Abstract

Glutamate excitotoxicity has been implicated in numerous neurodegenerative diseases, including motor neurone disease, MND/ALS. The glutamate transporter EAAT2 is the primary regulator of extracellular glutamate concentration and specific reductions in its expression and transport function have been reported in MND patients and rodent models of the disease. Previous studies have detected no abnormalities in the genomic DNA or mRNA of EAAT2 in MND patients. We now hypothesise that abnormalities in protein interactors of EAAT2 may cause its dysfunction in MND. Using yeast 2-hybrid screening followed by mammalian co-localisation and co-immunoprecipitation experiments, we have identified four novel protein interactors of EAAT2. We have undertaken a genetic screen of the exons of one of these interactors in 100 MND patients and 100 age-matched control individuals. Of interest, we identified single nucleotide variants that are predicted to alter the amino acid sequence in 24% of the ALS patients, compared to 4% of the controls, a highly statistically significant difference. These results suggest that genetic variants in this EAAT2 interacting gene are susceptibility factors for MND. Functional studies on this novel interactor are now required to assess the impact of these variants on EAAT2 function and shed light on their possible role in MND pathogenesis.