Topiramate Versus Naltrexone for Alcohol Use Disorder: A Genotype-Stratified Double-Blind Randomized Controlled Trial.

OBJECTIVE: There have been no well-controlled and well-powered comparative trials of topiramate with other pharmacotherapies for alcohol use disorder (AUD), such as naltrexone. Moreover, the literature is mixed on the effects of two polymorphisms-rs2832407 (in GRIK1) and rs1799971 (in OPRM1)-on response to topiramate and naltrexone, respectively. The authors sought to examine the comparative effectiveness of topiramate and naltrexone in improving outcomes in AUD and to examine the role of the rs2832407 and rs1799971 polymorphisms, respectively, on response to these medications. METHODS: In a 12-week, double-blind, placebo-controlled, randomized, multisite, genotype-stratified (rs2832407 and rs1799971) clinical trial comparing topiramate and naltrexone in treating AUD, 147 patients with AUD were randomly assigned to treatment with topiramate or naltrexone, stratified by genotype (rs2832407*CC and *AC/AA genotypes and rs1799971*AA and *AG/GG genotypes). The predefined primary outcome was number of heavy drinking days per week. Predefined secondary outcomes included standard drinks per drinking day per week, body mass index (BMI), craving, markers of liver injury, mood, and adverse events. RESULTS: For the number of heavy drinking days per week, there was a near-significant time-by-treatment interaction. For the number of standard drinks per drinking day per week, there was a significant time-by-treatment interaction, which favored topiramate. There were significant time-by-treatment effects, with greater reductions observed with topiramate than naltrexone for BMI, craving, and gamma-glutamyltransferase level. Withdrawal due to side effects occurred in 8% and 5% of the topiramate and naltrexone groups, respectively. Neither polymorphism showed an effect on treatment response. CONCLUSIONS: Topiramate is at least as effective and safe as the first-line medication, naltrexone, in reducing heavy alcohol consumption, and superior in reducing some clinical outcomes. Neither rs2832407 nor rs1799971 had effects on topiramate and naltrexone treatments, respectively.

The kainate receptor GluK2 mediates cold sensing in mice.

Thermosensors expressed in peripheral somatosensory neurons sense a wide range of environmental temperatures. While thermosensors detecting cool, warm and hot temperatures have all been extensively characterized, little is known about those sensing cold temperatures. Though several candidate cold sensors have been proposed, none has been demonstrated to mediate cold sensing in somatosensory neurons in vivo, leaving a knowledge gap in thermosensation. Here we characterized mice lacking the kainate-type glutamate receptor GluK2, a mammalian homolog of the Caenorhabditis elegans cold sensor GLR-3. While GluK2 knockout mice respond normally to heat and mechanical stimuli, they exhibit a specific deficit in sensing cold but not cool temperatures. Further analysis supports a key role for GluK2 in sensing cold temperatures in somatosensory DRG neurons in the periphery. Our results reveal that GluK2-a glutamate-sensing chemoreceptor mediating synaptic transmission in the central nervous system-is co-opted as a cold-sensing thermoreceptor in the periphery.

The positive allosteric modulator BPAM344 and L-glutamate introduce an active-like structure of the ligand-binding domain of GluK2.

Kainate receptors belong to the family of ionotropic glutamate receptors and contribute to the majority of fast excitatory neurotransmission. Consequently, they also play a role in brain diseases. Therefore, understanding how these receptors can be modulated is of importance. Our study provides a crystal structure of the dimeric ligand-binding domain of the kainate receptor GluK2 in complex with L-glutamate and the small-molecule positive allosteric modulator, BPAM344, in an active-like conformation. The role of Thr535 and Gln786 in modulating GluK2 by BPAM344 was investigated using a calcium-sensitive fluorescence-based assay on transiently transfected cells expressing GluK2 and mutants hereof. This study may aid in the design of compounds targeting kainate receptors, expanding their potential as targets for the treatment of brain diseases.

