Cardiac KATP Channels in Health and Disease

描述（由申请人提供）：心脏ATP敏感性K+（KATP）通道由成孔Kir6.2和调节性SUR 2A亚基形成，其特征在于核苷酸依赖性调节，允许通道复合物响应细胞能量状态的变化调节膜兴奋性。然而，目前尚不清楚心脏KATP通道如何将核苷酸信号转化为孔门控，通道活性对心脏稳态的全面影响是什么，以及最终通道缺陷是否会导致心脏疾病。在该提案的前一个资助期，我们确定了SUR 2A亚基固有的ATP酶活性，证明了KATP通道功能缺陷会降低心脏对肾上腺素能激发的耐受性，并在心力衰竭患者的初始筛选中发现了KATP通道突变。基于这些发现，我们在这里提出了一个新的概念，心脏KATP通道作为一个双功能通道/酶分子组合，在不同的压力下发挥重要作用。目标#1将定义控制Kir6.2孔的基于SUR 2A催化的核苷酸门控的分子机制。目的#2将确定KATP通道对预防适应不良的结构重塑以及在生理和病理应激心肌中保持能量和电稳定性的影响。目的#3将确定特发性扩张型心肌病患者心脏KATP通道突变的谱，并确定这些突变对KATP通道/酶表型、代谢传感和细胞适应应激的影响。为此，我们将采用小鼠基因敲除和疾病模型，沿着来自现有心肌病患者队列的基因组标本。将利用酶学、电生理学、生理基因组学、高通量DNA筛选和功能蛋白质组学分析等技术的互补，从生物体、器官、细胞和分子水平对心脏KATP通道进行研究。因此，该提议将提供对心脏KATP通道在代谢信号解码、应激适应及其对临床医学的影响的综合理解。

DESCRIPTION (provided by applicant): Cardiac ATP-sensitive K+ (KATP) channels, formed by the pore-forming Kir6.2 and regulatory SUR2A subunits, are characterized by nucleotide-dependent regulation that allows the channel complex to adjust membrane excitability in response to changes in the cellular energetic state. However, it is unknown how cardiac KATP channels translate nucleotide signals into pore gating, what is the full impact of channel activity on cardiac homeostasis, and ultimately whether channel defects contribute to heart disease. In the previous funding period of this proposal we identified an ATPase activity intrinsic to the SUR2A subunit, demonstrated that deficient KATP channel function reduces cardiac tolerance to adrenergic challenge, and discovered KATP channel mutations in initial screening of patients with heart failure. Based on these findings, we here put forward the novel concept that cardiac KATP channels operate as a bi-functional channel/enzyme molecular combination serving a vital role under diverse stressors. Aim #1 will define the molecular mechanisms governing the SUR2A catalysis-based nucleotide gating of the Kir6.2 pore. Aim #2 will establish the impact of KATP channels on prevention of maladaptive structural remodeling, and preservation of energetic and electrical stability in the physiologically and pathologically stressed myocardium. Aim #3 will determine the spectrum of cardiac KATP channel mutations in patients with idiopathic dilated cardiomyopathy, and define the consequences of these mutations on the KATP channel/enzyme phenotype, metabolic sensing and cell adaptation to stress. To this end, we will employ murine knockout and disease models, along with genomic specimens from an existing cohort of patients with cardiomyopathy. The complementary technologies of enzymology, electrophysiology, physiological genomics, high-throughput DNA screening and functional proteomic analysis will be applied to study the cardiac KATP channel at the organism, organ, cellular and molecular levels. Thus, this proposal will provide an integrated understanding of cardiac KATP channels in metabolic signal decoding, stress adaptation, and their impact for clinical medicine.