Premium
The calsequestrin mutation CASQ2‐K206N affects sarcoplasmic reticulum Ca handling and causes catecholaminergic polymorphic ventricular tachycardia
Author(s) -
Kirchhefer Uwe,
Wehrmeister Diana,
Müller Frank U.,
Postma Alex V.,
Schmitz Wilhelm,
Neumann Joachim
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1155.13
Subject(s) - catecholaminergic polymorphic ventricular tachycardia , calsequestrin , endoplasmic reticulum , ryanodine receptor 2 , ryanodine receptor , mutation , myocyte , biology , microbiology and biotechnology , medicine , endocrinology , genetics , gene
Catecholamine‐induced polymorphic ventricular tachycardia (CPVT) is a familial disorder caused by calsequestrin 2 ( CASQ2 ) gene mutations. Here, we report the identification of a new CASQ2 mutation, K206N, which transmitted autosomally and is associated with CPVT and sudden cardiac death in a young patient. To find a causal link between K206N and the CPVT phenotype, we studied biochemical and physiological effects of K206N overexpression, in comparison to the native form (NT) of the calsequestrin protein (CSQ), in both insect cells and isolated neonatal mouse myocytes by use of recombinant baculoviruses and adenoviruses, respectively. The CSQ mutation was associated with the insertion of a second glycosylation site resulting in a higher mobility form compared to NT. Consistently, the mutated CSQ colocalized with mannosidase II, whereas NT did not. Thus, hyperglycosylation of K206N may trigger the lower Ca binding (by 54%) observed in 45 Ca overlay blots. Moreover, we found a higher binding (by 40%) of the mutated CSQ to a GST‐triadin fusion protein in pull‐down assays. [ 3 H]ryanodine binding was increased by 115% in homogenates of myocytes infected with K206N compared to NT, suggesting a higher open probability of the SR Ca release channel. In line with these findings, myocytes with K206N overexpression had a higher rate of spontaneous Ca transients, when exposed to isoproterenol. The data of the present study demonstrate that overexpression of K206N in myocytes causes an abnormal Ca handling and therefore, may predispose to the CPVT phenotype observed in the human patient. This study was supported by the Deutsche Forschungsgemeinschaft (Ki 653/13‐1/2).