MIR-NATs repress MAPT translation and aid proteostasis in neurodegeneration.

The human genome expresses thousands of natural antisense transcripts (NAT) that can regulate epigenetic state, transcription, RNA stability or translation of their overlapping genes1,2. Here we describe MAPT-AS1, a brain-enriched NAT that is conserved in primates and contains an embedded mammalian-wide interspersed repeat (MIR), which represses tau translation by competing for ribosomal RNA pairing with the MAPT mRNA internal ribosome entry site3. MAPT encodes tau, a neuronal intrinsically disordered protein (IDP) that stabilizes axonal microtubules. Hyperphosphorylated, aggregation-prone tau forms the hallmark inclusions of tauopathies4. Mutations in MAPT cause familial frontotemporal dementia, and common variations forming the MAPT H1 haplotype are a significant risk factor in many tauopathies5 and Parkinson's disease. Notably, expression of MAPT-AS1 or minimal essential sequences from MAPT-AS1 (including MIR) reduces-whereas silencing MAPT-AS1 expression increases-neuronal tau levels, and correlate with tau pathology in human brain. Moreover, we identified many additional NATs with embedded MIRs (MIR-NATs), which are overrepresented at coding genes linked to neurodegeneration and/or encoding IDPs, and confirmed MIR-NAT-mediated translational control of one such gene, PLCG1. These results demonstrate a key role for MAPT-AS1 in tauopathies and reveal a potentially broad contribution of MIR-NATs to the tightly controlled translation of IDPs6, with particular relevance for proteostasis in neurodegeneration.

Spinocerebellar ataxia type 4 is caused by a GGC expansion in the ZFHX3 gene and is associated with prominent dysautonomia and motor neuron signs.

BACKGROUND: Spinocerebellar ataxia 4 (SCA4), characterized in 1996, features adult-onset ataxia, polyneuropathy, and linkage to chromosome 16q22.1; its underlying mutation has remained elusive. OBJECTIVE: To explore the radiological and neuropathological abnormalities in the entire neuroaxis in SCA4 and search for its mutation. METHODS: Three Swedish families with undiagnosed ataxia went through clinical, neurophysiological, and neuroimaging tests, including PET studies and genetic investigations. In four cases, neuropathological assessments of the neuroaxis were performed. Genetic testing included short read whole genome sequencing, short tandem repeat analysis with ExpansionHunter de novo, and long read sequencing. RESULTS: Novel features for SCA4 include dysautonomia, motor neuron affection, and abnormal eye movements. We found evidence of anticipation; neuroimaging demonstrated atrophy in the cerebellum, brainstem, and spinal cord. [18F]FDG-PET demonstrated brain hypometabolism and [11C]Flumazenil-PET reduced binding in several brain lobes, insula, thalamus, hypothalamus, and cerebellum. Moderate to severe loss of Purkinje cells in the cerebellum and of motor neurons in the anterior horns of the spinal cord along with pronounced degeneration of posterior tracts was also found. Intranuclear, mainly neuronal, inclusions positive for p62 and ubiquitin were sparse but widespread in the CNS. This finding prompted assessment for nucleotide expansions. A polyglycine stretch encoding GGC expansions in the last exon of the zink finger homeobox 3 gene was identified segregating with disease and not found in 1000 controls. CONCLUSIONS: SCA4 is a neurodegenerative disease caused by a novel GGC expansion in the coding region of ZFHX3, and its spectrum is expanded to include dysautonomia and neuromuscular manifestations.

ß2-Adrenoreceptor Agonists, Montelukast, and Parkinson Disease Risk.

