1
|
Transactivation of TrkB Receptors by Oxytocin and Its G Protein-Coupled Receptor. Front Mol Neurosci 2022; 15:891537. [PMID: 35721318 PMCID: PMC9201241 DOI: 10.3389/fnmol.2022.891537] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 04/11/2022] [Indexed: 12/28/2022] Open
Abstract
Brain-derived Neurotrophic Factor (BDNF) binds to the TrkB tyrosine kinase receptor, which dictates the sensitivity of neurons to BDNF. A unique feature of TrkB is the ability to be activated by small molecules in a process called transactivation. Here we report that the brain neuropeptide oxytocin increases BDNF TrkB activity in primary cortical neurons and in the mammalian neocortex during postnatal development. Oxytocin produces its effects through a G protein-coupled receptor (GPCR), however, the receptor signaling events that account for its actions have not been fully defined. We find oxytocin rapidly transactivates TrkB receptors in bath application of acute brain slices of 2-week-old mice and in primary cortical culture by increasing TrkB receptor tyrosine phosphorylation. The effects of oxytocin signaling could be distinguished from the related vasopressin receptor. The transactivation of TrkB receptors by oxytocin enhances the clustering of gephyrin, a scaffold protein responsible to coordinate inhibitory responses. Because oxytocin displays pro-social functions in maternal care, cognition, and social attachment, it is currently a focus of therapeutic strategies in autism spectrum disorders. Interestingly, oxytocin and BDNF are both implicated in the pathophysiology of depression, schizophrenia, anxiety, and cognition. These results imply that oxytocin may rely upon crosstalk with BDNF signaling to facilitate its actions through receptor transactivation.
Collapse
|
2
|
Nerve Growth Factor transfer from cardiomyocytes to innervating sympathetic neurons activates TrkA receptors at the neuro-cardiac junction. J Physiol 2022; 600:2853-2875. [PMID: 35413134 PMCID: PMC9321700 DOI: 10.1113/jp282828] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 03/28/2022] [Indexed: 11/08/2022] Open
Abstract
The integration of ex vivo and in vitro data, described in this manuscript, together with our previous demonstration that sympathetic neurons (SNs) contact target cardiomyocytes (CMs) at the neuro-cardiac junction (NCJ), which underlies intercellular synaptic communication (Prando et al., 47), demonstrate that: CMs are the cell source of Nerve Growth Factor (NGF), required to sustain innervating cardiac SNs; NCJ is the place of the intimate liaison, between SNs and CMs, allowing on the one hand neurons to peremptorily control CM activity, and on the other, CMs to adequately sustain the contacting, everchanging, neuronal actuators; alterations in NCJ integrity may compromise the efficiency of 'CM-to-SN' signaling, thus representing a potentially novel mechanism of sympathetic denervation in cardiac diseases. ABSTRACT: Background Sympathetic neurons densely innervate the myocardium with non-random topology and establish structured contacts (i.e. neuro-cardiac junctions, NCJ) with cardiomyocytes, allowing synaptic intercellular communication. Establishment of heart innervation is regulated by molecular mediators released by myocardial cells. The mechanisms underlying maintenance of cardiac innervation in the fully developed heart, are, however, less clear. Notably, several cardiac diseases, primarily affecting cardiomyocytes, are associated to sympathetic denervation, supporting that retrograde 'cardiomyocyte-to-sympathetic neuron' communication is essential for heart cellular homeostasis. Objective We aimed to determine whether cardiomyocytes provide Nerve Growth Factor (NGF) to sympathetic neurons, and the role of the NCJ in supporting such retrograde neurotrophic signaling. Methods and Results Immunofluorescence on murine and human heart slices shows that NGF and its receptor, Tropomyosin-receptor-kinase-A, accumulate respectively in the pre- and post-junctional sides of the NCJ. Confocal immunofluorescence, scanning ion conductance microscopy and molecular analyses, in co-cultures, demonstrate that cardiomyocytes feed NGF to sympathetic neurons, and that such mechanism requires a stable intercellular contact at the NCJ. Consistently, cardiac fibroblasts, devoid of NCJ, are unable to sustain SN viability. ELISA assay and competition binding experiments suggest that this depends on the NCJ being an insulated microenvironment, characterized by high [NGF]. In further support, real-time imaging of Tropomyosin-receptor-kinase-A-vesicle movements demonstrate that efficiency of neurotrophic signaling parallels the maturation of such structured intercellular contacts. Conclusions Altogether, our results demonstrate the mechanisms which link sympathetic neuron survival to neurotrophin release by directly innervated cardiomyocytes, conceptualizing sympathetic neurons as cardiomyocyte-driven heart drivers. Abstract figure legend Sympathetic neuron (SN, green) varicosities establish synaptic contacts with target cardiomyocytes (CMs, pink), which we previously called Neuro-Cardiac Junction (NCJ, Prando et al. J Physiol 47). At NCJs, CMs release selectively NGF, which by activating TrkA signaling, is key to sustain neuronal survival. This article is protected by copyright. All rights reserved.
