RNA EDITING OF A HUMAN GLUTAMATE-RECEPTOR SUBUNIT

AMPA receptors are comprised of individual subunits, and the divalent cation permeability of assembled AMPA receptors is determined by a single amino acid residue in the second transmembrane region of the GluR-B subunit. At this site, GluR-B subunits contain an arginine while other AMPA receptor subunits contain glutamine. Interestingly, the murine gene for GluR-B actually specifies a glutamine at the divalent cation permeability site. The appearance of arginine and not glutamine in the mature GluR-B protein is thought to be a result of RNA editing of the GluR-B messenger RNA. In that AMPA receptors are thought to mediate the bulk of fast excitatory signalling within the mammalian central nervous system, this process of RNA editing may play a pivotal role in normal neural function by mediating divalent cation permeability of AMPA receptors. Disruptions of RNA editing could lead to phenotypically altered AMPA receptors, with implications for pathogenic brain processes. We report that the human GluR-B gene sequence is also edited such that there is a difference between the human GluR-B gene and the complementary DNA (cDNA), as demonstrated both with allele-specific polymerase chain reaction (PCR) and restriction enzyme digestion of PCR products. Thus, as in the rodent brain, RNA editing of an AMPA receptor subunit appears to be an important process in the human brain. Disruptions of RNA editing may have neuropathological consequences.