Glutamate regulates kainate-binding protein expression in cultured chick Bergmann glia through an activator protein-1 binding site

The expression of the chick kainate-binding protein, a member of the ionotr opic glutamate receptor family, is restricted to the cerebellum, specifical ly to Bergmann glia. Glutamate induces a membrane to nuclei signaling invol ved in gene expression regulation. Exposure of cultured chick Bergmann glia cells to glutamate leads to an increase in kainate binding protein and mRN A levels, suggesting a transcriptional level of regulation. The 5 ' proxima l region of the chick kainate binding gene was cloned and transfected 4into Bergmann glia cells. Three main regulatory regions could be defined, a min imal promoter region, a negative regulatory region, and interestingly, a gl utamate-responsive element. Deletion of this element abolishes the agonist effect. Moreover, electrophoretic mobility shift assays, cotransfection exp eriments, and site-directed mutagenesis clearly suggest that the glutamate effect is mediated through an AP-1 site by a Fos/Jun heterodimer. The prese nt results favor the notion of a functional role of kainate-binding protein in glutamatergic cerebellar neurotransmission.