Neuronal Synaptic Function Research Articles

Exploratory analysis of a Novel RACK1 mutation and its potential role in epileptic seizures via Microglia activation

Seizures is a prevalent neurological disorder with a largely elusive pathogenesis. In this study, we identified the key gene RACK1 and its novel mutation RACK1-p.L206P as being associated with seizures through single-cell transcriptome sequencing (scRNA-seq) and whole exome sequencing (WES) techniques. Our findings reveal that the RACK1-p.L206P mutation significantly enhances proliferation, migration, phagocytic ability, and inflammatory activation in human microglia, which in turn affects neuronal excitability and synaptic function, culminating in typical seizure symptoms in the seizures. These effects were further validated in a mouse model using CRISPR/Cas9 gene editing technology. Mutant microglia exhibited increased activation and induced apoptosis in hippocampal neurons, leading to higher action potential frequency and excitatory synaptic marker expression. In vivo experiments demonstrated that RACK1-p.L206P mutant mice displayed classic seizure symptoms, with increased neuronal excitability and a tendency for action potential bursts during initial depolarization, along with more frequent spike discharges. Additionally, excitatory synapse density and size in the hippocampal CA1 region of mutant mice were significantly elevated, accompanied by increased expression of VGLUT1 and PSD95 within microglia. This study offers novel insights into the molecular mechanisms underlying seizures in the seizures and presents valuable clues for the development of future therapeutic strategies.

MiRNAs as major players in brain health and disease: current knowledge and future perspectives.

MicroRNAs are regulators of gene expression and their dysregulation can lead to various diseases. MicroRNA-135 (MiR-135) exhibits brain-specific expression, and performs various functions such as neuronal morphology, neural induction, and synaptic function in the human brain. Dysfunction of miR-135 has been reported in brain tumors, and neurodegenerative and neurodevelopmental disorders. Several reports show downregulation of miR-135 in glioblastoma, indicating its tumor suppressor role in the pathogenesis of brain tumors. In this review, by performing in silico analysis of molecular targets of miR-135, we reveal the significant pathways and processes modulated by miR-135. We summarize the biological significance, roles, and signaling pathways of miRNAs in general, with a focus on miR-135 in different neurological diseases including brain tumors, and neurodegenerative and neurodevelopmental disorders. We also discuss methods, limitations, and potential of glioblastoma organoids in recapitulating disease initiation and progression. We highlight the promising therapeutic potential of miRNAs as antitumor agents for aggressive human brain tumors including glioblastoma.

Deep proteomics and network pharmacology reveal sex- and age-shared neuropathic pain signatures in mouse dorsal root ganglia.

Our understanding of how sex and age influence chronic pain at the molecular level is still limited with wide-reaching consequences for adolescent patients. Here, we leveraged deep proteome profiling of mouse dorsal root ganglia (DRG) from adolescent (4-week-old) and adult (12-week-old) male and female mice to investigate the establishment of neuropathic pain in the spared nerve injury (SNI)-model in parallel. We quantified over 12,000 proteins, including notable ion channels involved in pain, highlighting the sensitivity of our approach. Differential expression revealed sex- and age-dependent proteome changes upon nerve injury. In contrast to most previous studies, our comprehensive dataset enabled us to determine differentially expressed proteins (DEPs), which were shared between male and female mice of both age groups. Among these, the vast majority (94 %) were also expressed and, in part, altered in human DRG of neuropathic pain patients, indicating evolutionary conservation. Proteome signatures represented numerous targets of FDA-approved drugs comprising both (i) known pain therapeutics (e.g. Pregabalin and opioids) and, importantly, (ii) compounds with high potential for future re-purposing, e.g. Ptprc-modulators and Epoetins. Protein network and multidimensional analysis uncovered distinct hubs of sex- and age-shared biological pathways impacted by neuropathic pain, such as neuronal activity and synaptic function, DNA-damage, and neuroimmune interactions. Taken together, our results capture the complexity of nerve injury-associated DRG alterations in mice at the network level, moving beyond single-candidate studies. Consequently, we provide an innovative resource of the molecular landscape of neuropathic pain, enabling novel opportunities for translational pain research and network-based drug discovery.

