The Molecular Transitions that Initiate EC Coupling in Skeletal Muscle

项目概要/摘要 这些研究的动机是需要了解基本的生物物理 骨骼电压门控L型钙通道CaV1.1的特性。虽然离子传导是一种 CaV1.1是绝大多数离子通道的关键特征（通常也是唯一的职责）， 独特：其电压传感器的激活打开其孔，但不需要Ca2+进入触发 肌肉收缩。相反，Cav1.1电压传感器的构象变化直接门控 Ryanodine受体（RyR1）通过这两个通道之间的物理耦合，触发释放 肌浆网Ca~（2+）。在这种情况下，Cav1.1的四个电压传感元件确实是 RyR1通道的电压传感器。由于Cav1.1通道在卵母细胞中表达的可能性， 由于发现了一种必需的衔接蛋白（Stac3），Olcese 实验室处于一个特权地位，直接解决电压调节机制，在这一点上， 蛋白质，具有独特的能力（迄今为止），以实现尖端的电压钳荧光测定法 接近CaV通道。 在接下来的五年里，利用电生理学、光学和计算技术， 研究者将描述CaV1.1通道电压依赖性的基础， 胚胎剪接变体。他们将询问这种电压依赖性是如何被调制的。 辅助亚基（β、α 2 δ和γ）参与CaV1.1大分子复合物。他们将 确定四个同源但不相同的CaV1.1电压感应结构域中的哪一个赋予 电压敏感性RyR1介导的钙释放。最后，研究人员将解决分子 一种引起恶性高热的突变机制，特异性地影响电压敏感 CaV1.1的装置。所收集的知识对于理解 肌肉生理学和收缩的电压依赖性控制。

PROJECT SUMMARY/ABSTRACT The motivation for these studies is the need to gain an understanding of the fundamental biophysical properties of the skeletal voltage-gated L-type Calcium channel CaV1.1. While ion conduction is a critical feature (and often the only duty) of the vast majority of ion channels, CaV1.1 is somewhat unique: the activation of its voltage sensors opens its pore, but Ca2+ entry is not required to trigger muscle contraction. Instead, the conformational changes of Cav1.1 voltage sensors directly gate Ryanodine receptors (RyR1) via a physical coupling between these two channels, to trigger the release of sarcoplasmic reticulum Ca2+. In this context, the four voltage-sensing elements of Cav1.1 are indeed the voltage sensors of RyR1 channels. As the possibility to express Cav1.1 channel in oocytes has recently become feasible thanks to the discovery of an essential adaptor protein (Stac3), the Olcese laboratory is in a privileged position to directly address the mechanism of voltage regulation in this protein, with a unique capability (to date) to implement the cutting-edge voltage clamp fluorometry approach to CaV channels. During the next five years, using electrophysiological, optical and computational techniques, the investigators will delineate the basis of voltage dependence in CaV1.1 channels, in both adult and embryonic splice variants. They will interrogate how this voltage dependence is modulated by the participation of auxiliary subunits (β, α2δ, and γ) in the CaV1.1 macromolecular complex. They will determine which of the four homologous, but non-identical CaV1.1 Voltage Sensing Domains confer voltage sensitivity to RyR1-mediated Ca release. Finally, the investigators will address the molecular mechanism of a malignant-hyperthermia-causing mutation that specifically affects the voltage-sensing apparatus of CaV1.1. The knowledge gathered by is critical to understand fundamental aspects of muscle physiology and the voltage-dependent control of contraction.