L-type calcium channel gating and modulation in normal and failure states

心力衰竭的功能特征包括动作电位持续时间延长，收缩和细胞内Ca2+瞬变抑制，以及肾上腺素能反应迟钝。在作为潜在参与者的分子中，l型通道尤为重要。例如，在从起搏诱导心力衰竭（HF细胞）犬身上分离的细胞中，动作电位延长的一个关键因素似乎是l型通道失活的减少。然而，对l型通道在心力衰竭中的作用的严格评估受到对辅助通道亚基失活和功能调节的理解的关键空白的阻碍。总体目标是加深对这些间隙区域的l型通道的基本理解，并将增强的基础知识与对这些通道如何导致心力衰竭的新认识联系起来。使用来自狗和人类的HF细胞，我们将追求以下5个目标，每个目标都针对了解故障时通道性能的显着差距。1. 阐明心脏l型通道电压依赖性失活的基本不确定性。2. 发现心脏l型通道Ca2+依赖性失活的结构机制。3. 确定l型通道功能的调节潜力和Ca通道β亚基的表达。4. 鉴定正常、衰竭犬和人心脏组织中Ca通道β亚基的分布。5. 建立HF细胞l型通道特性的功能谱。，并测试重组β亚基的表达是否可以改变或“正常化”已确定的功能异常。后一项实验将有助于为兴奋性障碍和心力衰竭的基因治疗奠定基础。

Functional hallmarks of heart failure include prolonged action-potential duration, depressed contraction and intracellular Ca2+ transients, as well as blunted adrenergic responsiveness. Among the molecules implicated as underlying players, the L-type channel is particularly important. For example, in cells isolated from dogs with pacing-induced heart failure (HF cells), a key factor underlying action potential prolongation appears to be decreased L-type channel inactivation. However, rigorous assessment of the role of L-type channels in heart failure is hampered by crucial gaps in understanding inactivation and functional modulation by auxiliary channel subunits. The overall goal is to deepen fundamental understanding of L-type channels in these gap areas, and to bridge the enhance basic knowledge to a new appreciation of how these channels contribute to heart failure. Using HF cells from dogs and humans, we will pursue the following 5 Aims, each targeting a salient gap in understanding channel performance during failure. 1. To clarify fundamental uncertainties about voltage-dependent inactivation of cardiac L-type channels. 2. To discover structure-based mechanisms of Ca2+- dependent inactivation of cardiac L-type channels. 3. To determine the potential for tuning L-type channel function and expression by Ca channel beta subunits. 4. To identify the profile of Ca channel beta subunits in normal and failing dog and human heart tissue. 5. To establish a functional profile of L-type channel properties in HF cells., and to test whether expression of recombinant beta subunits can alter or "normalize" identified irregularities in function. The latter experiments will help lay the groundwork for gene therapy of excitability disorders and heart failure.