OBJECTIVE: This study was undertaken to examine the association between montelukast use, ß2-adrenoreceptor (ß2AR) agonist use, and later Parkinson disease (PD). METHODS: We ascertained use of ß2AR agonists (430,885 individuals) and montelukast (23,315 individuals) from July 1, 2005 to June 30, 2007, and followed 5,186,886 PD-free individuals from July 1, 2007 to December 31, 2013 for incident PD diagnosis. We estimated hazard ratios and 95% confidence intervals using Cox regressions. RESULTS: We observed 16,383 PD cases during on average 6.1 years of follow-up. Overall, use of ß2AR agonists and montelukast were not related to PD incidence. A 38% lower PD incidence was noted among high-dose montelukast users when restricted to PD registered as the primary diagnosis. INTERPRETATION: Overall, our data do not support inverse associations between ß2AR agonists, montelukast, and PD. The prospect of lower PD incidence with high-dose montelukast exposure warrants further investigation, especially with adjustment for high-quality data on smoking. ANN NEUROL 2023;93:1023-1028.

Risk of Dementia in Parkinson's Disease: A Systematic Review and Meta-Analysis.

Estimates of the risk of dementia in Parkinson's disease (PDD) vary widely. We aimed to review the incidence of PDD and in a meta-analysis estimate the pooled annual incidence and relative risk of PDD while also exploring factors that may contribute to heterogeneity between studies. Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed and MEDLINE and EMBASE were searched for articles reporting the number of cases of dementia in a population, followed longitudinally, with a minimum of 100 dementia-free Parkinson's disease (PD) patients at baseline. Meta-analyses and meta-regressions were used to estimate the pooled incidence rate of PDD and the relative risk of PDD versus healthy controls (HC). A total of 32 studies were identified, 25 reporting the incidence of PDD and 10 reporting the relative risk of PDD versus HC. The pooled incidence rate of PDD was 4.45 (95% confidence interval [CI], 3.91-4.99) per 100 person-years at risk, equating to a 4.5% annual risk of dementia in a PD prevalent population. The relative risk of PDD was estimated to be 3.25 (95% CI, 2.62-4.03) times greater than HC. Factors contributing to study heterogeneity and disparities in the estimated risk of PDD include the age of patients, year of recruitment, and study location. Significant gaps remain with no studies identified in several geographical regions. Future studies should stratify by age and standardize reporting to reduce overall heterogeneity. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Increased CSF DOPA Decarboxylase Correlates with Lower DaT-SPECT Binding: Analyses in Biopark and PPMI Cohorts.

BACKGROUND: Recent studies identified increased cerebrospinal fluid (CSF) DOPA decarboxylase (DDC) as a promising biomarker for parkinsonian disorders, suggesting a compensation to dying dopaminergic neurons. A correlation with 123I-FP-CIT-SPECT (DaT-SPECT) imaging could shed light on this link. OBJECTIVE: The objective is to assess the relationship between CSF DDC levels and DaT-SPECT binding values. METHODS: A total of 51 and 72 Parkinson's disease (PD) subjects with available DaT-SPECT and CSF DDC levels were selected from the PPMI and Biopark cohorts, respectively. DDC levels were analyzed using proximity extension assay and correlated with DaT-SPECT striatal binding ratios (SBR). All analyses were corrected for age and sex. RESULTS: CSF DDC levels in PD patients correlated negatively with DaT-SPECT SBR in both putamen and caudate nucleus. Additionally, SBR decreased with increased DDC levels over time in PD patients. CONCLUSION: CSF DDC levels negatively correlate with DaT-SPECT SBR in levodopa-treated PD. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Basic Science in Movement Disorders: Fueling the Engine of Translation into Clinical Practice.

Basic Science is crucial for the advancement of clinical care for Movement Disorders. Here, we provide brief updates on how basic science is important for understanding disease mechanisms, disease prevention, disease diagnosis, development of novel therapies and to establish the basis for personalized medicine. We conclude the viewpoint by a call to action to further improve interactions between clinician and basic scientists. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Involvement of Scratch2 in GalR1-mediated depression-like behaviors in the rat ventral periaqueductal gray.

