title: Identification of four functional NR3B isoforms in developing white matter reveals unexpected diversity among glutamate receptors.
abstract: Functional neurotransmitter receptors are expressed in central white matter, where they mediate ischemic damage to glia and may be involved in cell-cell signalling. In this study, we analysed NMDA receptor NR1, NR2B-C and NR3A-B subunit expression in the brain and optic nerve by molecular cloning. In addition to the canonical forms of NR1 and NR2, four previously unknown NR3B variants, generated by alternative splicing, were identified. The variants encoded for isoforms with deletions of 8/15 amino acids in the N-terminal domain or 200/375 amino acids removing one or three transmembrane domains and part of the C-terminal domain, as compared with the previously characterized NR3B isoform. Co-expression of NR3B isoforms with NR1/NR2A-C modulated the amplitude and Mg(2+)-sensitivity of glutamate responses in a NR2 subunit-dependent fashion, with significant variations in the effects produced by different isoforms. These effects were not the result of reduced surface expression of the receptor complex since all NR3B isoforms reduced surface expression by a similar degree. These data reveal previously uncharacterized regulation of NMDA receptor function by alternative splicing of the NR3B subunit.
authors.affiliation: Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, UK.
authors.forename: António M de Jesus
authors.initials: AM
authors.lastname: Domingues
authors.forename: Karla M
authors.initials: KM
authors.lastname: Neugebauer
authors.forename: Robert
authors.initials: R
authors.lastname: Fern
mesh_terms: D017398:Alternative Splicing / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001426:Bacterial Proteins / Q000235:genetics; D001921:Brain / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology*; D018698:Glutamic Acid / Q000494:pharmacology; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009900:Optic Nerve / Q000254:growth & development* / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment / Q000379:methods; D014162:Transfection / Q000379:methods
chemical_list: D001426:Bacterial Proteins; D008164:Luminescent Proteins; C409466:NR1 NMDA receptor; C121001:NR2B NMDA receptor; C501155:NR3B NMDA receptor; D020033:Protein Isoforms; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; C054562:yellow fluorescent protein, Bacteria; D018698:Glutamic Acid; D008274:Magnesium; D002118:Calcium