Disease-associated calmodulin mutations disrupt L-type Ca2+ channel (Cav1.2) activity and CaMKIIdelta phosphorylation in long QT syndrome

Abstract Introduction Long QT Syndrome (LQTS) is a major inherited arrhythmia syndrome that can cause sudden cardiac death. Using genome sequencing in human patients, mutations the ubiquitous calcium (Ca2+) sensor protein calmodulin (CaM) have been associated to LQTS. CaM an ion channel regulator and modulate activity of voltage-gated (Cav1.2) Ca2+/CaM-dependent kinase II (CaMKIIδ), involved muscle contraction. However molecular mechanism by which contribute irregular heartbeats remains unclear. Methods Interaction proteins with Cav1.2 CaMKIId synthetic peptides (Cav1.2-NSCaTE51–68, Cav1.2-IQ1665–1685, Cav1.2-C1627–1652, CaMKIIδ294–315,) was investigated using Isothermal Titration Calorimetry (ITC) X-ray crystallography. Whole-cell patch clamp electrophysiology used determine effect on L-type Ca2+ currents Ca2+-dependent inactivation (CDI). CaMKIIδ phosphorylation determined western blot fluorescence assay. Results Binding affinity LQTS-associated variants significantly reduced, up 7-fold. Interestingly, Cav1.2-IQ1665–1685 peptide showed stronger binding, 2-fold, towards LQTS-CaM mutants. Crystal structures Ca2+-CaM:CaMKIId294–315 structural alterations induced LQTS mutations. In addition, we demonstrated autophosphorylation be reduced Electrophysiological examination function revealed impaired CDI, without affecting voltage dependence activation inactivation. Conclusions These data demonstrate strong correlation between activity. We provide insights into diverse factors contributing CaM-mediated arrhythmias. Funding Acknowledgement Type funding sources: Foundation. Main source(s): British Heart Foundation Intermediate Basic Science Research Fellowship