Indirect influence on the BDNF/TrkB receptor signaling pathway via GPCRs, an emerging strategy in the treatment of neurodegenerative disorders.

Neuronal survival depends on neurotrophins and their receptors. There are two types of neurotrophin receptors: a nonenzymatic, trans-membrane protein of the tumor necrosis factor receptor (TNFR) family-p75 receptor and the tyrosine kinase receptors (TrkR) A, B, and C. Activation of the TrkBR by brain-derived neurotrophic factor (BDNF) or neurotrophin 4/5 (NT-4/5) promotes neuronal survival, differentiation, and synaptic function. It is shown that in the pathogenesis of several neurodegenerative conditions (Alzheimer's disease, Parkinson's disease, Huntington's disease) the BDNF/TrkBR signaling pathway is impaired. Since it is known that GPCRs and TrkR are regulating several cell functions by interacting with each other and generating a cross-communication in this review we have focused on the interaction between different GPCRs and their ligands on BDNF/TrkBR signaling pathway.

Brain microenvironment-remodeling nanomedicine improves cerebral glucose metabolism, mitochondrial activity and synaptic function in a mouse model of Alzheimer's disease.

The development of disease-modifying therapeutics for Alzheimer's disease remains challenging due to the complex pathology and the presence of the blood-brain barrier. Previously we have described the investigation of a brain-penetrating multifunctional bioreactive nanoparticle system capable of remodeling the hypoxic and inflammatory brain microenvironment and reducing beta-amyloid plaques improving cognitive function in a mouse model of Alzheimer's disease. Despite the linkage of hypoxia and inflammation to metabolic alteration, the effects of this system on modulating cerebral glucose metabolism, mitochondrial activity and synaptic function remained to be elucidated. To examine this, a transgenic mouse model of Alzheimer's disease (TgCRND8) in vivo were treated intravenously with beta-amyloid antibody-conjugated (Ab), blood-brain barrier-crossing terpolymer (TP) containing polymer-lipid based manganese dioxide nanoparticles (Ab-TP-MDNPs). Alterations in cerebral glucose utilization were determined by [1⁸F]FDG-PET imaging in vivo, with glucose metabolism and mitochondrial activity analyzed by biomarkers and studies with primary neurons in vitro. Synaptic function was evaluated by both biomarkers and electrophysiologic analysis. Current study shows that intravenously administered Ab-TP-MDNPs enhanced cerebral glucose utilization, improved glucose metabolism, mitochondrial activity, and increased the levels of neprilysin, O-glycosylation. The consequence of this was enhanced glucose and ATP availability, resulting in improved long-term potentiation for promoting neuronal synaptic function. This study highlights the importance of targeting the metabolism of complex disease pathologies in addressing disease-modifying therapeutics for neurodegenerative disorders such as Alzheimer's disease.

Lipoprotein Lipase and Neurological Health: Investigating its Impact on Brain Function and Alzheimer's Disease

Lipoprotein Lipase (LPL) is an essential lipid metabolism enzyme affecting both the brain and peripheral tissues. Its impact on neuronal lipid homeostasis, synaptic function, and plasticity is increasingly recognized. This review explores the various functions of LPL in the brain and how it may affect neurological health, especially in Alzheimer's disease. We explore how LPL regulates lipid uptake and utilization in the brain, its influence on synaptic function, neurogenesis, and myelination, and its role in the pathophysiology of AD. Genetic and environmental factors modulating LPL activity are also discussed. The review provides insights into LPL's role in neurodegenerative diseases, acknowledges current limitations and challenges in research, and highlights the therapeutic potential of targeting LPL for AD treatment. Ultimately, this review underscores the importance of LPL in maintaining brain health and its promising potential as a therapeutic target for AD.

Do glial‐reactivity and cerebral blood flow modulate cerebral glucose metabolism in Alzheimer’s disease?

