Kainate receptor channel opening and gating mechanism.

Kainate receptors, a subclass of ionotropic glutamate receptors, are tetrameric ligand-gated ion channels that mediate excitatory neurotransmission1-4. Kainate receptors modulate neuronal circuits and synaptic plasticity during the development and function of the central nervous system and are implicated in various neurological and psychiatric diseases, including epilepsy, depression, schizophrenia, anxiety and autism5-11. Although structures of kainate receptor domains and subunit assemblies are available12-18, the mechanism of kainate receptor gating remains poorly understood. Here we present cryo-electron microscopy structures of the kainate receptor GluK2 in the presence of the agonist glutamate and the positive allosteric modulators lectin concanavalin A and BPAM344. Concanavalin A and BPAM344 inhibit kainate receptor desensitization and prolong activation by acting as a spacer between the amino-terminal and ligand-binding domains and a stabilizer of the ligand-binding domain dimer interface, respectively. Channel opening involves the kinking of all four pore-forming M3 helices. Our structures reveal the molecular basis of kainate receptor gating, which could guide the development of drugs for treatment of neurological disorders.

JNK activity modulates postsynaptic scaffold protein SAP102 and kainate receptor dynamics in dendritic spines.

Synapse formation depends on the coordinated expression and regulation of scaffold proteins. The JNK family kinases play a role in scaffold protein regulation, but the nature of this functional interaction in dendritic spines requires further investigation. Here, using a combination of biochemical methods and live-cell imaging strategies, we show that the dynamics of the synaptic scaffold molecule SAP102 are negatively regulated by JNK inhibition, that SAP102 is a direct phosphorylation target of JNK3, and that SAP102 regulation by JNK is restricted to neurons that harbor mature synapses. We further demonstrate that SAP102 and JNK3 cooperate in the regulated trafficking of kainate receptors to the cell membrane. Specifically, we observe that SAP102, JNK3, and the kainate receptor subunit GluK2 exhibit overlapping expression at synaptic sites and that modulating JNK activity influences the surface expression of the kainate receptor subunit GluK2 in a neuronal context. We also show that SAP102 participates in this process in a JNK-dependent fashion. In summary, our data support a model in which JNK-mediated regulation of SAP102 influences the dynamic trafficking of kainate receptors to postsynaptic sites, and thus shed light on common pathophysiological mechanisms underlying the cognitive developmental defects associated with diverse mutations.

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.

Epigenetic signature discriminates lymphatic metastasis in BRAF wild-type thyroid carcinoma: methylation role of GRIK2.

Aim: Conservative treatment approaches for thyroid carcinoma (TC) patients with wild-type B-type Raf kinase (BRAF) pose risks of long-term recurrence. The association of DNA methylation with TC metastasis is unclear. Patients & methods: Here we analyzed data from 179 BRAF wild-type TC patients in the The Cancer Genome Atlas database, identifying significant metastasis-associated CpGs. A logistic regression model was developed and validated for discriminating lymphatic metastasis in BRAF wild-type TC. Results: The model showed high accuracy (AUC: 0.924 training set; 0.812 and 0.773 external cohorts). TAGLN, MRPL4, CLDN10 and GRIK2 emerged as diagnostic markers. GRIK2, downregulated due to promoter hypermethylation, acted as a TC suppressor. Conclusion: Our 5-CpG epigenetic signature effectively discriminates lymphatic metastasis in BRAF wild-type TC, highlighting GRIK2's tumor-suppressive role influenced by promoter hypermethylation.

NETO2-GluK2 interaction contributes to postoperative pain hypersensitivity through inducing PKCγ activation and synaptic incorporation of AMPA receptor GluR1 subunits in rat dorsal horn.

