporating effects of alternative-splicing and RNA-editing, and by rigorous quantification of stac effects on CDI, baseline channel activity (PO), and surface-membrane trafficking (Nmem). (2) What are molecular determinants and mechanisms that support and refine stac regulation of CaV1? Informed by our prior mechanistic study, we seek to elucidate the molecular underpinnings for stac-regulation of CaV1.3 PO and Nmem and whether physiological or pathophysiological processes may fine-tune stac modulation. (3) How does multiprong- modulation of CaV1 by stac tune SNc pacemaking and Ca2+ signaling? Here, we elucidate whether either downregulation or upregulation of stac2 tunes endogenous CaV1 leading to alterations in pacemaking and action potential morphology of SNc neurons. This project promises unprecedented progress in elucidating multifaceted mechanisms for stac regulation of CaV1, an emerging frontier for Ca2+-channel physiology. Furthermore, this work may shed new insights into regulatory process that sculpt Ca2+-influx via CaV1.3 into SNc neurons, an important vulnerability for PD pathogenesis and a potentially promising therapeutic target.