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

Autor: Javier García-Sancho, Jonathan Rojo-Ruiz, Maria Teresa Alonso, Macarena Rodríguez-Prados
Přispěvatelé: Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Junta de Castilla y León
Rok vydání: 2020
Předmět:
Zdroj: Digital.CSIC. Repositorio Institucional del CSIC
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ISSN: 1432-2013
0031-6768
DOI: 10.1007/s00424-020-02364-7
Popis: 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 membrane Ca2+ entry triggered a fast ER Ca2+ release coordinated with an increase in cytosolic Ca2+. Thus, we identify a Ca2+-induced Ca2+-release (CICR) mechanism that is likely to participate in spontaneous astroglial oscillations, providing a graded amplification of the cytosolic Ca2+ signal.
This work was supported by grants from The Spanish MINECO (BFU2017-83066-P) and the Junta de Castilla y León (GR175). Macarena Rodriguez-Prados and Jonathan Rojo-Ruiz were supported by fellowships from the Spanish MINECO.
Databáze: OpenAIRE
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