Galanin receptor1 (GalR1) transcript levels are elevated in the rat ventral periaqueductal gray (vPAG) after chronic mild stress (CMS) and are related to depression-like behavior. To explore the mechanisms underlying the elevated GalR1 expression, we carried out molecular biological experiments in vitro and in animal behavioral experiments in vivo. It was found that a restricted upstream region of the GalR1 gene, from -250 to -220, harbors an E-box and plays a negative role in the GalR1 promoter activity. The transcription factor Scratch2 bound to the E-box to down-regulate GalR1 promoter activity and lower expression levels of the GalR1 gene. The expression of Scratch2 was significantly decreased in the vPAG of CMS rats. Importantly, local knockdown of Scratch2 in the vPAG caused elevated expression of GalR1 in the same region, as well as depression-like behaviors. RNAscope analysis revealed that GalR1 mRNA is expressed together with Scratch2 in both GABA and glutamate neurons. Taking these data together, our study further supports the involvement of GalR1 in mood control and suggests a role for Scratch2 as a regulator of depression-like behavior by repressing the GalR1 gene in the vPAG.

Secretome Analyses Identify FKBP4 as a GBA1-Associated Protein in CSF and iPS Cells from Parkinson's Disease Patients with GBA1 Mutations.

Mutations in the GBA1 gene increase the risk of developing Parkinson's disease (PD). However, most carriers of GBA1 mutations do not develop PD throughout their lives. The mechanisms of how GBA1 mutations contribute to PD pathogenesis remain unclear. Cerebrospinal fluid (CSF) is used for detecting pathological conditions of diseases, providing insights into the molecular mechanisms underlying neurodegenerative disorders. In this study, we utilized the proximity extension assay to examine the levels of metabolism-linked protein in the CSF from 17 PD patients carrying GBA1 mutations (GBA1-PD) and 17 idiopathic PD (iPD). The analysis of CSF secretome in GBA1-PD identified 11 significantly altered proteins, namely FKBP4, THOP1, GLRX, TXNDC5, GAL, SEMA3F, CRKL, APLP1, LRP11, CD164, and NPTXR. To investigate GBA1-associated CSF changes attributed to specific neuronal subtypes responsible for PD, we analyzed the cell culture supernatant from GBA1-PD-induced pluripotent stem cell (iPSC)-derived midbrain dopaminergic (mDA) neurons. The secretome analysis of GBA1-PD iPSC-derived mDA neurons revealed that five differently regulated proteins overlapped with those identified in the CSF analysis: FKBP4, THOP1, GLRX, GAL, and CRKL. Reduced intracellular level of the top hit, FKPB4, was confirmed via Western Blot. In conclusion, our findings identify significantly altered CSF GBA1-PD-associated proteins with FKPB4 being firmly attributed to mDA neurons.

GBA1-Associated Parkinson's Disease Is a Distinct Entity.

GBA1-associated Parkinson's disease (GBA1-PD) is increasingly recognized as a distinct entity within the spectrum of parkinsonian disorders. This review explores the unique pathophysiological features, clinical progression, and genetic underpinnings that differentiate GBA1-PD from idiopathic Parkinson's disease (iPD). GBA1-PD typically presents with earlier onset and more rapid progression, with a poor response to standard PD medications. It is marked by pronounced cognitive impairment and a higher burden of non-motor symptoms compared to iPD. Additionally, patients with GBA1-PD often exhibit a broader distribution of Lewy bodies within the brain, accentuating neurodegenerative processes. The pathogenesis of GBA1-PD is closely associated with mutations in the GBA1 gene, which encodes the lysosomal enzyme beta-glucocerebrosidase (GCase). In this review, we discuss two mechanisms by which GBA1 mutations contribute to disease development: 'haploinsufficiency,' where a single functional gene copy fails to produce a sufficient amount of GCase, and 'gain of function,' where the mutated GCase acquires harmful properties that directly impact cellular mechanisms for alpha-synuclein degradation, leading to alpha-synuclein aggregation and neuronal cell damage. Continued research is advancing our understanding of how these mechanisms contribute to the development and progression of GBA1-PD, with the 'gain of function' mechanism appearing to be the most plausible. This review also explores the implications of GBA1 mutations for therapeutic strategies, highlighting the need for early diagnosis and targeted interventions. Currently, small molecular chaperones have shown the most promising clinical results compared to other agents. This synthesis of clinical, pathological, and molecular aspects underscores the assertion that GBA1-PD is a distinct clinical and pathobiological PD phenotype, necessitating specific management and research approaches to better understand and treat this debilitating condition.