Collapse
|
3
|
γ-Enolase enhances Trk endosomal trafficking and promotes neurite outgrowth in differentiated SH-SY5Y cells. Cell Commun Signal 2021; 19:118. [PMID: 34895236 PMCID: PMC8665614 DOI: 10.1186/s12964-021-00784-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 09/03/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Neurotrophins can activate multiple signalling pathways in neuronal cells through binding to their cognate receptors, leading to neurotrophic processes such as cell survival and differentiation. γ-Enolase has been shown to have a neurotrophic activity that depends on its translocation towards the plasma membrane by the scaffold protein γ1-syntrophin. The association of γ-enolase with its membrane receptor or other binding partners at the plasma membrane remains unknown. METHODS In the present study, we used immunoprecipitation and immunofluorescence to show that γ-enolase associates with the intracellular domain of the tropomyosin receptor kinase (Trk) family of tyrosine kinase receptors at the plasma membrane of differentiated SH-SY5Y cells. RESULTS In differentiated SH-SY5Y cells with reduced expression of γ1-syntrophin, the association of γ-enolase with the Trk receptor was diminished due to impaired translocation of γ-enolase towards the plasma membrane or impaired Trk activity. Treatment of differentiated SH-SY5Y cells with a γ-Eno peptide that mimics γ-enolase neurotrophic activity promoted Trk receptor internalisation and endosomal trafficking, as defined by reduced levels of Trk in clathrin-coated vesicles and increased levels in late endosomes. In this way, γ-enolase triggers Rap1 activation, which is required for neurotrophic activity of γ-enolase. Additionally, the inhibition of Trk kinase activity by K252a revealed that increased SH-SY5Y cell survival and neurite outgrowth mediated by the γ-Eno peptide through activation of signalling cascade depends on Trk kinase activity. CONCLUSIONS These data therefore establish the Trk receptor as a binding partner of γ-enolase, whereby Trk endosomal trafficking is promoted by γ-Eno peptide to mediate its neurotrophic signalling. Video abstract.
Collapse
|
4
|
Behavioral aspects and neurobiological properties underlying medical cannabis treatment in Shank3 mouse model of autism spectrum disorder. Transl Psychiatry 2021; 11:524. [PMID: 34645786 PMCID: PMC8514476 DOI: 10.1038/s41398-021-01612-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 07/16/2021] [Accepted: 08/04/2021] [Indexed: 12/27/2022] Open
Abstract
Autism spectrum disorder (ASD) is a neurodevelopmental disease with a wide spectrum of manifestation. The core symptoms of ASD are persistent deficits in social communication, and restricted and repetitive patterns of behavior, interests, or activities. These are often accompanied by intellectual disabilities. At present, there is no designated effective treatment for the core symptoms and co-morbidities of ASD. Recently, interest is rising in medical cannabis as a treatment for ASD, with promising clinical data. However, there is a notable absence of basic pre-clinical research in this field. In this study, we investigate the behavioral and biochemical effects of long-term oral treatment with CBD-enriched medical cannabis oil in a human mutation-based Shank3 mouse model of ASD. Our findings show that this treatment alleviates anxiety and decreases repetitive grooming behavior by over 70% in treated mutant mice compared to non-treated mutant mice. Furthermore, we were able to uncover the involvement of CB1 receptor (CB1R) signaling in the Avidekel oil mechanism, alongside a mitigation of cerebrospinal fluid (CSF) glutamate concentrations. Subsequently, RNA sequencing (RNA seq) of cerebellar brain samples revealed changes in mRNA expression of several neurotransmission-related genes post-treatment. Finally, our results question the relevancy of CBD enrichment of medical cannabis for treating the core symptoms of ASD, and emphasize the importance of the THC component for alleviating deficits in repetitive and social behaviors in ASD.
Collapse
|
5
|
Inhibition of Tropomyosin Receptor Kinase A Signaling Negatively Regulates Megakaryopoiesis and induces Thrombopoiesis. Sci Rep 2019; 9:2781. [PMID: 30808933 PMCID: PMC6391490 DOI: 10.1038/s41598-019-39385-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 12/05/2018] [Indexed: 02/07/2023] Open
Abstract
Neurotrophin signaling modulates the differentiation and function of mature blood cells. The expression of neurotrophin receptors and ligands by hematopoietic and stromal cells of the bone marrow indicates that neurotrophins have the potential to regulate hematopoietic cell fate decisions. This study investigates the role of neurotrophins and Tropomyosin receptor kinases (Trk) in the development of megakaryocytes (MKs) and their progeny cells, platelets. Results indicate that primary human MKs and MK cells lines, DAMI, Meg-01 and MO7e express TrkA, the primary receptor for Nerve Growth Factor (NGF) signaling. Activation of TrkA by NGF enhances the expansion of human MK progenitors (MKPs) and, to some extent, MKs. Whereas, inhibition of TrkA receptor by K252a leads to a 50% reduction in the number of both MKPs and MKs and is associated with a 3-fold increase in the production of platelets. In order to further confirm the role of TrkA signaling in platelet production, TrkA deficient DAMI cells were generated using CRISPR-Cas9 technology. Comparative analysis of wild-type and TrkA-deficient Dami cells revealed that loss of TrkA signaling induced apoptosis of MKs and increased platelet production. Overall, these findings support a novel role for TrkA signaling in platelet production and highlight its potential as therapeutic target for Thrombocytopenia.
