CaMKIIalphaB mediates a survival response in retinal ganglion cells subjected to a glutamate stimulus.
OBJECTIVE
During N-methyl-d-aspartate-induced cell death in the neural retina, levels of the nuclear isoform of CaMKIIalpha, CaMKIIalphaB, previously reported to be detected only in the midbrain and diencephalon, become elevated. The purpose of this study was to investigate whether CaMKIIalphaB 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 CaMKIIalphaB was investigated in RGCs with the aid of RT-PCR and immunostaining under normal and glutamate-stressed conditions. siRNA targeted to CaMKIIalphaB was used to knock down the level of endogenous mRNA in RGCs, and cell viability was tested. The putative role of CaMKIIalphaB in the downstream expression of survival genes such as BDNF was evaluated in CaMKIIalphaB knocked-down RGCs with the aid of RT-PCR, real-time PCR, and immunofluorescence microscopy.


RESULTS
Basal levels of CaMKIIalphaB 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 CaMKIIalphaB, a glutamate stimulus led to an increase in cell death. When CaMKIIalphaB 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 CaMKIIalphaB 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 CaMKIIalpha gene.
Fan
Wei
W
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky, USA.
Li
Xiaohong
X
Cooper
Nigel G F
NG
D000818:Animals; D000831:Animals, Newborn; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002467:Cell Nucleus / Q000201:enzymology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*
D019208:Brain-Derived Neurotrophic Factor; D018698:Glutamic Acid; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases