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.
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