Raynal P, Kuijpers G, Rojas E, Pollard H B
Laboratory of Cell Biology and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
FEBS Lett. 1996 Sep 2;392(3):263-8. doi: 10.1016/0014-5793(96)00827-7.
Following incubation of human fibroblasts with Ca2+ ionophore A23187, we found strong immunofluorescence labelling of the nuclear envelope by annexin IV antibody. Using confocal imaging of cells loaded with Fluo-3, we showed that A23187 generates an intense and sustained rise of Ca2+ in the nucleus. By contrast, stimulation without extracellular Ca2+ produces only a brief rise in nuclear Ca2+ that does not promote annexin IV translocation to the nuclear envelope, and compounds that induce only a transient increase of nuclear Ca2+ do not support translocation of annexin IV. In addition, annexin V was also translocated to the nuclear envelope by A23187, but distribution of annexins I, II, VI and VII is unaffected. In in vitro assays with isolated nuclei, annexin V was also found to bind to the nuclear envelope in a Ca2+-dependent manner. These results demonstrate that the translocation to the nuclear envelope of different types of Ca2+-regulated proteins is directly triggered by a major rise of Ca2+ in the nucleus.
在用钙离子载体A23187孵育人成纤维细胞后，我们发现膜联蛋白IV抗体对核膜有强烈的免疫荧光标记。通过对加载了Fluo-3的细胞进行共聚焦成像，我们发现A23187会使细胞核内的钙离子产生强烈且持续的升高。相比之下，在无细胞外钙离子的情况下进行刺激，只会使细胞核内的钙离子短暂升高，且不会促使膜联蛋白IV转位至核膜，而仅能诱导细胞核内钙离子短暂增加的化合物也无法支持膜联蛋白IV的转位。此外，膜联蛋白V也会被A23187转位至核膜，但膜联蛋白I、II、VI和VII的分布未受影响。在对分离细胞核进行的体外实验中，还发现膜联蛋白V能以钙离子依赖的方式与核膜结合。这些结果表明，细胞核内钙离子的大幅升高直接触发了不同类型钙离子调节蛋白向核膜的转位。