Behavioral analysis of kainate receptor KO mice and the role of GluK3 subunit in anxiety.

Kainate receptors (KARs) are one of the ionotropic glutamate receptors in the central nervous system (CNS) comprised of five subunits, GluK1-GluK5. There is a growing interest in the association between KARs and psychiatric disorders, and there have been several studies investigating the behavioral phenotypes of KAR deficient mice, however, the difference in the genetic background has been found to affect phenotype in multiple mouse models of human diseases. Here, we examined GluK1-5 single KO mice in a pure C57BL/6N background and identified that GluK3 KO mice specifically express anxiolytic-like behavior with an alteration in dopamine D2 receptor (D2R)-induced anxiety, and reduced D2R expression in the striatum. Biochemical studies in the mouse cortex confirmed that GluK3 subunits do not assemble with GluK4 and GluK5 subunits, that can be activated by lower concentration of agonists. Overall, we found that GluK3-containing KARs function to express anxiety, which may represent promising anti-anxiety medication targets.

Small-molecule positive allosteric modulation of homomeric kainate receptors GluK1-3: development of screening assays and insight into GluK3 structure.

The kainate receptors GluK1-3 (glutamate receptor ionotropic, kainate receptors 1-3) belong to the family of ionotropic glutamate receptors and are essential for fast excitatory neurotransmission in the brain, and are associated with neurological and psychiatric diseases. How these receptors can be modulated by small-molecule agents is not well understood, especially for GluK3. We show that the positive allosteric modulator BPAM344 can be used to establish robust calcium-sensitive fluorescence-based assays to test agonists, antagonists, and positive allosteric modulators of GluK1-3. The half-maximal effective concentration (EC50) of BPAM344 for potentiating the response of 100 µm kainate was determined to be 26.3 µm for GluK1, 75.4 µm for GluK2, and 639 µm for GluK3. Domoate was found to be a potent agonist for GluK1 and GluK2, with an EC50 of 0.77 and 1.33 µm, respectively, upon co-application of 150 µm BPAM344. At GluK3, domoate acts as a very weak agonist or antagonist with a half-maximal inhibitory concentration (IC50) of 14.5 µm, in presence of 500 µm BPAM344 and 100 µm kainate for competition binding. Using H523A-mutated GluK3, we determined the first dimeric structure of the ligand-binding domain by X-ray crystallography, allowing location of BPAM344, as well as zinc-, sodium-, and chloride-ion binding sites at the dimer interface. Molecular dynamics simulations support the stability of the ion sites as well as the involvement of Asp761, Asp790, and Glu797 in the binding of zinc ions. Using electron microscopy, we show that, in presence of glutamate and BPAM344, full-length GluK3 adopts a dimer-of-dimers arrangement.

A Pathogenic Missense Mutation in Kainate Receptors Elevates Dendritic Excitability and Synaptic Integration through Dysregulation of SK Channels.

