The molecular and functional properties of neurotransmitter ligand-gated ion channels in glial cells were studied, in order to understand their regulation and function in the brain. Studies were carried out to: A. characterize the physiological role of glutamate-gated ion channels in glial development and B. to clone a glutamate receptor gene and analyze its 5' regulatory region in order to understand its transcriptional regulation in glia. A. Physiological properties and functional role. Primary cultures of rat oligodendrocyte progenitors (O-2A) were used as a model system. O-2A cells develop into oligodendrocytes in vitro similarly to O-2A progenitors in vivo. Kainate- and AMPA-preferring glutamate receptors are co-expressed in O-2A cells. AMPA receptor activation inhibits O-2A cell proliferation and prevents lineage progression at early developmental stages. Intracellular Ca2+ transients, due to transmembrane influx of the divalent cations, and immediate early gene (NGFI-A and c-fos) transcription are regulated by AMPA receptors. Immediate early gene induction occurs at the transcriptional level through protein kinase C-mediated phosphorylation of the transcription factor CREB. Genes encoding separate kainate-preferring glutamate receptor subunits are co-expressed in undifferentiated, nestin-positive multi-potential precursor cells of the rat neural tube. B. Glutamate receptor genes and analysis of their 5' regulatory region. Genes encoding kainate receptor subunits are highly expressed in cells of the oligodendrocyte lineage. The cloning of the entire rat GRIK5 gene, which encodes the kainate-preferring subunit KA2, was accomplished, and its intron-exon organization was partially determined. Two kb of the 5' flanking region of the rat GRIK5 were sequenced and found to comprise 3 independent transcription start sites. The transcriptional potential of the 2kb region was analyzed in an oligodendrocyte cell line as well as in PC12 cells.
| Gallo, V; Ghiani, C A (2000) Glutamate receptors in glia: new cells, new inputs and new functions. Trends Pharmacol Sci 21:252-8 |
| Ghiani, C A; Yuan, X; Eisen, A M et al. (1999) Voltage-activated K+ channels and membrane depolarization regulate accumulation of the cyclin-dependent kinase inhibitors p27(Kip1) and p21(CIP1) in glial progenitor cells. J Neurosci 19:5380-92 |
