title: The catecholaminergic polymorphic ventricular tachycardia mutation R33Q disrupts the N-terminal structural motif that regulates reversible calsequestrin polymerization.
abstract: Calsequestrin undergoes dynamic polymerization with increasing calcium concentration by front-to-front dimerization and back-to-back packing, forming wire-shaped structures. A recent finding that point mutation R33Q leads to lethal catecholaminergic polymorphic ventricular tachycardia (CPVT) implies a crucial role for the N terminus. In this study, we demonstrate that this mutation resides in a highly conserved alternately charged residue cluster (DGKDR; cluster 1) in the N-terminal end of calsequestrin. We further show that this cluster configures itself as a ring system and that the dipolar arrangement within the cluster brings about a critical conformational flip of Lys(31)-Asp(32) essential for dimer stabilization by formation of a H-bond network. We additionally show that Ca(2+)-induced calsequestrin aggregation is nonlinear and reversible and can regain the native conformation by Ca(2+) chelation with EGTA. This study suggests that cluster 1 works as a molecular switch and governs the bidirectional transition between the CASQ2 monomer and dimer. We further demonstrate that mutations disrupting the alternating charge pattern of the cluster, including R33Q, impair Ca(2+)-CASQ2 interaction, leading to altered polymerization-depolymerization dynamics. This study provides new mechanistic insight into the functional effects of the R33Q mutation and its potential role in CPVT.
authors.affiliation: Department of Physiology and Cell Biology, The Ohio State University College of Medicine, and the Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Naresh C
authors.initials: NC
authors.lastname: Bal
authors.forename: Ashoke
authors.initials: A
authors.lastname: Sharon
authors.forename: Subash C
authors.initials: SC
authors.lastname: Gupta
authors.forename: Nivedita
authors.initials: N
authors.lastname: Jena
authors.forename: Sana
authors.initials: S
authors.lastname: Shaikh
authors.forename: Sandor
authors.initials: S
authors.lastname: Gyorke
authors.forename: Muthu
authors.initials: M
authors.lastname: Periasamy
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002155:Calsequestrin / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D002938:Ciona intestinalis; D019295:Computational Biology / Q000379:methods; D019281:Dimerization; D004533:Egtazic Acid / Q000737:chemistry; D006801:Humans; D006860:Hydrogen Bonding; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D051381:Rats; D017386:Sequence Homology, Amino Acid; D017180:Tachycardia, Ventricular / Q000235:genetics* / Q000378:metabolism
chemical_list: D002155:Calsequestrin; D002395:Catecholamines; D002614:Chelating Agents; D004533:Egtazic Acid; D002118:Calcium