Numerous rare variants that cause neurodevelopmental disorders (NDDs) occur within genes encoding synaptic proteins, including ionotropic glutamate receptors. However, in many cases, it remains unclear how damaging missense variants affect brain function. We determined the physiological consequences of an NDD causing missense mutation in the GRIK2 kainate receptor (KAR) gene, that results in a single amino acid change p.Ala657Thr in the GluK2 receptor subunit. We engineered this mutation in the mouse Grik2 gene, yielding a GluK2(A657T) mouse, and studied mice of both sexes to determine how hippocampal neuronal function is disrupted. Synaptic KAR currents in hippocampal CA3 pyramidal neurons from heterozygous A657T mice exhibited slow decay kinetics, consistent with incorporation of the mutant subunit into functional receptors. Unexpectedly, CA3 neurons demonstrated elevated action potential spiking because of downregulation of the small-conductance Ca2+ activated K+ channel (SK), which mediates the post-spike afterhyperpolarization. The reduction in SK activity resulted in increased CA3 dendritic excitability, increased EPSP-spike coupling, and lowered the threshold for the induction of LTP of the associational-commissural synapses in CA3 neurons. Pharmacological inhibition of SK channels in WT mice increased dendritic excitability and EPSP-spike coupling, mimicking the phenotype in A657T mice and suggesting a causative role for attenuated SK activity in aberrant excitability observed in the mutant mice. These findings demonstrate that a disease-associated missense mutation in GRIK2 leads to altered signaling through neuronal KARs, pleiotropic effects on neuronal and dendritic excitability, and implicate these processes in neuropathology in patients with genetic NDDs.SIGNIFICANCE STATEMENT Damaging mutations in genes encoding synaptic proteins have been identified in various neurodevelopmental disorders, but the functional consequences at the cellular and circuit level remain elusive. By generating a novel knock-in mutant mouse, this study examined the role of a pathogenic mutation in the GluK2 kainate receptor (KAR) subunit, a subclass of ionotropic glutamate receptors. Analyses of hippocampal CA3 pyramidal neurons determined elevated action potential firing because of an increase in dendritic excitability. Increased dendritic excitability was attributable to reduced activity of a Ca2+ activated K+ channel. These results indicate that a pathogenic KAR mutation results in dysregulation of dendritic K+ channels, which leads to an increase in synaptic integration and backpropagation of action potentials into distal dendrites.

Depressive-like Behaviors Induced by mGluR5 Reduction in 6xTg in Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is one representative dementia characterized by the accumulation of amyloid beta (Aß) plaques and neurofibrillary tangles (NFTs) in the brain, resulting in cognitive decline and memory loss. AD is associated with neuropsychiatric symptoms, including major depressive disorder (MDD). Recent studies showed a reduction in mGluR5 expression in the brains of stress-induced mice models and individuals with MDD compared to controls. In our study, we identified depressive-like behavior and memory impairment in a mouse model of AD, specifically in the 6xTg model with tau and Aß pathologies. In addition, we investigated the expression of mGluR5 in the brains of 6xTg mice using micro-positron emission tomography (micro-PET) imaging, histological analysis, and Western blot analysis, and we observed a decrease in mGluR5 levels in the brains of 6xTg mice compared to wild-type (WT) mice. Additionally, we identified alterations in the ERK/AKT/GSK-3ß signaling pathway in the brains of 6xTg mice. Notably, we identified a significant negative correlation between depressive-like behavior and the protein level of mGluR5 in 6xTg mice. Additionally, we also found a significant positive correlation between depressive-like behavior and AD pathologies, including phosphorylated tau and Aß. These findings suggested that abnormal mGluR5 expression and AD-related pathologies were involved in depressive-like behavior in the 6xTg mouse model. Further research is warranted to elucidate the underlying mechanisms and explore potential therapeutic targets in the intersection of AD and depressive-like symptoms.

Asymmetry and Ion Selectivity Properties of Bacterial Channel NaK Mutants Derived from Ionotropic Glutamate Receptors.

Ionotropic glutamate receptors are ligand-gated cation channels that play essential roles in the excitatory synaptic transmission throughout the central nervous system. A number of open-pore structures of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic-acid (AMPA)-type glutamate receptors became available recently by cryo-electron microscopy (cryo-EM). These structures provide valuable insights into the conformation of the selectivity filter (SF), the part of the ion channel that determines the ion selectivity. Nonetheless, due to the moderate resolution of the cryo-EM structures, detailed information such as ion occupancy of monovalent and divalent cations as well as positioning of the side-chains in the SF is still missing. Here, in an attempt to obtain high-resolution information about glutamate receptor SFs, we incorporated partial SF sequences of the AMPA and kainate receptors into the bacterial tetrameric cation channel NaK, which served as a structural scaffold. We determined a series of X-ray structures of NaK-CDI, NaK-SDI and NaK-SELM mutants at 1.42-2.10 Å resolution, showing distinct ion occupation of different monovalent cations. Molecular dynamics (MD) simulations of NaK-CDI indicated the channel to be conductive to monovalent cations, which agrees well with our electrophysiology recordings. Moreover, previously unobserved structural asymmetry of the SF was revealed by the X-ray structures and MD simulations, implying its importance in ion non-selectivity of tetrameric cation channels.

