Transcription and translation of two glutamate decarboxylase genes in the ileum of rat, mouse and guinea pig

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Abstract

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter, synthesised from glutamate by glutamate decarboxylase (GAD), in the central nervous system. Two forms of GAD, designated GAD 65 and GAD 67, are encoded by distinct genes and have been demonstrated in the mammalian brain. GABA has been postulated to be synthesised in neurons of the enteric nervous system (ENS), but evidence for its role as an enteric neurotransmitter is equivocal. We therefore aimed to determine whether GAD 65 and GAD 67 messenger RNAs (mRNAs) and proteins were expressed in the ileum of mice, rats and guinea pigs. Using an RNase protection assay, both GAD 65 and GAD 67 mRNAs were detected in the rodent small intestine. Antisera specific for GAD 65 or GAD 67, used in immunoblot analyses, revealed GAD 65-like and GAD 67-like immunoreactivity in rat and guinea pig ileum. Anti-GAD 65 antisera detected a major band of 65 kDa. Anti-GAD 67 antisera detected a major band of 55 kDa, which probably represented a breakdown product, and a minor band of 67 kDa. Analysis of immunoblot extracts of rat and guinea pig ileum revealed more GAD 67-like than GAD 65-like immunoreactivity. GAD enzymatic activity was high in the rat and guinea-pig brain, and low in the whole and dissected ileum. These results demonstrate that both GAD 65 and GAD 67 genes are transcribed and translated in the ileum of three rodent species and lend indirect support to the postulate that GABA is synthesised by neurons of the ENS and intestinal endocrine cells.

References (52)

  • A. Krantis et al.

    [3H]GABA uptake and GABA localization in mucosal endocrine cells of the rat stomach and colon

    J. Auton. Nerv. Syst.

    (1994)
  • A. Krantis et al.

    Autoradiographic localization of [3H]γ-aminobutyric acid in neuronal elements of the rat gastric antrum and intestine

    J. Auton. Nerv. Syst.

    (1989)
  • A. Minocha et al.

    Excitatory and inhibitory responses mediated by GABAA and GABAB receptors in guinea pig distal colon

    Eur. J. Pharmacol.

    (1993)
  • B. Nathan et al.

    Purification and characterization of a novel form of brain l-glutamate decarboxylase, a Ca2+-dependent peripheral membrane protein

    J. Biol. Chem.

    (1994)
  • W.H. Oertel et al.

    Comparison of cysteine sulphinic acid decarboxylase isoenzymes and glutamic acid decarboxylase in rat liver and brain

    Neuroscience

    (1981)
  • N. Saito et al.

    Immunohistochemical demonstration of GABA containing neurons in the guinea-pig ileum using purified GABA antiserum

    Brain Res.

    (1986)
  • D.C. Spink et al.

    Kinetically different, multiple forms of glutamate decarboxylase in rat brain

    Brain Res.

    (1987)
  • C. Tanaka

    GABA in peripheral tissues

    Life Sci.

    (1985)
  • J.-Y. Wu et al.

    Purification and characterization of glutamate decarboxylase from mouse brain

    J. Biol. Chem.

    (1973)
  • T. Beiganski et al.

    Distribution and properties of human intestinal diamine oxidase and its relevance for the histamine catabolism

    Biochim. Biophys. Acta

    (1983)
  • J. Blindermann et al.

    Purification and some properties of l-glutamate decarboxylase from human brain

    Eur. J. Biochem.

    (1978)
  • D.F. Bu et al.

    Two human glutamate decarboxylases, 65-kDa GAD and 67-kDa GAD are each encoded by a single gene

  • Y.-C. Chang et al.

    Characterization of the proteins purified with monoclonal antibodies to glutamic acid decarboxylase

    J. Neurosci.

    (1988)
  • M.R. Christie et al.

    Binding of antibodies in sera from Type 1 (insulin-dependent) diabetic patients to glutamate decarboxylase from rat tissues. Evidence for antigenic and non-antigenic forms of the enzyme

    Diabetologia

    (1992)
  • O. Chude et al.

    A rapid method for assaying enzymes whose substrate and products differ by charge. Application to brain l-glutamate decarboxylase

    J. Neurochem.

    (1976)
  • S. Davanger et al.

    GABA-immunoreactive cells in the rat gastrointestinal epithelium

    Anat. Embryol.

    (1989)
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