scholarly journals C-terminal-dependent control of EAAT2 signaling, corticostriatal synaptic glutamate clearance and spontaneous motor activity in mice with hypokinesia

2020 ◽  
Author(s):  
Stefan Hirschberg ◽  
Anton Dvorzhak ◽  
Seyed M. A. Rasooli-Nejad ◽  
Svilen Angelov ◽  
Marieluise Kirchner ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Motor Activity ◽  
Excitatory Amino Acid ◽  
Glutamate Uptake ◽  
Excitatory Amino Acid Transporter ◽  
Intracellular Regulation ◽  
Functional Consequences ◽  
Exploratory Movements

SUMMARYDeficiency of the astrocytic excitatory amino acid transporter type 2 (EAAT2) and, consequently, inefficient glutamate clearance at corticostriatal synapses may contribute to the depression of self-initiated movements in Huntington’s disease (HD). Here we report that the removal of the last 68 amino-acids in the C-terminal of EAAT2 increases the levels of native EAAT2 in striatal lysates and counteracts some of the HD-related changes in the interactor spectrum of mYFP-tagged EAAT2. Using the Q175 mouse model of HD, we explored the functional consequences of C-terminal modifications. It was found that astrocytic expression of EAAT2-S506X or -4KR alleviates the HD-related decrease in the incidence and velocity of exploratory movements. It also stimulates astrocytic glutamate uptake, increases the level of synaptic EAAT2 and improves glutamate clearance at single corticostriatal synapse. The experiments illuminate a link between the intracellular regulation of astrocytic glutamate transport in the striatum and symptoms of hypokinesia in HD mice.

scholarly journals Cryo-EM structures of excitatory amino acid transporter 3 visualize coupled substrate, sodium, and proton binding and transport

2021 ◽  
Vol 7 (10) ◽  
pp. eabf5814
Author(s):  
Biao Qiu ◽  
Doreen Matthies ◽  
Eva Fortea ◽  
Zhiheng Yu ◽  
Olga Boudker
Keyword(s):  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Glutamate Uptake ◽  
Amino Acid Transporter ◽  
Sodium Ions ◽  
Excitatory Amino Acid Transporter ◽  
Proton Symport ◽  
Functional States ◽  
Rapid Transport ◽  
Acid Transporter

Human excitatory amino acid transporter 3 (hEAAT3) mediates glutamate uptake in neurons, intestine, and kidney. Here, we report cryo-EM structures of hEAAT3 in several functional states where the transporter is empty, bound to coupled sodium ions only, or fully loaded with three sodium ions, a proton, and the substrate aspartate. The structures suggest that hEAAT3 operates by an elevator mechanism involving three functionally independent subunits. When the substrate-binding site is near the cytoplasm, it has a remarkably low affinity for the substrate, perhaps facilitating its release and allowing the rapid transport turnover. The mechanism of the coupled uptake of the sodium ions and the substrate is conserved across evolutionarily distant families and is augmented by coupling to protons in EAATs. The structures further suggest a mechanism by which a conserved glutamate residue mediates proton symport.

scholarly journals Transport mechanism of the neuronal excitatory amino acid transporter

2020 ◽  
Author(s):  
Biao Qiu ◽  
Doreen Matthies ◽  
Eva Fortea ◽  
Zhiheng Yu ◽  
Olga Boudker
Keyword(s):  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Glutamate Uptake ◽  
Amino Acid Transporter ◽  
Sodium Ions ◽  
Excitatory Amino Acid Transporter ◽  
Proton Symport ◽  
Functional States ◽  
Rapid Transport ◽  
Acid Transporter

AbstractHuman excitatory amino acid transporter 3 (hEAAT3) mediates glutamate uptake in neurons, intestine, and kidney. Here, we report Cryo-EM structures of hEAAT3 in several functional states where the transporter is empty, bound to coupled sodium ions only, or fully loaded with three sodium ions, a proton, and the substrate aspartate. The structures suggest that hEAAT3 operates by an elevator mechanism involving three functionally independent subunits. When the substrate-binding site is near the cytoplasm, it has a remarkably low affinity for the substrate, perhaps facilitating its release and allowing for the rapid transport turnover. The mechanism of the coupled uptake of the sodium ions and the substrate is conserved across evolutionarily distant families and is augmented by coupling to protons in EAATs. The structures further suggest a mechanism by which conserved glutamate mediates proton symport.

scholarly journals A computational approach yields selective inhibitors of human excitatory amino acid transporter 2 (EAAT2)

