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Store-Operated Calcium Entry in Müller Glia Is Controlled by Synergistic Activation of TRPC and Orai Channels.
J Neurosci. 2016 Mar 16; 36(11):3184-98.JN

Abstract

The endoplasmic reticulum (ER) is at the epicenter of astrocyte Ca(2+) signaling. We sought to identify the molecular mechanism underlying store-operated calcium entry that replenishes ER stores in mouse Müller cells. Store depletion, induced through blockade of sequestration transporters in Ca(2+)-free saline, induced synergistic activation of canonical transient receptor potential 1 (TRPC1) and Orai channels. Store-operated TRPC1 channels were identified by their electrophysiological properties, pharmacological blockers, and ablation of the Trpc1 gene. Ca(2+) release-activated currents (ICRAC) were identified by ion permeability, voltage dependence, and sensitivity to selective Orai antagonists Synta66 and GSK7975A. Depletion-evoked calcium influx was initiated at the Müller end-foot and apical process, triggering centrifugal propagation of Ca(2+) waves into the cell body. EM analysis of the end-foot compartment showed high-density ER cisternae that shadow retinal ganglion cell (RGC) somata and axons, protoplasmic astrocytes, vascular endothelial cells, and ER-mitochondrial contacts at the vitreal surface of the end-foot. The mouse retina expresses transcripts encoding both Stim and all known Orai genes; Müller glia predominantly express stromal interacting molecule 1 (STIM1), whereas STIM2 is mainly confined to the outer plexiform and RGC layers. Elimination of TRPC1 facilitated Müller gliosis induced by the elevation of intraocular pressure, suggesting that TRPC channels might play a neuroprotective role during mechanical stress. By characterizing the properties of store-operated signaling pathways in Müller cells, these studies expand the current knowledge about the functional roles these cells play in retinal physiology and pathology while also providing further evidence for the complexity of calcium signaling mechanisms in CNS astroglia.

SIGNIFICANCE STATEMENT

Store-operated Ca(2+) signaling represents a major signaling pathway and source of cytosolic Ca(2+) in astrocytes. Here, we show that the store-operated response in Müller cells, radial glia that perform key structural, signaling, osmoregulatory, and mechanosensory functions within the retina, is mediated through synergistic activation of transient receptor potential and Orai channels. The end-foot disproportionately expresses the depletion sensor stromal interacting molecule 1, which contains an extraordinarily high density of endoplasmic reticulum cisternae that shadow neuronal, astrocytic, vascular, and axonal structures; interface with mitochondria; but also originate store-operated Ca(2+) entry-induced transcellular Ca(2+) waves that propagate glial excitation into the proximal retina. These results identify a molecular mechanism that underlies complex interactions between the plasma membrane and calcium stores, and contributes to astroglial function, regulation, and response to mechanical stress.

Authors+Show Affiliations

Departments of Ophthalmology & Visual Sciences.Departments of Ophthalmology & Visual Sciences.Departments of Ophthalmology & Visual Sciences.Departments of Ophthalmology & Visual Sciences.Departments of Ophthalmology & Visual Sciences.Departments of Ophthalmology & Visual Sciences.Departments of Ophthalmology & Visual Sciences.Departments of Ophthalmology & Visual Sciences, Neurobiology & Anatomy, and Bioengineering, University of Utah School of Medicine, Salt Lake City, Utah 84132 david.krizaj@hsc.utah.edu.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Video-Audio Media

