Basic FGF regulates the expression of a functional 71 kDa NMDA receptor protein that mediates calcium influx and neurotoxicity in hippocampal neurons.
Basic fibroblast growth factor (bFGF) was recently found to modulate the outgrowth-regulating effects of glutamate, and protected neurons from several brain regions against excitotoxi/ischemic damage. We provide evidence that the excitoprotective mechanism of bFGF involves suppression of the expression of a 71 kDa NMDA receptor protein (NMDARP-71). NMDARP-71 protein and mRNA levels were reduced in neurons in bFGF-treated hippocampal cell cultures. The levels of the NMDARP-71 were not reduced by NGF or epidermal growth factor, and bFGF did not reduce the level of mRNA for the GluR1 kainate/AMPA receptor, demonstrating the specificity of the effect of bFGF on the NMDARP-71. The reduction in NMDARP-71 expression in bFGF-treated neurons was correlated with reduced vulnerability to NMDA neurotoxicity. A major role for NMDARP-71 in calcium responses to NMDA and excitotoxicity was demonstrated using antisense oligonucleotides directed against NMDARP-71. Northern and Western blot analysis and immunocytochemistry showed that NMDARP-71 antisense oligonucleotides caused a selective suppression of NMDARP-71 mRNA and protein levels during 12-44 hr exposure periods. Elevations in intracellular calcium levels normally caused by glutamate and NMDA were attenuated in neurons exposed to NMDARP-71 antisense oligonucleotide; calcium responses to kainate were relatively unaffected. NMDARP-71 antisense oligonucleotides protected the neurons against excitotoxicity. Thus, NMDARP-71 is a necessary component of an NMDA receptor mediating calcium responses and neurotoxicity in hippocampal neurons. Taken together, these data identify a mechanism whereby bFGF can modify neuronal responses to glutamate, and suggest that regulating the expression of excitatory amino acid receptors may provide a means for growth factors to influence the plasticity and degeneration of neural circuits.
Mattson
M P
MP
Sanders-Brown Research Center on Aging, University of Kentucky, Lexington 40536-0230.
Kumar
K N
KN
Wang
H
H
Cheng
B
B
Michaelis
E K
EK
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D005971:Glutamates / Q000633:toxicity; D018698:Glutamic Acid; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D007608:Kainic Acid / Q000633:toxicity; D007700:Kinetics; D008969:Molecular Sequence Data; D016202:N-Methylaspartate / Q000633:toxicity; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D009498:Neurotoxins / Q000633:toxicity*; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis* / Q000187:drug effects / Q000302:isolation & purification
D005971:Glutamates; D009498:Neurotoxins; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D016222:Fibroblast Growth Factor 2; D018698:Glutamic Acid; D016202:N-Methylaspartate; D007608:Kainic Acid; D002118:Calcium