CaMKIIαB mediates a survival response in retinal ganglion cells subjected to a glutamate stimulus

Abstract

PURPOSE. During N-methyl-D-aspartate-induced cell death in the neural retina, levels of the nuclear isoform of CaMKIIα, CaMKIIαB, previously reported to be detected only in the midbrain and diencephalon, become elevated. The purpose of this study was to investigate whether CaMKIIαB is present specifically in retinal ganglion cells (RGCs) and to determine whether it can be implicated in the cell death or cell survival of signal transduction pathways. METHODS. Pan-purified RGCs were obtained from the retinas of postnatal day (P)6 to P8 Sprague-Dawley rats. The expression level of CaMKIIαB was investigated in RGCs with the aid of RT-PCR and immunostaining under normal and glutamate-stressed conditions. siRNA targeted to CaMKIIαB was used to knock down the level of endogenous mRNA in RGCs, and cell viability was tested. The putative role of CaMKIIαB in the downstream expression of survival genes such as BDNF was evaluated in CaMKIIαB knocked-down RGCs with the aid of RT-PCR, real-time PCR, and immunofluorescence microscopy. RESULTS. Basal levels of CaMKIIαB were expressed in RGCs. Expression levels became increased in response to glutamate treatment and were translocated to the nuclei after a glutamate stimulus. In pan-purified RGCs with knocked down levels of CaMKIIαB, a glutamate stimulus led to an increase in cell death. When CaMKIIαB was knocked down in RGCs, a corresponding decrease occurred in the level of BDNF expression. CONCLUSIONS. These data indicate that the presence of basal levels of CaMKIIαB in RGCs may afford them some ongoing protection from a stressful environment. In response to the glutamate stimulus, the expression of survival genes such as BDNF may be enhanced through elevation of this particular isoform of the CaMKIIα gene. Copyright © Association for Research in Vision and Ophthalmology.