Neuronal Growth Research Articles

Monomeric pilose antler peptide improves depression-like behavior in mice by inhibiting FGFR3 protein expression

Ethnopharmacological relevanceIt has been found that pilose antler peptide has an antidepressant effect on depression. However, the exact molecular mechanism of its antidepressant effect is still unclear. Aim of the studyThe study sought to determine the impact of monomeric pilose antler peptide (PAP; sequence LVLVEAELRE) on depression as well as investigate potential molecular mechanisms. Materials and methodsChronic unexpected mild stress (CUMS) was used to establish the model, and the effect of PAP on CUMS mice was detected by the behavioral test. The influence of PAP on neuronal cells and dendritic spine density was observed by immunofluorescence and Golgi staining. FGFR3 and the CaMKII-associated pathway were identified using quantitative real-time polymerase chain reaction, and Western blot analysis was utilized to measure their proteins and gene expression levels. Molecular docking and microscale thermophoresis were applied to detect the binding of PAP and FGFR3. Finally, the effect of FGFR3's overexpression on PAP treatment of depression was detected. ResultsPAP alleviated the changes in depressive behavior induced by CUMS, promoted the growth of nerve cells, and the density of dendritic spines was increased to its original state. PAP therapy successfully downregulated the expression of FGFR3 and ERK1/2 while upregulating the expression of CREB, BDNF, and CaMKII. ConclusionBased on the current research, PAP has a therapeutic effect on depression brought on by CUMS by inhibiting FGFR3 expression and enhancing synaptic plasticity.

Lithium response in bipolar disorder is associated with focal adhesion and PI3K-Akt networks: a multi-omics replication study

Lithium is the gold standard treatment for bipolar disorder (BD). However, its mechanism of action is incompletely understood, and prediction of treatment outcomes is limited. In our previous multi-omics study of the Pharmacogenomics of Bipolar Disorder (PGBD) sample combining transcriptomic and genomic data, we found that focal adhesion, the extracellular matrix (ECM), and PI3K-Akt signaling networks were associated with response to lithium. In this study, we replicated the results of our previous study using network propagation methods in a genome-wide association study of an independent sample of 2039 patients from the International Consortium on Lithium Genetics (ConLiGen) study. We identified functional enrichment in focal adhesion and PI3K-Akt pathways, but we did not find an association with the ECM pathway. Our results suggest that deficits in the neuronal growth cone and PI3K-Akt signaling, but not in ECM proteins, may influence response to lithium in BD.

The effect of psychedelics on the level of brain-derived neurotrophic factor: A systematic review and meta-analysis.

Recent interest in the potential therapeutic effects of psychedelics has led to investigations into their influence on molecular signaling pathways within the brain. Integrated review and analysis of different studies in this field. A systematic search was conducted across international databases including Embase, Scopus, Web of Science, and PubMed from inception to 9 July 2023. Eligibility criteria encompassed published and peer-reviewed studies evaluating changes in brain-derived neurotrophic factor (BDNF) levels after psychedelic consumption. A total of nine studies were included in our study. The meta-analysis demonstrated significantly higher BDNF levels in psychedelic consumers compared to healthy controls, with a pooled standardized mean difference of 0.26 (95% CI: 0.10-0.42, I2 = 38.51%, p < 0.001). Leave-one-out analysis indicated robustness in results upon removal of individual psychedelics. No significant publication bias was observed. The results highlight the potential influence of psychedelics on neuroplasticity by altering BDNF levels. More precisely, the documented rise in BDNF levels indicates a neurobiological mechanism by which psychedelics could enhance synaptic plasticity and foster the growth of neurons. Given the limited data available on this topic, the conclusions remain uncertain. Consequently, we highly recommend additional research with more extensive sample sizes to yield more reliable evidence in this field.