AbstractBackgroundAlzheimer’s disease is a devastating neurodegenerative disorder with a complex pathogenesis. One main pathological feature utilised in diagnosis is neurodegeneration or neuronal injury, which is reflected in reductions in cerebral glucose metabolism measured by [18F]Fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET). Here we evaluated the involvement of glial reactivity measured with magnetic resonance spectroscopy (MRS) and cerebral blood flow measured with arterial spin labelling (ASL) on [18F]FDG PET as a measure of cerebral glucose metabolism.Method123 people living with early Alzheimer’s disease who completed baseline evaluations on the evaluating liraglutide in Alzheimer’s disease trial were enrolled. Participants completed [18F]FDG PET scans with arterial input, T1 weighted MRI, single‐voxel 1HMRS, and pulsed ASL scans at Imperial College London Clinical Imaging Facility. The Totally Automatic Robust Quantitation in NMR (TARQUIN) package was used to process MRS scans and identify the concentration of myo‐inositol within the posterior cingulate cortex (PCC), a marker of glial activation. Oxford‐ASL was utilised to process ASL and quantify cerebral blood flow in the PCC. Finally, spectral analysis was performed on the [18F]FDG PET scans to assess the cerebral metabolic rate of glucose in the PCC.ResultPearson’s correlations were performed between the cerebral metabolic rate of glucose, cerebral blood flow and glial activity measured by the level of myo‐inositol in the PCC. Increased cerebral glucose metabolism was correlated with higher myo‐inositol in this sample of Alzheimer’s disease participants. In contrast, cerebral blood flow was not associated with cerebral glucose metabolism.ConclusionHere we demonstrate that increased glial reactivity contributes to [18F]FDG PET signal in the early stages of Alzheimer’s disease. In response to early neuronal injury, astrocytes and microglia may become activated and enhance regional rates of glucose consumption. Hence, the contribution from these cells in addition to neurons should be considered in interpreting [18F]FDG PET as a measure of cerebral glucose metabolism. Interestingly, cerebral blood flow did not influence glucose metabolism. Microglia and astrocyte reactivity may contribute to an increase the cerebral glucose metabolism while neuronal loss and synaptic function may contribute to lower glucose metabolism measured by [18F]FDG in the early stages of Alzheimer's disease.

Aberrance of GAP43/p-GAP43 Closely Associates with the Pathology of Neuron Loss in Prion-Infected Rodent Models.

Prion diseases are fatal neurodegenerative disorders characterized by neuron damage and loss. Growth-associated protein 43 (GAP43) functions in neuronal plasticity and synaptic function, but its role in prion diseases is not fully elucidated. In this study, we investigated the changes of GAP43 in the central nerve system (CNS) of several prion-infected rodent models and explored the potential relationship of GAP43 with PrPSc deposit and neuron loss using various methods. We found that GAP43 levels were significantly decreased in the brain tissues of scrapie-infected rodent models at the terminal stage of the disease. Immunohistochemical analysis showed that GAP43 colocalized with NeuN-positive cells morphologically, indicating the presence of GAP43 in mature neurons. On contrary, the levels of GAP43 and p-GAP43 increased in a prion-infected cell line SMB-S15 in vitro, accompanying with the increase of intracellular calcium. Stimulation of lipopolysaccharide (LPS) upregulated while removal of PrPSc propagation downregulated the level of GAP43 in SMB-S15 cells. Morphological colocalization and molecular interaction between GAP43 and PrPSc have been addressed in the brains of prion-infected rodents and prion-infected cell line. Histological assays of the serial sections of the whole brains of prion-infected mice proposed that the reduced GAP43 level correlated with large amount of PrPSc deposits and notable neuron damage and loss showing cell crumpled and nuclear pyknosis. The impairment of GAP43 signaling and disturbance of calcium homeostasis by aberrance of brain GAP43/p-GAP43 not only reflect but also likely contribute to the pathology of severe neuron loss at the end of prion disease.

Neuronal Vulnerability of the Entorhinal Cortex to Tau Pathology in Alzheimer's Disease.