Important roles in the initiation and maintenance of postoperative pain are played by the functional control of kainate (KA) and α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors in the rat dorsal horn (DH). However, the mechanisms underpinning the cross-talk between spinal KA and AMPA receptors in postoperative pain are poorly understood. We hypothesized that after the rat's plantar incision, the synaptic incorporation of AMPA receptor GluR1 subunits in the DH ipsilateral to the incision would increase due to the interaction between GluK2 and neuropilin tolloid-like 2 (NETO2). Our findings showed that incision stimuli caused severe pain responses, as measured by cumulative pain scores. GluK2-NETO2 but not GluK2-NETO1interaction was upregulated in ipsilateral dorsal horn neurons (DHNs) at 6 h post-incision. At 6 h post-incision, NETO2 small interfering ribonucleic acid (siRNA) intrathecal pretreatment increased mechanical withdrawal thresholds to von Freys and decreased ipsilateral paw cumulative pain scores. Further, PKCγactivation and synaptic abundance of GluK2 and GluR1 subunits in the ipsilateral DH were decreased by intrathecal pretreatment with NETO2 siRNA at 6 h post-incision. In conclusion, our findings imply that GluK2-NETO2 interaction could trigger PKCγactivation and the synaptic incorporation of AMPA receptor GluR1 subunits in rat DHs, which in turn led to the enhanced pain hypersensitivity after surgery. It sheds light on the interplay between KA and AMPA receptors in DHNs, which is thought to contribute to postoperative pain.

Presenilin and APP Regulate Synaptic Kainate Receptors.

Kainate receptors (KARs) form a family of ionotropic glutamate receptors that regulate the activity of neuronal networks by both presynaptic and postsynaptic mechanisms. Their implication in pathologies is well documented for epilepsy. The higher prevalence of epileptic symptoms in Alzheimer's disease (AD) patients questions the role of KARs in AD. Here we investigated whether the synaptic expression and function of KARs was impaired in mouse models of AD. We addressed this question by immunostaining and electrophysiology at synapses between mossy fibers and CA3 pyramidal cells, in which KARs are abundant and play a prominent physiological role. We observed a decrease of the immunostaining for GluK2 in the stratum lucidum in CA3, and of the amplitude and decay time of synaptic currents mediated by GluK2-containing KARs in an amyloid mouse model (APP/PS1) of AD. Interestingly, a similar phenotype was observed in CA3 pyramidal cells in male and female mice with a genetic deletion of either presenilin or APP/APLP2 as well as in organotypic cultures treated with γ-secretase inhibitors. Finally, the GluK2 protein interacts with full-length and C-terminal fragments of APP. Overall, our data suggest that APP stabilizes KARs at synapses, possibly through a transsynaptic mechanism, and this interaction is under the control the γ-secretase proteolytic activity of presenilin.SIGNIFICANCE STATEMENT Synaptic impairment correlates strongly with cognitive deficits in Alzheimer's disease (AD). In this context, many studies have addressed the dysregulation of AMPA and NMDA ionotropic glutamate receptors. Kainate receptors (KARs), which form the third family of iGluRs, represent an underestimated actor in the regulation of neuronal circuits and have not yet been examined in the context of AD. Here we provide evidence that synaptic KARs are markedly impaired in a mouse model of AD. Additional experiments indicate that the γ-secretase activity of presenilin acting on the amyloid precursor protein controls synaptic expression of KAR. This study clearly indicates that KARs should be taken into consideration whenever addressing synaptic dysfunction and related cognitive deficits in the context of AD.

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 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.

Kainate receptor modulation by NETO2.

Glutamate-gated kainate receptors are ubiquitous in the central nervous system of vertebrates, mediate synaptic transmission at the postsynapse and modulate transmitter release at the presynapse1-7. In the brain, the trafficking, gating kinetics and pharmacology of kainate receptors are tightly regulated by neuropilin and tolloid-like (NETO) proteins8-11. Here we report cryo-electron microscopy structures of homotetrameric GluK2 in complex with NETO2 at inhibited and desensitized states, illustrating variable stoichiometry of GluK2-NETO2 complexes, with one or two NETO2 subunits associating with GluK2. We find that NETO2 accesses only two broad faces of kainate receptors, intermolecularly crosslinking the lower lobe of ATDA/C, the upper lobe of LBDB/D and the lower lobe of LBDA/C, illustrating how NETO2 regulates receptor-gating kinetics. The transmembrane helix of NETO2 is positioned proximal to the selectivity filter and competes with the amphiphilic H1 helix after M4 for interaction with an intracellular cap domain formed by the M1-M2 linkers of the receptor, revealing how rectification is regulated by NETO2.