Granulocyte macrophage colony-stimulating factor-induced macrophages of individuals with autism spectrum disorder adversely affect neuronal dendrites through the secretion of pro-inflammatory cytokines

BackgroundA growing body of evidence suggests that immune dysfunction and inflammation in the peripheral tissues as well as the central nervous system are associated with the neurodevelopmental deficits observed in autism spectrum disorder (ASD). Elevated expression of pro-inflammatory cytokines in the plasma, serum, and peripheral blood mononuclear cells of ASD has been reported. These cytokine expression levels are associated with the severity of behavioral impairments and symptoms in ASD. In a prior study, our group reported that tumor necrosis factor-α (TNF-α) expression in granulocyte–macrophage colony-stimulating factor-induced macrophages (GM-CSF MΦ) and the TNF-α expression ratio in GM-CSF MΦ/M-CSF MΦ (macrophage colony-stimulating factor-induced macrophages) was markedly higher in individuals with ASD than in typically developed (TD) individuals. However, the mechanisms of how the macrophages and the highly expressed cytokines affect neurons remain to be addressed.MethodsTo elucidate the effect of macrophages on human neurons, we used a co-culture system of control human-induced pluripotent stem cell-derived neurons and differentiated macrophages obtained from the peripheral blood mononuclear cells of five TD individuals and five individuals with ASD. All participants were male and ethnically Japanese.ResultsOur results of co-culture experiments showed that GM-CSF MΦ affect the dendritic outgrowth of neurons through the secretion of pro-inflammatory cytokines, interleukin-1α and TNF-α. Macrophages derived from individuals with ASD exerted more severe effects than those derived from TD individuals.LimitationsThe main limitations of our study were the small sample size with a gender bias toward males, the use of artificially polarized macrophages, and the inability to directly observe the interaction between neurons and macrophages from the same individuals.ConclusionsOur co-culture system revealed the non-cell autonomous adverse effects of GM-CSF MΦ in individuals with ASD on neurons, mediated by interleukin-1α and TNF-α. These results may support the immune dysfunction hypothesis of ASD, providing new insights into its pathology.

The secretome of macrophages has a differential impact on spinal cord injury recovery according to the polarization protocol.

The inflammatory response after spinal cord injury (SCI) is an important contributor to secondary damage. Infiltrating macrophages can acquire a spectrum of activation states, however, the microenvironment at the SCI site favors macrophage polarization into a pro-inflammatory phenotype, which is one of the reasons why macrophage transplantation has failed. In this study, we investigated the therapeutic potential of the macrophage secretome for SCI recovery. We investigated the effect of the secretome in vitro using peripheral and CNS-derived neurons and human neural stem cells. Moreover, we perform a pre-clinical trial using a SCI compression mice model and analyzed the recovery of motor, sensory and autonomic functions. Instead of transplanting the cells, we injected the paracrine factors and extracellular vesicles that they secrete, avoiding the loss of the phenotype of the transplanted cells due to local environmental cues. We demonstrated that different macrophage phenotypes have a distinct effect on neuronal growth and survival, namely, the alternative activation with IL-10 and TGF-β1 (M(IL-10+TGF-β1)) promotes significant axonal regeneration. We also observed that systemic injection of soluble factors and extracellular vesicles derived from M(IL-10+TGF-β1) macrophages promotes significant functional recovery after compressive SCI and leads to higher survival of spinal cord neurons. Additionally, the M(IL-10+TGF-β1) secretome supported the recovery of bladder function and decreased microglial activation, astrogliosis and fibrotic scar in the spinal cord. Proteomic analysis of the M(IL-10+TGF-β1)-derived secretome identified clusters of proteins involved in axon extension, dendritic spine maintenance, cell polarity establishment, and regulation of astrocytic activation. Overall, our results demonstrated that macrophages-derived soluble factors and extracellular vesicles might be a promising therapy for SCI with possible clinical applications.

