The objective of this proposal is to study the molecular mechanisms leading to impairment and loss of the glial glutamate transporter GLT1 in amyotrophic lateral sclerosis (ALS). ALS is an age-dependent neurodegenerative disorder of motor neurons in the spinal cord, motor cortex and brain stem. There is a growing body of evidence indicating that deficient glutamate uptake may be a contributory factor to motor neuron loss in ALS. In ALS patients, a marked decrease in the maximal velocity of synaptosomal glutamate uptake was reported. The impairment was found in regions affected by the disease, such as the spinal cord and motor cortex and a specific reduction of GLT1 immunoreactivity (30-90 percent) in the motor cortex of 60 percent of sporadic ALS patients was reported. A marked loss of GLT1 immunoreactivity was also detected in transgenic mice expressing the SOD1(G85R) mutation, suggesting that the sporadic and the familial form of ALS (SOD component) share common molecular mechanisms. The precise events leading to GLT1 loss in ALS are not yet understood. The levels of GLT1 mRNA are unchanged, letting investigator suspect that the reduction of GLT1 is not due to decreased transcription of mRNA, but rather to some other events at the translation or post translational level. We have recently reported that intracellular delivery of H2O2 in cells expressing SOD mutations led to selective GLT1 inhibition. Moreover, we showed that the cytoplasmic C-terminal domain of GLT1 is involved in the inhibition. These observations provided the first link between the SOD1 mutations and GLT1 impairment in ALS. Why is GLT1 selectively damaged while other glutamate transporters are insensitive? GLT1 has the highest number of oxidant vulnerable amino acid residues, such as cysteines histidines and tyrosines and therefore is the most prone to oxidative modifications and damage. We expect that a damaged GLT1 caused by the SOD1 mutants would undergo to a sustained internalization and/or selective degradation. Little is known about glutamate transporters regulation and degradation and how their functional inhibition or stimulation affects the pathophysiological events of neurodegenerative diseases such as ALS. We plan to determine the pathways that lead to GLT1 loss in ALS by taking the following approaches: I) defining the molecular events responsible for the inactivation of GLT1 mediated by the SOD1 mutants and identifying the sites in the C-terminal domain of GLT1 that are targets for the inactivation; 2) defining the pathways of GLT1 degradation under normal conditions and under conditions initiated by the ALS-linked SOD1 mutations 3) using transgenic technology we will establish in vivo what role the inactivation of GLT1 is playing in the onset and progression of ALS.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS044292-02
Application #
6604684
Study Section
Special Emphasis Panel (ZRG1-BDCN-2 (01))
Project Start
2002-07-01
Project End
2007-06-30
Budget Start
2003-07-01
Budget End
2004-06-30
Support Year
2
Fiscal Year
2003
Total Cost
$246,525
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
073130411
City
Boston
State
MA
Country
United States
Zip Code
02199
Maimon, Roy; Ionescu, Ariel; Bonnie, Avichai et al. (2018) miR126-5p Downregulation Facilitates Axon Degeneration and NMJ Disruption via a Non-Cell-Autonomous Mechanism in ALS. J Neurosci 38:5478-5494
Rosenblum, Lauren Taylor; Trotti, Davide (2017) EAAT2 and the Molecular Signature of Amyotrophic Lateral Sclerosis. Adv Neurobiol 16:117-136
Rosenblum, Lauren Taylor; Shamamandri-Markandaiah, Shashirekha; Ghosh, Biswarup et al. (2017) Mutation of the caspase-3 cleavage site in the astroglial glutamate transporter EAAT2 delays disease progression and extends lifespan in the SOD1-G93A mouse model of ALS. Exp Neurol 292:145-153
Wen, Xinmei; Tan, Wenzhi; Westergard, Thomas et al. (2014) Antisense proline-arginine RAN dipeptides linked to C9ORF72-ALS/FTD form toxic nuclear aggregates that initiate in vitro and in vivo neuronal death. Neuron 84:1213-25
Tan, Wenzhi; Pasinelli, Piera; Trotti, Davide (2014) Role of mitochondria in mutant SOD1 linked amyotrophic lateral sclerosis. Biochim Biophys Acta 1842:1295-301
Foran, E; Rosenblum, L; Bogush, A et al. (2014) Sumoylation of the astroglial glutamate transporter EAAT2 governs its intracellular compartmentalization. Glia 62:1241-53
Foran, Emily; Rosenblum, Lauren; Bogush, Alexey I et al. (2013) Sumoylation of critical proteins in amyotrophic lateral sclerosis: emerging pathways of pathogenesis. Neuromolecular Med 15:760-70
Jablonski, Michael R; Jacob, Dena A; Campos, Christopher et al. (2012) Selective increase of two ABC drug efflux transporters at the blood-spinal cord barrier suggests induced pharmacoresistance in ALS. Neurobiol Dis 47:194-200
Foran, Emily; Bogush, Alexey; Goffredo, Michael et al. (2011) Motor neuron impairment mediated by a sumoylated fragment of the glial glutamate transporter EAAT2. Glia 59:1719-31
Boston-Howes, William; Williams, Eric O; Bogush, Alexey et al. (2008) Nordihydroguaiaretic acid increases glutamate uptake in vitro and in vivo: therapeutic implications for amyotrophic lateral sclerosis. Exp Neurol 213:229-37

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