This review delves into the entorhinal cortex (EC) as a central player in the pathogenesis of Alzheimer's Disease (AD), emphasizing its role in the accumulation and propagation of tau pathology. It elucidates the multifaceted functions of the EC, encompassing memory formation, spatial navigation, and olfactory processing, while exploring how disruptions in these processes contribute to cognitive decline in AD. The review discusses the intricate interplay between tau pathology and EC vulnerability, highlighting how alterations in neuronal firing patterns and synaptic function within the EC exacerbate cognitive impairments. Furthermore, it elucidates how specific neuronal subtypes within the EC exhibit differential susceptibility to tau-induced damage, contributing to disease progression. Early detection methods, such as imaging techniques and assessments of EC blood flow, are examined as potential tools for identifying tau pathology in the preclinical stages of AD. These approaches offer promise for improving diagnostic accuracy and enabling timely intervention. Therapeutic strategies targeting tau pathology within the EC are explored, including the clearance of pathological tau aggregates and the inhibition of tau aggregation processes. By understanding the molecular and cellular mechanisms underlying EC vulnerability, researchers can develop more targeted and effective interventions to slow disease progression. The review underscores the importance of reliable biomarkers to assess disease progression and therapeutic efficacy in clinical trials targeting the EC. Ultimately, it aims to contribute to the development of more effective management strategies for AD, emphasizing the translation of research findings into clinical practice to address the growing societal burden of the disease.

Postnatal Neuronal Nogo-A Knockdown Decreased the Message of Glutamatergic Synaptic Proteins.

It is well known that oligodendrocyte-associated Nogo-A protein is an important regulator of axonal outgrowth and an important inhibitor of functional recovery and anatomical plasticity after central nervous system (CNS) injury. Abundant studies of oligodendrocyte-associated Nogo-A function in the uninjured rodent have suggested a role in neuronal development and synaptic function. On the other hand, the roles of neuron-associated (i.e., neuronal) Nogo-A have not been fully investigated. We have previously shown that neuronal Nogo-A influence dendritic spine density and morphology in pyramidal neurons of the intact neocortex. To further examine the role of neuronal Nogo-A in this synaptic population, we designed an RNAi directed against Nogo-A, delivered to the developing rat sensorimotor cortex using a neurotropic viral vector adeno-associated virus (AAV) 2/8. We examined the transduced neocortex for molecules important for synaptic plasticity, including N-Methyl-D-Aspartate (NMDA) receptor subunits GRIN2A; glutamate receptor subunit epsilon-1 (NR2A), and GRIN2B; glutamate receptor subunit epsilon-2 (NR2B), as well as postsynaptic density-95 (PSD-95). Furthermore, we also determined the density of excitatory synapses by examining the presynaptic protein vesicular glutamate transporter 1 (vGLut1) as a marker for potential excitatory synapses. Our results showed that neuronal Nogo-A knockdown in postnatal pyramidal neurons of the sensorimotor cortex led to a significant decrease in NMDA receptor subunits NR2A and NR2B messenger RNA when examined as adults. However, there was no difference in PSD-95 expression in comparison to controls. In addition, the decrease in the number of vGlut1(+) puncta on branches of apical dendrites of pyramidal neurons indicated the loss of synapses that have a strong influence on direct current entering the dendrite. Taken together, these results indicate that neuronal Nogo-A may regulate synaptic plasticity by modulating the components of excitatory synapses. This finding represents a novel role in excitatory synaptic formation for neuronal Nogo-A in developing neurons of the uninjured CNS.

ProSAAS is preferentially up-regulated during homeostatic scaling and reduces amyloid plaque burden in the 5xFAD mouse hippocampus.

