Article ID Journal Published Year Pages File Type
10954017 Journal of Molecular and Cellular Cardiology 2010 11 Pages PDF
Abstract
Mutations in the human cardiac calsequestrin gene (CASQ2) are linked to catecholaminergic polymorphic ventricular tachycardia (CPVT-2). This inherited disorder is characterized by life-threatening arrhythmias induced by physical and emotional stress in young patients. Here we identified a novel heterozygous missense mutation (K206N) in the CASQ2 gene in a symptomatic family in which one member died of cardiac arrest. The functional properties of CSQK206N were investigated in comparison to the wild-type form of CASQ2 (CSQWT) by expression in eukaryotic cell lines and neonatal mouse myocytes. The mutation created an additional N-glycosylation site resulting in a higher molecular weight form of the recombinant protein on immunoblots. The mutation reduced the Ca2+ binding capacity of the protein and exhibited an altered aggregation state. Consistently, CSQK206N-expressing myocytes exhibited an impaired response to caffeine administration, suggesting a lower Ca2+ load of the sarcoplasmic reticulum (SR). The interaction of the mutated CSQ with triadin and the protein levels of the ryanodine receptor were unchanged but the maximal specific [3H]ryanodine binding was increased in CSQK206N-expressing myocytes, suggesting a higher opening state of the SR Ca2+ release channel. Myocytes with expression of CSQK206N showed a higher rate of spontaneous SR Ca2+ releases under basal conditions and after β-adrenergic stimulation. We conclude that CSQK206N caused a reduced Ca2+ binding leading to an abnormal regulation of intracellular Ca2+ in myocytes. This may then contribute to the increased propensity to trigger spontaneous Ca2+ transients in CSQK206N-expressing myocytes.
Related Topics
Life Sciences Biochemistry, Genetics and Molecular Biology Cell Biology
Authors
, , , , , , , , , , ,