Grimaldi Maurizio
Laboratory of Neuropharmacology, Department of Biochemistry, Drug Discovery Division, Southern Research Institute, Birmingham, AL 35025, USA.
J Neurosci Res. 2006 Dec;84(8):1738-49. doi: 10.1002/jnr.21064.
Capacitative Ca(2+) entry (CCE) is a phenomenon triggered by depletion of Ca(2+) content in intracellular stores (ICS). Data about this phenomenon in astrocytes are limited. We analyzed CCE in astrocytes by means of fura-2 based digital imaging. We found that in astrocytes CCE is not associated with an increase of cytosolic Ca(2+) concentration (Ca(2+)), although ICS are efficiently refilled. We used Mn(2+), thapsigargin and prolonged ATP exposure to show that CCE is not associated with cytosolic diffusion of Ca(2+) entering astrocytes. Our data suggest that the ion is being quickly sequestered in the ICS by the smooth endoplasmic reticulum Ca(2+)-ATP-ase (SERCA). Several experiments were carried out with the goal of failing the efficient uptake in the endoplasmic reticulum (ER). In fact, inhibition of SERCA activity, increased extracellular Ca(2+) or pharmacologic potentiation of CCE all caused Ca(2+) elevation during CCE, suggesting that the control of this phenomenon could have physiologic and pathological relevance. The molecular components involved in CCE have been proposed to be organized in a multi-molecular complex tethered by cytoskeleton components and arranged via a secretion coupling model. We show here that the efficient routing of Ca(2+) into the ICS in astrocytes is not affected by disruption of cytoskeleton organization or Golgi's function, but it is instead linked to the high efficiency of SERCA. We conclude that depleted ICS in astrocytes are efficiently refilled by CCE activation, although Ca(2+) influx is not accompanied by elevation of Ca(2+). This ability seems to be functional rather than structural in nature.
容量性钙内流（CCE）是一种由细胞内钙库（ICS）中钙含量耗竭引发的现象。关于星形胶质细胞中这一现象的数据有限。我们通过基于fura-2的数字成像分析了星形胶质细胞中的CCE。我们发现，在星形胶质细胞中，尽管ICS能有效重新充盈，但CCE与胞质钙浓度（[Ca²⁺]i）的升高并无关联。我们使用锰离子（Mn²⁺）、毒胡萝卜素和延长ATP暴露时间来表明CCE与进入星形胶质细胞的钙的胞质扩散无关。我们的数据表明，该离子正被光滑内质网钙ATP酶（SERCA）迅速隔离在ICS中。为了使内质网（ER）中的有效摄取失败，我们进行了几项实验。事实上，抑制SERCA活性、增加细胞外[Ca²⁺]i或CCE的药理学增强均导致CCE期间[Ca²⁺]i升高，这表明对这一现象的控制可能具有生理和病理相关性。有人提出，参与CCE的分子成分以多分子复合物的形式组织，该复合物由细胞骨架成分束缚并通过分泌偶联模型排列。我们在此表明，星形胶质细胞中钙向ICS的有效转运不受细胞骨架组织破坏或高尔基体功能的影响，而是与SERCA的高效率相关。我们得出结论，尽管钙内流不伴随[Ca²⁺]i升高，但通过激活CCE可有效重新充盈星形胶质细胞中耗竭的ICS。这种能力在本质上似乎是功能性而非结构性的。