Collapse
|
6
|
Konjac Ceramide (kCer) Regulates NGF-Induced Neurite Outgrowth via the Sema3A Signaling Pathway. J Oleo Sci 2018; 67:77-86. [PMID: 29238028 DOI: 10.5650/jos.ess17141] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The tuber of the konjac plant is a source enriched with GlcCer (kGlcCer), and has been used as a dietary supplement to improve the dry skin and itching that are caused by a deficiency of epidermal ceramide. Previously, we showed chemoenzymatically prepared konjac ceramide has a neurite-outgrowth inhibitory effect that is very similar to that of Sema3A and is not seen with animal-type ceramides. While, it has been unclear whether kCer may act on Sema3A or TrkA signaling pathway. In the present study, we showed kCer induces phosphorylation of CRMP2 and microtubules depolymerization via Sema3A signaling pathway not TrkA. It is concluded that kCer may be a potential Sema3A-like agonist that activates Sema3A signaling pathway directly.
Collapse
|
7
|
Derivatives of caffeic acid, a natural antioxidant, as the basis for the discovery of novel nonpeptidic neurotrophic agents. Bioorg Med Chem 2017; 25:3235-3246. [PMID: 28495385 DOI: 10.1016/j.bmc.2017.04.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/09/2017] [Indexed: 01/01/2023]
Abstract
Neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease, threaten the lives of millions of people and the number of affected patients is constantly growing with the increase of the aging population. Small molecule neurotrophic agents represent promising therapeutics for the pharmacological management of neurodegenerative diseases. In this study, a series of caffeic acid amide analogues with variable alkyl chain lengths, including ACAF3 (C3), ACAF4 (C4), ACAF6 (C6), ACAF8 (C8) and ACAF12 (C12) were synthesized and their neurotrophic activity was examined by different methods in PC12 neuronal cells. We found that all caffeic acid amide derivatives significantly increased survival in PC12 neuronal cells in serum-deprived conditions at 25μM, as measured by the MTT assay. ACAF4, ACAF6 and ACAF8 at 5µM also significantly enhanced the effect of nerve growth factor (NGF) in inducing neurite outgrowth, a sign of neuronal differentiation. The neurotrophic effects of amide derivatives did not seem to be mediated by direct activation of tropomyosin receptor kinase A (TrkA) receptor, since K252a, a potent TrkA antagonist, did not block the neuronal survival enhancement effect. Similarly, the active compounds did not activate TrkA as measured by immunoblotting with anti-phosphoTrkA antibody. We also examined the effect of amide derivatives on signaling pathways involved in survival and differentiation by immunoblotting. ACAF4 and ACAF12 induced ERK1/2 phosphorylation in PC12 cells at 5 and 25µM, while ACAF12 was also able to significantly increase AKT phosphorylation at 5 and 25µM. Molecular docking studies indicated that compared to the parental compound caffeic acid, ACAF12 exhibited higher binding energy with phosphoinositide 3-kinase (PI3K) as a putative molecular target. Based on Lipinski's rule of five, all of the compounds obeyed three molecular descriptors (HBD, HBA and MM) in drug-likeness test. Taken together, these findings show for the first time that caffeic amides possess strong neurotrophic effects exerted via modulation of ERK1/2 and AKT signaling pathways presumably by activation of PI3K and thus represent promising agents for the discovery of neurotrophic compounds for management of neurodegenerative diseases.
Collapse
|
8
|
Exercise promotes the expression of brain derived neurotrophic factor (BDNF) through the action of the ketone body β-hydroxybutyrate. eLife 2016; 5. [PMID: 27253067 PMCID: PMC4915811 DOI: 10.7554/elife.15092] [Citation(s) in RCA: 407] [Impact Index Per Article: 50.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 05/24/2016] [Indexed: 01/01/2023] Open
Abstract
Exercise induces beneficial responses in the brain, which is accompanied by an increase in BDNF, a trophic factor associated with cognitive improvement and the alleviation of depression and anxiety. However, the exact mechanisms whereby physical exercise produces an induction in brain Bdnf gene expression are not well understood. While pharmacological doses of HDAC inhibitors exert positive effects on Bdnf gene transcription, the inhibitors represent small molecules that do not occur in vivo. Here, we report that an endogenous molecule released after exercise is capable of inducing key promoters of the Mus musculus Bdnf gene. The metabolite β-hydroxybutyrate, which increases after prolonged exercise, induces the activities of Bdnf promoters, particularly promoter I, which is activity-dependent. We have discovered that the action of β-hydroxybutyrate is specifically upon HDAC2 and HDAC3, which act upon selective Bdnf promoters. Moreover, the effects upon hippocampal Bdnf expression were observed after direct ventricular application of β-hydroxybutyrate. Electrophysiological measurements indicate that β-hydroxybutyrate causes an increase in neurotransmitter release, which is dependent upon the TrkB receptor. These results reveal an endogenous mechanism to explain how physical exercise leads to the induction of BDNF. DOI:http://dx.doi.org/10.7554/eLife.15092.001 Exercise is not only good for our physical health but it benefits our mental health and abilities too. Physical exercise can affect how much of certain proteins are made in the brain. In particular, the levels of a protein called brain derived neurotrophic factor (or BDNF for short) increase after exercise. BDNF has already been shown to enhance mental abilities at the same time as acting against anxiety and depression in mice, and might act in similar way in humans. Nevertheless, it is currently not clear how exercise increases the production of BDNF by cells in the brain. Sleiman et al. have now investigated this question by comparing mice that were allowed to use a running wheel for 30 days with control mice that did not exercise. The comparison showed that the exercising mice had higher levels of BDNF in their brains than the control