2020 ◽  
Vol 295 (13) ◽  
pp. 4359-4366
Author(s):  
Kelly L. Damm-Ganamet ◽  
Marie-Laure Rives ◽  
Alan D. Wickenden ◽  
Heather M. McAllister ◽  
Taraneh Mirzadegan
Keyword(s):  
Amino Acid ◽  
Drug Target ◽  
Therapeutic Potential ◽  
Excitatory Amino Acid ◽  
Glutamate Uptake ◽  
Homology Model ◽  
Binding Pocket ◽  
Amino Acid Transporters ◽  
Excitatory Amino Acid Transporter ◽  
Significant Interest

Excitatory amino acid transporters (EAATs) represent a protein family that is an emerging drug target with great therapeutic potential for managing central nervous system disorders characterized by dysregulation of glutamatergic neurotransmission. As such, it is of significant interest to discover selective modulators of EAAT2 function. Here, we applied computational methods to identify specific EAAT2 inhibitors. Utilizing a homology model of human EAAT2, we identified a binding pocket at the interface of the transport and trimerization domain. We next conducted a high-throughput virtual screen against this site and identified a selective class of EAAT2 inhibitors that were tested in glutamate uptake and whole-cell electrophysiology assays. These compounds represent potentially useful pharmacological tools suitable for further exploration of the therapeutic potential of EAAT2 and may provide molecular insights into mechanisms of allosteric modulation for glutamate transporters.

scholarly journals Effect of co-ingestion of amino acids with rice on glycaemic and insulinaemic response

2015 ◽  
Vol 114 (11) ◽  
pp. 1845-1851 ◽  
Author(s):  
Yean Yean Soong ◽  
Joseph Lim ◽  
Lijuan Sun ◽  
Christiani Jeyakumar Henry
Keyword(s):  
Amino Acids ◽  
Blood Glucose ◽  
Amino Acid ◽  
Glycaemic Index ◽  
Amino Acid Mixture ◽  
Postprandial Blood Glucose ◽  
Acid Mixture ◽  
White Rice ◽  
Amino Acid Mixtures

AbstractConsumption of high glycaemic index (GI) and glycaemic response (GR) food such as white rice has been implicated in the development of type 2 diabetes. Previous studies have reported the ability of individual amino acids to reduce GR of carbohydrate-rich foods. Because of the bitter flavour of amino acids, they have rarely been used to reduce GR. We now report the use of a palatable, preformed amino acid mixture in the form of essence of chicken. In all, sixteen healthy male Chinese were served 68 or 136 ml amino acid mixture together with rice, or 15 or 30 min before consumption of white rice. Postprandial blood glucose and plasma insulin concentrations were measured at fasting and every 15 min after consumption of the meal until 60 min after the consumption of the white rice. Subsequent blood samples were taken at 30-min intervals until 210 min. The co-ingestion of 68 ml of amino acid mixture with white rice produced the best results in reducing the peak blood glucose and GR of white rice without increasing the insulinaemic response. It is postulated that amino acid mixtures prime β-cell insulin secretion and peripheral tissue uptake of glucose. The use of ready-to-drink amino acid mixtures may be a useful strategy for lowering the high-GI rice diets consumed in Asia.

EAAT1 is involved in transport ofl-glutamate during differentiation of the Caco-2 cell line

2000 ◽  
Vol 279 (2) ◽  
pp. G366-G373 ◽  
Author(s):  
Agnès Mordrelle ◽  
Eric Jullian ◽  
Cyrille Costa ◽  
Estelle Cormet-Boyaka ◽  
Robert Benamouzig ◽  
...  
Keyword(s):  
Amino Acid ◽  
Cell Line ◽  
Excitatory Amino Acid ◽  
Kinetic Studies ◽  
Glutamate Transport ◽  
Hill Coefficient ◽  
Amino Acid Transporters ◽  
Intestinal Epithelial ◽  
Transport Capacity ◽  
Excitatory Amino Acid Transporter

Little is known concerning the expression of amino acid transporters during intestinal epithelial cell differentiation. The transport mechanism ofl-glutamate and its regulation during the differentiation process were investigated using the human intestinal Caco-2 cell line. Kinetic studies demonstrated the presence of a single, high-affinity,d-aspartate-sensitive l-glutamate transport system in both confluent and fully differentiated Caco-2 cells. This transport was clearly Na+ dependent, with a Hill coefficient of 2.9 ± 0.3, suggesting a 3 Na+-to-1 glutamate stoichiometry and corresponding to the well-characterized XA,G − system. The excitatory amino acid transporter (EAAT)1 transcript was consistently expressed in the Caco-2 cell line, whereas the epithelial and neuronal EAAT3 transporter was barely detected. In contrast with systems B0 and y+, which have previously been reported to be downregulated when Caco-2 cells stop proliferating, l-glutamate transport capacity was found to increase steadily between day 8 and day 17. This increase was correlated with the level of EAAT1 mRNA, which might reflect an increase in EAAT1 gene transcription and/or stabilization of the EAAT1 transcript.

Sign in / Sign up

Export Citation Format

Share Document