Excitatory Amino Acid Transporter 1 (EAAT1), also known as GLAST-1 and SLC1A3, is a member of the SDF symporter family of proteins. Human EAAT1/GLAST-1 is a 542 amino acid (aa), 8-transmembrane variably glycosylated protein with a predicted molecular weight of 60-62 kDa. Its N- and C-terminus are cytoplasmic. EAAT1/GLAST-1 homodimers are reported to exist, but only when the protein is glycosylated. There are at least two potential isoform variants. One shows an Arg substitution for aa 430-475, while a second shows a four aa substitution for aa 62-542. Over the extracellular loop that encompasses aa 146-237, human EAAT1/GLAST-1 shares 92% aa identity with the mouse ortholog. EAAT1/GLAST-1 is expressed by glia, fibroblasts, and select neuron cell types such as hippocampal neurons. EAAT1/GLAST-1 is known to transport L-glutamate into glia, thus removing glutamate from synaptic areas where it either acts too long, or becomes toxic at elevated concentrations. Its action is dependent on its ability to cotransport sodium. Aberrant expression of EAAT1/GLAST-1 is associated with multiple neurological and neurodegenerative disorders including epilepsy and multiple sclerosis.