Kainate receptors GluK1 and GluK2 differentially regulate synapse morphology.

The regulation of dendritic spine morphology is a critical aspect of neuronal network refinement during development and modulation of neurotransmission. Previous studies revealed that glutamatergic transmission plays a central role in synapse development. AMPA receptors and NMDA receptors regulate spine morphology in an activity dependent manner. However, whether and how Kainate receptors (KARs) regulate synapse development remains poorly understood. In this study, we found that GluK1 and GluK2 may play distinct roles in synapse development. In primary cultured hippocampal neurons, we found overexpression of the calcium-permeable GluK2(Q) receptor variant increased spine length and spine head area compared to overexpression of the calcium-impermeable GluK2(R) variant or EGFP transfected, control neurons, indicating that Q/R editing may play a role in GluK2 regulation of synapse development. Intriguingly, neurons transfected with GluK1(Q) showed decreased spine length and spine head area, while the density of dendritic spines was increased, suggesting that GluK1(Q) and GluK2(Q) have different effects on synaptic development. Swapping the critical domains between GluK2 and GluK1 demonstrated the N-terminal domain (NTD) is responsible for the different effects of GluK1 and GluK2. In conclusion, Kainate receptors GluK1 and GluK2 have distinct roles in regulating spine morphology and development, a process likely relying on the NTD.

Kainate receptor subunit 1 (GRIK1) risk variants and GRIK1 deficiency were detected in the Indian ADHD probands.

Executive dysfunctions caused by structural and functional abnormalities of the prefrontal cortex were reported in patients with Attention deficit hyperactivity disorder (ADHD). Owing to a higher expression of the glutamate ionotropic receptor kainate type subunit 1 (GluK1), encoded by the GRIK1 gene, in brain regions responsible for learning and memory, we hypothesized that GRIK1 might have a role in ADHD. GRIK1 variants rs363504 and rs363538, affecting the receptor function, were analyzed by case-control and family-based methods to identify the association with ADHD. The impact of these variants on ADHD-associated traits and pharmacological intervention were also analyzed. GRIK1 expression was quantified in the peripheral blood. The probands and their fathers had a higher frequency of rs363504 'CC' and rs363538 'CA' genotypes. Family-based investigation revealed maternal over transmission of rs363504 'C' and rs363538 'A' alleles to the probands. Quantitative trait analysis exhibited an association of rs363504 'TT' and rs363538 'AA' genotypes with higher hyperactivity scores of the probands. In the presence of rs363504 'TT' and rs363538 'CC' genotypes, MPH treatment improved hyperactivity and inattention, respectively. GRIK1 expression was significantly downregulated in the probands. We infer that GRIK1 affects ADHD etiology, warranting further in-depth investigation involving a larger cohort and more functional variants.

Structure, Function, and Regulation of the Kainate Receptor.

Neural communication and modulation are complex processes. Ionotropic glutamate receptors (iGluRs) significantly contribute to mediating the fast-excitatory branch of neurotransmission in the mammalian brain. Kainate receptors (KARs), a subfamily of the iGluRs, act as modulators of the neuronal circuitry by playing important roles at both the post- and presynaptic sites of specific neurons. The functional tetrameric receptors are formed by two different gene families, low agonist affinity (GluK1-GluK3) and high agonist affinity (GluK4-GluK5) subunits. These receptors garnered attention in the past three decades, and since then, much work has been done to understand their localization, interactome, physiological functions, and regulation. Cloning of the receptor subunits (GluK1-GluK5) in the early 1990s led to recombinant expression of kainate receptors in heterologous systems. This facilitated understanding of the functional differences between subunit combinations, splice variants, trafficking, and drug discovery. Structural studies of individual domains and recent full-length homomeric and heteromeric kainate receptors have revealed unique functional mechanisms, which have answered several long-standing questions in the field of kainate receptor biology. In this chapter, we review the current understanding of kainate receptors and associated disorders.

