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Subcellular localization of the glutamate transporters GLAST and GLT at the neuromuscular junction in rodents

Rinholm, JE; Slettalokken, G; Marcaggi, P; Skare, O; Storm-Mathisen, J; Bergersen, LH; (2007) Subcellular localization of the glutamate transporters GLAST and GLT at the neuromuscular junction in rodents. NEUROSCIENCE , 145 (2) 579 - 591. 10.1016/j.neuroscience.2006.12.041.

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Abstract

The vertebrate neuromuscular junction (NMJ) is known to be a cholinergic synapse at which acetylcholine (ACh) is released from the presynaptic terminal to act on postsynaptic nicotinic ACh receptors. There is now growing evidence that glutamate, which is the main excitatory transmitter in the CNS and at invertebrate NMJs, may have a signaling function together with ACh also at the vertebrate NMJ. In the CNS, the extracellular concentration of glutamate is kept at a subtoxic level by Na+-driven high-affinity glutamate transporters located in plasma membranes of astrocytes and neurons. The glutamate transporters are also pivotal for shaping glutamate receptor responses at synapses. In order to throw further light on the potential role of glutamate as a cotransmitter at the NMJ we used high-resolution immunocytochemical methods to investigate the localization of the plasma membrane glutamate transporters GLAST (glutamate aspartate transporter) and GILT (glutamate transporter 1) in rat and mice NMJ regions. Confocal laser-scanning immunocytochemistry showed that GILT is restricted to the NMJ in rat and mouse skeletal muscle. Lack of labeling signal in knock-out mice confirmed that the immunoreactivity observed at the NMJ was specific for GILT. GLAST was also localized at the NMJ in rat but not detected in mouse NMJ (while abundant in mouse brain). Post-embedding electron microscopic immunocytochemistry and quantitative analyses in rat showed that GLAST and GILT are enriched in the functional folds of the postsynaptic membrane at the NMJ. GILT was relatively higher in the slow-twitch muscle soleus than in the fast-twitch muscle extensor digitorum longus, whereas GLAST was relatively higher in extensor digitorum longus than in soleus. The findings show-together with previous demonstration of vesicular glutamate, a vesicular glutamate transporter glutamate receptors-that mammalian NMJs contain the machinery required for synaptic release and action of glutamate. This indicates a signaling role for glutamate at the normal NMJ and provides a basis for the ability of denervated muscle to be reinnervated by glutamatergic axons from the CNS. (c) 2006 IBRO. Published by Elsevier Ltd. All rights reserved.

Type: Article
Title: Subcellular localization of the glutamate transporters GLAST and GLT at the neuromuscular junction in rodents
DOI: 10.1016/j.neuroscience.2006.12.041
Keywords: EAAT1, EAAT2, skeletal muscle, mammalian, neurotransmitter, RAT SKELETAL-MUSCLE, GATED CHLORIDE CHANNEL, AMINO-ACID TRANSPORTER, EXCITATORY TRANSMITTER, NERVE-ENDINGS, BRAIN, ACETYLCHOLINE, SYNAPSES, EXPRESSION, RECEPTORS
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Neuro, Physiology and Pharmacology
URI: http://discovery.ucl.ac.uk/id/eprint/9664
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