Modulation of neuronal morphology by antipsychotic drug: Involvement of serotonin receptor 7

Antipsychotic drugs (APDs) are the primary pharmacological treatment for schizophrenia, a complex disorder characterized by altered neuronal connectivity. Atypical or second-generation antipsychotics, such as Risperidone (RSP) and Clozapine (CZP) predominantly block dopaminergic D2 and serotonin receptor 2A (5-HT2A) neurotransmission. Both compounds also exhibit affinity for the 5-HT7R, with RSP acting as an antagonist and CZP as an inverse agonist. Our study aimed to determine whether RSP and CZP can influence neuronal morphology through a 5-HT7R-mediated mechanism. Here, we demonstrated that CZP promotes neurite outgrowth of early postnatal cortical neurons, and the 5-HT7R mediates its effect. Conversely, RSP leads to a reduction of neurite length of early postnatal cortical neurons, in a 5-HT7R-independent way.Furthermore, we found that the effects of CZP, mediated by 5-HT7R activation, require the participation of ERK and Cdk5 kinase pathways. At the same time, the modulation of neurite length by RSP does not involve these pathways.In conclusion, our findings provide valuable insights into the morphological changes induced by these two APDs in neurons and elucidate some of the associated molecular pathways. Investigating the 5-HT7R-dependent signaling pathways underlying the neuronal morphogenic effects of APDs may contribute to the identification of novel targets for the treatment of schizophrenia.

Netrin1-carrying magnetic microspheres with magnetic field activate neurotrophin factors to guide neuronal outgrowth in vitro and in vivo

Nerve injuries often result in the failure of functional synapses connections, primarily due to the absence of neurotrophic factors and guidance at the injury sites. In response to this challenge, an effective approach involving magnetic microspheres carrying axonal guidance cue (Netrin1) was presented. These microspheres were prepared using Fe3O4 and PLGA via electrospray. Netrin1 was incorporated into structural particles that could be oriented in a magnetic field and released at the injury sites. In this study, oriented and longer axons were observed in the cortical neurons after 10 μg/mL magnetic microspheres (MMSs) treatment. Under an applied magnetic field of 5 mT, Netrin1-carrying magnetic microspheres (N@MMSs) demonstrated a more significant increase in cell viability, mitochondrial membrane potential, mRNA expressions of BDNF and NGF compared to MMSs. These findings were assessed using the cell counting kit-8, tetramethyl rhodamine fluorescence, and real time PCR assay, respectively. Furthermore, N@MMSs demonstrated significant protection against glutamate-induced neuronal oxidative toxicity, as evaluated by mitochondrial respiratory function and glycolysis stress using the Seahorse Extracellular Flux analyzer. Subsequently, N@MMSs and a magnetic field were applied to adult mice after sciatic nerve injury. Behavior analysiss, including the open field test, indicated that N@MMSs typically increased motor activity under the magnetic field and significantly decreased paw licking latency on the 14th day. Finally, both BDNF and NGF expressions increased compared to the injury group. In conclusion, N@MMSs show promise as alternative particles for nerve regeneration.

Optimizing Visualization of Axonal Transport of Endogenous Cargo by Fluorescence Microscopy in Living Caenorhabditis elegans.

Axonal transport is a prerequisite to deliver axonal proteins from their site of synthesis in the neuronal cell body to their destination in the axon. Consequently, loss of axonal transport impairs neuronal growth and function. Studying axonal transport therefore improves our understanding of neuronal cell biology. With recent improvements in CRISPR Cas9 genome editing, endogenous labeling of axonal cargos has become accessible, enabling to move beyond ectopic expression-based visualization of transport. However, endogenous labeling often comes at the cost of low signal intensity and necessitates optimization strategies to obtain robust data. Here, we describe a protocol to optimize the visualization of axonal transport by discussing acquisition parameters and a bleaching approach to improve the signal of endogenous labeled cargo over diffuse cytoplasmic background. We apply our protocol to optimize the visualization of synaptic vesicle precursors (SVPs) labeled by green fluorescent protein (GFP)-tagged RAB-3 to highlight how fine-tuning acquisition parameters can improve the analysis of endogenously labeled axonal cargo in Caenorhabditis elegans (C. elegans).

