Physiological requirement for the glutamate transporter dEAAT1 at the adult Drosophila neuromuscular junction.
L-glutamate is the major excitatory neurotransmitter in the mammalian brain. Specific proteins, the Na+/K+-dependent high affinity excitatory amino acid transporters (EAATs), are involved in the extracellular clearance and recycling of this amino acid. Type I synapses of the Drosophila neuromuscular junction (NMJ) similarly use L-glutamate as an excitatory transmitter. However, the localization and function of the only high-affinity glutamate reuptake transporter in Drosophila, dEAAT1, at the NMJ was unknown. Using a specific antibody and transgenic strains, we observed that dEAAT1 is present at the adult, but surprisingly not at embryonic and larval NMJ, suggesting a physiological maturation of the junction during metamorphosis. We found that dEAAT1 is not localized in motor neurons but in glial extensions that closely follow motor axons to the adult NMJ. Inactivation of the dEAAT1 gene by RNA interference generated viable adult flies that were able to walk but were flight-defective. Electrophysiological recordings of the thoracic dorso-lateral NMJ were performed in adult dEAAT1-deficient flies. The lack of dEAAT1 prolonged the duration of the individual responses to motor nerve stimulation and this effect was progressively increased during physiological trains of stimulations. Therefore, glutamate reuptake by glial cells is required to ensure normal activity of the Drosophila NMJ, but only in adult flies.
Rival
Thomas
T
Laboratoire de Génétique et Physiologie du Développement, Developmental Biology Institute of Marseille, CNRS-INSERM-Université de la Méditerranée, Campus de Luminy, Case 907, F-13288 Marseille Cedex 9, France.
Soustelle
Laurent
L
Cattaert
Daniel
D
Strambi
Colette
C
Iché
Magali
M
Birman
Serge
S
D000367:Age Factors; D000818:Animals; D030801:Animals, Genetically Modified; D000906:Antibodies; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D027341:Excitatory Amino Acid Transporter 1 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005426:Flight, Animal / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018698:Glutamic Acid / Q000378:metabolism; D009457:Neuroglia / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D034741:RNA, Small Interfering; D011817:Rabbits; D014170:Transformation, Genetic
D000906:Antibodies; D029721:Drosophila Proteins; D027341:Excitatory Amino Acid Transporter 1; D034741:RNA, Small Interfering; D018698:Glutamic Acid