title: Glutamate-dependent transcriptional regulation of GLAST: role of PKC.
abstract: The Na+-dependent glutamate/aspartate transporter GLAST plays a major role in the removal of glutamate from the synaptic cleft. Short-term, as well as long-term changes in transporter activity are triggered by glutamate. An important locus of regulation is the density of transporter molecules present at the plasma membrane. A substrate-dependent change in the translocation rate of the transporter molecules accounts for the short-term effect, whereas the long-term modulation apparently involves transcriptional regulation. Using cultured chick cerebellar Bergmann glial cells, we report here that glutamate receptors activation mediate a substantial reduction in the transcriptional activity of the chglast promoter through the Ca2+/diacylglicerol-dependent protein kinase (PKC) signaling cascade. Overexpression of constitutive active PKC isoforms of mimic the glutamate effect. Accordingly, increased levels of c-Jun or c-Fos, but not Jun-B, Jun-D or Fos-B, lower the chglast promoter activity. Serial deletions and electrophorectic mobility shift assays were used to define a specific region within the 5' proximal region of the chglast promoter, associated with transcriptional repression. A putative glutamate response element could be defined in the proximal promoter stretch more likely between nts -40 and -78. These results demonstrate that GLAST is under glutamate-dependent transcriptional control through PKC, and support the notion of a pivotal role of this neurotransmitter in the regulation of its own removal from the synaptic cleft, thereby modulating, mainly in the long term, glutamatergic transmission.
authors.affiliation: Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México.
authors.forename: Esther
authors.initials: E
authors.lastname: López-Bayghen
authors.forename: Arturo
authors.initials: A
authors.lastname: Ortega
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D060829:Arthropod Proteins; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects; D002642:Chick Embryo; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D004347:Drug Interactions; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D017353:Gene Deletion; D017930:Genes, Reporter / Q000187:drug effects / Q000502:physiology; D016762:Genes, fos / Q000187:drug effects / Q000502:physiology; D016758:Genes, jun / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D007447:Invertebrate Hormones; D008301:Maleimides / Q000494:pharmacology; D008954:Models, Biological; D009457:Neuroglia / Q000187:drug effects* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D017422:Sequence Analysis, DNA / Q000379:methods; D019311:Staurosporine / Q000494:pharmacology; D016385:TATA Box / Q000187:drug effects / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection / Q000379:methods; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D027322:Amino Acid Transport System X-AG; D060829:Arthropod Proteins; C116855:CHH-like protein, shrimp; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D007211:Indoles; D007447:Invertebrate Hormones; D008301:Maleimides; D011725:Pyridines; C431843:tris(2-pyridylmethyl)amine; D018698:Glutamic Acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D015500:Chloramphenicol O-Acetyltransferase; D011493:Protein Kinase C; D019311:Staurosporine; C070515:bisindolylmaleimide I