Functional expression of two system A glutamine transporter isoforms in rat auditory brainstem neurons

• Published in: Neuroscience Vol. 164; no. 3; pp. 998 - 1008
• Main Authors: Blot, A, Billups, D, Bjørkmo, M, Quazi, A.Z, Uwechue, N.M, Chaudhry, F.A, Billups, B
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 15-12-2009; Elsevier; Elsevier Science
• Subjects: Amino Acid Transport System A - metabolism; Animals; Auditory Pathways - cytology; Auditory Pathways - metabolism; beta-Alanine - analogs & derivatives; beta-Alanine - pharmacology; Biological and medical sciences; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cellular Neuroscience; Fundamental and applied biological sciences. Psychology; Glutamine - metabolism; Immunohistochemistry; Neurology; Neurons - drug effects; Neurons - metabolism; Organ Culture Techniques; Patch-Clamp Techniques; Proline - metabolism; Proline - pharmacology; Protein Isoforms - metabolism; Rats; Rats, Wistar; Rhombencephalon - cytology; Rhombencephalon - metabolism; SAT1; SAT2; Signal Transduction - drug effects; Signal Transduction - physiology; Slc38a1; Slc38a2; SNAT1; SNAT2; Sodium Channel Blockers - pharmacology; Vertebrates: nervous system and sense organs; glutathione-S-transferase; I pro; dl-2-amino-5-phosphonopentanoic acid; I gln; APV; VGLUT; MeAIB; SAT2; N-(methylamino)isobutyric acid; dl-threo-b-benzyloxyaspartate; SAT1; proline-induced current; I/V; SNAT2; SNAT1; vesicular glutamate transporter; dizocilpine maleate; TTX; Slc38a2; 2-aminobicyclo-[2.2.1]-heptane-2-carboxylic acid; glutamine-induced current; current–voltage; medial nucleus of the trapezoid body; 2,3-Dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide; tricarboxylic acid; Slc38a1; system A transporter 1; BCH; GST; MNTB; system A transporter 2; EAAT; excitatory amino acid transporter; TCA; MK801; tetrodotoxin; dl-TBOA; NBQX; Igln; Ipro; Molecular form; Rat; Brain stem; Rodentia; Central nervous system; Encephalon; Vertebrata; Mammalia; Neuron; Animal; Carrier protein; Glutamine
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2009.09.015

Abstract Glutamine plays multiple roles in the CNS, including metabolic functions and production of the neurotransmitters glutamate and GABA. It has been proposed to be taken up into neurons via a variety of membrane transport systems, including system A, which is a sodium-dependent electrogenic amino acid transporter system. In this study, we investigate glutamine transport by application of amino acids to individual principal neurons of the medial nucleus of the trapezoid body (MNTB) in acutely isolated rat brain slices. A glutamine transport current was studied in patch-clamped neurons, which had the electrical and pharmacological properties of system A: it was sodium-dependent, had a non-reversing current-voltage relationship, was activated by proline, occluded by N-(methylamino)isobutyric acid (MeAIB), and was unaffected by 2-aminobicyclo-[2.2.1]-heptane-2-carboxylic acid (BCH). Additionally, we examined the expression of different system A transporter isoforms using immunocytochemical staining with antibodies raised against system A transporter 1 and 2 (SAT1 and SAT2). Our results indicate that both isoforms are expressed in MNTB principal neurons, and demonstrate that functional system A transporters are present in the plasma membrane of neurons. Since system A transport is highly regulated by a number of cellular signaling mechanisms and glutamine then goes on to activate other pathways, the study of these transporters in situ gives an indication of the mechanisms of neuronal glutamine supply as well as points of regulation of neurotransmitter production, cellular signaling and metabolism in the native neuronal environment.