Cardiac KATP Channels in Health and Disease

描述(由申请人提供)：心脏ATP敏感K(KATP)通道由成孔的Kir6.2和调节的SUR2A亚基形成，其特征是核苷酸依赖的调节，允许通道复合体调整膜的兴奋性，以响应细胞能量状态的变化。然而，目前尚不清楚心脏KATP通道如何将核苷酸信号翻译成孔门，通道活动对心脏动态平衡的全面影响，以及最终通道缺陷是否会导致心脏病。在这项提案的前一个资助期，我们发现了SUR2A亚单位固有的ATPase活性，证明KATP通道功能缺陷降低了心脏对肾上腺素能挑战的耐受性，并在心力衰竭患者的初始筛查中发现了KATP通道突变。基于这些发现，我们在这里提出了心脏KATP通道作为双功能通道/酶分子组合在不同应激源下发挥重要作用的新概念。目的#1将定义控制Kir6.2孔的SUR2A催化核苷酸门控的分子机制。目的#2建立KATP通道在防止生理性和病理性应激心肌结构重建不良和维持能量和电稳定性方面的作用。目的#3将确定特发性扩张型心肌病患者的心肌KATP通道突变谱，并确定这些突变对KATP通道/酶表型、代谢感知和细胞应激适应的影响。为此，我们将使用小鼠基因敲除和疾病模型，以及来自现有心肌病患者队列的基因组样本。将应用酶学、电生理学、生理基因组学、高通量DNA筛选和功能蛋白质组学等辅助技术，从生物、器官、细胞和分子水平对心肌KATP通道进行研究。因此，这一建议将提供对心脏KATP通道在代谢信号解码、应激适应以及它们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.