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Expression of SOD1 G93A or wild-type SOD1 in primary cultures of astrocytes down-regulates the glutamate transporter GLT-1: lack of involvement of oxidative stress

Tortarolo, M., Crossthwaite, A.J., Conforti, L., Spencer, J.P.E., Williams, R.J. , Bendotti, C. and Rattray, M. (2004) Expression of SOD1 G93A or wild-type SOD1 in primary cultures of astrocytes down-regulates the glutamate transporter GLT-1: lack of involvement of oxidative stress. Journal of Neurochemistry, 88 (2). pp. 481-493. ISSN 0022-3042

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To link to this article DOI: 10.1046/j.1471-4159.2003.02208.x

Abstract/Summary

Glutamate excitotoxicity is implicated in the aetiology of amyotrophic lateral sclerosis (ALS) with impairment of glutamate transport into astrocytes a possible cause of glutamate-induced injury to motor neurons. It is possible that mutations of Cu/Zn superoxide dismutase (SOD1), responsible for about 20% of familial ALS, down-regulates glutamate transporters via oxidative stress. We transfected primary mouse astrocytes to investigate the effect of the FALS-linked mutant hSOD1(G93A) and wild-type SOD1 (hSOD1(wt)) on the glutamate uptake system. Using western blotting, immunocytochemistry and RT-PCR it was shown that expression of either hSOD1(G93A) or hSOD1(wt) in astrocytes produced down-regulation of the levels of a glutamate transporter GLT-1, without alterations in its mRNA level. hSOD1(G93A) or hSOD1(wt) expression caused a decrease of the monomeric form of GLT-1 without increasing oxidative multimers of GLT-1. The effects were selective to GLT-1, since another glutamate transporter GLAST protein and mRNA levels were not altered. Reflecting the decrease in GLT-1 protein, [H-3]D-aspartate uptake was reduced in cultures expressing hSOD1(G93A) or hSOD1(wt). The hSOD1-induced decline in GLT-1 protein and [H-3]D-aspartate uptake was not blocked by the antioxidant Trolox nor potentiated by antioxidant depletion using catalase and glutathione peroxidase inhibitors. Measurement of 2',7'-dichlorofluorescein (DCF)-induced fluorescence revealed that expression of hSOD1(G93A) or hSOD1(wt) in astrocytes does not lead to detectable increase of intracellular reactive oxygen species. This study suggests that levels of GLT-1 protein in astrocytes are reduced rapidly by overexpression of hSOD1, and is due to a property shared between the wild-type and G93A mutant form, but does not involve the production of intracellular oxidative stress.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > School of Pharmacy > Division of Pharmacology
Interdisciplinary centres and themes > Institute for Cardiovascular and Metabolic Research (ICMR)
Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Food and Nutritional Sciences
ID Code:12948
Uncontrolled Keywords:excitatory amino acid transporter 1, excitatory amino acid transporter 2, glutamate aspartate transporter, glutamate transporter, motor neuron disease, superoxide dismutase , AMYOTROPHIC-LATERAL-SCLEROSIS, CU,ZN-SUPEROXIDE DISMUTASE MUTANT, CU,ZN SUPEROXIDE-DISMUTASE, HYDROGEN-PEROXIDE, HIGH-AFFINITY, SPINAL-CORD, TRANSGENIC MICE, K-M, MODEL, DEGENERATION

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