Rapid Metabolic Profiling of 1 µL Crude Cerebrospinal Fluid by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging Can Differentiate De Novo Parkinson's Disease.

Parkinson's disease (PD) is a highly prevalent neurodegenerative disorder affecting the motor system. However, the correct diagnosis of PD and atypical parkinsonism may be difficult with high clinical uncertainty. There is an urgent need to identify reliable biomarkers using high-throughput, molecular-specific methods to improve current diagnostics. Here, we present a matrix-assisted laser desorption/ionization mass spectrometry imaging method that requires minimal sample preparation and only 1 µL of crude cerebrospinal fluid (CSF). The method enables analysis of hundreds of samples in a single experiment while simultaneously detecting numerous metabolites with subppm mass accuracy. To test the method, we analyzed CSF samples from 12 de novo PD patients (that is, newly diagnosed and previously untreated) and 12 age-matched controls. Within the identified molecules, we found neurotransmitters and their metabolites such as γ-aminobutyric acid, 3-methoxytyramine, homovanillic acid, serotonin, histamine, amino acids, and metabolic intermediates. Limits of detection were estimated for multiple neurotransmitters with high linearity (R2 > 0.99) and sensitivity (as low as 16 pg/µL). Application of multivariate classification led to a highly significant (P < 0.001) model of PD prediction with a 100% classification rate, which was further thoroughly validated with a permutation test and univariate analysis. Molecules related to the neuromelanin pathway were found to be significantly increased in the PD group, indicated by their elevated relative intensities compared to the control group. Our method enables rapid detection of PD-related biomarkers in low sample volumes and could serve as a valuable tool in the development of robust PD diagnostics.

In Vitro Comparison of Ulotaront (SEP-363856) and Ralmitaront (RO6889450): Two TAAR1 Agonist Candidate Antipsychotics.

BACKGROUND: Trace amine-associated receptor-1 (TAAR1) agonists have been proposed as potential antipsychotics, with ulotaront and ralmitaront having reached clinical trials. While ulotaront demonstrated efficacy in a recent Phase II trial, a corresponding study studies of ralmitaront failed to show efficacy as a monotherapy or as an adjunct to atypical antipsychotics. In addition to TAAR1 agonism, ulotaront is a partial agonist at the serotonin 1A receptor (5-HT1AR). However, little is known about ralmitaront. METHODS: We compared ulotaront and ralmitaront at TAAR1, 5-HT1AR, and dopamine D2 using luciferase complementation-based G protein recruitment, cAMP accumulation, and G protein-coupled inward rectifier potassium channel activation assays. RESULTS: Ralmitaront showed lower efficacy at TAAR1 in G protein recruitment, cAMP accumulation, and GIRK activation assays. Moreover, ralmitaront lacked detectable activity at 5-HT1AR and dopamine D2. CONCLUSIONS: Compared with ulotaront, ralmitaront shows lower efficacy and slower kinetics at TAAR1 and lacks efficacy at 5-HT1AR. These data may be relevant to understanding differences in clinical profiles of these 2 compounds.

Intraputamenal Cerebral Dopamine Neurotrophic Factor in Parkinson's Disease: A Randomized, Double-Blind, Multicenter Phase 1 Trial.