Glutamate can act as a signaling molecule in mouse preimplantation embryos†.

Free amino acids are present in the natural environment of the preimplantation embryo, and their availability can influence early embryo development. Glutamic acid is one of the amino acids with the highest concentrations in female reproductive fluids, and we investigated whether glutamic acid/glutamate can affect preimplantation embryo development by acting through cell membrane receptors. Using reverse transcription-polymerase chain reaction, we detected 15 ionotropic glutamate receptor transcripts and 8 metabotropic glutamate receptor transcripts in mouse ovulated oocytes and/or in vivo developed blastocysts. Using immunohistochemistry, we detected the expression of two α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits, three kainate receptor subunits, and member 5 metabotropic glutamate receptor protein in blastocysts. Extracellular concentrations of glutamic acid starting at 5 mM impaired mouse blastocyst development, and this fact may be of great practical importance since glutamic acid and its salts (mainly monosodium glutamate) are widely used as food additives. Experiments with glutamate receptor agonists (in combination with gene expression analysis) revealed that specific AMPA receptors (formed from glutamate receptor, ionotropic, AMPA3 [GRIA3] and/or glutamate receptor, ionotropic, AMPA4 [GRIA4] subunits), kainate receptors (formed from glutamate receptor, ionotropic, kainate 3 [GRIK3] and glutamate receptor, ionotropic, kainate 4 [GRIK4] or glutamate receptor, ionotropic, kainate 5 [GRIK5] subunits), and member 5 metabotropic glutamate receptor (GRM5) were involved in this effect. The glutamic acid-induced effects were prevented or reduced by pretreatment of blastocysts with AMPA, kainate, and GRM5 receptor antagonists, further confirming the involvement of these receptor types. Our results show that glutamic acid can act as a signaling molecule in preimplantation embryos, exerting its effects through the activation of cell membrane receptors.

mRNA editing of kainate receptor subunits: what do we know so far?

Kainate receptors (KARs) are considered one of the key modulators of synaptic activity in the mammalian central nervous system. These receptors were discovered more than 30 years ago, but their role in brain functioning remains unclear due to some peculiarities. One such feature of these receptors is the editing of pre-mRNAs encoding GluK1 and GluK2 subunits. Despite the long history of studying this phenomenon, numerous questions remain unanswered. This review summarizes the current data about the mechanism and role of pre-mRNA editing of KAR subunits in the mammalian brain and proposes a perspective of future investigations.

Post-treatment effects of topiramate on alcohol-related outcomes: A combined analysis of two placebo-controlled trials.

Topiramate reduces drinking and alcohol-related problems and is increasingly being used to treat alcohol use disorder (AUD). In a randomized controlled trial (RCT) of topiramate, rs2832407, a single nucleotide polymorphism (SNP) in the GRIK1 gene moderated topiramate's effects (Study 1). However, a second RCT (Study 2) did not replicate the SNP's moderating effect during treatment. The current analysis combines data from these two studies to examine topiramate's effects on alcohol-related outcomes and on its pharmacogenetic moderation during a 6-month post-treatment period. This analysis includes 308 individuals with problematic alcohol use (67% male; mean age = 51.1; topiramate: 49%, placebo: 51%). It uses generalized linear mixed models to examine changes in self-reported alcohol consumption and alcohol-related problems and concentrations of the liver enzyme γ-glutamyltransferase. The report combines published 3- and 6-month follow-up data from Study 1 with similar, unpublished data from Study 2. Despite robust effects of topiramate on drinking during treatment, the overall multivariate medication effects on outcomes during 3- and 6-month follow-up were not significant (p = 0.08 and p = 0.26, respectively). The moderating effect of the SNP on primary treatment outcomes was also not significant during either follow-up period (p = 0.13 and p = 0.16, respectively). However, during the 3-month post-treatment period, drinks per day was significantly lower in the topiramate group than the placebo group in the rs2832407*CC-genotype group. The robust effects of topiramate on alcohol-related outcomes during treatment diminish substantially once the medication is discontinued. Research is needed both to determine the optimal treatment duration and to identify clinically useful pharmacogenetic moderators of topiramate for treating AUD.