The accumulation of β-amyloid in Alzheimer's disease greatly impacts neuronal health and synaptic function. To maintain network stability in the face of altered synaptic activity, neurons engage a feedback mechanism termed homeostatic scaling; however, this process is thought to be disrupted during disease progression. Previous proteomics studies have shown that one of the most highly regulated proteins in cell culture models of homeostatic scaling is the small secretory chaperone proSAAS. Our prior work has shown that proSAAS exhibits anti-aggregant behavior against alpha-synuclein and β-amyloid fibrillation invitro and is up-regulated in cell models of proteostatic stress. However, the specific role that this protein might play in homeostatic scaling, and its anti-aggregant role in Alzheimer's progression, is not clear. To learn more about the role of proSAAS in maintaining hippocampal proteostasis, we compared its expression in a primary neuron model of homeostatic scaling to other synaptic components using western blotting and qPCR, revealing that proSAAS protein responses to homeostatic up- and down-regulation were significantly higher than those of two other synaptic vesicle components, 7B2 and carboxypeptidase E. However, proSAAS mRNA expression was static, suggesting translational control and/or altered protein degradation. ProSAAS was readily released upon depolarization of differentiated hippocampal cultures, supporting its synaptic localization. Immunohistochemical analysis demonstrated abundant proSAAS within the mossy fiber layer of the hippocampus in both wild-type and 5xFAD mice; in the latter, proSAAS was also concentrated around amyloid plaques. Importantly, overexpression of proSAAS in the CA1 region via stereotaxic injection of proSAAS-encoding AAV2/1 significantly decreased amyloid plaque burden in 5xFAD mice. We hypothesize that dynamic changes in proSAAS expression play a critical role in hippocampal proteostatic processes, both in the context of normal homeostatic plasticity and in the control of protein aggregation during Alzheimer's disease progression.

Membrane remodeling by FAM92A1 during brain development regulates neuronal morphology, synaptic function, and cognition

The Bin/Amphiphysin/Rvs (BAR) domain protein FAM92A1 is a multifunctional protein engaged in regulating mitochondrial ultrastructure and ciliogenesis, but its physiological role in the brain remains unclear. Here, we show that FAM92A1 is expressed in neurons starting from embryonic development. FAM92A1 knockout in mice results in altered brain morphology and age-associated cognitive deficits, potentially due to neuronal degeneration and disrupted synaptic plasticity. Specifically, FAM92A1 deficiency impairs diverse neuronal membrane morphology, including the mitochondrial inner membrane, myelin sheath, and synapses, indicating its roles in membrane remodeling and maintenance. By determining the crystal structure of the FAM92A1 BAR domain, combined with atomistic molecular dynamics simulations, we uncover that FAM92A1 interacts with phosphoinositide- and cardiolipin-containing membranes to induce lipid-clustering and membrane curvature. Altogether, these findings reveal the physiological role of FAM92A1 in the brain, highlighting its impact on synaptic plasticity and neural function through the regulation of membrane remodeling and endocytic processes.

A molecularly defined subpopulation of oligodendrocyte precursor cells controls the generation of myelinating oligodendrocytes during postnatal development.

Oligodendrocyte precursor cells (OPCs) are a class of glial cells that uniformly tiles the entire central nervous system (CNS). They play several key functions across the brain including the generation of oligodendrocytes and the control of myelination. Whether the functional diversity of OPCs is the result of genetically defined subpopulations or of their regulation by external factors has not been definitely established. We discovered that a subpopulation of OPCs found across the brain is defined by the expression of C1ql1, a gene previously described for its synaptic function in neurons. This subpopulation starts to appear during the first postnatal week in the mouse cortex. Ablation of C1ql1-expressing OPCs in the mouse leads to a massive lack of oligodendrocytes and myelination in many brain regions. This deficit cannot be rescued, even though some OPCs escape Sox10-driven ablation and end up partially compensating the OPC loss in the adult. Therefore, C1ql1 is a molecular marker of a functionally non-redundant subpopulation of OPCs, which controls the generation of myelinating oligodendrocytes.

Low-frequency RTMS attenuates social impairment in the VPA-induced mouse model

BackgroundAutism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interactions and repetitive behaviors. Despite its prevalence, effective treatments remain elusive. Recent studies have highlighted the importance of the balance between GABAergic and glutamatergic neuronal synaptic functions in ASD development. Repetitive transcranial magnetic stimulation (RTMS) is a painless and effective treatment allowed for use in depression and obsessive-compulsive disorder. However, its efficacy in treating autism is still under investigation. Low-frequency RTMS (LF-RTMS), which shows promise in reducing autism-like behaviors, is considered to regulate synaptic function. ObjectiveWe observed and recorded the behaviors of mice to assess the impact of RTMS on their social interactions and repetitive activities. Subsequently, we examined GABAergic and glutamatergic neuronal markers along with synaptic marker proteins to understand the underlying changes associated with these behaviors. MethodsTo evaluate behaviors associated with autism spectrum disorder (ASD), several behavioral tests were conducted, focusing on sociability, repetitive behaviors, locomotion, anxiety, and depression. Additionally, Western blot and immunofluorescence staining were employed to investigate the activity of GABAergic and glutamatergic neurons in the hippocampus, aiming to understand the synaptic mechanisms underlying these behaviors. ResultsLF-RTMS treatment effectively relieved the social disability and normalized synaptic function in the hippocampus of ASD mice model induced by valproate (VPA). Importantly, this treatment did not lead to any adverse effects on repetitive behavior, locomotion, anxiety, or depression. ConclusionLF-RTMS attenuated social disability without affecting repetitive behavior, locomotion, anxiety, or depression. Changes in the expression of GABAergic and glutamatergic neuronal synaptic proteins in the hippocampus were also observed.

