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Possible role for the FosB/JunD AP‐1 transcription factor complex in glutamate‐mediated excitotoxicity in cultured cerebellar granule cells
Author(s) -
Lidwell Kate,
Griffiths Roger
Publication year - 2000
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/1097-4547(20001101)62:3<427::aid-jnr13>3.0.co;2-o
Subject(s) - glutamate receptor , fosb , excitotoxicity , biology , cerebellum , transcription factor , microbiology and biotechnology , biochemistry , gene , neuroscience , receptor
Abstract The potent excitatory and neurotoxic actions of glutamate are known to influence the expression of a variety of genes, including those encoding the AP‐1 transcription factor, which comprises proteins belonging to the Fos and Jun families. However, the precise role of Fos‐ and Jun‐like transcription factors in these events remains elusive. Here we demonstrate, using primary cultures of mouse brain cerebellar granule cells as an in vitro model system, a possible involvement of the FosB/JunD heterodimer in excitotoxicity. Granule cells were grown for either 2 or 7 days in vitro (DIV) before exposure to varying concentrations (1–3000 μM) of the excitotoxin glutamate. In 7‐DIV cells, glutamate induced a concentration‐dependent neuronal death, whereas, in 2‐DIV cells, no glutamate‐induced neuronal damage was seen. We were particularly interested in comparing the protein composition of the AP‐1 transcription factor complex in cells exposed to excitotoxic and to nontoxic conditions. AP‐1 DNA binding activity was demonstrated by gel shift analysis in nuclear extracts derived from 7‐DIV cells following exposure to either a nontoxic (10 μM) or an excitotoxic (250 μM) dose of glutamate and was similarly observed in extracts of 2‐DIV cells exposed to the same levels of glutamate. Gel supershift analysis using antibodies against the different Fos and Jun family members allowed differentiation between AP‐1 DNA binding in nuclear extracts as a function of both 1) viability status and 2) the stage of development. Of major significance was the finding that FosB could be detected as a component of AP‐1 in 7‐DIV cells only under excitotoxic conditions, whereas c‐Fos, Fra‐2, and JunD proteins were detectable under both excitotoxic and nontoxic conditions in cells of this age. In 2‐DIV cells (in which glutamate is nontoxic), AP‐1 comprised combinations of only Fra‐1, Fra‐2, c‐Jun, and JunD. Because Fos family members are unable to form homodimers, this finding raises the possibility that the FosB/JunD heterodimer may have special significance in the mechanism of excitotoxic neuronal death. J. Neurosci. Res. 62:427–439, 2000. © 2000 Wiley‐Liss, Inc.