mice, which confirms the results of previous studies. Next, biochemical experiments showed that this change occurred when enzymes known as histone deacetylases stopped inhibiting the production of BDNF. Therefore Sleiman et al. hypothesised that exercise might produce a chemical that itself inhibits the histone deacetylases. Indeed, the exercising mice produced more of a molecule called β-hydroxybutyrate in their livers, which travels through the blood into the brain where it could inhibit histone deacetylases. Further experiments showed that injecting β-hydroxybutyrate directly into the brains of mice led to increase in BDNF. These new findings reveal with molecular detail one way in which exercise can affect the expression of proteins in the brain. This new understanding may provide ideas for new therapies to treat psychiatric diseases, such as depression, and neurodegenerative disorders, such as Alzheimer’s disease. DOI:http://dx.doi.org/10.7554/eLife.15092.002
Collapse
|
9
|
Role of TrkB in the anxiolytic-like and antidepressant-like effects of vagal nerve stimulation: Comparison with desipramine. Neuroscience 2016; 322:273-86. [PMID: 26899129 DOI: 10.1016/j.neuroscience.2016.02.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Revised: 01/23/2016] [Accepted: 02/09/2016] [Indexed: 12/27/2022]
Abstract
A current hypothesis regarding the mechanism of antidepressant (AD) action suggests the involvement of brain-derived neurotrophic factor (BDNF). Consistent with this hypothesis, the receptor for BDNF (and neurotrophin 4/5 (NT-4/5)), Tropomyosin-related kinase B (TrkB), is activated in rodents by treatment with classical AD drugs. Vagal nerve stimulation (VNS), a therapy for treatment resistant depression (TRD), also activates TrkB in rodents. However, the role of this receptor in the therapeutic effects of VNS is unclear. In the current study, the involvement of TrkB in the effects of VNS was investigated in rats using its inhibitor, K252a. Anxiolytic-like and AD-like effects were analyzed using the novelty suppressed feeding test (NSFT) and forced swim test (FST), respectively. K252a blocked the anxiolytic-like effect of chronic VNS treatment and the AD-like effect of acute VNS treatment. By contrast, blocking TrkB did not prevent either the anxiolytic-like or AD-like effect of chronic treatment with desipramine (DMI), a selective noradrenergic reuptake inhibitor; it did, however, block the acute effect of DMI in the FST. To examine whether the activation of TrkB caused by either VNS or DMI is ligand-dependent, use was made of TrkB-Fc, a molecular scavenger for ligands of TrkB. Intraventricular administration of TrkB-Fc blocked the acute activation of TrkB induced by either treatment, indicating that treatment-induced activation of this receptor is ligand-dependent. The behavioral results highlight differences in the involvement of TrkB in the chronic effects of an AD drug and a stimulation therapy as well as its role in acute versus chronic effects of DMI.
Collapse
|
10
|
Identification of the oncogenic kinase TOPK/PBK as a master mitotic regulator of C2H2 zinc finger proteins. Oncotarget 2015; 6:1446-61. [PMID: 25575812 PMCID: PMC4359306 DOI: 10.18632/oncotarget.2735] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 11/08/2014] [Indexed: 11/25/2022] Open
Abstract
TOPK/PBK is an oncogenic kinase upregulated in most human cancers and its high expression correlates with poor prognosis. TOPK is known to be activated by Cdk1 and needed for mitotic cell division; however, its mitotic functions are not yet fully understood. In this study, we show that TOPK plays a global mitotic role by simultaneously regulating hundreds of DNA binding proteins. C2H2 zinc finger proteins (ZFPs) constitute the largest family of human proteins. All C2H2 ZFPs contain a highly conserved linker sequence joining their multi-zinc finger domains. We have previously shown that phosphorylation of this conserved motif serves as a global mechanism for the coordinate dissociation of C2H2 ZFPs from condensing chromatin, during mitosis. Here, using a panel of kinase inhibitors, we identified K252a as a potent inhibitor of mitotic ZFP linker phosphorylation. We generated a biotinylated form of K252a and used it to purify candidate kinases. From these candidates we identified TOPK/PBK, in vitro and in vivo, as the master ZFP linker kinase. Furthermore, we show precise temporal correlation between TOPK activating phosphorylation by Cdk1 and linker phosphorylation in mitosis. The identification of this fundamental role of TOPK underscores its significance as a promising novel target of cancer therapeutics.
Collapse
|
11
|
Src mediates endocytosis of TWIK-related acid-sensitive K+ 1 channels in PC12 cells in response to nerve growth factor. Am J Physiol Cell Physiol 2015; 309:C251-63. [DOI: 10.1152/ajpcell.00354.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 06/10/2015] [Indexed: 01/17/2023]
Abstract
TWIK-related acid-sensitive K+ (TASK) channels produce background K+ currents. We elucidated that TASK1 channels in rat adrenal medullary cells and PC12 cells are internalized in a clathrin-dependent manner in response to nerve growth factor (NGF). Here, the molecular mechanism for this internalization in PC12 cells was explored. The combination of enzyme inhibitors with tropomyosin receptor kinase A mutants revealed that the internalization was mediated by both phospholipase C and phosphatidylinositol 3-kinase pathways that converge on protein kinase C with the consequent activation of Src, a nonreceptor tyrosine kinase. The NGF-induced endocytosis of TASK1 channels did not occur in the presence of the Src inhibitor or with the expression of a kinase-dead Src mutant. Additionally, NGF induced a transient colocalization of Src with the TASK1 channel, but not the TASK1 mutant, in which tyrosine at 370 was replaced with phenylalanine. This TASK1 mutant showed no increase in tyrosine phosphorylation and markedly diminished internalization in response to NGF. We concluded that NGF induces endocytosis of TASK1 channels via tyrosine phosphorylation in its carboxyl terminus.