Loss of protein tyrosine phosphatase receptor delta PTPRD increases the number of cortical neurons, impairs synaptic function and induces autistic-like behaviors in adult mice

BackgroundThe brain cortex is responsible for many higher-level cognitive functions. Disruptions during cortical development have long-lasting consequences on brain function and are associated with the etiology of brain disorders. We previously found that the protein tyrosine phosphatase receptor delta Ptprd, which is genetically associated with several human neurodevelopmental disorders, is essential to cortical brain development. Loss of Ptprd expression induced an aberrant increase of excitatory neurons in embryonic and neonatal mice by hyper-activating the pro-neurogenic receptors TrkB and PDGFRβ in neural precursor cells. However, whether these alterations have long-lasting consequences in adulthood remains unknown.ResultsHere, we found that in Ptprd+/- or Ptprd-/- mice, the developmental increase of excitatory neurons persists through adulthood, affecting excitatory synaptic function in the medial prefrontal cortex. Likewise, heterozygosity or homozygosity for Ptprd also induced an increase of inhibitory cortical GABAergic neurons and impaired inhibitory synaptic transmission. Lastly, Ptprd+/- or Ptprd-/- mice displayed autistic-like behaviors and no learning and memory impairments or anxiety.ConclusionsThese results indicate that loss of Ptprd has long-lasting effects on cortical neuron number and synaptic function that may aberrantly impact ASD-like behaviors.

Overexpression of solute carrier family 6 member 12 promotes cell injury in Parkinson's disease via MAPK signaling pathway

BackgroundNeurotransmitter transport disorders may play a crucial role in Parkinson's Disease (PD), and Solute carrier family 6 member 12 (SLC6A12) encodes a neurotransmitter transporter. However, the relationship between SLC6A12 and PD remains largely unexplored. MethodsWe utilized the GEO database (107 samples) and clinical data (80 samples) to investigate the role of SLC6A12 in PD through differential expression analysis, ROC analysis, and RT-qPCR experiments. Subsequently, in vitro model, axon length measurement, CCK8 assay, flow cytometry, and JC-1 assays were conducted. Additionally, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, protein-protein interaction (PPI) network, gene set enrichment analysis (GSEA), and western blot experiments were assessed to explore the functional and mechanistic pathways of SLC6A12 in PD. Finally, CIBERSORT analysis was performed to investigate the correlation between SLC6A12 and immune cells in PD. ResultsThe expression of SLC6A12 was significantly higher in individuals with PD compared to healthy controls. Inhibiting SLC6A12 expression in PD models enhanced neuronal growth and proliferation activity while reducing cell apoptosis. Furthermore, SLC6A12 was found to be involved in neuronal development, synaptic function, and neural protein transport processes in PD, potentially regulating the MAPK signaling pathway through the Ras/Raf/MEK/ERK axis, contributing to the pathological process of PD. Additionally, SLC6A12 was implicated in immune environment disturbances in PD, notably affecting CD4 T cell expression. ConclusionThis study documented the pathogenicity of SLC6A12 in PD for the first time, expanding the understanding of its molecular function and providing a potential target for precise treatment of PD.

An Epigenetic Manifestation of Alzheimer's Disease: DNA Methylation.

