Store-operated Ca2+ entry in astrocytes: different spatial arrangement of endoplasmic reticulum explains functional diversity in vitro and in situ.
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.
Cytology Department, Bogomoletz Institute of Physiology, Bogomoletz Str. 4, 01024 Kiev, Ukraine.
Tatjyana
T
Pivneva
Brigitte
B
Haas
Daniel
D
Reyes-Haro
Gregor
G
Laube
Ruediger W
RW
Veh
Christiane
C
Nolte
Galina
G
Skibo
Helmut
H
Kettenmann
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000814:Aniline Compounds; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D006624:Hippocampus / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D046529:Microscopy, Electron, Transmission; D009685:Nuclear Envelope / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009924:Organ Culture Techniques; D013194:Staining and Labeling; D014966:Xanthenes; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology
D000814:Aniline Compounds; C409648:Fluo 4; D005456:Fluorescent Dyes; D014966:Xanthenes; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D015032:Zinc; D002118:Calcium