Epidermal growth factor receptor agonists increase expression of glutamate transporter GLT-1 in astrocytes through pathways dependent on phosphatidylinositol 3-kinase and transcription factor NF-κB

Olga Zelenaia, Brian D. Schlag, Gordon E. Gochenauer, Raquelli Ganel, Wei Song, Jacqueline S. Beesley, Judith B. Grinspan, Jeffrey D. Rothstein, Michael B. Robinson

Research output: Contribution to journalArticlepeer-review

Abstract

The glial glutamate transporter GLT-1 may be the predominant Na+- dependent glutamate transporter in forebrain. Expression of GLT-1 correlates with astrocyte maturation in vivo and increases during synaptogenesis. In astrocyte cultures, GLT-1 expression parallels differentiation induced by cAMP analogs or by coculturing with neurons. Molecule(s) secreted by neuronal cultures contribute to this induction of GLT-1, but little is known about the signaling pathways mediating this regulation. In the present study, we determined whether growth factors previously implicated in astrocyte differentiation regulate GLT-1 expression. Of the six growth factors tested, two [epidermal growth factor (EGF-) and transforming growth factor-α] induced expression of GLT-1 protein in cultured astrocytes. Induction of GLT- 1 protein was accompanied by an increase in mRNA and in the V(max) for Na+- dependent glutamate transport activity. The effects of dibutyryl-cAMP and EGF were additive but were independently blocked by inhibitors of protein kinase A or protein tyrosine kinases, respectively. The induction of GLT-1 in both EGF- and dibutyryl-cAMP-treated astrocytes was blocked by inhibitors targeting phosphatidylinositol 3-kinase (PI3K) or the nuclear transcription factor-κB. Furthermore, transient transfection of astrocyte cultures with a constitutively active PI3K construct was sufficient to induce expression of GLT-1. These data suggest that independent but converging pathways mediate expression of GLT-1. Although an EGF receptor-specific antagonist did not block the effects of neuron-conditioned medium, the induction of GLT-1 by neuron-conditioned medium was completely abolished by inhibition of PI3K or nuclear factor-κB. EGF also increased expression of GLT-1 in spinal cord organotypic cultures. Together, these data suggest that activation of specific signaling pathways with EGF-like molecules may provide a novel approach for limiting excitotoxic brain injury.

Original languageEnglish (US)
Pages (from-to)667-678
Number of pages12
JournalMolecular Pharmacology
Volume57
Issue number4
DOIs
StatePublished - 2000

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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