Alzheimer's disease (AD), the most common form of dementia, has a complex pathogenesis. The number of AD patients has increased in recent years due to population aging, while a trend toward a younger age of onset has arisen, imposing a substantial burden on society and families, and garnering extensive attention. DNA methylation has recently been revealed to play an important role in AD onset and progression. DNA methylation is a critical mechanism regulating gene expression, and alterations in this mechanism dysregulate gene expression and disrupt important pathways, including oxidative stress responses, inflammatory reactions, and protein degradation processes, eventually resulting in disease. Studies have revealed widespread changes in AD patients' DNA methylation in the peripheral blood and brain tissues, affecting multiple signaling pathways and severely impacting neuronal cell and synaptic functions. This review summarizes the role of DNA methylation in the pathogenesis of AD, aiming to provide a theoretical basis for its early prevention and treatment.

Netrin-1 signaling pathway mechanisms in neurodegenerative diseases.

Netrin-1 and its receptors play crucial roles in inducing axonal growth and neuronal migration during neuronal development. Their profound impacts then extend into adulthood to encompass the maintenance of neuronal survival and synaptic function. Increasing amounts of evidence highlight several key points: (1) Diminished Netrin-1 levels exacerbate pathological progression in animal models of Alzheimer's disease and Parkinson's disease, and potentially, similar alterations occur in humans. (2) Genetic mutations of Netrin-1 receptors increase an individuals' susceptibility to neurodegenerative disorders. (3) Therapeutic approaches targeting Netrin-1 and its receptors offer the benefits of enhancing memory and motor function. (4) Netrin-1 and its receptors show genetic and epigenetic alterations in a variety of cancers. These findings provide compelling evidence that Netrin-1 and its receptors are crucial targets in neurodegenerative diseases. Through a comprehensive review of Netrin-1 signaling pathways, our objective is to uncover potential therapeutic avenues for neurodegenerative disorders.

Discovery of a pocket network on the domain 5 of the TrkB receptor - A potential new target in the quest for the new ligands.

The important role that the neurotrophin tyrosine kinase receptor - TrkB has in the pathogenesis of several neurodegenerative conditions such are Alzheimer's disease, Parkinson's disease, Huntington's disease, has been well described. This shouldn't be a surprise, since in the physiological conditions, once activated by brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5), the TrkB receptor promotes neuronal survival, differentiation and synaptic function. Considering that the natural ligands for TrkB receptor are large proteins, it is a challenge to discover small molecule capable to mimic their effects. Even though, the surface of receptor that is interacting with BDNF or NT-4/5 is known, there was always a question which pocket and interaction is responsible for activation of it. In order to answer this challenging question, we have used molecular dynamic (MD) simulations and Pocketron algorithm which enabled us to detect, for the first time, a pocket network existing in the interacting domain (d5) of the receptor; to describe them and to see how they are communicating with each other. This new discovery gave us potential new areas on receptor that can be targeted and used for structure-based drug design approach in the development of the new ligands.

The lncRNA Malat1 is trafficked to the cytoplasm as a localized mRNA encoding a small peptide in neurons.

Synaptic function in neurons is modulated by local translation of mRNAs that are transported to distal portions of axons and dendrites. The metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is broadly expressed across cell types, almost exclusively as a nuclear long noncoding RNA. We found that in differentiating neurons, a portion of Malat1 RNA redistributes to the cytoplasm. Depletion of Malat1 using antisense oligonucleotides (ASOs) stimulates the expression of particular pre- and postsynaptic proteins, implicating Malat1 in their regulation. Neuronal Malat1 is localized in puncta of both axons and dendrites that costain with Staufen1 protein, similar to neuronal RNA granules formed by locally translated mRNAs. Ribosome profiling of cultured mouse cortical neurons identified ribosome footprints within a 5' region of Malat1 containing short open reading frames. The upstream-most reading frame (M1) of the Malat1 locus was linked to the GFP-coding sequence in mouse embryonic stem cells. When these gene-edited cells were differentiated into glutamatergic neurons, the M1-GFP fusion protein was expressed. Antibody staining for the M1 peptide confirmed its presence in wild-type neurons and showed that M1 expression was enhanced by synaptic stimulation with KCl. Our results indicate that Malat1 serves as a cytoplasmic coding RNA in the brain that is both modulated by and modulates synaptic function.