BACKGROUND: Cerebral dopamine neurotrophic factor (CDNF) is an unconventional neurotrophic factor that protects dopamine neurons and improves motor function in animal models of Parkinson's disease (PD). OBJECTIVE: The primary objectives of this study were to assess the safety and tolerability of both CDNF and the drug delivery system (DDS) in patients with PD of moderate severity. METHODS: We assessed the safety and tolerability of monthly intraputamenal CDNF infusions in patients with PD using an investigational DDS, a bone-anchored transcutaneous port connected to four catheters. This phase 1 trial was divided into a placebo-controlled, double-blind, 6-month main study followed by an active-treatment 6-month extension. Eligible patients, aged 35 to 75 years, had moderate idiopathic PD for 5 to 15 years and Hoehn and Yahr score ≤ 3 (off state). Seventeen patients were randomized to placebo (n = 6), 0.4 mg CDNF (n = 6), or 1.2 mg CDNF (n = 5). The primary endpoints were safety and tolerability of CDNF and DDS and catheter implantation accuracy. Secondary endpoints were measures of PD symptoms, including Unified Parkinson's Disease Rating Scale, and DDS patency and port stability. Exploratory endpoints included motor symptom assessment (PKG, Global Kinetics Pty Ltd, Melbourne, Australia) and positron emission tomography using dopamine transporter radioligand [18 F]FE-PE2I. RESULTS: Drug-related adverse events were mild to moderate with no difference between placebo and treatment groups. No severe adverse events were associated with the drug, and device delivery accuracy met specification. The severe adverse events recorded were associated with the infusion procedure and did not reoccur after procedural modification. There were no significant changes between placebo and CDNF treatment groups in secondary endpoints between baseline and the end of the main and extension studies. CONCLUSIONS: Intraputamenally administered CDNF was safe and well tolerated, and possible signs of biological response to the drug were observed in individual patients. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

[11 C]PBB3 binding in Aß(-) or Aß(+) corticobasal syndrome.

Corticobasal syndrome (CBS) is associated with 4-repeat tauopathy and/or Alzheimer's disease pathologies. To examine tau and amyloid-ß (Aß) deposits in CBS patients using positron emission tomography (PET). Eight CBS patients and three healthy individuals lacking amyloid pathology underwent PET with [11 C]PBB3 for tau imaging, and [11 C]AZD2184 for Aß. Subcortical and cortical binding of [11 C]PBB3 was compared between Aß(-) and Aß(+) CBS patients and reference group. Postmortem analysis was done in one CBS patient. Three CBS patients were considered Aß(+). Total binding was higher in all patients compared to the reference group. Similar regional binding profiles of [11 C]PBB3 in Aß(+) and Aß(-) CBS patients were found. Elevated [11 C]PBB3 binding in pallidum was observed in all CBS patients. Cortical [11 C]PBB3 binding was higher in Aß(+) compared to Aß(-) patients. Postmortem analysis of a CBS patient revealed corticobasal degeneration neuropathology and [11 C]PBB3 autofluorescence in some tau-positive structures. [11 C]PBB3 is elevated in CBS patients with binding in relevant areas capturing some, but not all, 4-repeat tauopathy in CBS.

Update on GPCR-based targets for the development of novel antidepressants.

Traditional antidepressants largely interfere with monoaminergic transport or degradation systems, taking several weeks to have their therapeutic actions. Moreover, a large proportion of depressed patients are resistant to these therapies. Several atypical antidepressants have been developed which interact with G protein coupled receptors (GPCRs) instead, as direct targeting of receptors may achieve more efficacious and faster antidepressant actions. The focus of this review is to provide an update on how distinct GPCRs mediate antidepressant actions and discuss recent insights into how GPCRs regulate the pathophysiology of Major Depressive Disorder (MDD). We also discuss the therapeutic potential of novel GPCR targets, which are appealing due to their ligand selectivity, expression pattern, or pharmacological profiles. Finally, we highlight recent advances in understanding GPCR pharmacology and structure, and how they may provide new avenues for drug development.

In Silico and In Vitro Study towards the Rational Design of 4,4'-Disarylbisthiazoles as a Selective α-Synucleinopathy Biomarker.