Locus specific epigenetic modalities of random allelic expression imbalance.

Most autosomal genes are thought to be expressed from both alleles, with some notable exceptions, including imprinted genes and genes showing random monoallelic expression (RME). The extent and nature of RME has been the subject of debate. Here we investigate the expression of several candidate RME genes in F1 hybrid mouse cells before and after differentiation, to define how they become persistently, monoallelically expressed. Clonal monoallelic expression is not present in embryonic stem cells, but we observe high frequencies of monoallelism in neuronal progenitor cells by assessing expression status in more than 200 clones. We uncover unforeseen modes of allelic expression that appear to be gene-specific and epigenetically regulated. This non-canonical allelic regulation has important implications for development and disease, including autosomal dominant disorders and opens up therapeutic perspectives.

Clustered mutations in the GRIK2 kainate receptor subunit gene underlie diverse neurodevelopmental disorders.

Kainate receptors (KARs) are glutamate-gated cation channels with diverse roles in the central nervous system. Bi-allelic loss of function of the KAR-encoding gene GRIK2 causes a nonsyndromic neurodevelopmental disorder (NDD) with intellectual disability and developmental delay as core features. The extent to which mono-allelic variants in GRIK2 also underlie NDDs is less understood because only a single individual has been reported previously. Here, we describe an additional eleven individuals with heterozygous de novo variants in GRIK2 causative for neurodevelopmental deficits that include intellectual disability. Five children harbored recurrent de novo variants (three encoding p.Thr660Lys and two p.Thr660Arg), and four children and one adult were homozygous for a previously reported variant (c.1969G>A [p.Ala657Thr]). Individuals with shared variants had some overlapping behavioral and neurological dysfunction, suggesting that the GRIK2 variants are likely pathogenic. Analogous mutations introduced into recombinant GluK2 KAR subunits at sites within the M3 transmembrane domain (encoding p.Ala657Thr, p.Thr660Lys, and p.Thr660Arg) and the M3-S2 linker domain (encoding p.Ile668Thr) had complex effects on functional properties and membrane localization of homomeric and heteromeric KARs. Both p.Thr660Lys and p.Thr660Arg mutant KARs exhibited markedly slowed gating kinetics, similar to p.Ala657Thr-containing receptors. Moreover, we observed emerging genotype-phenotype correlations, including the presence of severe epilepsy in individuals with the p.Thr660Lys variant and hypomyelination in individuals with either the p.Thr660Lys or p.Thr660Arg variant. Collectively, these results demonstrate that human GRIK2 variants predicted to alter channel function are causative for early childhood development disorders and further emphasize the importance of clarifying the role of KARs in early nervous system development.

Encephalitis with Autoantibodies against the Glutamate Kainate Receptors GluK2.

OBJECTIVE: The objective of this study was to report the identification of antibodies against the glutamate kainate receptor subunit 2 (GluK2-abs) in patients with autoimmune encephalitis, and describe the clinical-immunological features and antibody effects. METHODS: Two sera from 8 patients with similar rat brain immunostaining were used to precipitate the antigen from neuronal cultures. A cell-based assay (CBA) with GluK2-expressing HEK293 cells was used to assess 596 patients with different neurological disorders, and 23 healthy controls. GluK2-ab effects were determined by confocal microscopy in cultured neurons and electrophysiology in GluK2-expressing HEK293 cells. RESULTS: Patients' antibodies precipitated GluK2. GluK2 antibody-specificity was confirmed by CBA, immunoprecipitation, GluK2-immunoabsorption, and GluK2 knockout brain immunohistochemistry. In 2 of 8 samples, antibodies reacted with additional GluK2 epitopes present in GluK1 or GluK3; in both, the reactivity was abrogated after GluK2 immuno-absorption. Six of 8 patients developed acute encephalitis and clinical or magnetic resonance imaging (MRI) features of predominant cerebellar involvement (4 presenting as cerebellitis, which in 2 patients caused obstructive hydrocephalus), and 2 patients had other syndromes (1 with cerebellar symptoms). One of the samples showed mild reactivity with non-kainate receptors (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors [AMPAR] and N-methyl-D-aspartate receptors [NMDAR]) leading to identify 6 additional cases with GluK2-abs among patients with anti-AMPAR (5/71) or anti-NMDAR encephalitis (1/73). GluK2-abs internalized GluK2 in HEK293 cells and neurons; these antibody-effects were reversible in neurons. A significant reduction of GluK2-mediated currents was observed in cells treated with patients' GluK2 serum following the time frame of antibody-mediated GluK2 internalization. INTERPRETATION: GluK2-abs associate with an encephalitis with prominent clinicoradiological cerebellar involvement. The antibody effects are predominantly mediated by internalization of GluK2. ANN NEUROL 2021;90:107-123.

