title: Functional plasticity of GAT-3 in avian Müller cells is regulated by neurons via a glutamatergic input.
abstract: GABA (γ-amino butyric acid) is the major inhibitory transmitter in the central nervous system and its action is terminated by specific transporters (GAT), found in neurons and glial cells. We have previously described that GAT-3 is responsible for GABA uptake activity in cultured avian Müller cells and that it operates in a Na(+) and Cl(-) dependent manner. Here we show that glutamate decreases [(3)H] GABA uptake in purified cultured glial cells up to 50%, without causing cell death. This effect is mediated by ionotropic glutamatergic receptors. Glutamate inhibition on GABA uptake is not reverted by inhibitors of protein kinase C or modified by agents that modulate cyclic AMP/PKA. Biotinylation experiments demonstrate that this reduction in GABA uptake correlates with a decrease in GAT-3 plasma membrane levels. Interestingly, both GAT-1 and GAT-3 mRNA levels are also decreased by glutamate. Conditioned media (CM) prepared from retinal neurons could also decrease GABA influx, and glutamate receptor antagonists (MK-801 + CNQX) were able to prevent this effect. However, glutamate levels in CM were not different from those found in fresh media, indicating that a glutamatergic co-agonist or modulator could be regulating GABA uptake by Müller cells in this scenario. In the whole avian retina, GAT-3 is present from embryonic day 5 (E5) increasing up to the end of embryonic development and post-hatch period exclusively in neuronal layers. However, this pattern may change in pathological conditions, which drive GAT-3 expression in Müller cells. Our data suggest that in purified cultures and upon extensive neuronal lesion in vivo, shown as a Brn3a reduced neuronal cells and an GFAP increased gliosis, Müller glia may change its capacity to take up GABA due to GAT-3 up regulation and suggests a regulatory interplay mediated by glutamate between neurons and glial cells in this process.
authors.affiliation: Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Clarissa S
authors.initials: CS
authors.lastname: Schitine
authors.affiliation: Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Dept. Genética y Biología Molecular, Ciudad de Mexico, Mexico.
authors.forename: Orquidia G
authors.initials: OG
authors.lastname: Mendez-Flores
authors.affiliation: Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Santos
authors.affiliation: Dept. Neurobiologia, Programa de Pós-graduação em Neurociências, Instituto de Biologia, Universidade Federal Fluminense, Niterói, Rio de Janeiro, Brazil.
authors.forename: Isis
authors.initials: I
authors.lastname: Ornelas
authors.affiliation: Dept. Neurobiologia, Programa de Pós-graduação em Neurociências, Instituto de Biologia, Universidade Federal Fluminense, Niterói, Rio de Janeiro, Brazil.
authors.forename: Karin C
authors.initials: KC
authors.lastname: Calaza
authors.affiliation: Dept. Genética y Biología Molecular, Ciudad de Mexico, Mexico.
authors.forename: Karla
authors.initials: K
authors.lastname: Pérez-Toledo
authors.affiliation: Dept. Toxicología Cinvestav-IPN, Ciudad de Mexico, Mexico.
authors.forename: Esther
authors.initials: E
authors.lastname: López-Bayghen
authors.affiliation: Dept. Toxicología Cinvestav-IPN, Ciudad de Mexico, Mexico.
authors.forename: Arturo
authors.initials: A
authors.lastname: Ortega
authors.affiliation: Lab. Neurobiologia da Retina, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Patrícia F
authors.initials: PF
authors.lastname: Gardino
authors.affiliation: Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Fernando G
authors.initials: FG
authors.lastname: de Mello
authors.affiliation: Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. Electronic address: ramreis@biof.ufrj.br.
authors.forename: Ricardo A M
authors.initials: RA
authors.lastname: Reis
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D019921:Biotinylation; D002118:Calcium / Q000032:analysis; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D017077:Culture Media, Conditioned; D063928:Ependymoglial Cells / Q000187:drug effects / Q000502:physiology*; D050485:GABA Plasma Membrane Transport Proteins / Q000235:genetics / Q000502:physiology*; D020869:Gene Expression Profiling; D018698:Glutamic Acid / Q000494:pharmacology / Q000502:physiology*; D007608:Kainic Acid / Q000494:pharmacology; D016202:N-Methylaspartate / Q000008:administration & dosage / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012160:Retina / Q000254:growth & development; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D017077:Culture Media, Conditioned; D050485:GABA Plasma Membrane Transport Proteins; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D007608:Kainic Acid; D002118:Calcium
keywords: GABA transporters; Glutamate receptors; Müller glia