The α-synucleinopathies are a group of neurodegenerative diseases characterized by the deposition of α-synuclein aggregates (α-syn) in the brain. Currently, there is no suitable tracer to enable a definitive early diagnosis of these diseases. We reported candidates based on 4,4'-disarylbisthiazole (DABTA) scaffold with a high affinity towards α-syn and excellent selectivity over Aß and tau fibrils. Based on prior in silico studies, a focused library of 23 halogen-containing and O-methylated DABTAs was prepared. The DABTAs were synthesized via a modified two-step Hantzsch thiazole synthesis, characterized, and used in competitive binding assays against [3H]PiB and [3H]DCVJ. The DABTAs were obtained with an overall chemical yield of 15-71%, and showed a calculated lipophilicity of 2.5-5.7. The ligands demonstrated an excellent affinity to α-syn with both [3H]PiB and [3H]DCVJ: Ki 0.1-4.9 nM and up to 20-3900-fold selectivity over Aß and tau fibrils. It could be concluded that in silico simulation is useful for the rational design of a new generation of DABTAs. Further investigation of the leads in the next step is encouraged: radiolabeling of the ligands with radioisotopes such as fluorine-18 or carbon-11 for in vivo, ex vivo, and translational research and for further in vitro experiments on human-derived protein aggregates.

Comprehensive mapping of neurotransmitter networks by MALDI-MS imaging.

We present a mass spectrometry imaging (MSI) approach for the comprehensive mapping of neurotransmitter networks in specific brain regions. Our fluoromethylpyridinium-based reactive matrices facilitate the covalent charge-tagging of molecules containing phenolic hydroxyl and/or primary or secondary amine groups, including dopaminergic and serotonergic neurotransmitters and their associated metabolites. These matrices improved the matrix-assisted laser desorption/ionization (MALDI)-MSI detection limit toward low-abundance neurotransmitters and facilitated the simultaneous imaging of neurotransmitters in fine structures of the brain at a lateral resolution of 10 µm. We demonstrate strategies for the identification of unknown molecular species using the innate chemoselectivity of the reactive matrices and the unique isotopic pattern of a brominated reactive matrix. We illustrate the capabilities of the developed method on Parkinsonian brain samples from human post-mortem tissue and animal models. The direct imaging of neurotransmitter systems provides a method for exploring how various neurological diseases affect specific brain regions through neurotransmitter modulation.

Glycosphingolipid Changes in Plasma in Parkinson's Disease Independent of Glucosylceramide Levels.

BACKGROUND: Alteration in glycosphingolipids (GSLs) in Parkinson's disease (PD) still needs to be determined. OBJECTIVES: We evaluated if PD subjects show abnormal GSLs levels compared to healthy controls (HC) and if GSLs correlate with clinical features. METHODS: We analyzed GSLs and glucosylceramide (GlcCer) in plasma using two normal-phase high-performance liquid chromatography assays; clinico-demographic data were extracted. RESULTS: Eighty PD subjects and 25 HCs were analyzed. Levels of GlcCer, GD1b, Gb4, GalNAcGA1, and b-series were higher in PD patients than in HCs; total GSLs, GT1b, GM1a, GM3, GM2, and a-series levels were lower in PD patients than in HCs. Changes in GSLs were present in PD subjects, with GlcCer levels similar to those in HCs. The results were similar after excluding certain GBA1 mutation carriers. Movement Disorder Society Unified Parkinson's Disease Rating Scale, Part III, correlated with Gb4 and Montreal Cognitive Assessment with GD1b levels. CONCLUSIONS: Multiple GSL abnormalities in plasma were detected in patients with and without GlcCer changes, indicating a broader shift in lipid homeostasis. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.

Glia Imaging Differentiates Multiple System Atrophy from Parkinson's Disease: A Positron Emission Tomography Study with [11 C]PBR28 and Machine Learning Analysis.

