Activation and Dimerization of CREB Following NMDA-induced Neurotoxicity in the Rat Retina

Abstract

Abstract: : Purpose: The cyclic AMP response element-binding protein (CREB) is a transcription factor involved in synaptic functions. The aim of present study is to examine whether NMDA actives a signal transduction cascade via phosphorylation of CREB in the rat retina. Methods: Male Wistar rats were used. Anesthetized rats (8 weeks old) were given 200nM of NMDA in PBS intravitreally. Control eyes were injected with PBS. The eyes were enucleated after 1 day of injection. Nuclear and cytosolic extracts were prepared from retinas. The expression of CREB protein and phospho-CREB (p- CREB ) protein were examined by Western blot analysis. CREB DNA binding activity of nuclear extracts was analyzed by electrophoretic mobility shift assay (EMSA). Results: Western blot analysis showed that p-CREB protein levels of cytosolic extracts were increased by NMDA treatments. Moreover, we found the dimer form of CREB in NMDA treated retina but not control retina. EMSA showed that NMDA also increased in CREB DNA binding activity in retina. Conclusions: Dimerization of CREB, phosphorylation of CREB and the increase in CREB DNA binding activity were seen at early step of NMDA-induced neurotoxicity. These events might contribute to the pathogenesis of NMDA-induced neurotoxicity in the rat retina.

Keywords: transcription factors • excitatory amino acid receptors • retina: neurochemistry