A modified motor-clutch model reveals that neuronal growth cones respond faster to soft substrates.

Neuronal growth cones sense a variety of cues including chemical and mechanical ones to establish functional connections during nervous system development. Substrate-cytoskeletal coupling is an established model for adhesion-mediated growth cone advance; however, the detailed molecular and biophysical mechanisms underlying the mechanosensing and mechanotransduction process remain unclear. Here, we adapted a motor-clutch model to better understand the changes in clutch and cytoskeletal dynamics, traction forces, and substrate deformation when a growth cone interacts with adhesive substrates of different stiffnesses. Model parameters were optimized using experimental data from Aplysia growth cones probed with force-calibrated glass microneedles. We included a reinforcement mechanism at both motor and clutch level. Furthermore, we added a threshold for retrograde F-actin flow that indicates when the growth cone is strongly coupled to the substrate. Our modeling results are in strong agreement with experimental data with respect to the substrate deformation and the latency time after which substrate-cytoskeletal coupling is strong enough for the growth cone to advance. Our simulations show that it takes the shortest time to achieve strong coupling when substrate stiffness was low at 4 pN/nm. Taken together, these results suggest that Aplysia growth cones respond faster and more efficiently to soft than stiff substrates.

Investigating LIM (Lin-11, Isl-1, and Mec-3) Kinases and Their Correlation with Pathological Events and Microtubule Dynamics in an Experimental Model of Spinal Cord Injury in Rats.

The spinal cord injury (SCI) and the neurodegenerative processes accompanying it follow an intricate pathway with very limited options for treatment strategies until now. Microtubules, essential for the growth and maintenance of neurons, are mostly disorganized and destabilized due to neurodegeneration. Regeneration or plasticity is restricted to the adult central nervous system (CNS) due to several intrinsic and extrinsic mechanisms. Some fundamental or injury-induced expressions of specific molecules can be inhibited or antagonized pharmacologically to protect neurons to a certain extent after neurodegeneration. Accordingly, these molecules offer an excellent target as a therapeutic approach to promote neuroprotection. LIM kinases (LIMKs) are one of these molecules that phosphorylates members of the actin-depolymerizing factor (ADF)/cofilin family of actin-binding and filament-severing proteins. The individual role of LIMKs has not yet been studied in the pathology of SCI. In this study, we targeted LIMK and checked its role in microtubule destabilization in vitro. LIMK1 was found to be upregulated after microtubule depolymerization and inhibition of LIMK with specific inhibitor-protected neurons. Then, we checked the expressions of individual LIMKs throughout different time points across SCI in a rat contusion model, correlating with established pathophysiological markers. The phosphorylated form of LIMK1 was found to be elevated at chronic time points after injury, where scar formation and diminution of neurons prevail. Finally, we targeted the LIMK pathway with its specific inhibitor BMS-5, which showed neuroprotection after SCI. Overall, our results provided a concept concerning how a small-molecule inhibitor of LIMK may offer a strategy to treat SCI-associated neurodegeneration.

Grafted human-induced pluripotent stem cells-derived oligodendrocyte progenitor cells combined with human umbilical vein endothelial cells contribute to functional recovery following spinal cord injury

