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性减弱。在作为潜在参与者的分子中，L型通道特别重要。例如，在从患有起搏诱导的心力衰竭的狗中分离的细胞（HF细胞）中，动作电位延长的关键因素似乎是降低的L型通道失活。然而，严格评估L型通道在心力衰竭中的作用受到理解辅助通道亚基失活和功能调节的关键差距的阻碍。总体目标是加深对这些空白区域中L型通道的基本理解，并将增强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，每个目标都针对理解故障期间通道性能的显著差距。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型通道钙依赖性失活的结构机制。3.确定钙通道β亚基调节L型通道功能和表达的潜力。4.确定正常和衰竭犬和人心脏组织中钙通道β亚基的分布。5.建立HF细胞中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”鉴定的功能不规则性。后者的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.