BACKGROUND: The clinical diagnosis of multiple system atrophy (MSA) is challenged by overlapping features with Parkinson's disease (PD) and late-onset ataxias. Additional biomarkers are needed to confirm MSA and to advance the understanding of pathophysiology. Positron emission tomography (PET) imaging of the translocator protein (TSPO), expressed by glia cells, has shown elevations in MSA. OBJECTIVE: In this multicenter PET study, we assess the performance of TSPO imaging as a diagnostic marker for MSA. METHODS: We analyzed [11 C]PBR28 binding to TSPO using imaging data of 66 patients with MSA and 24 patients with PD. Group comparisons were based on regional analysis of parametric images. The diagnostic readout included visual reading of PET images against clinical diagnosis and machine learning analyses. Sensitivity, specificity, and receiver operating curves were used to discriminate MSA from PD and cerebellar from parkinsonian variant MSA. RESULTS: We observed a conspicuous pattern of elevated regional [11 C]PBR28 binding to TSPO in MSA as compared with PD, with "hotspots" in the lentiform nucleus and cerebellar white matter. Visual reading discriminated MSA from PD with 100% specificity and 83% sensitivity. The machine learning approach improved sensitivity to 96%. We identified MSA subtype-specific TSPO binding patterns. CONCLUSIONS: We found a pattern of significantly increased regional glial TSPO binding in patients with MSA. Intriguingly, our data are in line with severe neuroinflammation in MSA. Glia imaging may have potential to support clinical MSA diagnosis and patient stratification in clinical trials on novel drug therapies for an α-synucleinopathy that remains strikingly incurable. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Cytosolic GPR37, but not GPR37L1, multimerization and its reversal by Parkin: A live cell imaging study.

Biochemical data have shown aggregated G protein-coupled receptor 37 (GPR37) in the cytoplasm and Lewy bodies in Parkinson's disease (PD). Properly folded GPR37 at the plasma membrane appears to be neuroprotective. GPR37, and its homologue GPR37L1, are orphan G protein-coupled receptors and their homo- and hetero-dimers have not been established. We therefore examined GPR37 and GPR37L1 dimerization and extended studies of multimerization of GPR37 to live cells. In this study, we investigated GPR37 and GPR37L1 dimerization and multimerization in live cells using three quantitative imaging methods: Fluorescence Cross-Correlation Spectroscopy, Förster Resonance Energy Transfer, and Fluorescence Lifetime Imaging Microscopy. Our data show that GPR37 and GPR37L1 form homo- and heterodimers in live N2a cells. Importantly, aggregation of GPR37, but not GPR37L1, was identified in the cytoplasm, which could be counteracted by Parkin overexpression. These data provide further evidence that GPR37 participate in cytosolic aggregation processes implicated in PD pathology.

Ketamine decreases neuronally released glutamate via retrograde stimulation of presynaptic adenosine A1 receptors.

Ketamine produces a rapid antidepressant response in patients with major depressive disorder (MDD), but the underlying mechanisms appear multifaceted. One hypothesis, proposes that by antagonizing NMDA receptors on GABAergic interneurons, ketamine disinhibits afferens to glutamatergic principal neurons and increases extracellular glutamate levels. However, ketamine seems also to reduce rapid glutamate release at some synapses. Therefore, clinical studies in MDD patients have stressed the need to identify mechanisms whereby ketamine decreases presynaptic activity and glutamate release. In the present study, the effect of ketamine and its antidepressant metabolite, (2R,6R)-HNK, on neuronally derived glutamate release was examined in rodents. We used FAST methodology to measure depolarization-evoked extracellular glutamate levels in vivo in freely moving or anesthetized animals, synaptosomes to detect synaptic recycling ex vivo and primary cortical neurons to perform functional imaging and to examine intracellular signaling in vitro. In all these versatile approaches, ketamine and (2R,6R)-HNK reduced glutamate release in a manner which could be blocked by AMPA receptor antagonism. Antagonism of adenosine A1 receptors, which are almost exclusively expressed at nerve terminals, also counteracted ketamine's effect on glutamate release and presynaptic activity. Signal transduction studies in primary neuronal cultures demonstrated that ketamine reduced P-T286-CamKII and P-S9-Synapsin, which correlated with decreased synaptic vesicle recycling. Moreover, systemic administration of A1R antagonist counteracted the antidepressant-like actions of ketamine and (2R,6R)-HNK in the forced swim test. To conclude, by studying neuronally released glutamate, we identified a novel retrograde adenosinergic feedback mechanism that mediate inhibitory actions of ketamine on glutamate release that may contribute to its rapid antidepressant action.