BackgroundSpinal cord injury (SCI) is a devastating disease that causes extensive damage to oligodendrocytes and neurons leading to demyelination and axonal degeneration. In this study, we co-transplanted cell grafts containing oligodendrocyte progenitor cells (OPCs) derived from human-induced pluripotent stem cells (iPSCs) combined with human umbilical vein endothelial cells (HUVECs), which were reported to promote OPCs survival and migration, into rat contusion models to promote functional recovery after SCI.MethodsOPCs were derived from iPSCs and identified by immunofluorescence at different time points. Functional assays in vitro were performed to evaluate the effect of HUVECs on the proliferation, migration, and survival of OPCs by co-culture and migration assay, as well as on the neuronal axonal growth. A combination of OPCs and HUVECs was transplanted into the rat contusive model. Upon 8 weeks, immunofluorescence staining was performed to test the safety of transplanted cells and to observe the neuronal repairment, myelination, and neural circuit reconstruction at the injured area; also, the functional recovery was assessed by Basso, Beattie, and Bresnahan open-field scale, Ladder climb, SEP, and MEP. Furthermore, the effect of HUVECs on grafts was also determined in vivo.ResultsData showed that HUVECs promote the proliferation, migration, and survival of OPCs both in vitro and in vivo. Furthermore, 8 weeks upon engraftment, the rats with OPCs and HUVECs co-transplantation noticeably facilitated remyelination, enhanced functional connection between the grafts and the host and promoted functional recovery. In addition, compared with the OPCs-alone transplantation, the co-transplantation generated more sensory neurons at the lesion border and significantly improved the sensory functional recovery.ConclusionsOur study demonstrates that transplantation of OPCs combined with HUVECs significantly enhances both motor and sensory functional recovery after SCI. No significance was observed between OPCs combined with HUVECs group and OPCs-alone group in motor function recovery, while the sensory function recovery was significantly promoted in OPCs combined with HUVECs groups compared with the other two groups. These findings provide novel insights into the field of SCI research.

A genome-wide association study on hematopoietic stem cell transplantation reveals novel genomic loci associated with transplant outcomes.

Data on genomic susceptibility for adverse outcomes after hematopoietic stem cell transplantation (HSCT) for recipients are scarce. We performed a genome wide association study (GWAS) to identify genes associated with survival/mortality, relapse, and severe graft-versus-host disease (sGvHD), fitting proportional hazard and subdistributional models to data of n=1,392 recipients of European ancestry from three centres. The single nucleotide polymorphism (SNP) rs17154454, intronic to the neuronal growth guidant semaphorin 3C gene (SEMA3C), was genome-wide significantly associated with event-free survival (p=7.0x10-8) and sGvHD (p=7.5x10-8). Further associations were detected for SNPs in the Paxillin gene (PXN) with death without prior relapse or sGvHD, as well as for SNPs of the Plasmacytoma Variant Translocation 1 gene (PVT1, a long non-coding RNA gene), the Melanocortin 5 Receptor (MC5R) gene and the WW Domain Containing Oxidoreductase gene (WWOX), all associated with the occurrence of sGvHD. Functional considerations support the observed associations. Thus, new genes were identified, potentially influencing the outcome of HSCT.

A mammalian-specific Alex3/Gαq protein complex regulates mitochondrial trafficking, dendritic complexity, and neuronal survival.

Mitochondrial dynamics and trafficking are essential to provide the energy required for neurotransmission and neural activity. We investigated how G protein-coupled receptors (GPCRs) and G proteins control mitochondrial dynamics and trafficking. The activation of Gαq inhibited mitochondrial trafficking in neurons through a mechanism that was independent of the canonical downstream PLCβ pathway. Mitoproteome analysis revealed that Gαq interacted with the Eutherian-specific mitochondrial protein armadillo repeat-containing X-linked protein 3 (Alex3) and the Miro1/Trak2 complex, which acts as an adaptor for motor proteins involved in mitochondrial trafficking along dendrites and axons. By generating a CNS-specific Alex3 knockout mouse line, we demonstrated that Alex3 was required for the effects of Gαq on mitochondrial trafficking and dendritic growth in neurons. Alex3-deficient mice had altered amounts of ER stress response proteins, increased neuronal death, motor neuron loss, and severe motor deficits. These data revealed a mammalian-specific Alex3/Gαq mitochondrial complex, which enables control of mitochondrial trafficking and neuronal death by GPCRs.

