Direct monitoring of ER Ca2+ dynamics reveals that Ca2+ entry induces ER-Ca2+ release in astrocytes.

Direct monitoring of ER Ca2+ dynamics reveals that Ca2+ entry induces ER-Ca2+ release in astrocytes. Pflugers Arch. 2020 Apr 03;: Authors: Rodríguez-Prados M, Rojo-Ruiz J, García-Sancho J, Alonso MT Abstract Excitability in astroglia is controlled by Ca2+ fluxes from intracellular organelles, mostly from the endoplasmic reticulum (ER). Astrocytic ER possesses inositol 1,4,5-trisphosphate receptors (InsP3R) that can be activated upon stimulation through a vast number of metabotropic G-protein-coupled receptors. By contrast, the role of Ca2+-gated Ca2+ release channels is less explored in astroglia. Here we address this process by monitoring Ca2+ dynamics directly in the cytosol and the ER of astroglial cells. Cultured astrocytes exhibited spontaneous and high-K-evoked cytosolic Ca2+ transients, both of them reversibly abolished by external Ca2+ removal, addition of plasma membrane channel blockers or ER Ca2+ depletion with SERCA inhibitors. Resting astrocyte [Ca2+]ER averaged 400 μM and maximal stimulation with ATP provoked a complete and reversible ER discharge. Direct monitoring of Ca2+ in the lumen of ER showed that high-K induced a Ca2+ release from the ER, and its amplitude was proportional to the [K]. Furthermore, by combining the low affinity GAP3 indicator targeted to the ER with the high affinity cytosolic Rhod-2, we simultaneously imaged ER- and cytosolic-Ca2+ signals, in astrocytes in culture and in situ. Plasma membran...
Source: Pflugers Archiv : European Journal of Physiology - Category: Physiology Authors: Tags: Pflugers Arch Source Type: research
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