Identification of alternative protein targets of glutamate-ureido-lysine associated with PSMA tracer uptake in prostate cancer cells.

Prostate-specific membrane antigen (PSMA) is highly overexpressed in most prostate cancers and is clinically visualized using PSMA-specific probes incorporating glutamate-ureido-lysine (GUL). PSMA is effectively absent from certain high-mortality, treatment-resistant subsets of prostate cancers, such as neuroendocrine prostate cancer (NEPC); however, GUL-based PSMA tracers are still reported to have the potential to identify NEPC metastatic tumors. These probes may bind unknown proteins associated with PSMA-suppressed cancers. We have identified the up-regulation of PSMA-like aminopeptidase NAALADaseL and the metabotropic glutamate receptors (mGluRs) in PSMA-suppressed prostate cancers and find that their expression levels inversely correlate with PSMA expression and are associated with GUL-based radiotracer uptake. Furthermore, we identify that NAALADaseL and mGluR expression correlates with a unique cell cycle signature. This provides an opportunity for the future study of the biology of NEPC and potential therapeutic directions. Computationally predicting that GUL-based probes bind well to these targets, we designed and synthesized a fluorescent PSMA tracer to investigate these proteins in vitro, where it shows excellent affinity for PSMA, NAALADaseL, and specific mGluRs associated with poor prognosis.

The Deletion of GluK2 Alters Cholinergic Control of Neuronal Excitability.

Kainate receptors (KARs) are key regulators of synaptic circuits by acting at pre- and postsynaptic sites through either ionotropic or metabotropic actions. KARs can be activated by kainate, a potent neurotoxin, which induces acute convulsions. Here, we report that the acute convulsive effect of kainate mostly depends on GluK2/GluK5 containing KARs. By contrast, the acute convulsive activity of pilocarpine and pentylenetetrazol is not alleviated in the absence of KARs. Unexpectedly, the genetic inactivation of GluK2 rather confers increased susceptibility to acute pilocarpine-induced seizures. The mechanism involves an enhanced excitability of GluK2-/- CA3 pyramidal cells compared with controls upon pilocarpine application. Finally, we uncover that the absence of GluK2 increases pilocarpine modulation of Kv7/M currents. Taken together, our findings reveal that GluK2-containing KARs can control the excitability of hippocampal circuits through interaction with the neuromodulatory cholinergic system.

Kainate receptors: from synaptic activity to disease.

Kainate receptors (KARs) are glutamate receptors that participate in the postsynaptic transmission of information and in the control of neuronal excitability, as well as presynaptically modulating the release of the neurotransmitters GABA and glutamate. These modulatory effects, general follow a biphasic pattern, with low KA concentrations provoking an increase in GABA and glutamate release, and higher concentrations mediating a decrease in the release of these neurotransmitters. In addition, KARs are involved in different forms of long- and short-term plasticity. Importantly, altered activity of these receptors has been implicated in different central nervous system diseases and disturbances. Here, we describe the pre- and postsynaptic actions of KARs, and the possible role of these receptors in disease, a field that has seen significant progress in recent years.

A Two-Color Haploid Genetic Screen Identifies Novel Host Factors Involved in HIV-1 Latency.

