Nucleoplasmic Ca2+ loading is regulated by mobilization of perinuclear Ca2+

被引:42
作者
Abrenica, B
Gilchrist, JSC
机构
[1] Univ Manitoba, Dept Oral Biol & Physiol, Div Stroke & Vasc Dis, Winnipeg, MB, Canada
[2] Univ Manitoba, Dept Physiol, Div Stroke & Vasc Dis, Winnipeg, MB R2H 2A6, Canada
基金
英国医学研究理事会;
关键词
D O I
10.1054/ceca.2000.0137
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
Regulation of nucleoplasmic calcium (Ca2+) concentration may occur by the mobilization of perinuclear luminal Ca2+ pools involving specific Ca2+ pumps and channels of both inner and outer perinuclear membranes. To determine the role of perinuclear luminal Ca2+, we examined freshly cultured 10 day-old embryonic chick ventricular cardiomyocytes. We obtained evidence suggesting the existence of the molecular machinery required for the bi-directional Ca2+ fluxes using confocal imaging techniques. Embryonic cardiomyocytes were probed with antibodies specific for ryanodine-sensitive Ca2+ channels (RyR2), sarco/endoplasmic reticulum Ca2+ ATPase (SERCA2)-pumps, and fluorescent BODIPY derivatives of ryanodine and thapsigargin. Using immunocytochemistry techniques, confocal imaging showed the presence of RyR2 Ca2+ channels and SERCA2-pumps highly localized to regions surrounding the nucleus, referable to the nuclear envelope. Results obtained from Fluo-3, AM loaded ionomycin-perforated embryonic cardiomyocytes demonstrated that gradual increases of extranuclear Ca2+ from 100 to 1600 nM Ca2+ was localized to the nucleus. SERCA2-pump inhibitors thapsigargin and cyclopiazonic acid showed a concentration-dependent inhibition of nuclear Ca2+ loading. Furthermore, ryanodine demonstrated a biphasic concentration-dependence upon active nuclear Ca2+ loading. The concomitant addition of thapsigargin or cyclopiazonic acid with ryanodine at inhibitory concentrations caused an significant increase in nuclear Ca2+ loading at low concentrations of extranuclear added Ca2+. Our results show that the perinuclear lumen in embryonic chick ventricular cardiomyocytes is capable of autonomously regulating nucleoplasmic Ca2+ fluxes. (C) 2000 Harcourt Publishers Ltd.
引用
收藏
页码:127 / 136
页数:10
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