Alternative splicing of human metabotropic glutamate receptor 3

Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, UK.
Journal of Neurochemistry (Impact Factor: 4.28). 03/2006; 96(4):1139-48. DOI: 10.1111/j.1471-4159.2005.03609.x
Source: PubMed

ABSTRACT The metabotropic glutamate receptor 3 (GRM3, mGluR3) is important in regulating synaptic glutamate. Here, we report the existence of three splice variants of GRM3 in human brain arising from exon skipping events. The transcripts are expressed in prefrontal cortex, hippocampus and cerebellum, and in B lymphoblasts. We found no evidence for alternative splicing of GRM2. The most abundant GRM3 variant lacks exon 4 (GRM3Delta4). In silico translation analysis of GRM3Delta4 predicts a truncated protein with a conserved extracellular ligand binding domain, absence of a seven-transmembrane domain, and a unique 96-amino acid C-terminus. When expressed in rat hippocampal neurons, GRM3Delta4 is translated into a 60 kDa protein. Immunostaining and cell fractionation data indicate that the truncated protein is primarily membrane-associated. An antibody developed against the GRM3Delta4 C-terminus detects a protein of approximately 60 kDa in human brain lysates and in B lymphoblasts, suggesting translation of GRM3Delta4 in vivo. The existence of the GRM3Delta4 isoform is relevant in the light of the reported association of non-coding single nucleotide polymorphisms (SNPs) in GRM3 with schizophrenia, and with the potential of GRM3 as a therapeutic target for several neuropsychiatric disorders.

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Available from: Barbara K Lipska, Oct 17, 2014
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    • "Other isoforms such as mGlu5c, 5d and 5e have been reported in humans (Minakami et al., 1994). Exon-skipping events lead to three spliced variants in mGlu3 (Sartorius et al., 2006). For group III receptors, mGlu4 exists as mGlu4a, and mGlu4b (Thomsen et al., 1997). "
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    ABSTRACT: Storage and processing of information at the synaptic level is enabled by the ability of synapses to persistently alter their efficacy. This phenomenon, known as synaptic plasticity, is believed to underlie multiple forms of long-term memory in the mammalian brain. It has become apparent that the metabotropic glutamate (mGlu) receptor is critically required for both persistent forms of memory and persistent synaptic plasticity. Persistent forms of synaptic plasticity comprise long-term potentiation (LTP) and long-term depression (LTD) that last at least for 4 h but can be followed in vivo for days and weeks. These types of plasticity are believed to be analogous to forms of memory that persist for similar time-spans. The mGlu receptors are delineated into three distinct groups based on their G-protein coupling and agonist affinity and also exercise distinct roles in the way they regulate both long-term plasticity and long-term hippocampus-dependent memory. Here, the mGlu receptors will be reviewed both in general, and in the particular context of their role in persistent (>4 h) forms of hippocampus-dependent synaptic plasticity and memory, as well as forms of synaptic plasticity that have been shown to be directly regulated by memory events. This article is part of a Special Issue entitled 'mGluR'.
    Neuropharmacology 06/2012; 66. DOI:10.1016/j.neuropharm.2012.06.005 · 5.11 Impact Factor
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    • "Moreover, our biochemical analysis suggests that the association with the membrane is strong, consistent with that of a tightly-bound peripheral or integral membrane protein. These results are similar to a recent investigation of the truncated splice variant of the mammalian mGluR3 receptor, which also lacks its 7-TM segment and yet was found to be associated with the plasma membrane [42]. In this case, the authors identified a short hydrophobic segment located at the C-terminal end that was predicted to serve as a single transmembrane domain [42]. "
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    ABSTRACT: A novel glutamate-binding protein was identified in Schistosoma mansoni. The protein (SmGBP) is related to metabotropic glutamate receptors from other species and has a predicted glutamate binding site located within a Venus Flytrap module but it lacks the heptahelical transmembrane segment that normally characterizes these receptors. The SmGBP cDNA was cloned, verified by 5' and 3' Rapid Amplification of cDNA Ends (RACE) and shown to be polyadenylated at the 3'end, suggesting the transcript is full-length. The cloned cDNA was subsequently expressed in bacteria and shown to encode a functional glutamate-binding protein. Other studies, using a specific peptide antibody, determined that SmGBP exists in two forms, a monomer of the expected size and a stable but non-covalent dimer. The monomer and dimer are both present in the membrane fraction of S. mansoni and are resistant to extraction with high-salt, alkaline pH and urea, suggesting SmGBP is either an integral membrane protein or a peripheral protein that is tightly associated with the membrane. Surface biotinylation experiments combined with western blot analyses and confocal immunolocalization revealed that SmGBP localized to the surface membranes of adult male schistosomes, especially the dorsal tubercles. In contrast, we detected little or no expression of SmGBP either in the females or larval stages. A comparative quantitative PCR analysis confirmed that the level of SmGBP expression is several-fold higher in male worms than cercariae, and it is barely detectable in adult females. Together, the results identify SmGBP as a new type of schistosome glutamate receptor that is both gender- and stage-specific. The high-level expression of this protein in the male tubercles suggests a possible role in host-parasite interaction.
    PLoS ONE 11/2011; 6(11):e27119. DOI:10.1371/journal.pone.0027119 · 3.23 Impact Factor
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    • "The proximity of the GRM1 nsSNP cluster to the exon 6 donor site and exon 7 acceptor site suggest these nsSNPs might perturb the regulatory balance of alternative splicing of this receptor. Consistent with the discovery of GRM1 nsSNP cluster is the discovery of exon skipping in a close homologue of GRM1, GRM3 and its association with schizophrenia [34]. "
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    ABSTRACT: Current models of schizophrenia and bipolar disorder implicate multiple genes, however their biological relationships remain elusive. To test the genetic role of glutamate receptors and their interacting scaffold proteins, the exons of ten glutamatergic 'hub' genes in 1304 individuals were re-sequenced in case and control samples. No significant difference in the overall number of non-synonymous single nucleotide polymorphisms (nsSNPs) was observed between cases and controls. However, cluster analysis of nsSNPs identified two exons encoding the cysteine-rich domain and first transmembrane helix of GRM1 as a risk locus with five mutations highly enriched within these domains. A new splice variant lacking the transmembrane GPCR domain of GRM1 was discovered in the human brain and the GRM1 mutation cluster could perturb the regulation of this variant. The predicted effect on individuals harbouring multiple mutations distributed in their ten hub genes was also examined. Diseased individuals possessed an increased load of deleteriousness from multiple concurrent rare and common coding variants. Together, these data suggest a disease model in which the interplay of compound genetic coding variants, distributed among glutamate receptors and their interacting proteins, contribute to the pathogenesis of schizophrenia and bipolar disorders.
    PLoS ONE 04/2011; 6(4):e19011. DOI:10.1371/journal.pone.0019011 · 3.23 Impact Factor
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