2,3-Benzodiazepine (2,3-BDZ) compounds are a group of AMPA receptor inhibitors and are drug candidates for treating neurological diseases involving excessive AMPA receptor activity. We investigated the mechanism by which GluA2Qflip receptor channel opening is inhibited by two 2,3-BDZ derivatives, i.e.,1-(4-aminophenyl)-3,5-dihydro-7,8-ethylenedioxy-4H-2,3-benzodiazepin-4-one (2,3-BDZ-11-2) and its 1-(4-amino-3-chlorophenyl) analogue (2,3-BDZ-11-4). Both compounds have a 7,8-ethylenedioxy moiety instead of the 7,8-methylenedioxy feature present in the structure of GYKI 52466, the prototypic 2,3-BDZ compound. Using a laser-pulse photolysis approach with a time resolution of ~60 μs and a rapid solution flow technique, we characterized the effect of the two compounds on the channel-opening process of the homomeric GluA2Qflip receptor. We found that both 2,3-BDZ-11-2 and 2,3-BDZ-11-4 are noncompetitive inhibitors with specificity for the closed-channel conformation of the GluA2Qflip receptor. However, 2,3-BDZ-11-4 is ~10-fold stronger, defined by its inhibition constant for the closed-channel conformation (i.e., KI = 2 μM), than 2,3-BDZ-11-2. From double-inhibitor experiments, we determined that both compounds bind to the same site, but this site is different from two other known, noncompetitive binding sites on the GluA2Qflip receptor previously reported. Our results provide both mechanistic clues to better understand AMPA receptor regulation and a structure-activity relationship for designing more potent 2,3-BDZ compounds with predictable properties for this new noncompetitive site.

AMPA receptors (AMPARs) mediate the majority of fast excitatory transmission in the brain and critically contribute to synaptic plasticity and pathology. AMPAR trafficking and gating are tightly controlled by auxiliary transmembrane AMPAR regulatory proteins (TARPs). Here, using systematic domain swaps with the TARP-insensitive kainate receptor GluK2, we show that AMPAR interaction with the prototypical TARP stargazin/γ2 primarily involves the AMPAR membrane domains M1 and M4 of neighboring subunits, initiated or stabilized by the AMPAR C-tail, and that these interactions are sufficient to enable full receptor modulation. Moreover, employing TARP chimeras disclosed a key role in this process also for the TARP transmembrane domains TM3 and TM4 and extracellular loop 2. Mechanistically, our data support a two-step action in which binding of TARP to the AMPAR membrane domains destabilizes the channel closed state, thereby enabling an efficient opening upon agonist binding, which then stabilizes the open state via subsequent interactions.

SUMMARY Altering AMPA receptor (AMPAR) content at synapses is a key mechanism underlying the regulation of synaptic strength during learning and memory. Previous work demonstrated that SynDIG1 (synapse differentiation-induced gene 1) encodes a transmembrane AMPAR-associated protein that regulates excitatory synapse strength and number. Here we show that the related protein SynDIG4 (also known as Prrt1) modifies AMPAR gating properties in a subunit-dependent manner. Young SynDIG4 knockout (KO) mice have weaker excitatory synapses, as evaluated by immunocytochemistry and electrophysiology. Adult SynDIG4 KO mice show complete loss of tetanus-induced long-term potentiation (LTP), while mEPSC amplitude is reduced by only 25%. Furthermore, SynDIG4 KO mice exhibit deficits in two independent cognitive assays. Given that SynDIG4 colocalizes with the AMPAR subunit GluA1 at non-synaptic sites, we propose that SynDIG4 maintains a pool of extrasynaptic AMPARs necessary for synapse development and function underlying higher-order cognitive plasticity.

BackgroundThroughout history, every civilization in the world used plants or their derivatives for treatment or prevention of diseases. In Palestine as in many other countries, herbal medicines are broadly used in the treatment of wide range of diseases including urological diseases. The main objective of this research is to study the use of herbal remedies by herbalists and traditional healers for treatment of various urological diseases in the West Bank regions of Palestine and to assess their efficacy and safety through the literature review of the most cited plants.MethodThe study included a survey part, plant identification and a review study. The first part was a cross-sectional descriptive study. Face to face questionnaires were distributed to 150 traditional healers and herbalist in all regions of the West Bank of Palestine. The literature review part was to assess the most cited plants for their efficacy and toxicity.ResultsOne hundred forty four herbalists and traditional healers accepted to participate in this study which was conducted between March and April, 2016. The results showed that 57 plant species belonging to 30 families were used by herbalists and traditional healers for treatment of various urinary tract diseases in Palestine. Of these, Apiaceae family was the most prevalent. Paronychia argentea, Plantago ovata, Punica granatum, Taraxacum syriacum, Morus alba and Foeniculum vulgare were the most commonly used plant species in the treatment of kidney stones, while Capsella bursa-pastoris, Ammi visnaga and Ammi majus were the most recommended species for treatment of urinary tract infections and Portulaca oleracea used for renal failure. In addition Curcuma longa and Crocus sativus were used for enuresis while Juglans regia, Quercus infectoria, Sambucus ebulus and Zea mays were used for treatment symptoms of benign prostate hyperplasia. Fruits were the most common parts used, and a decoction was the most commonly used method of preparation. Through literature review, it was found that Paronychia argentea has a low hemolytic effect and contains oxalic acid and nitrate. Therefore, it could be harmful to renal failure patients, also Juglans regia, Quercus infectoria and, Sambucus ebulus are harmful plants and cannot be used for treatment of any disease.ConclusionsOur data provided that ethnopharmacological flora in the West Bank regions of Palestine can be quite wealthy and diverse in the treatments of urinary tract diseases. Clinical trials and pharmacological tests are required evaluate safety and efficacy of these herbal remedies.

Lavandula dentata L. and Origanum syriacum L. essential oils have numerous health benefits and properties, such as possessing common components with a variant degree of depressive actions in the central nervous system. We investigated the depressive property of these oils on AMPA receptors, which are responsible for most of the fast-excitatory neurotransmission in the CNS and play a critical role in synaptic plasticity. Since excessive activation of AMPARs has been linked to neurotoxicity leading to various pathologies, we hypothesize that these oils have a neuroprotective role by acting directly on the kinetics of AMPARs. Using Gas Chromatography-Mass Spectrometry (GC/MS) and patch-clamp electrophysiology, the essential oils of L. dentata flowers and O. syriacum leaves were characterized and the whole cell currents were measured with and without the administration of the oils onto HEK293 cells. The current study results showed that the biophysical properties of AMPA receptor subunits showed a decrease in desensitization rate of GluA1 and GluA2 homomers, using O. syriacum, while administering L. dentata oil decreased the desensitization rate of GluA1 and GluA2 homomers, as well as GluA1/2 heteromers. As for the deactivation rate, both oils slowed the deactivation kinetics of all AMPA receptor subunits. Intriguingly, between the two oils, the effect of desensitization and deactivation was of a greater significance for L. dentata oil than O. syriacum. Our data suggest that the two oils contain components that are essential to identify, as those active components underlie the oils’ neuronal depressive properties reported, and to extract them to synthesize a potent neuroprotective drug to treat neurological diseases potentially.