Validation of the functions and prognostic values of synapse-associated proteins in lower-grade glioma.

Synapse and synapse-associated proteins (SAPs) play critical roles in various neurodegeneration diseases and brain tumors. However, in lower-grade gliomas (LGG), SAPs have not been explored systematically. Herein, we are going to explore SAPs expression profile and its clinicopathological significance in LGG which can offer new insights to glioma therapy. In the present study, we integrate a list of SAPs that covered 231 proteins with synaptogenesis activity and post synapse formation. The LGG RNA-seq data were downloaded from GEO, TCGA and CGGA database. The prognosis associated SAPs in key modules of PPI (protein-protein interaction networks) was regarded as hub SAPs. Western blot, quantitative reverse transcription PCR (qRT-PCR) and immunochemistry results from HPA database were used to verify the expression of hub SAPs. There were 68 up-regulated SAPs and 44 down-regulated SAPs in LGG tissue compared with normal brain tissue. Data from function enrichment analysis revealed functions of differentially expressed SAPs in synapse organization and glutamatergic receptor pathway in LGGs. Survival analysis revealed that four SAPs, GRIK2, GABRD, GRID2 and ARC were correlate with the prognosis of LGG patients. Interestingly, we found that GABRD were up-regulated in LGG patients with seizures, indicating that SAPs may link to the pathogenesis of seizures in glioma patients. The four-SAPs signature was revealed as an independent prognostic factor in gliomas. Our study presented a novel strategy to assess the prognostic risks of LGGs, based on the expression of SAPs.

Proteomic and Transcriptomic Analyses Reveal Pathological Changes in the Entorhinal Cortex Region that Correlate Well with Dysregulation of Ion Transport in Patients with Alzheimer's Disease.

Alzheimer's disease (AD) is the most common neurodegenerative disorder. The earliest neuropathology of AD appears in entorhinal cortex (EC) regions. Therapeutic strategies and preventive measures to protect against entorhinal degeneration would be of substantial value in the early stages of AD. In this study, transcriptome based on the Illumina RNA-seq and proteome based on TMT-labelling were performed for RNA and protein profiling on AD EC samples and non-AD control EC samples. Immunohistochemistry was used to validate proteins expressions. After integrated analysis, 57 genes were detected both in transcriptome and proteome data, including 51 in similar altering trends (7 upregulated, 44 downregulated) and 6 in inverse trends when compared AD vs. control. The top 6 genes (GABRG2, CACNG3, CACNB4, GABRB2, GRIK2, and SLC17A6) within the 51 genes were selected and related to "ion transport". Correlation analysis demonstrated negative relationship of protein expression level with the neuropathologic changes. In conclusion, the integrate transcriptome and proteome analysis provided evidence for dysregulation of ion transport across brain regions in AD, which might be a critical signaling pathway that initiates pathology. This study might provide new insight into the earliest changes occurring in the EC of AD and novel targets for AD prevention and treatment.

Intrathecal Injection of GRIP-siRNA Reduces Postoperative Synaptic Abundance of Kainate Receptor GluK2 Subunits in Rat Dorsal Horns and Pain Hypersensitivity.

