br Results br Discussion Arc p

Results
Discussion Arc1p forms a ternary complex with ScMetRS and ScGluRS and acts as a tIF in trans of both synthetases to improve their catalytic efficiencies.20., 24. The human homolog of Arc1p, the p43 protein, is associated within a multi-enzyme complex containing nine aminoacyl-tRNA synthetases and two other non-synthetase proteins. Yeast Arc1p, human p43 as well as rice MetRS (OsMetRS) possess EMAPII-like C-terminal domains.16., 18., 20.In vitro, the EMAPII-like domain of OsMetRS interacts non-specifically with tRNA, decreases the Km value of the enzyme for tRNAMet, improves the catalytic efficiency of MetRS at the non-saturating tRNA concentrations that prevail in vivo but does not significantly affect its kcat value. The EMAPII-like domain of OsMetRS acts as a tIF in cis of the catalytic core of the enzyme (OsMetRSΔ(M+C), with our notation). Whereas the tRNA-binding capacity of the EMAPII domain of human p43 has been clearly shown in vitro,18., 30. its possible involvement in vivo as a tIF in trans of an aminoacyl-tRNA synthetase was not demonstrated. The results reported here reveal that the EMAPII-like domain of OsMetRS and the EMAPII domain of human p43 have the potential to act as functional tIFs in vivo and put new perspectives on the role of Arc1p in yeast.
Materials and Methods
Acknowledgements We acknowledge the technical assistance of Françoise Triniolles and Florence Ruaudel and thank K. Galani and G. Simos (Heidelberg, Germany and Larissa, Greece) for the gifts of pRS316-URA3-MetRS, pUN100-Arc1 and pRS425-ProtA-Arc1 plasmids and of mes1−arc1− and los1−arc1− yeast strains; J. Dijck (Leiden, The Netherlands) for the gift of pET-16b-HsEF1A; and F. Fasiolo (Strasbourg, France) for the gift of γ-Secretase inhibitor IX mg directed to ScMetRS and ScGluRS. A.Z. was supported by a grant from the Jumelage Franco-Polonais program from the CNRS.
Introduction For human beings all over the world, epilepsy has had a tremendous impact, resulting in the death of one to two percent of the world's population. Moreover, the incidence of epilepsy is increasing, and the mortality rate is also increasing [1]. Unfortunately, about 30–40% of epilepsy patients still can not control their seizures with antiepileptic drugs (AEDs), and even their condition has a great probability of developing into drug-resistant epilepsy or refractory epilepsy [2]. Neuronal dysfunction has a high probability of causing imbalance between excitatory and inhibitory neuronal circuits, which is also regarded as the core mechanism of refractory epilepsy, especially temporal lobe epilepsy (TLE) [3]. In addition, there are many types of proteins involved in this process, such as glucagon-like peptide-1 (GLP-1), which is mainly generated in L cells and is closely related to the mediation of glucose homeostasis [4]. However, GLP-1 can be synthesized not only in L cells, but also in other tissues, especially in solitary tract area, posterior area and caudal brainstem [5]. Moreover, its receptor GLP-1R is also distributed in many areas, such as pancreatic beta cells, central nervous system (CNS), including hippocampus, cortex, brainstem and solitary tract [6]. Due to their neuroprotective effects, GLP-1 or GLP-1R analogs and agonists represent novel therapeutic approaches for neurological disorders, and their therapeutic effects on various diseases, including Alzheimer's disease (AD) [7], stroke [8], Parkinson's disease (PD) [9], and amyotrophic lateral sclerosis [10], have been previously verified. Nevertheless, there have been few researches to address the inhibitory effects of GLP-1R on epilepsy, and whether GLP-1R exerts antiepileptic effects and the mechanism through which GLP-1R exerts these effects remain unclear. Thus, we aimed to look into the antiepileptic effects of GLP-1R and the underlying mechanisms. Therefore, the authors hypothesize that activated GLP-1R can scientifically and effectively regulate the excitability of the central nervous system, and can also effectively regulate the expression level of neuronal receptors, thereby effectively inhibiting the excitability of neurons, including gamma-aminobutyric acid (GABA) A receptor (GABAAR), a-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptors (GluAs) and N-methyl-D-aspartate (NMDA) receptors (GluNs). To further test this hypothesis, we analyzed and studied the level of GLP-1R in the TLE patients and in the rats treated with pentylenetetrazole (PTZ). The interaction between GLP-1R and various neuronal receptors (GABAARβ2/3, GluA1-4, GluNR1, GluN2A and GluN2B) was also tested. Experimental rats and neurons were treated with the GLP-1R agonist liraglutide and the GLP-1R antagonist exendin fragment 9–39 (ex9-39), and their effects on the expression levels of GLP-1R and neuronal receptors were then determined.