Activation of Ca2+/calmodulin (CaM) dependent kinase II (CaMKII) in heart failure (HF) contributes to cardiomyocyte apoptosis, early-after depolarization-induced arrhythmias, and maladaptive remodeling. In heart, most activated CaMKII is associated with the sarcolemma and we have shown that CaMKII is bound to the pore-forming 11C subunit of CaV1.2 (L-type) Ca2+ channels, where it functions as a dedicated integrator of Ca2+ signals. CaMKII also is a CaV1.2 Ca2+ channel-dependent and PKA-independent downstream effector of 2-adrenergic stimulation, thus placing CaMKII at the convergence of the two major signaling pathways affected in HF: hyperadrenergic stimulation and Ca2+ dysregulation. Based upon recent structural information and our new biochemical data, we propose a novel model for the interaction between CaMKII and 11C that offers insight into its function and regulation and provides a basis for understanding how CaMKII activity could be perturbed in HF. The objective of this proposal is to identify and test the molecular details underlying this interaction, and determine how this regulation is altered in HF. We propose three specific aims.
In Aim 1, we will test the hypothesis that CaMKII regulation of, and interaction with, CaV1.2 Ca2+ channels involves mimicry of the CaMKII autoinhibitory peptide (AIP). A variety of complex biochemical and biophysical techniques will be employed to test this novel mimicry model in which we propose that CaMKII interacts with pseudo-AIP domains in the 11C N and/or C termini and that, CaMs or CaM-like Ca2+-binding proteins bound to these 11C domains serve as the Ca2+-sensors that regulate CaMKII and fine-tune the regulation. Building upon those findings, in Aim 2 we will test the hypothesis that CaMKII sits at the convergence of two major signaling pathways perturbed in HF, 2-adrenergic activation and intracellular Ca2+ signaling, by nature of its tethered interaction with CaV1.2 Ca2+ in cardiomyocytes. Using novel strategies to generate functional """"""""knock-ins"""""""" of CaV1.2 subunits in cultured myocytes, we will test the consequences of perturbing the quaternary structure of CaMKII, CaV1.2, CaM and/or other Ca2+-binding proteins upon the bidirectional regulation of CaMKII and CaV1.2 and upon the PKA-dependent 2-adrenergic regulation of CaMKII signaling. These data will then allow us to apply our model in Aim 3 to test the hypothesis that HF perturbs the bidirectional regulation inherent in the CaMKII/CaV1.2 tethered interaction. We will employ several mouse models of HF which result from high """"""""throughput"""""""" through 2-adrenergic signaling pathways. We hypothesize that HF alters the tethering between CaMKII and CaV1.2 Ca2+ channels resulting in mislocalized and dysregulated CaMKII activity, therefore promoting the pathophysiological consequences associated with HF. Not only will this work will lead to a better understanding of cardiac physiology, but it will provide new insights into arrhythmogenesis and impaired cardiac function during HF.
Statement Heart failure affects about 500, 000 Americans annually and is a leading cause of morbidity and mortality. The molecular mechanisms underlying heart failure and the consequences that lead to an increased risk of sudden cardiac death are not well understood. Recently, activation of Ca2+/calmodulin (CaM) dependent kinase II (CaMKII) in heart failure has been shown to contribute to cardiomyocyte apoptosis, early-after depolarization-induced arrhythmias, and maladaptive remodeling, at least in part to an unexpected stimulation by the 2-adrenergic signaling system. We have recently shown that normal CaMKII activity results from tethering of CaMKII to the L-type (CaV1.2) Ca2+ channel. Here we test a novel model for CaMKII tethering to CaV1.2 channels and propose that HF alters this dynamic to lead to abnormal CaMKII activation.
|Pablo, Juan L; Pitt, Geoffrey S (2016) Fibroblast Growth Factor Homologous Factors: New Roles in Neuronal Health and Disease. Neuroscientist 22:19-25|
|Wang, Hong-Gang; He, Xiao Ping; Li, Qiang et al. (2013) The auxiliary subunit KChIP2 is an essential regulator of homeostatic excitability. J Biol Chem 288:13258-68|
|Wang, Chaojian; Chung, Ben C; Yan, Haidun et al. (2012) Crystal structure of the ternary complex of a NaV C-terminal domain, a fibroblast growth factor homologous factor, and calmodulin. Structure 20:1167-76|
|Daubert, James P; Pitt, Geoffrey S (2012) Can polymorphisms predict response to antiarrhythmic drugs in atrial fibrillation? J Am Coll Cardiol 60:546-7|
|Wang, Chaojian; Wang, Chuan; Hoch, Ethan G et al. (2011) Identification of novel interaction sites that determine specificity between fibroblast growth factor homologous factors and voltage-gated sodium channels. J Biol Chem 286:24253-63|
|Wang, Chuan; Hennessey, Jessica A; Kirkton, Robert D et al. (2011) Fibroblast growth factor homologous factor 13 regulates Na+ channels and conduction velocity in murine hearts. Circ Res 109:775-82|
|Wei, Eric Q; Barnett, Adam S; Pitt, Geoffrey S et al. (2011) Fibroblast growth factor homologous factors in the heart: a potential locus for cardiac arrhythmias. Trends Cardiovasc Med 21:199-203|
|Wang, Hong-Gang; Wang, Chuan; Pitt, Geoffrey S (2011) Rem2-targeted shRNAs reduce frequency of miniature excitatory postsynaptic currents without altering voltage-gated Ca²? currents. PLoS One 6:e25741|
|Sun, Albert Y; Pitt, Geoffrey S (2011) Pinning down the CaMKII targets in the L-type Ca(2+) channel: an essential step in defining CaMKII regulation. Heart Rhythm 8:631-3|
|Sun, Albert Y; Koontz, Jason I; Shah, Svati H et al. (2011) The S1103Y cardiac sodium channel variant is associated with implantable cardioverter-defibrillator events in blacks with heart failure and reduced ejection fraction. Circ Cardiovasc Genet 4:163-8|
Showing the most recent 10 out of 15 publications