Decreasing glutamate buffering capacity triggers oxidative stress and neuropil degeneration in the Drosophila brain.
L-glutamate is both the major brain excitatory neurotransmitter and a potent neurotoxin in mammals. Glutamate excitotoxicity is partly responsible for cerebral traumas evoked by ischemia and has been implicated in several neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). In contrast, very little is known about the function or potential toxicity of glutamate in the insect brain. Here, we show that decreasing glutamate buffering capacity is neurotoxic in Drosophila. We found that the only Drosophila high-affinity glutamate transporter, dEAAT1, is selectively addressed to glial extensions that project ubiquitously through the neuropil close to synaptic areas. Inactivation of dEAAT1 by RNA interference led to characteristic behavior deficits that were significantly rescued by expression of the human glutamate transporter hEAAT2 or the administration in food of riluzole, an anti-excitotoxic agent used in the clinic for human ALS patients. Signs of oxidative stress included hypersensitivity to the free radical generator paraquat and rescue by the antioxidant melatonin. Inactivation of dEAAT1 also resulted in shortened lifespan and marked brain neuropil degeneration characterized by widespread microvacuolization and swollen mitochondria. This suggests that the dEAAT1-deficient fly provides a powerful genetic model system for molecular analysis of glutamate-mediated neurodegeneration.
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
Strambi
Colette
C
Besson
Marie-Thérèse
MT
Iché
Magali
M
Birman
Serge
S
D000818:Animals; D001921:Brain / Q000502:physiology* / Q000648:ultrastructure; D017931:DNA Primers; D004330:Drosophila; D018691:Excitatory Amino Acid Antagonists / Q000378:metabolism; D027341:Excitatory Amino Acid Transporter 1 / Q000235:genetics / Q000378:metabolism*; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D005453:Fluorescence; D020868:Gene Silencing / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008550:Melatonin / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D009068:Movement / Q000187:drug effects; D009410:Nerve Degeneration / Q000503:physiopathology*; D019581:Neuropil / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology*; D010269:Paraquat / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019782:Riluzole / Q000378:metabolism
D017931:DNA Primers; D018691:Excitatory Amino Acid Antagonists; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D018698:Glutamic Acid; D019782:Riluzole; D008550:Melatonin; D010269:Paraquat