Collapse
|
12
|
The TrkAIII oncoprotein inhibits mitochondrial free radical ROS-induced death of SH-SY5Y neuroblastoma cells by augmenting SOD2 expression and activity at the mitochondria, within the context of a tumour stem cell-like phenotype. PLoS One 2014; 9:e94568. [PMID: 24736663 PMCID: PMC3988074 DOI: 10.1371/journal.pone.0094568] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 03/17/2014] [Indexed: 12/19/2022] Open
Abstract
The developmental and stress-regulated alternative TrkAIII splice variant of the NGF receptor TrkA is expressed by advanced stage human neuroblastomas (NBs), correlates with worse outcome in high TrkA expressing unfavourable tumours and exhibits oncogenic activity in NB models. In the present study, we report that constitutive TrkAIII expression in human SH-SY5Y NB cells inhibits Rotenone, Paraquat and LY83583-induced mitochondrial free radical reactive oxygen species (ROS)-mediated death by stimulating SOD2 expression, increasing mitochondrial SOD2 activity and attenuating mitochondrial free radical ROS production, in association with increased mitochondrial capacity to produce H2O2, within the context of a more tumour stem cell-like phenotype. This effect can be reversed by the specific TrkA tyrosine kinase inhibitor GW441756, by the multi-kinase TrkA inhibitors K252a, CEP-701 and Gö6976, which inhibit SOD2 expression, and by siRNA knockdown of SOD2 expression, which restores the sensitivity of TrkAIII expressing SH-SY5Y cells to Rotenone, Paraquat and LY83583-induced mitochondrial free radical ROS production and ROS-mediated death. The data implicate the novel TrkAIII/SOD2 axis in promoting NB resistance to mitochondrial free radical-mediated death and staminality, and suggest that the combined use of TrkAIII and/or SOD2 inhibitors together with agents that induce mitochondrial free radical ROS-mediated death could provide a therapeutic advantage that may also target the stem cell niche in high TrkA expressing unfavourable NB.
Collapse
|
13
|
BDNF-mediated migration of cardiac microvascular endothelial cells is impaired during ageing. J Cell Mol Med 2014; 16:3105-15. [PMID: 22925160 PMCID: PMC4393738 DOI: 10.1111/j.1582-4934.2012.01621.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Accepted: 08/16/2012] [Indexed: 12/01/2022] Open
Abstract
This study indicates that brain-derived neurotrophic factor (BDNF) can promote young cardiac microvascular endothelial cells (CMECs) to migrate via the activation of the BDNF-TrkB-FL-PI3K/Akt pathway, which may benefit angiogenesis after myocardial infarction (MI). However, the ageing of CMECs led to changes in the expression of receptor Trk isoforms in that among the three isoforms (TrkB-FL, TrkB-T1 and TrkB-T2), only one of its truncated isoforms, TrkB-T1, continued to be expressed, which leads to the dysfunction of its ligand, a decrease in the migration of CMECs and increased injury in ageing hearts. This shift in receptor isoforms in aged CMECs, together with changes in the ageing microenvironment, might predispose ageing hearts to decreased angiogenic potential and increased cardiac pathology.
Collapse
|
14
|
Adenosine A(2A) Receptors as novel upstream regulators of BDNF-mediated attenuation of hippocampal Long-Term Depression (LTD). Neuropharmacology 2013; 79:389-98. [PMID: 24361450 DOI: 10.1016/j.neuropharm.2013.12.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 11/08/2013] [Accepted: 12/08/2013] [Indexed: 01/05/2023]
Abstract
Hippocampal Long-Term Potentiation (LTP) is facilitated by BDNF, through the activation of tropomyosin-related kinase B (TrkB) receptors. However, an influence of BDNF upon Long-Term Depression (LTD) was also shown. The present work aimed to further evaluate the effect of BDNF and TrkB receptors upon CA1 hippocampal LTD and to elucidate whether this effect is under the upstream control of other signalling processes, such as the adenosine A(2A)Receptors (A(2A)Rs). LTD, induced by a Low-Frequency Stimulation (LFS, 900 pulses, 1 Hz) in the CA1 area of rat hippocampal slices, was significantly attenuated when these slices were exposed to BDNF (60-100 ng/mL). A lower BDNF concentration (20 ng/ml) was only effective to inhibit LTD if A(2A)Rs were activated by a selective agonist, CGS 21680 (10 nM), or if the extracellular adenosine level was increased by 5-iodotubercidin (100 nM). BDNF (100 ng/ml) effect upon LTD was prevented by K252a (200 nM), which is known to prevent TrkB transphosphorylation, hence suggesting that this action requires TrkB receptor activation. BDNF (100 ng/ml) lacked effect on an adenosine-depleted background (adenosine deaminase, 2 U/ml) or under selective A(2A)R blockade (SCH 58261, 100 nM), indicating that it relies on tonic A(2A)R activation. Forskolin (10 μM), a cell-permeable activator of adenylate cyclase, rescued BDNF (100 ng/ml) effect in slices where A(2A)Rs were blocked with SCH 58261 (100 nM), whereas a PKA inhibitor, H-89 (1 μM), prevented LTD attenuation by BDNF (100 ng/ml). We conclude that the influence of BDNF TrkB receptors upon LTD is under the strict control of A(2A)Rs activation, through a mechanism that requires the cAMP/PKA transducing system.
