Molecular determinants of voltage-dependent gating in T-type calcium channels

神经细胞或神经元是神经系统活动的关键角色。它通过电和化学两种方式传递信息。神经元内部信号传递的机制是基于细胞内外存在的电压差异。这种膜电位是由带电粒子或离子的不均匀分布产生的，如钠（Na）、钾(K)、氯（Cl）和钙（Ca）。这些离子通过细胞膜上特定的蛋白质通道（离子通道）进出细胞。这些通道根据细胞膜电位的变化而“打开”或“关闭”。由此产生的电荷重新分配可能会改变膜上的电压差。电压差的减小称为去极化。如果去极化超过一定的阈值，脉冲（即动作电位）将沿着神经元传播。去极化导致钙通过钙通道进入细胞。因此钙通道在神经传递中起着重要的作用。在过去的20年里，三(3)个不同的钙通道蛋白家族已经根据它们的药理学、遗传和电压敏感性被鉴定和表征。t型（CaV3）通道是非典型通道，其打开和关闭的速度比CaV1和CaV2通道快得多。我们对这些差异背后的分子机制所知相对较少。我们建议确定控制t型钙通道响应膜电位打开和关闭速率的分子和细胞元件。一系列分子、生物化学和细胞技术将被用来回答这些问题。突变通道的功能将利用电生理和蛋白质化学技术进行研究。然后通过计算机建模分析突变体的行为，以计算机模拟通道结构。这一知识将为未来的药物治疗提供有价值的见解，如改进钙通道阻滞剂。

The nerve cell, or neuron, is the key player in the activity of the nervous system. It conveys information both electrically and chemically. The mechanism underlying signal transmission within neurons is based on voltage differences that exist between the inside and the outside of the cell. This membrane potential is created by the uneven distribution of electrically charged particles, or ions, such as sodium (Na), potassium (K), chloride (Cl), and calcium (Ca). These ions enter and exit the cell through specific protein channels (ion channels) in the cell's membrane. The channels "open" or "close" in response to changes in the cell's membrane potential. The resulting redistribution of electric charges may alter the voltage difference across the membrane. A decrease in the voltage difference is called depolarization. If depolarization exceeds a certain threshold, an impulse (i.e., action potential) will travel along the neuron. The depolarization causes Ca to enter the cell through calcium channels. Hence calcium channels play an important role in neurotransmission. Over the last 20 years, three (3) different families of calcium channel proteins have been identified and characterized based upon their pharmacological, genetic and voltage sensitivities. The T-type (CaV3) channels are atypical channels that open and close much more rapidly than CaV1 and CaV2 channels. We know relatively little about the molecular mechanisms underlying these differences. We propose to identify the molecular and cellular elements controlling the rate at which T-type calcium channels open and close in response to membrane potential. An array of molecular, biochemical, and cellular techniques will be used to answer these questions. The function of mutant channels will be studied using electrophysiological and protein chemistry techniques. The behavior of the mutants will then be analyzed by computer modeling to simulate by computer the channel structure. This knowledge will provide valuable insight into future pharmacological therapies such as improved calcium channel blockers.