The Role of Bestrophin-1 in Intracellular Ca2+ Signaling
The Role of Bestrophin-1 in Intracellular Ca2+ Signaling
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DOI：
10.1007/978-1-4614-3209-8_15
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发表时间：
2014-01-01
期刊：
影响因子：
--
通讯作者：
Gomez, Nestor Mas
中科院分区：
文献类型：
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作者：
Strauss, Olaf;Mueller, Claudia;Gomez, Nestor Mas
BEST1基因的突变会导致多种视网膜变性，其中包括贝斯特的黄斑黄斑变性。为了阐明该病的发病机制，必须了解BEST1基因产物Bestrophin-1的功能。在过度表达的研究中，Bestrophin-1似乎是一种钙依赖的氯离子通道。另一方面，Bestrophin-1能够参与细胞内的钙信号转导。差速离心法、免疫组织化学和透射电子显微镜显示，内源性表达的Bestrophin-1主要定位于视网膜色素上皮(RPE)基底侧膜附近的胞浆室。为了阐明Bestrophin-1的胞浆功能，我们研究了短期培养的猪RPE细胞内钙离子内流。SERCA抑制导致细胞内钙库耗尽，导致Orai-1钙通道激活。这导致细胞外钙离子流入细胞内，而当使用siRNA技术下调Bestrophin-1的表达时，细胞外钙离子的内流减少。对胞浆钙库中可释放的钙离子进行定量，结果显示在Bestrophin-1表达降低后，内质网钙库中的钙库中存储的钙离子较少。因此，Bestrophin-1作为细胞内的氯离子通道，通过传导钙离子的反离子来帮助蓄积和释放钙离子。
Mutations in the BEST1 gene lead to a variety of retinal degenerations, among them Best's vitelliforme macular degeneration. To clarify the mechanism of the disease, the understanding of the function of BEST1 gene product, bestrophin-1, is mandatory. In overexpression studies bestrophin-1 appeared to function as a Ca2+-dependent Cl channel. On the other hand, bestrophin-1 is able to participate in intracellular Ca2+ signaling. Endogenously expressed bestrophin-1 largely localized to the cytosolic compartment close to the basolateral membrane of the retinal pigment epithelium (RPE) as it can be shown using differential centrifugation, immunohistochemistry, and transmission electron microscopy. To elucidate a cytosolic function of bestrophin-1, we explored the store-operated Ca2+ entry in short-time cultured porcine RPE cells. Depletion of cytosolic Ca2+ stores by SERCA inhibition led to activation of Orai-1 Ca2+ channels. This resulted in an influx of extracellular Ca2+ into the cell which was reduced when bestrophin-1 expression was knocked down using siRNA techniques. Quantification of Ca2+ which can be released from cytosolic Ca2+ stores revealed that after reduction of bestrophin-1 expression less Ca2+ is stored in ER Ca2+ stores. Thus, bestrophin-1 functions as an intracellular Cl channel which helps to accumulate and to release Ca2+ from stores by conducting the counterion for Ca2+.