Collapse
|
15
|
The role of Src protein in the process formation of PC12 cells induced by the proteasome inhibitor MG-132. Neurochem Int 2013; 63:413-22. [DOI: 10.1016/j.neuint.2013.07.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 07/05/2013] [Accepted: 07/23/2013] [Indexed: 11/20/2022]
|
16
|
Retinoid X receptor activation is essential for docosahexaenoic acid protection of retina photoreceptors. J Lipid Res 2013; 54:2236-2246. [PMID: 23723389 PMCID: PMC3708373 DOI: 10.1194/jlr.m039040] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/28/2013] [Indexed: 01/12/2023] Open
Abstract
We have established that docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in the retina, promotes survival of rat retina photoreceptors during early development in vitro and upon oxidative stress by activating the ERK/MAPK signaling pathway. Here we have investigated whether DHA turns on this pathway through activation of retinoid X receptors (RXRs) or by inducing tyrosine kinase (Trk) receptor activation. We also evaluated whether DHA release from phospholipids was required for its protective effect. Addition of RXR antagonists (HX531, PA452) to rat retinal neuronal cultures inhibited DHA protection during early development in vitro and upon oxidative stress induced with Paraquat or H2O2. In contrast, the Trk inhibitor K252a did not affect DHA prevention of photoreceptor apoptosis. These results imply that activation of RXRs was required for DHA protection whereas Trk receptors were not involved in this protection. Pretreatment with 4-bromoenol lactone, a phospholipase A2 inhibitor, blocked DHA prevention of oxidative stress-induced apoptosis of photoreceptors. It is noteworthy that RXR agonists (HX630, PA024) also rescued photoreceptors from H2O2-induced apoptosis. These results provide the first evidence that activation of RXRs prevents photoreceptor apoptosis and suggest that DHA is first released from phospholipids and then activates RXRs to promote the survival of photoreceptors.
Collapse
|
17
|
Nerve growth factor receptor TrkA, a new receptor in insulin signaling pathway in PC12 cells. J Biol Chem 2013; 288:23807-13. [PMID: 23749991 DOI: 10.1074/jbc.m112.436279] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TrkA is a cell surface transmembrane receptor tyrosine kinase for nerve growth factor (NGF). TrkA has an NPXY motif and kinase regulatory loop similar to insulin receptor (INSR) suggesting that NGF→TrkA signaling might overlap with insulin→INSR signaling. During insulin or NGF stimulation TrkA, insulin receptor substrate-1 (IRS-1), INSR (and presumably other proteins) forms a complex in PC12 cells. In PC12 cells, tyrosine phosphorylation of INSR and IRS-1 is dependent upon the functional TrkA kinase domain. Moreover, expression of TrkA kinase-inactive mutant blocked the activation of Akt and Erk5 in response to insulin or NGF. Based on these data, we propose that TrkA participates in insulin signaling pathway in PC12 cells.
Collapse
|
18
|
Scribble controls NGF-mediated neurite outgrowth in PC12 cells. Eur J Cell Biol 2013; 92:213-21. [DOI: 10.1016/j.ejcb.2013.07.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 07/04/2013] [Accepted: 07/11/2013] [Indexed: 12/21/2022] Open
|
19
|
Brain-derived neurotrophic factor-dependent cdk1 inhibition prevents G2/M progression in differentiating tetraploid neurons. PLoS One 2013; 8:e64890. [PMID: 23741412 PMCID: PMC3669015 DOI: 10.1371/journal.pone.0064890] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 04/19/2013] [Indexed: 11/28/2022] Open
Abstract
Neurodegeneration is often associated with DNA synthesis in neurons, the latter usually remaining for a long time as tetraploid cells before dying by apoptosis. The molecular mechanism preventing G2/M transition in these neurons remains unknown, but it may be reminiscent of the mechanism that maintains tetraploid retinal ganglion cells (RGCs) in a G2-like state during normal development, thus preventing their death. Here we show that this latter process, known to depend on brain-derived neurotrophic factor (BDNF), requires the inhibition of cdk1 by TrkB. We demonstrate that a subpopulation of chick RGCs previously shown to become tetraploid co-expresses TrkB and cdk1 in vivo. By using an in vitro system that recapitulates differentiation and cell cycle re-entry of chick retinal neurons we show that BDNF, employed at concentrations specific for the TrkB receptor, reduces the expression of cdk1 in TrkB-positive, differentiating neurons. In this system, BDNF also inhibits the activity of both endogenous cdk1 and exogenously-expressed cdk1/cyclin B1 complex. This inhibition correlates with the phosphorylation of cdk1 at Tyr15, an effect that can be prevented with K252a, a tyrosine kinase inhibitor commonly used to prevent the activity of neurotrophins through their Trk receptors. The effect of BDNF on cdk1 activity is Tyr15-specific since BDNF cannot prevent the activity of a constitutively active form of cdk1 (Tyr15Phe) when expressed in differentiating retinal neurons. We also show that BDNF-dependent phosphorylation of cdk1 at Tyr15 could not be blocked with MK-1775, a Wee1-selective inhibitor, indicating that Tyr15 phosphorylation in cdk1 does not seem to occur through the canonical mechanism observed in proliferating cells. We conclude that the inhibition of both expression and activity of cdk1 through a BDNF-dependent mechanism contributes to the maintenance of tetraploid RGCs in a G2-like state.