Language

eng

PubMed ID

26985029

Citation

Molnár, Tünde, et al. "Store-Operated Calcium Entry in Müller Glia Is Controlled By Synergistic Activation of TRPC and Orai Channels." The Journal of Neuroscience : the Official Journal of the Society for Neuroscience, vol. 36, no. 11, 2016, pp. 3184-98.
Molnár T, Yarishkin O, Iuso A, et al. Store-Operated Calcium Entry in Müller Glia Is Controlled by Synergistic Activation of TRPC and Orai Channels. J Neurosci. 2016;36(11):3184-98.
Molnár, T., Yarishkin, O., Iuso, A., Barabas, P., Jones, B., Marc, R. E., Phuong, T. T., & Križaj, D. (2016). Store-Operated Calcium Entry in Müller Glia Is Controlled by Synergistic Activation of TRPC and Orai Channels. The Journal of Neuroscience : the Official Journal of the Society for Neuroscience, 36(11), 3184-98. https://doi.org/10.1523/JNEUROSCI.4069-15.2016
Molnár T, et al. Store-Operated Calcium Entry in Müller Glia Is Controlled By Synergistic Activation of TRPC and Orai Channels. J Neurosci. 2016 Mar 16;36(11):3184-98. PubMed PMID: 26985029.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Store-Operated Calcium Entry in Müller Glia Is Controlled by Synergistic Activation of TRPC and Orai Channels. AU - Molnár,Tünde, AU - Yarishkin,Oleg, AU - Iuso,Anthony, AU - Barabas,Peter, AU - Jones,Bryan, AU - Marc,Robert E, AU - Phuong,Tam T T, AU - Križaj,David, PY - 2016/3/18/entrez PY - 2016/3/18/pubmed PY - 2016/7/28/medline KW - ER stores KW - TRPC KW - astrocyte end-feet KW - calcium KW - reactive gliosis KW - store-operated channels SP - 3184 EP - 98 JF - The Journal of neuroscience : the official journal of the Society for Neuroscience JO - J Neurosci VL - 36 IS - 11 N2 - UNLABELLED: The endoplasmic reticulum (ER) is at the epicenter of astrocyte Ca(2+) signaling. We sought to identify the molecular mechanism underlying store-operated calcium entry that replenishes ER stores in mouse Müller cells. Store depletion, induced through blockade of sequestration transporters in Ca(2+)-free saline, induced synergistic activation of canonical transient receptor potential 1 (TRPC1) and Orai channels. Store-operated TRPC1 channels were identified by their electrophysiological properties, pharmacological blockers, and ablation of the Trpc1 gene. Ca(2+) release-activated currents (ICRAC) were identified by ion permeability, voltage dependence, and sensitivity to selective Orai antagonists Synta66 and GSK7975A. Depletion-evoked calcium influx was initiated at the Müller end-foot and apical process, triggering centrifugal propagation of Ca(2+) waves into the cell body. EM analysis of the end-foot compartment showed high-density ER cisternae that shadow retinal ganglion cell (RGC) somata and axons, protoplasmic astrocytes, vascular endothelial cells, and ER-mitochondrial contacts at the vitreal surface of the end-foot. The mouse retina expresses transcripts encoding both Stim and all known Orai genes; Müller glia predominantly express stromal interacting molecule 1 (STIM1), whereas STIM2 is mainly confined to the outer plexiform and RGC layers. Elimination of TRPC1 facilitated Müller gliosis induced by the elevation of intraocular pressure, suggesting that TRPC channels might play a neuroprotective role during mechanical stress. By characterizing the properties of store-operated signaling pathways in Müller cells, these studies expand the current knowledge about the functional roles these cells play in retinal physiology and pathology while also providing further evidence for the complexity of calcium signaling mechanisms in CNS astroglia. SIGNIFICANCE STATEMENT: Store-operated Ca(2+) signaling represents a major signaling pathway and source of cytosolic Ca(2+) in astrocytes. Here, we show that the store-operated response in Müller cells, radial glia that perform key structural, signaling, osmoregulatory, and mechanosensory functions within the retina, is mediated through synergistic activation of transient receptor potential and Orai channels. The end-foot disproportionately expresses the depletion sensor stromal interacting molecule 1, which contains an extraordinarily high density of endoplasmic reticulum cisternae that shadow neuronal, astrocytic, vascular, and axonal structures; interface with mitochondria; but also originate store-operated Ca(2+) entry-induced transcellular Ca(2+) waves that propagate glial excitation into the proximal retina. These results identify a molecular mechanism that underlies complex interactions between the plasma membrane and calcium stores, and contributes to astroglial function, regulation, and response to mechanical stress. SN - 1529-2401 UR - https://www.unboundmedicine.com/medline/citation/26985029/Store_Operated_Calcium_Entry_in_Müller_Glia_Is_Controlled_by_Synergistic_Activation_of_TRPC_and_Orai_Channels_ L2 - http://www.jneurosci.org/cgi/pmidlookup?view=long&pmid=26985029 DB - PRIME DP - Unbound Medicine ER -