Modulation of the neuronal glutamate transporter EAAT4 by two interacting proteins

Abstract

Glutamate is the main excitatory neurotransmitter in the mammalian central nervous system and is removed from the synaptic cleft by sodium-dependent glutamate transporters. To date, five distinct glutamate transporters have been cloned from animal and human tissue: GLAST (EAAT1), GLT-1 (EAAT2), EAAC1 (EAAT3), EAAT4, and EAAT5 (refs 1-5). GLAST and GLT-1 are localized primarily in astrocytes, whereas EAAC1 (refs 8, 9), EAAT4 (refs 9-11) and EAAT5 (ref 5) are neuronal. Studies of EAAT4 and EAAC1 indicate an extrasynaptic localization on perisynaptic membranes that are near release sites. This localization facilitates rapid glutamate binding, and may have a role in shaping the amplitude of postsynaptic responses in densely packed cerebellar terminals. We have used a yeast two-hybrid screen to identify interacting proteins that may be involved in regulating EAAT4--the glutamate transporter expressed predominately in the cerebellum--or in targeting and/or anchoring or clustering the transporter to the target site. Here we report the identification and characterization of two proteins, GTRAP41 and GTRAP48 (for glutamate transporter EAAT4 associated protein) that specifically interact with the intracellular carboxy-terminal domain of EAAT4 and modulate its glutamate transport activity.

Genome-wide association study to identify genetic variants present in Japanese patients harboring intracranial aneurysms

“…Intriguingly, in rat, overexpression of the ortholog induces the reorganization of the actin cytoskeleton and the formation of membrane ruffling. 23 The SNP rs9864101, whose effect on IA was modified by gender, is located in the gene IQSEC1. ARF-GEP100 protein (ADP-ribosylation factorguanine nucleotide-exchange protein-100 kDa) encoded by this gene activates ADP-ribosylation factor protein, ARF6, and regulates cell adhesion through recycling E-cadherin and remodeling actin cytoskeleton.…”

Glutamate transporters in platelets: EAAT1 decrease in aging and in Alzheimer’s disease

“…As recent studies have also shown that glutamate transporter expression and activity may be regulated by different endogenous or exogenous factors [6,8,10,13,15,27,31,35,44,48,53], we are now studying the possible role of physiological stimuli, such as PKC activation, or oxidative stress on glutamate transporter activation/inactivation or translocation in platelets. The final goal of these studies is the possibility of using platelets as peripheral model to investigate the role of glutamate, its transporters and its effect pathway in neurodegenerative disorders, with the clear advantage of being easy to obtain, suitable for pharmacological and clinical studies and, compared to human brain tissue studies, of being independent from postmortem or end-stage changes.…”

Spectrin mutations that cause spinocerebellar ataxia type 5 impair axonal transport and induce neurodegeneration inDrosophila

“…In particular, recent work suggests that wild-type -III-spectrin, but not SCA5 mutant spectrin, can stabilize the glutamate transporter EAAT4 at the cell membrane (Jackson et al, 2001;Ikeda et al, 2006). Consistent with possible dominant-negative effects, expression of the SCA5 mutant proteins results in reduced numbers of synaptic boutons at synaptic termini.…”

“…First, wild-type but not mutant -III-spectrin stabilizes the Purkinje cellspecific excitatory amino acid transporter 4 (EAAT4) at the surface of the plasma membrane (Ikeda et al, 2006). In addition, cell fractionation studies have shown differences in the localization of EAAT4 and the glutamate receptor delta 2 subunit (GluR2) in cerebellar synaptosomal fractions from SCA5 versus control autopsy tissue (Ikeda et al, 2006), and the C-terminal domains of GluR2 and EAAT4 have been shown to physically interact with spectrin (Hirai and Matsuda, 1999;Jackson et al, 2001). Finally, -III-spectrin is a Golgi-and vesicle-associated protein that interacts with dynactin (Holleran et al, 2001).…”