The work proposed in this application will test the hypothesis that L-type Cav1.2 channel activity varies along the sarcolemma of ventricular myocytes due to signaling micro-domains created by a subpopulation of these channels interacting with the scaffolding protein AKAP150. Preliminary data suggest the novel concept that AKAP150-associated Cav1.2 channels play a critical role in shaping action potential waveform, arrhythmogenesis, excitation-contraction (EC) coupling, and excitation-transcription (ET) coupling in ventricular myocytes. A key discovery is that small clusters of AKAP150-associated Cav1.2 channels are capable of undergoing coordinated openings and closings ("coupled gating"). The frequency of coupled gating events increases in cells expressing a mutant Cav1.2 channel that causes arrhythmias and autism in humans with long QT syndrome 8 (LQT8). The project has three specific aims designed to investigate the physiological and pathophysiological implications of these findings.
Specific aim 1 is to test the hypothesis that AKAP150 is required for coupled gating of wild type (WT) and Cav1.2-LQT8 channels.
Specific aim 2 is to test the hypothesis that coupled gating of WT and Cav1.2-LQT8 channels modulates EC coupling in ventricular myocytes. Finally, Specific aim 3 is to test the hypothesis that loss of AKAP150 protects against arrhythmias in WT and LQT8 mice. The methods that will be used to achieve these aims include patch-clamp electrophysiology, optical clamping, light- and chemically-induced dynamic targeting of kinases to cellular membranes, light-induced activation of adrenergic signaling (i.e., optogenetics), confocal, and TIRF microscopy. Experiments will involve a transgenic mouse specially created for this project and that expresses fluorescently labeled Cav1.2-LQT8 channels in ventricular myocytes as well as other transgenic, knock in, and knock out mice created by collaborators. This work will generate fundamental information on the mechanisms by which AKAP150 and Cav1.2 channels control of excitability, gene expression, and EC coupling in the heart under physiological and pathological conditions.
The experiments outlined in this application have important implications to public health because they investigate a new Ca2+ signaling modality that regulates the electrical and contractile activity of the heart under normal conditions and disease. The information resulting from the proposed work will contribute to understanding of the mechanisms controlling the function of the heart and may lead to the development of rational strategies for the treatment of arrhythmias and heart failure.
|Drum, Benjamin M L; Yuan, Can; Li, Lei et al. (2016) Oxidative stress decreases microtubule growth and stability in ventricular myocytes. J Mol Cell Cardiol 93:32-43|
|Nieves-CintrÃ³n, Madeline; Hirenallur-Shanthappa, Dinesh; Nygren, Patrick J et al. (2016) AKAP150 participates in calcineurin/NFAT activation during the down-regulation of voltage-gated K(+) currents in ventricular myocytes following myocardial infarction. Cell Signal 28:733-40|
|Dickson, Eamonn J; Jensen, Jill B; Vivas, Oscar et al. (2016) Dynamic formation of ER-PM junctions presents a lipid phosphatase to regulate phosphoinositides. J Cell Biol 213:33-48|
|Dixon, Rose E; Moreno, Claudia M; Yuan, Can et al. (2015) Graded CaÂ²âº/calmodulin-dependent coupling of voltage-gated CaV1.2 channels. Elife 4:|
|Drum, Benjamin M L; Santana, Luis F (2015) The long and winding road home: how junctin and triadin find their way to the junctional SR. J Mol Cell Cardiol 81:15-7|
|Drum, Benjamin M L; Dixon, Rose E; Yuan, Can et al. (2014) Cellular mechanisms of ventricular arrhythmias in a mouse model of Timothy syndrome (long QT syndrome 8). J Mol Cell Cardiol 66:63-71|
|Zhang, Caimei; Chen, Biyi; Guo, Ang et al. (2014) Microtubule-mediated defects in junctophilin-2 trafficking contribute to myocyte transverse-tubule remodeling and Ca2+ handling dysfunction in heart failure. Circulation 129:1742-50|
|Guan, Xuan; Mack, David L; Moreno, Claudia M et al. (2014) Dystrophin-deficient cardiomyocytes derived from human urine: new biologic reagents for drug discovery. Stem Cell Res 12:467-80|
|Nystoriak, Matthew A; Nieves-CintrÃ³n, Madeline; Nygren, Patrick J et al. (2014) AKAP150 contributes to enhanced vascular tone by facilitating large-conductance Ca2+-activated K+ channel remodeling in hyperglycemia and diabetes mellitus. Circ Res 114:607-15|
|Dixon, Rose E; Santana, Luis F (2013) A Ca2+- and PKC-driven regulatory network in airway smooth muscle. J Gen Physiol 141:161-4|
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