The Relationship between Sleep Parameters Measured by Polysomnography and Selected Neurotrophic Factors.

The molecular underpinnings of insufficient sleep remain underexplored, with disruptions in the neurotrophic signaling pathway emerging as a potential explanation. Neurotrophins (NTs), including brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), neurotrophin 4 (NT4), and glial-cell-line-derived growth factor (GDNF), play crucial roles in nerve cell growth and repair. However, their associations with sleep patterns are poorly understood. This study aimed to investigate the relationship between the chosen neurotrophins and objective sleep parameters. The study involved 81 participants subjected to polysomnography (PSG). Blood samples were collected after PSG. The mRNA expression and serum protein concentrations of BDNF, GDNF, NT3, and NT4 were measured using real-time quantitative reverse-transcription PCR (qRT-PCR) or enzyme-linked immunosorbent assay (ELISA) methods, respectively. BDNF and NT3 proteins were negatively correlated with NREM events, while NT4 protein positively correlated with REM events. Electroencephalography power analysis revealed BDNF protein's negative correlation with delta waves during rapid eye movement and non-rapid eye movement sleep. The study highlights associations between neurotrophins and sleep, emphasizing BDNF's role in regulating NREM and REM sleep. The EEG power analysis implicated BDNF in delta wave modulation, shedding light on potential neurotrophic mechanisms underlying sleep effects on cognitive and mood processes.

Knockdown of best1 Gene in Zebrafish Caused Abnormal Neuronal and Skeletal Development - A Subtype of Craniovertebral Junction Malformation?

To investigate the developmental defects caused by knockdown of best1 gene in zebrafish as a model for a subtype of craniovertebral junction (CVJ) malformation. Two antisense morpholinos (MOs) were designed targeting zebrafish best1 to block translation (ATG-MO) or to disrupt splicing (I3E4-MO). MOs were microinjected into fertilized one-cell embryos. Efficacy of splicing MO was confirmed by reverse transcription-polymerase chain reaction. Phenotypes were analyzed and quantified by microscopy at multiple developmental stages. Neuronal outgrowth was assessed in transgenic zebrafish expressing green fluorescent protein in neurons. Skeletal ossification was visualized by Calcein staining. Knockdown of best1 resulted in zebrafish embryos with shorter body length, curved axis, low survival rate, microcephaly, reduced eye size, smaller head and brain, impaired neuronal outgrowth, and reduced ossification of craniofacial and vertebral bone. Best1 gene plays critical roles in ophthalmologic, neurological and skeletal development in zebrafish. A patient with a premature stop codon in BEST1 gene exhibited similar phenotypes, implying a subtype of CVJ malformation.

Abstract WP322: GluN2A-NMDAR Mediated Increased Neuronal Prostaglandin E2 Release and Microglial Activation Exacerbates Ischemic Brain Injury Under Hyperhomocysteinemic Condition

