Splice‐specific roles of glycine receptor α3 in the hippocampus

Abstract

Glycine receptor (GlyR) alpha3 is involved in vision, and processing of acoustic and nociceptive signals, and RNA editing of GLRA3 transcripts was associated with hippocampal pathophysiology of mesial temporal lobe epilepsy (TLE). However, neither the role of GlyR alpha3 splicing in hippocampal neurons nor the expression of splice variants have yet been elucidated. We report here that the long (L) splice variant of GlyR alpha3 predominates in the brain of rodents. Cellular analysis using primary hippocampal neurons and hippocampus cryosections revealed preferential association of synaptic alpha3L clusters with glutamatergic nerve endings in strata granulare and pyramidale. In primary hippocampal neurons GlyR alpha3L clusters also preferred glutamatergic nerve endings while alpha3K was mainly in a diffuse state. Co-expression of GlyR beta subunit with alpha3L or alpha3K produced heteromeric receptor clusters and favoured their association with GABAergic terminals. However, heteromeric alpha3L was still more efficient than heteromeric alpha3K in associating with glutamatergic nerve endings. To give physiological relevance to these results we have finally analysed GlyR alpha3 splicing in human hippocampus obtained from patients with intractable TLE. As up-regulation of alpha3K occurred at the expense of alpha3L in TLE patients with a severe course of disease and a high degree of hippocampal damage, our results again involve post-transcriptional processing of GLRA3 transcripts in the pathophysiology of TLE.

Electrophysiological Signature of Homomeric and Heteromeric Glycine Receptor Channels

“…In vivo, GlyR ␣2 and ␣3 are expressed in different brain regions, including the neocortex and hippocampus, in both post-and presynaptic neuronal compartments (2,4,8,59,60). The intracellular chloride concentration of most mature neurons in the CNS is relatively low, shifting the onset of GlyR rectification in the physiological range of membrane potentials.…”

Intracellular glycine receptor function facilitates glioma formation in vivo

“…It has been established that this protein region influences GlyR protein structure as, for example, inclusion of exon 8A (coding for TAEFALEKFYRFSDT) changes receptor desensitization kinetics, clustering and subcellular trafficking in neurons (Eichler et al, 2009;Nikolic et al, 1998;Notelaers et al, 2012;Winkelmann et al, 2014). The tumor-cell-specific preponderant expression of GlyR a1ins and a3K RNA splice variants identifies a functional role for GlyR a1ins and sets glioma cells apart from neurons with regard to RNA splicing of GlyR a3-coding gene transcripts (Eichler et al, 2009). Our results also identify a possible crucial functional role for non-charged amino acids corresponding to the RNA splice insert downstream of the NLS in GlyR a1.…”

“…GlyR a3-coding mRNA was detected in all the analyzed samples (supplementary material Table S2). Moreover, the vast majority (nine out of 11) of stem-cell-like cells expressed the GlyR a3K RNA splice variant (Nikolic et al, 1998), which sets this cell type apart from neurons with regard to prevailing expression of the long GlyR a3L RNA splice variant in neurons (Eichler et al, 2009). …”

Glycine receptor α3 and α2 subunits mediate tonic and exogenous agonist-induced currents in forebrain

“…For example, polymorphisms resulting in single amino acid mutations in both GlyR α and β subunits have been identified in human hyperekplexia (startle disease) (33). In addition, differential splicing of the human GlyR α3 subunit gene (Glra3) and changes in the expression of high-affinity (RNA-edited) GlyR α2 and α3 subunits have been observed in cases of intractable temporal lobe epilepsy (32,34). More recently, the Glra3 gene has been genetically linked to alcoholism (35), and Glra3 −/− mice have been found to show increased ethanol preference in a two-bottle choice model, while Glra2 −/Y animals display the opposite behavior (36).…”

“…GlyR α subunits exist in many higher brain regions (30) and may include populations of homopentameric GlyRs expressed in the absence of β subunits (31,32).…”