Dataset Information

Local Resting Ca²⁺ Controls the Scale of Astroglial Ca²⁺ Signals.

ABSTRACT: Astroglia regulate neurovascular coupling while engaging in signal exchange with neurons. The underlying cellular machinery is thought to rely on astrocytic Ca²⁺ signals, but what controls their amplitude and waveform is poorly understood. Here, we employ time-resolved two-photon excitation fluorescence imaging in acute hippocampal slices and in cortex in vivo to find that resting [Ca²⁺] predicts the scale (amplitude) and the maximum (peak) of astroglial Ca²⁺ elevations. We bidirectionally manipulate resting [Ca²⁺] by uncaging intracellular Ca²⁺ or Ca²⁺ buffers and use ratiometric imaging of a genetically encoded Ca²⁺ indicator to establish that alterations in resting [Ca²⁺] change co-directionally the peak level and anti-directionally the amplitude of local Ca²⁺ transients. This relationship holds for spontaneous and for induced (for instance by locomotion) Ca²⁺ signals. Our findings uncover a basic generic rule of Ca²⁺ signal formation in astrocytes, thus also associating the resting Ca²⁺ level with the physiological "excitability" state of astroglia.

SUBMITTER: King CM

PROVIDER: S-EPMC7068654 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Publications

Local Resting Ca2+ Controls the Scale of Astroglial Ca2+ Signals.

King Claire M CM Bohmbach Kirsten K Minge Daniel D Delekate Andrea A Zheng Kaiyu K Reynolds James J Rakers Cordula C Zeug Andre A Petzold Gabor C GC Rusakov Dmitri A DA Henneberger Christian C

Cell reports 20200301 10

Astroglia regulate neurovascular coupling while engaging in signal exchange with neurons. The underlying cellular machinery is thought to rely on astrocytic Ca2+ signals, but what controls their amplitude and waveform is poorly understood. Here, we employ time-resolved two-photon excitation fluorescence imaging in acute hippocampal slices and in cortex in vivo to find that resting [Ca2+] predicts the scale (amplitude) and the maximum (peak) of astroglial Ca2+ ele ...[more]

PMID: 32160550

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Project description:Store-operated Ca²+ entry (SOCE) has been associated with two types of channels: CRAC channels that require Orai1 and STIM1 and SOC channels that involve TRPC1, Orai1, and STIM1. While TRPC1 significantly contributes to SOCE and SOC channel activity, abrogation of Orai1 function eliminates SOCE and activation of TRPC1. The critical role of Orai1 in activation of TRPC1-SOC channels following Ca²+ store depletion has not yet been established. Herein we report that TRPC1 and Orai1 are components of distinct channels. We show that TRPC1/Orai1/STIM1-dependent I(SOC), activated in response to Ca²+ store depletion, is composed of TRPC1/STIM1-mediated non-selective cation current and Orai1/STIM1-mediated I(CRAC); the latter is detected when TRPC1 function is suppressed by expression of shTRPC1 or a STIM1 mutant that lacks TRPC1 gating, STIM1(⁶⁸⁴EE⁶⁸⁵). In addition to gating TRPC1 and Orai1, STIM1 mediates the recruitment and association of the channels within ER/PM junctional domains, a critical step in TRPC1 activation. Importantly, we show that Ca²+ entry via Orai1 triggers plasma membrane insertion of TRPC1, which is prevented by blocking SOCE with 1 µM Gd³+, removal of extracellular Ca²+, knockdown of Orai1, or expression of dominant negative mutant Orai1 lacking a functional pore, Orai1-E106Q. In cells expressing another pore mutant of Orai1, Orai1-E106D, TRPC1 trafficking is supported in Ca²+-containing, but not Ca²+-free, medium. Consistent with this, I(CRAC) is activated in cells pretreated with thapsigargin in Ca²+-free medium while I(SOC) is activated in cells pretreated in Ca²+-containing medium. Significantly, TRPC1 function is required for sustained K(Ca) activity and contributes to NFκB activation while Orai1 is sufficient for NFAT activation. Together, these findings reveal an as-yet unidentified function for Orai1 that explains the critical requirement of the channel in the activation of TRPC1 following Ca²+ store depletion. We suggest that coordinated regulation of the surface expression of TRPC1 by Orai1 and gating by STIM1 provides a mechanism for rapidly modulating and maintaining SOCE-generated Ca²+ signals. By recruiting ion channels and other signaling pathways, Orai1 and STIM1 concertedly impact a variety of critical cell functions that are initiated by SOCE.

Dataset Information

Local Resting Ca²⁺ Controls the Scale of Astroglial Ca²⁺ Signals.

Publications

Local Resting Ca<sup>2+</sup> Controls the Scale of Astroglial Ca<sup>2+</sup> Signals.

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