Hyperhomocysteinemia (Hhcy), a metabolic disorder is recognized as a risk factor for ischemic stroke. However, the impact of Hhcy on stroke outcome is not known. Using a rodent model of experimental stroke, we recently showed that predisposition to Hhcy exacerbates ischemic brain injury. The findings also showed that Hhcy triggers GluN2A subunit containing NMDA receptor (GluN2A-NMDAR) stimulation that act in conjunction with ischemia-induced pathways involving GluN2B subunit containing NMDAR (GluN2B-NMDAR) stimulation to enhance stroke pathology. The current study evaluated whether GluN2A-NMDAR-mediated increased expression of cyclooxygenase-2 (COX-2) and excessive release of the pro-inflammatory mediator prostaglandin E2 (PGE2) from neurons results in increased microglial activation and exacerbated ischemic brain injury. HHcy was induced by implantation of Alzet pumps with L-homocysteine in adult male Wistar rats. Cerebral ischemia was induced by middle cerebral artery occlusion (60 min) in control and Hhcy rats. In a subset of Hhcy rats, NVP-AAM077, a pharmacological inhibitor of GluN2A-NMDAR was injected intravenously at the onset of stroke. At specified times following reperfusion, brain tissues were processed for FluroJade staining, immunoblotting with COX2 antibody, immunohistochemistry with COX2/NeuN and Iba1 antibodies, prostaglandin E2 (PGE2) assay and RT-PCR. FluroJade staining shows an early onset and exacerbation of ischemic injury in Hhcy rats. This involves increased expression of COX-2 in neurons, release of PGE2, and a shift in microglial morphology from ramified state to active amoeboid state, 6h after reperfusion. Administration of NVP-AAM077 attenuates the increase in COX2 expression and PGE2 levels as well as microglial activation. The findings demonstrate that an early onset of neuroinflammatory response mediated through GluN2A-NMDAR stimulation could contribute to the exacerbation of ischemic brain injury under Hhcy conditions. As GluN2A-NMDAR stimulation is primarily involved in promoting synaptic plasticity, neuronal growth, and survival, establishing their role in promoting neuroinflammatory response could lead to a paradigm shift in our understanding of the consequences of NMDAR signaling.

Advancements in the study of synaptic plasticity and mitochondrial autophagy relationship.

Synapses serve as the points of communication between neurons, consisting primarily of three components: the presynaptic membrane, synaptic cleft, and postsynaptic membrane. They transmit signals through the release and reception of neurotransmitters. Synaptic plasticity, the ability of synapses to undergo structural and functional changes, is influenced by proteins such as growth-associated proteins, synaptic vesicle proteins, postsynaptic density proteins, and neurotrophic growth factors. Furthermore, maintaining synaptic plasticity consumes more than half of the brain's energy, with a significant portion of this energy originating from ATP generated through mitochondrial energy metabolism. Consequently, the quantity, distribution, transport, and function of mitochondria impact the stability of brain energy metabolism, thereby participating in the regulation of fundamental processes in synaptic plasticity, including neuronal differentiation, neurite outgrowth, synapse formation, and neurotransmitter release. This article provides a comprehensive overview of the proteins associated with presynaptic plasticity, postsynaptic plasticity, and common factors between the two, as well as the relationship between mitochondrial energy metabolism and synaptic plasticity.

Ubiquitin ligase and signalling hub MYCBP2 is required for efficient EPHB2 tyrosine kinase receptor function

Eph receptor tyrosine kinases participate in a variety of normal and pathogenic processes during development and throughout adulthood. This versatility is likely facilitated by the ability of Eph receptors to signal through diverse cellular signalling pathways: primarily by controlling cytoskeletal dynamics, but also by regulating cellular growth, proliferation, and survival. Despite many proteins linked to these signalling pathways interacting with Eph receptors, the specific mechanisms behind such links and their coordination remain to be elucidated. In a proteomics screen for novel EPHB2 multi-effector proteins, we identified human MYC binding protein 2 (MYCBP2 or PAM or Phr1). MYCBP2 is a large signalling hub involved in diverse processes such as neuronal connectivity, synaptic growth, cell division, neuronal survival, and protein ubiquitination. Our biochemical experiments demonstrate that the formation of a complex containing EPHB2 and MYCBP2 is facilitated by FBXO45, a protein known to select substrates for MYCBP2 ubiquitin ligase activity. Formation of the MYCBP2-EPHB2 complex does not require EPHB2 tyrosine kinase activity and is destabilised by binding of ephrin-B ligands, suggesting that the MYCBP2-EPHB2 association is a prelude to EPHB2 signalling. Paradoxically, the loss of MYCBP2 results in increased ubiquitination of EPHB2 and a decrease of its protein levels suggesting that MYCBP2 stabilises EPHB2. Commensurate with this effect, our cellular experiments reveal that MYCBP2 is essential for efficient EPHB2 signalling responses in cell lines and primary neurons. Finally, our genetic studies in Caenorhabditis elegans provide in vivo evidence that the ephrin receptor VAB-1 displays genetic interactions with known MYCBP2 binding proteins. Together, our results align with the similarity of neurodevelopmental phenotypes caused by MYCBP2 and EPHB2 loss of function, and couple EPHB2 to a signalling effector that controls diverse cellular functions.

