GluA2 AMPA glutamate receptor subunit exhibits codon 607 Q/R RNA editing in the lens

Regulated GluA2 AMPA receptor subunit expression, RNA editing, and membrane localization are fundamental determinants of neuronal Ca(2+) influx, and underlie basic functions such as memory and the primary brain disorder epilepsy. Consistent with this, AMPARs, and specifically GluA2, are targets of common antiepileptic drugs (AEDs) and antidepressants. Recently, epidemiological associations between epilepsy and increased cataract prevalence were found comparable to cataract links with diabetes and smoking. Similarly, use of AEDs and several antidepressants also showed links with increased cataract. Here, we demonstrated GluA2 in lenses, consistent with REST/NRSF and REST4 we described previously in lenses, as well as GluA1 and ADAR2 in the lens. Surprisingly, we found predominant neuron-like Q/R editing of GluA2 RNAs also occurs in the lens and evidence of lens GluA2 phosphorylation and STEP phosphatases linked with GluA2 membrane localization in neurons. This study is among the first to show GluA2 expression and predominant Q/R RNA editing in a non-neural cell. Our results suggest GluA2 AMPARs have related roles in lens physiology and disease processes, and provide evidence these anticonvulsant and antidepressant drug targets also occur in the lens.