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Glutamate transporter‐associated anion channels adjust intracellular chloride concentrations during glial maturation
Author(s) -
Untiet Verena,
Kovermann Peter,
Gerkau Niklas J.,
Gensch Thomas,
Rose Christine R.,
Fahlke Christoph
Publication year - 2017
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.23098
Subject(s) - cotransporter , chloride channel , intracellular , chloride , biology , biophysics , neuroglia , glutamate receptor , biochemistry , intracellular ph , excitatory postsynaptic potential , microbiology and biotechnology , transporter , chemistry , neuroscience , sodium , central nervous system , receptor , gene , organic chemistry
Astrocytic volume regulation and neurotransmitter uptake are critically dependent on the intracellular anion concentration, but little is known about the mechanisms controlling internal anion homeostasis in these cells. Here we used fluorescence lifetime imaging microscopy (FLIM) with the chloride‐sensitive dye MQAE to measure intracellular chloride concentrations in murine Bergmann glial cells in acute cerebellar slices. We found Bergmann glial [Cl − ] int to be controlled by two opposing transport processes: chloride is actively accumulated by the Na + ‐K + ‐2Cl − cotransporter NKCC1, and chloride efflux through anion channels associated with excitatory amino acid transporters (EAATs) reduces [Cl − ] int to values that vary upon changes in expression levels or activity of these channels. EAATs transiently form anion‐selective channels during glutamate transport, and thus represent a class of ligand‐gated anion channels. Age‐dependent upregulation of EAATs results in a developmental chloride switch from high internal chloride concentrations (51.6 ± 2.2 mM, mean ± 95% confidence interval) during early development to adult levels (35.3 ± 0.3 mM). Simultaneous blockade of EAAT1/GLAST and EAAT2/GLT‐1 increased [Cl − ] int in adult glia to neonatal values. Moreover, EAAT activation by synaptic stimulations rapidly decreased [Cl − ] int . Other tested chloride channels or chloride transporters do not contribute to [Cl − ] int under our experimental conditions. Neither genetic removal of ClC‐2 nor pharmacological block of K + ‐Cl − cotransporter change resting Bergmann glial [Cl − ] int in acute cerebellar slices. We conclude that EAAT anion channels play an important and unexpected role in adjusting glial intracellular anion concentration during maturation and in response to cerebellar activity. GLIA 2017;65:388–400