To identify novel host factors as putative targets to reverse HIV-1 latency, we performed an insertional mutagenesis genetic screen in a latent HIV-1 infected pseudohaploid KBM7 cell line (Hap-Lat). Following mutagenesis, insertions were mapped to the genome, and bioinformatic analysis resulted in the identification of 69 candidate host genes involved in maintaining HIV-1 latency. A select set of candidate genes was functionally validated using short hairpin RNA (shRNA)-mediated depletion in latent HIV-1 infected J-Lat A2 and 11.1 T cell lines. We confirmed ADK, CHD9, CMSS1, EVI2B, EXOSC8, FAM19A, GRIK5, IRF2BP2, NF1, and USP15 as novel host factors involved in the maintenance of HIV-1 latency. Chromatin immunoprecipitation assays indicated that CHD9, a chromodomain helicase DNA-binding protein, maintains HIV-1 latency via direct association with the HIV-1 5' long terminal repeat (LTR), and its depletion results in increased histone acetylation at the HIV-1 promoter, concomitant with HIV-1 latency reversal. FDA-approved inhibitors 5-iodotubercidin, trametinib, and topiramate, targeting ADK, NF1, and GRIK5, respectively, were characterized for their latency reversal potential. While 5-iodotubercidin exhibited significant cytotoxicity in both J-Lat and primary CD4+ T cells, trametinib reversed latency in J-Lat cells but not in latent HIV-1 infected primary CD4+ T cells. Importantly, topiramate reversed latency in cell line models, in latently infected primary CD4+ T cells, and crucially in CD4+ T cells from three people living with HIV-1 (PLWH) under suppressive antiretroviral therapy, without inducing T cell activation or significant toxicity. Thus, using an adaptation of a haploid forward genetic screen, we identified novel and druggable host factors contributing to HIV-1 latency. IMPORTANCE A reservoir of latent HIV-1 infected cells persists in the presence of combination antiretroviral therapy (cART), representing a major obstacle for viral eradication. Reactivation of the latent HIV-1 provirus is part of curative strategies which aim to promote clearance of the infected cells. Using a two-color haploid screen, we identified 69 candidate genes as latency-maintaining host factors and functionally validated a subset of 10 of those in additional T-cell-based cell line models of HIV-1 latency. We further demonstrated that CHD9 is associated with HIV-1's promoter, the 5' LTR, while this association is lost upon reactivation. Additionally, we characterized the latency reversal potential of FDA compounds targeting ADK, NF1, and GRIK5 and identify the GRIK5 inhibitor topiramate as a viable latency reversal agent with clinical potential.

Structural and compositional diversity in the kainate receptor family.

The kainate receptors (KARs) are members of the ionotropic glutamate receptor family and assemble into tetramers from a pool of five subunit types (GluK1-5). Each subunit confers distinct functional properties to a receptor, but the compositional and stoichiometric diversity of KAR tetramers is not well understood. To address this, we first solve the structure of the GluK1 homomer, which enables a systematic assessment of structural compatibility among KAR subunits. Next, we analyze single-cell RNA sequencing data, which reveal extreme diversity in the combinations of two or more KAR subunits co-expressed within the same cell. We then investigate the composition of individual receptor complexes using single-molecule fluorescence techniques and find that di-heteromers assembled from GluK1, GluK2, or GluK3 can form with all possible stoichiometries, while GluK1/K5, GluK2/K5, and GluK3/K5 can form 3:1 or 2:2 complexes. Finally, using three-color single-molecule imaging, we discover that KARs can form tri- and tetra-heteromers.

Kainate receptors regulate the functional properties of young adult-born dentate granule cells.

Both inhibitory and excitatory neurotransmitter receptors can influence maturation and survival of adult-born neurons in the dentate gyrus; nevertheless, how these two neurotransmitter systems affect integration of new neurons into the existing circuitry is still not fully characterized. Here, we demonstrate that glutamate receptors of the kainate receptor (KAR) subfamily are expressed in adult-born dentate granule cells (abDGCs) and that, through their interaction with GABAergic signaling mechanisms, they alter the functional properties of adult-born cells during a critical period of their development. Both the intrinsic properties and synaptic connectivity of young abDGCs were affected. Timed KAR loss in a cohort of young adult-born neurons in mice disrupted their performance in a spatial discrimination task but not in a hippocampal-dependent fear conditioning task. Together, these results demonstrate the importance of KARs in the proper functional development of young abDGCs.