The mechanisms underlying postoperative pain differ from the inflammatory or neuropathic pain. Previous studies have demonstrated that intrathecal α-amino-3-hydroxy-5-methy-4-isoxazole propionate (AMPA) -kainate (KA) receptor antagonist inhibits the guarding pain behavior and mechanical hyperalgesia, indicating a critical role of spinal KA receptors in postoperative pain hypersensitivity. However, how the functional regulations of spinal KA receptor subunits are involved in the postoperative pain hypersensitivity remains elusive. Therefore, in the current study, we investigated the synaptic delivery of spinal KA receptor subunits and the interaction between KA receptor subunits and glutamate receptor-interacting protein (GRIP) during the postoperative pain. Our data indicated that plantar incision induced the synaptic delivery of GluK2, but not GluK1 or GluK3 in ipsilateral spinal cord dorsal horns. The co-immunoprecipitation showed an increased GluK2 -GRIP interaction in ipsilateral dorsal horn neurons at 6 h post-incision. Interestingly, Intrathecal pretreatment of GRIP siRNA increased the paw withdrawal thresholds to mechanical stimuli and decreased the cumulative pain scores in the paws ipsilateral to the incision at 6 h post-incision. Additionally, Intrathecal pretreatment of GRIP siRNA reduced the synaptic abundance of GluK2 in ipsilateral spinal dorsal horn at 6 h after plantar incision. In general, our data have demonstrated that the GluK2- GRIP interaction-mediated synaptic abundance of GluK2 in dorsal horn neurons plays an important role in the postoperative pain hypersensitivity. Disrupting the GluK2- GRIP interaction may provide a new approach for relieving postoperative pain.

Architecture and structural dynamics of the heteromeric GluK2/K5 kainate receptor.

Kainate receptors (KARs) are L-glutamate-gated ion channels that regulate synaptic transmission and modulate neuronal circuits. KARs have strict assembly rules and primarily function as heteromeric receptors in the brain. A longstanding question is how KAR heteromer subunits organize and coordinate together to fulfill their signature physiological roles. Here we report structures of the GluK2/GluK5 heteromer in apo, antagonist-bound, and desensitized states. The receptor assembles with two copies of each subunit, ligand binding domains arranged as two heterodimers and GluK5 subunits proximal to the channel. Strikingly, during desensitization, GluK2, but not GluK5, subunits undergo major structural rearrangements to facilitate channel closure. We show how the large conformational differences between antagonist-bound and desensitized states are mediated by the linkers connecting the pore helices to the ligand binding domains. This work presents the first KAR heteromer structure, reveals how its subunits are organized, and resolves how the heteromer can accommodate functionally distinct closed channel structures.

Intrathecal injection of ozone alleviates CCI­induced neuropathic pain via the GluR6­NF­κB/p65 signalling pathway in rats.

Ozone is widely used to relieve chronic pain clinically, but the precise mechanisms governing its action have yet to be elucidated. The present study aimed to investigate the mechanisms underlying the pain­alleviating effect of ozone in the chronic constriction injury (CCI) model of sciatic nerve in rats. Pain behaviours of rats were assessed by mechanical allodynia and thermal hyperalgesia. The expression of spinal glutamate receptor 6 (GluR6) and NF­κB/p65 was detected by western blotting and reverse transcription­quantitative PCR. Meanwhile, the expression of spinal IL­1ß, IL­6 and TNF­α was detected by ELISA. GluR6 short interfering (si)RNAs were used intrathecally immediately following CCI once per day. Ozone (10, 20 or 30 µg/ml) or oxygen was injected intrathecally on day 7 after CCI. The expression level of spinal GluR6 increased on day 3 and reached a peak on day 7 after CCI. The expression level of spinal IL­1ß, IL­6, TNF­α and NF­κB/p65 also increased on day 7 after CCI. In addition, pre­intrathecal injection of GluR6 siRNAs inhibited pain behaviours and suppressed the expression of spinal GluR6, IL­1ß, IL­6, TNF­α and NF­κB/p65 in CCI rats on day 7. Intrathecal injection of ozone was also observed to inhibit pain behaviours and suppress the expression of spinal GluR6, IL­1ß, IL­6, TNF­α and NF­κB/p65 in CCI rats on day 7. The present study suggested that GluR6 served a pivotal role in neuropathic pain and that intrathecal injection of ozone may alleviate neuropathic pain via the GluR6­NF­κB/p65 signalling pathway.