Collapse
|
20
|
Plasticity and metaplasticity of adult rat hippocampal mossy fibers induced by neurotrophin-3. Eur J Neurosci 2013; 37:1248-59. [DOI: 10.1111/ejn.12141] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 12/18/2012] [Accepted: 12/23/2012] [Indexed: 12/29/2022]
|
21
|
Nerve growth factor-induced endocytosis of TWIK-related acid-sensitive K+ 1 channels in adrenal medullary cells and PC12 cells. Pflugers Arch 2013; 465:1051-64. [DOI: 10.1007/s00424-013-1222-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 01/13/2013] [Accepted: 01/20/2013] [Indexed: 11/27/2022]
|
22
|
Nerve growth factor: A key local regulator in the pathogenesis of inflammatory arthritis. ACTA ACUST UNITED AC 2013; 63:3243-52. [PMID: 21792838 DOI: 10.1002/art.30564] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The effect of nerve growth factor (NGF) and its receptor (NGFR) in inflammatory diseases is a novel research field. The purpose of this study was to investigate the role of NGF/NGFR in human T cell subpopulations and fibroblast-like synovial cells (FLS) and examine its pathophysiologic significance in psoriatic arthritis (PsA) and rheumatoid arthritis (RA). METHODS Expression of NGF/NGFR was examined in synovial fluid (SF), FLS, peripheral blood (PB)-derived T cells, and SF-derived T cells from patients with PsA, RA, and osteoarthritis (OA). NGF levels were determined by enzyme-linked immunosorbent assay. NGF-induced T cell/FLS proliferation was examined by MTT assay. Low-affinity (p75)/high-affinity (TrkA) NGFR expression was determined by high-dimensional fluorescence-activated cell sorting. A monochlorobimane assay was used to determine the effect of NGF on T cell survival. RESULTS Levels of NGF were higher in SF samples from PsA and RA patients as compared to SF samples from OA patients. NGF-induced FLS proliferation was more marked in PsA and RA patients. TrkA was up-regulated on activated SF T cells from PsA (mean ± SD 22 ± 6.2%) and RA (8 ± 1.3%) patients, whereas in SF samples from OA patients, TrkA+CD3+ T cells were not detectable. NGF induced the proliferation of PB T cells, induced the phosphorylation of Akt in activated T cells, and consistent with known pAkt activity, inhibited tumor necrosis factor α-induced cell death in these T cells. CONCLUSION Based on our findings, we propose a model in which NGF secreted by FLS into PsA and RA synovium promotes the survival of activated autoreactive T cells as well as FLS proliferation. Thus, NGF has the potential to sustain the chronic inflammatory cascades of arthritis of autoimmune origin.
Collapse
|
23
|
Pronerve growth factor induces angiogenesis via activation of TrkA: possible role in proliferative diabetic retinopathy. J Diabetes Res 2013; 2013:432659. [PMID: 23998130 PMCID: PMC3753742 DOI: 10.1155/2013/432659] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 07/04/2013] [Accepted: 07/12/2013] [Indexed: 01/08/2023] Open
Abstract
Proliferative diabetic retinopathy (PDR) is the leading cause of blindness in working age Americans. We demonstrated that diabetes disturbs the homeostasis of nerve growth factor (NGF) resulting in accumulation of its precursor proNGF. Increases in proNGF were positively correlated with progression of diabetic retinopathy, having the highest level in ocular fluids from PDR patients compared to nondiabetic patients. Here, we attempted to evaluate the contribution and the possible mechanism of proNGF to PDR. The angiogenic response of aqueous humor samples from PDR patients was examined in human retinal endothelial cells in the presence or absence of anti-proNGF antibody. Additional cultures were treated with mutant-proNGF in the presence of specific pharmacological inhibitors of TrkA and p75(NTR) receptors. PDR-aqueous humor samples exerted significant angiogenic response including cell proliferation, migration, and alignment into tube-like structures. These effects were significantly reduced by anti-proNGF antibody but not by IgG. Treatment of retinal endothelial cells with mutant-proNGF activated phosphorylation of TrkA and p38MAPK; however, it did not alter p75(NTR) expression. Inhibition of TrkA but not p75(NTR) significantly reduced mutant-proNGF-induced cell proliferation, cell migration, and tube formation. Taken together, these results provide evidence that proNGF can contribute to PDR at least in part via activation of TrkA.