Tirzepatide prevents neurodegeneration through multiple molecular pathways

BackgroundSeveral evidence demonstrated that glucagon-like peptide 1 receptor agonists (GLP1-RAs) reduce the risk of dementia in type 2 diabetes patients by improving memory, learning, and overcoming cognitive impairment. In this study, we elucidated the molecular processes underlying the protective effect of Tirzepatide (TIR), a dual glucose-dependent insulinotropic polypeptide receptor agonist (GIP-RA)/ GLP-1RA, against learning and memory disorders.MethodsWe investigated the effects of TIR on markers of neuronal growth (CREB and BDNF), apoptosis (BAX/Bcl2 ratio) differentiation (pAkt, MAP2, GAP43, and AGBL4), and insulin resistance (GLUT1, GLUT4, GLUT3 and SORBS1) in a neuroblastoma cell line (SHSY5Y) exposed to normal and high glucose concentration. The potential role on DNA methylation of genes involved in neuroprotection and epigenetic modulators of neuronal growth (miRNA 34a), apoptosis (miRNA 212), and differentiation (miRNA 29c) was also investigated. The cell proliferation was detected by measuring Ki-67 through flow cytometry. The data were analysed by SPSS IBM Version 23 or GraphPad Prism 7.0 software and expressed as the means ± SEM. Differences between the mean values were considered significant at a p-value of < 0.05. GraphPad Prism software was used for drawing figures.ResultsFor the first time, it was highlighted: (a) the role of TIR in the activation of the pAkt/CREB/BDNF pathway and the downstream signaling cascade; (b) TIR efficacy in neuroprotection; (c) TIR counteracting of hyperglycemia and insulin resistance-related effects at the neuronal level.ConclusionsWe demonstrated that TIR can ameliorate high glucose-induced neurodegeneration and overcome neuronal insulin resistance. Thus, this study provides new insight into the potential role of TIR in improving diabetes-related neuropathy.Graphical

ISL1 and POU4F1 Directly Interact to Regulate the Differentiation and Survival of Inner Ear Sensory Neurons.

The inner ear sensory neurons play a pivotal role in auditory processing and balance control. Though significant progresses have been made, the underlying mechanisms controlling the differentiation and survival of the inner ear sensory neurons remain largely unknown. During development, ISL1 and POU4F transcription factors are co-expressed and are required for terminal differentiation, pathfinding, axon outgrowth and the survival of neurons in the central and peripheral nervous systems. However, little is understood about their functional relationship and regulatory mechanism in neural development. Here, we have knocked out Isl1 or Pou4f1 or both in mice of both sexes. In the absence of Isl1, the differentiation of cochleovestibular ganglion (CVG) neurons is disturbed and with that Isl1-deficient CVG neurons display defects in migration and axon pathfinding. Compound deletion of Isl1 and Pou4f1 causes a delay in CVG differentiation and results in a more severe CVG defect with a loss of nearly all of spiral ganglion neurons (SGNs). Moreover, ISL1 and POU4F1 interact directly in developing CVG neurons and act cooperatively as well as independently in regulating the expression of unique sets of CVG-specific genes crucial for CVG development and survival by binding to the cis-regulatory elements including the promoters of Fgf10, Pou4f2, and Epha5 and enhancers of Eya1 and Ntng2 These findings demonstrate that Isl1 and Pou4f1 are indispensable for CVG development and maintenance by acting epistatically to regulate genes essential for CVG development.