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Regulation of glial glutamate transporter expression by growth factors

Lookup NU author(s): Dr Nadhim Bayatti

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Abstract

Injuries to the brain result in the decline of glial glutamate transporter expression within hours and a recovery after several days. One consequence of this disturbed expression seems to consist in the temporary accumulation of toxic extracellular glutamate levels followed by secondary neuronal cell death. Whereas evidence exists that the decline in glutamate transporter expression results from a loss of neuronal PACAP influences on astroglia, the mechanism(s) inducing the reexpression of glial glutamate transporters is presently unknown. We now demonstrate that the injury-induced growth factors EGF, TGFalpha, FGF-2, and PDGF all promote the expression of the glutamate transporters GLT-1 and/or GLAST in cultured cortical astroglia. In contrast, similar stimulatory influences were absent with GDNF and BDNF, growth factors not affected by brain injuries. The effects of EGF, TGFalpha, FGF-2, and PDGF on glial glutamate transport were only partly redundant and involved distinctly different signaling pathways. Unlike EGF, TGFalpha, and FGF-2, PDGF promoted GLT-1, but not GLAST expression and further failed to increase the maximal velocity of sodium-dependent glutamate uptake. Moreover, FGF-2 only affected glial glutamate transport when the RAF-MEK-ERK signaling pathway was concomitantly inhibited with PD98059. Depending on the extracellular growth factor and glutamate transporter subtype, the observed stimulatory effects required the activation of PKA, PKC, and/or AKT. We suggest that after brain injury, reactive processes may limit secondary neuronal cell death by promoting glial glutamate transport. The detailed knowledge of these compensatory mechanisms will eventually allow us to therapeutically interfere with glutamate-associated neuronal cell death in the brain.


Publication metadata

Author(s): Bayatti N; Figiel M; Maucher T; Rozyczka J; Engele J

Publication type: Article

Publication status: Published

Journal: Experimental Neurology

Year: 2003

Volume: 183

Issue: 1

Pages: 124-135

ISSN (print): 0014-4886

ISSN (electronic): 1090-2430

Publisher: Academic Press

URL: http://dx.doi.org/10.1016/S0014-4886(03)00134-1

DOI: 10.1016/S0014-4886(03)00134-1


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