Functional and molecular mechanisms of human calmodulinopathy in cardiac arrhythmias and sudden cardiac death

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Abstract: Calmodulin (CaM) is a multifunctional Ca2+ binding protein that plays important roles in a wide range of intracellular signaling. It orchestrates a number of critical cellular processes. CaM is encoded by 3 distinct genes in human, namely CALM1, CALM2, and CALM3, each of which encodes for an identical CaM molecule at the protein level. CaM, a 17 kDa protein comprised of N- and C-terminal lobes linked by a flexible helix. Each lobe contains two EF hands, canonical Ca2+ binding motifs, with the N-lobe having slightly lower Ca2+ binding affinity. Ca2+ binding to the EF hands results in structural and functional changes of the target molecules. Recent studies have provided genetics links between human heritable CaM mutations to several types of cardiac arrhythmias and sudden cardiac death including catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS), and familial idiopathic ventricular fibrillation (IVF). The proposed study will use a combination of computational analyses including Rosetta computational modeling and molecular dynamics (MD) simulations as well as experimental approaches to decipher the molecular effects of mutant CaMs, linked to mechanisms of LQTS, on cardiac ion channels including Na+, Ca2+, and Ca2+-dependent K+ channels. We envision a reiterative process whereby the molecular modeling will inform the experimental designs and vice versa.