Glutamate-induced NFkappaB activation in the retina.
OBJECTIVE
To determine the distribution and glutamate-mediated activation of nuclear factor (NF) kappaB members in the retina and pan-purified retinal ganglion cells (RGCs) and to characterize steps in the signal transduction events that lead to NFkappaB activation.


METHODS
Retinal expression patterns and RGCs were evaluated for five NFkappaB proteins with the aid of immunohistochemistry. Retinal explants or RGCs were treated with glutamate with or without the presence of the NDMA receptor antagonist memantine, the calcium chelator EGTA, or a specific inhibitor for calcium/calmodulin-dependent protein kinase-II (CaMKII). Characterizations of NFkappaB activation were performed with the aid of electrophoretic mobility shift assays and supershift assays.


RESULTS
All five NFkappaB proteins were present in the retina and in the pan-purified RGCs. In response to a glutamate stimulus, all NFkappaB proteins except c-Rel were activated. P65 was unique in that it was not constitutively active but showed a glutamate-inducible activation in the retina and in the cultured RGCs. Memantine, EGTA, or autocamtide-2-related inhibitory peptide (AIP) inhibited NFkappaB activation in the retina. Furthermore, AIP significantly reduced the level of glutamate-induced degradation of IkappaBs.


CONCLUSIONS
These data indicate that glutamate activates distinct NFkappaB proteins in the retina. P65 activation may be especially important with regard to RGC responses to glutamate given that its activity is induced by conditions known to lead to the death of these cells. The NMDA receptor-Ca(2+)-CaMKII signaling pathway is involved in glutamate-induced NFkappaB activation. Because AIP blocks the degradation of IkappaB, its regulation is clearly downstream of CaMKII.
Fan
Wei
W
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
Cooper
Nigel G F
NG
D000818:Animals; D015153:Blotting, Western; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors; D018929:Cell Culture Techniques; D004533:Egtazic Acid / Q000494:pharmacology; D024202:Electrophoretic Mobility Shift Assay; D019084:Fluorescent Antibody Technique, Indirect; D018698:Glutamic Acid / Q000494:pharmacology*; D008559:Memantine / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000378:metabolism; D052003:NF-kappa B p52 Subunit / Q000378:metabolism; D009924:Organ Culture Techniques; D020569:Proto-Oncogene Proteins c-rel / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000187:drug effects* / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051996:Transcription Factor RelA / Q000378:metabolism; D051841:Transcription Factor RelB / Q000378:metabolism
D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D052003:NF-kappa B p52 Subunit; D020569:Proto-Oncogene Proteins c-rel; C497595:Relb protein, rat; D051996:Transcription Factor RelA; D051841:Transcription Factor RelB; D018698:Glutamic Acid; D004533:Egtazic Acid; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D008559:Memantine