A comparative analysis of kainate receptor GluK2 and GluK5 knockout mice in a pure genetic background.

Kainate receptors (KARs) are members of the glutamate receptor family that regulate synaptic function in the brain. Although they are known to be associated with psychiatric disorders, how they are involved in these disorders remains unclear. KARs are tetrameric channels assembled from a combination of GluK1-5 subunits. Among these, GluK2 and GluK5 subunits are the major heteromeric subunits in the brain. To determine the functional similarities and differences between GluK2 and GluK5 subunits, we generated GluK2 KO and GluK5 KO mice on a C57BL/6N background, a well-characterized inbred strain, and compared their behavioral phenotypes. We found that GluK2 KO and GluK5 KO mice exhibited the same phenotypes in many tests, such as reduced locomotor activity, impaired motor function, and enhanced depressive-like behavior. No change was observed in motor learning, anxiety-like behavior, or sociability. Additionally, we identified subunit-specific phenotypes, such as reduced motivation toward their environment in GluK2 KO mice and an enhancement in the contextual memory in GluK5 KO mice. These results revealed that GluK2 and GluK5 subunits not only function in a coordinated manner but also have a subunit-specific role in regulating behavior. To summarize, we demonstrated subunit-specific and common behavioral effects of GluK2 and GluK5 subunits for the first time. Moreover, to the best of our knowledge, this is the first evidence of the involvement of the GluK5 subunit in the expression of depressive-like behavior and contextual memory, which strongly indicates its role in psychiatric disorders.

Pharmacological antagonism of kainate receptor rescues dysfunction and loss of dopamine neurons in a mouse model of human parkin-induced toxicity.

Mutations in the PARK2 gene encoding the protein parkin cause autosomal recessive juvenile Parkinsonism (ARJP), a neurodegenerative disease characterized by dysfunction and death of dopamine (DA) neurons in the substantia nigra pars compacta (SNc). Since a neuroprotective therapy for ARJP does not exist, research efforts aimed at discovering targets for neuroprotection are critically needed. A previous study demonstrated that loss of parkin function or expression of parkin mutants associated with ARJP causes an accumulation of glutamate kainate receptors (KARs) in human brain tissues and an increase of KAR-mediated currents in neurons in vitro. Based on the hypothesis that such KAR hyperactivation may contribute to the death of nigral DA neurons, we investigated the effect of KAR antagonism on the DA neuron dysfunction and death that occur in the parkinQ311X mouse, a model of human parkin-induced toxicity. We found that early accumulation of KARs occurs in the DA neurons of the parkinQ311X mouse, and that chronic administration of the KAR antagonist UBP310 prevents DA neuron loss. This neuroprotective effect is associated with the rescue of the abnormal firing rate of nigral DA neurons and downregulation of GluK2, the key KAR subunit. This study provides novel evidence of a causal role of glutamate KARs in the DA neuron dysfunction and loss occurring in a mouse model of human parkin-induced toxicity. Our results support KAR as a potential target in the development of neuroprotective therapy for ARJP.

Genetic and non-genetic factors associated with the phenotype of exceptional longevity & normal cognition.

In this study, we split 2156 individuals from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) data into two groups, establishing a phenotype of exceptional longevity & normal cognition versus cognitive impairment. We conducted a genome-wide association study (GWAS) to identify significant genetic variants and biological pathways that are associated with cognitive impairment and used these results to construct polygenic risk scores. We elucidated the important and robust factors, both genetic and non-genetic, in predicting the phenotype, using several machine learning models. The GWAS identified 28 significant SNPs at p-value [Formula: see text] significance level and we pinpointed four genes, ESR1, PHB, RYR3, GRIK2, that are associated with the phenotype though immunological systems, brain function, metabolic pathways, inflammation and diet in the CLHLS cohort. Using both genetic and non-genetic factors, four machine learning models have close prediction results for the phenotype measured in Area Under the Curve: random forest (0.782), XGBoost (0.781), support vector machine with linear kernel (0.780), and [Formula: see text] penalized logistic regression (0.780). The top four important and congruent features in predicting the phenotype identified by these four models are: polygenic risk score, sex, age, and education.