Pivneva Tatjyana, Haas Brigitte, Reyes-Haro Daniel, Laube Gregor, Veh Ruediger W, Nolte Christiane, Skibo Galina, Kettenmann Helmut
Cytology Department, Bogomoletz Institute of Physiology, Bogomoletz Str. 4, 01024 Kiev, Ukraine.
Cell Calcium. 2008 Jun;43(6):591-601. doi: 10.1016/j.ceca.2007.10.004. Epub 2007 Dec 3.
Ca(2+) signaling is the astrocyte form of excitability and the endoplasmic reticulum (ER) plays an important role as an intracellular Ca(2+) store. Since the subcellular distribution of the ER influences Ca(2+) signaling, we compared the arrangement of ER in astrocytes of hippocampus tissue and astrocytes in cell culture by electron microscopy. While the ER was usually located in close apposition to the plasma membrane in astrocytes in situ, the ER in cultured astrocytes was close to the nuclear membrane. Activation of metabotropic receptors linked to release of Ca(2+) from ER stores triggered distinct responses in cultured and in situ astrocytes. In culture, Ca(2+) signals were commonly first recorded close to the nucleus and with a delay at peripheral regions of the cells. Store-operated Ca(2+) entry (SOC) as a route to refill the Ca(2+) stores could be easily identified in cultured astrocytes as the Zn(2+)-sensitive component of the Ca(2+) signal. In contrast, such a Zn(2+)-sensitive component was not recorded in astrocytes from hippocampal slices despite of evidence for SOC. Our data indicate that both, astrocytes in situ and in vitro express SOC necessary to refill stores, but that a SOC-related signal is not recorded in the cytoplasm of astrocytes in situ since the stores are close to the plasma membrane and the refill does not affect cytoplasmic Ca(2+) levels.
钙离子（Ca(2+)）信号传导是星形胶质细胞的兴奋性形式，而内质网（ER）作为细胞内钙离子储存库发挥着重要作用。由于内质网的亚细胞分布会影响钙离子信号传导，我们通过电子显微镜比较了海马组织星形胶质细胞和细胞培养中的星形胶质细胞内质网的排列情况。原位星形胶质细胞中的内质网通常紧邻质膜，而培养的星形胶质细胞中的内质网则靠近核膜。与内质网储存库中钙离子释放相关的代谢型受体激活在培养的星形胶质细胞和原位星形胶质细胞中引发了不同的反应。在培养中，钙离子信号通常首先在靠近细胞核处记录到，而在细胞周边区域则有延迟。作为补充钙离子储存库途径的储存-操作性钙离子内流（SOC）在培养的星形胶质细胞中可作为钙离子信号的锌离子（Zn(2+)）敏感成分轻松识别。相比之下，尽管有SOC的证据，但在海马切片的星形胶质细胞中未记录到这种锌离子敏感成分。我们的数据表明，原位和体外的星形胶质细胞都表达补充储存库所需的SOC，但由于储存库靠近质膜且补充过程不影响细胞质钙离子水平，因此在原位星形胶质细胞的细胞质中未记录到与SOC相关的信号。
