RNA editing produces glycine receptor α3P185L, resulting in high agonist potency

Abstract

The function of supramedullary glycine receptors (GlyRs) is still unclear. Using Wistar rat collicular slices, we demonstrate GlyR-mediated inhibition of spike discharge elicited by low glycine (10 microM). Searching for the molecular basis of this phenomenon, we identified a new GlyR isoform. GlyR alpha3(P185L), a result of cytidine 554 deamination, confers high glycine sensitivity (EC50 approximately 5 microM) to neurons and thereby promotes the generation of sustained chloride conductances associated with tonic inhibition. The level of GlyR alpha3-C554U RNA editing is sensitive to experimentally induced brain lesion, inhibition of cytidine deamination by zebularine and inhibition of mRNA transcription by actinomycin D, but not to blockade of protein synthesis by cycloheximide. Conditional regulation of GlyR alpha3(P185L) is thus likely to be part of a post-transcriptional adaptive mechanism in neurons with enhanced excitability.

Glycine Uptake Regulates Hippocampal Network Activity via Glycine Receptor-Mediated Tonic Inhibition

“…Accordingly, the function of GlyT1 is effectively regulated and thus the concentration of extracellular glycine is tightly controlled. Furthermore, the sensitivity of GlyRs, which mainly depends on the a-subunit present, may also be upregulated by expression of subunit splice variants with high agonist sensitivity (Miller et al, 2004) or by RNA editing to produce a high agonist potency receptor isoform (Meier et al, 2005). Under the latter conditions, the GlyRs could be activated even if the concentration of glycine is not elevated.…”

Glycine is able to induce both a motility speed in- and decrease during zebrafish neuronal migration

“…We aimed to increase the speed reduction effect by overexpressing gain-of-function mutations in glycine receptors. The mutations are modelled on available human patient data, and correspond to zebrafish GlyRa1 I67F [18,19], GlyRa1 V304M [18,20,21], and rat GlyRa3 P185L [22]. In contrast to expectations, all of these mutations led to a moderate THN speed increase in phase 2 (approx.…”

“…WISH analysis was carried out as described previously on PFA-fixed embryos [3]. Plasmids encoding for glycine receptor mutations were generated by point mutation based on the full-length wt described in [3] and [22]. Bumetanide (Sigma, B3023) was prepared as a 20 mM stock solution in DMSO and used at 100 µM dilution in 30% Danieau medium.…”

Molecular architecture of glycinergic synapses

“…There are four subunits genes (GLRA1-4, encoding 1-4) and a single one encoding the protein (GLRB) (Laube et al 2002;Lynch 2004). Alternative splicing and RNA editing can generate further heterogeneity among the subunits (Lynch 2004;Meier et al 2005). In the 1, 2 and 3 subunits, the alternative exons modify the structures of the extracellular domain or of the intracellular loop regions.…”

“…An eight amino acid insertion into the large intracellular loop of the rat 1 subunit adds a consensus site for protein kinase A (Malosio et al 1991) and thus, a potential element for regulating receptor function. RNA editing can generate 3 subunits, whose extracellular domain has a higher aYnity to glycine than the unedited form (Meier et al 2005). The edited subunit is suggested to confer high agonist aYnities to extrasynaptically localized GlyRs.…”