Characterization of two alternatively spliced forms of a metabotropic glutamate receptor in the central nervous system of the rat

• Published in: Neuroscience Vol. 60; no. 2; pp. 325 - 336
• Main Authors: Hampson, D.R., Theriault, E., Huang, X.-P., Kristensen, P., Pickering, D.S., Franck, J.E., Mulvihill, E.R.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.1994; Elsevier
• Subjects: Alternative Splicing; Amino Acid Sequence; Animals; Antibodies; Base Sequence; Biological and medical sciences; Brain - cytology; Brain - metabolism; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; DNA Primers; DNA, Complementary - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression; Immunoblotting; Immunohistochemistry; Molecular Sequence Data; Organ Specificity; Peptides - chemical synthesis; Peptides - immunology; Polymerase Chain Reaction - methods; Rats; Rats, Wistar; Receptors, Glutamate - analysis; Receptors, Glutamate - biosynthesis; RNA, Messenger - biosynthesis; Vertebrates: nervous system and sense organs; InsP; PBS; SDS-PAGE; BHK; mGluR; PCR; Alternative splicing; Vertebrata; Mammalia; Rat; Metabotropic receptor; Rodentia; Central nervous system; Glutamate receptor; Gene expression
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/0306-4522(94)90246-1

Amplification of complementary DNA by the polymerase chain reaction and anti-peptide antibodies were used to characterize the expression of two alternatively spliced forms of a metabotropic glutamate receptor (mGluR1α and mGluR1β) in the central nervous system of the rat. Polymerase chain reaction analysis showed that mGluR1α was the predominate of the two forms in the cerebellum, diencephalon, mesencephalon, olfactory bulb and brainstem, while mGluR1β was the major form present in the hippocampus. Approximately equal amounts of the two receptors were expressed in the cerebral cortex, septum and striatum. Immunochemical analyses of the two receptors were conducted in the rat cerebellum and hippocampus. An mGluR1α-specific antibody labelled a protein with a relative molecular weight of 146,000 on immunoblots of the hippocampus and cerebellum. Immunoblot analysis of the developmental expression of mGluR1α in the hippocampus and cerebellum demonstrated that in both structures, the levels of mGluR1α were at or near their maximum levels in the adult brain. In contrast, two mGluR1β -specific antibodies failed to detect mGluR1β on immunoblots of brain tissue, thus precluding an immunocytochemical analysis of this receptor. Although low levels of a higher-molecular weight protein, possibly a dimeric form of mGluR1β were seen with one of the mGluR1β-specific antibodies, we hypothesize that some of the mGluR1β present in brain tissue may undergo proteolytic cleavage of the carboxy terminus. Immunocytochemical analysis of mGluR1α showed that very high levels of this receptor were expressed in Purkinje cell bodies and dendrites. In the granule cell layer, some Golgi neurons were immunostained. The granule cells were not labelled. In the hippocampus, mGluR1α immunoreactivity was present in interneurons of the stratum oriens and the dentate hilar region. Double-labelling studies demonstrated that these interneurons were also immunopositive for the neuropeptide somatostatin. The presence of mGluR1α in cells of the hippocampus that are associated with the release of somatostatin, suggest that this receptor could play a role in regulating hippocampal excitability in both normal and epileptic tissues.