Collapse
|
24
|
Nerve injury increases brain-derived neurotrophic factor levels to suppress BK channel activity in primary sensory neurons. J Neurochem 2012; 121:944-53. [PMID: 22428625 DOI: 10.1111/j.1471-4159.2012.07736.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Abnormal hyperexcitability of primary sensory neurons contributes to neuropathic pain development after nerve injury. Nerve injury profoundly reduces the expression of big conductance Ca(2+) -activated K(+) (BK) channels in the dorsal root ganglion (DRG). However, little is known about how nerve injury affects BK channel activity in DRG neurons. In this study, we determined the changes in BK channel activity in DRG neurons in a rat model of neuropathic pain and the contribution of brain-derived neurotrophic factor (BDNF) to reduced BK channel activity. The BK channel activity was present predominantly in small and medium DRG neurons, and ligation of L5 and L6 spinal nerves profoundly decreased the BK current density in these neurons. Blocking BK channels significantly increased neuronal excitability in sham control, but not in nerve-injured, rats. The BDNF concentration in the DRG was significantly greater in nerve-injured rats than in control rats. BDNF treatment largely reduced BK currents in DRG neurons in control rats, which was blocked by either anti-BDNF antibody or K252a, a Trk receptor inhibitor. Furthermore, either anti-BDNF antibody or K252a reversed reduction in BK currents in injured DRG neurons. BDNF treatment reduced the mRNA levels of BKα1 subunit in DRG neurons, and anti-BDNF antibody attenuated the reduction in the BKα1 mRNA level in injured DRG neurons. These findings suggest that nerve injury primarily diminishes the BK channel activity in small and medium DRG neurons. Increased BDNF levels contribute to reduced BK channel activity in DRG neurons through epigenetic and transcriptional mechanisms in neuropathic pain.
Collapse
|
25
|
Mitogen-activated protein kinase (MAPK/ERK) regulates adenomatous polyposis coli during growth-factor-induced cell extension. J Cell Sci 2012; 125:1247-58. [PMID: 22399805 DOI: 10.1242/jcs.095166] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Regulation of the microtubule- and actin-binding protein adenomatous polyposis coli (APC) is crucial for the formation of cell extensions in many cell types. This process requires inhibition of glycogen synthase kinase-3β (GSK-3β), which otherwise phosphorylates APC and decreases APC-mediated microtubule bundling. Although it is assumed, therefore, that APC phosphorylation is decreased during initiation of cell extensions, the phosphorylation state of APC has never been analyzed directly. We show here that NGF- and EGF-induced initial cell extensions result in APC phosphorylation by the MAPK/ERK pathway, which, in parallel with inhibition of GSK-3β, promotes localization of APC to the tip of cell extensions. Whereas GSK-3β inhibition promotes APC binding and stabilization of microtubules, we show that phosphorylation by ERK inhibits the interaction of APC with F-actin, and APC-mediated F-actin bundling, but not APC-mediated microtubule bundling, in vitro. These results identify a previously unknown APC regulatory pathway during growth-factor-induced cell extension, and indicate that the GSK-3β and ERK pathways act in parallel to regulate interactions between APC and the cytoskeleton during the formation of cell extensions.
Collapse
|
26
|
AAK1 identified as an inhibitor of neuregulin-1/ErbB4-dependent neurotrophic factor signaling using integrative chemical genomics and proteomics. ACTA ACUST UNITED AC 2011; 18:891-906. [PMID: 21802010 DOI: 10.1016/j.chembiol.2011.03.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 02/18/2011] [Accepted: 03/07/2011] [Indexed: 12/15/2022]
Abstract
Target identification remains challenging for the field of chemical biology. We describe an integrative chemical genomic and proteomic approach combining the use of differentially active analogs of small molecule probes with stable isotope labeling by amino acids in cell culture-mediated affinity enrichment, followed by subsequent testing of candidate targets using RNA interference-mediated gene silencing. We applied this approach to characterizing the natural product K252a and its ability to potentiate neuregulin-1 (Nrg1)/ErbB4 (v-erb-a erythroblastic leukemia viral oncogene homolog 4)-dependent neurotrophic factor signaling and neuritogenesis. We show that AAK1 (adaptor-associated kinase 1) is a relevant target of K252a, and that the loss of AAK1 alters ErbB4 trafficking and expression levels, providing evidence for a previously unrecognized role for AAK1 in Nrg1-mediated neurotrophic factor signaling. Similar strategies should lead to the discovery of novel targets for therapeutic development.
Collapse
|
27
|
Facilitated intracellular transport of TrkA by an interaction with nerve growth factor. Dev Neurobiol 2011; 71:634-49. [PMID: 21312342 DOI: 10.1002/dneu.20879] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Intracellular transport of neurotrophin receptors together with neurotrophins is one of the key events of neurotrophin signaling for the growth and the survival of neurons. However, the involvement of neurotrophin signaling in the regulation of intracellular transport of neurotrophin receptors has been remained unclear. We visualized the behavior of TrkA, a receptor of nerve growth factor (NGF), by labeling with GFP in PC12 cells. We found remarkable changes of the behavior of TrkA-GFP upon the application of NGF. Before the application, only ~37% of the fluorescent dots of TrkA showed translocations along neurites of PC12 cells. After the application, number of the dots showing the directional movement increased to ~65%. The averaged velocities of the directional movement of TrkA-GFP dots became higher after the application of NGF. We tested the idea whether NGF binding accelerated the translocations of TrkA by simultaneously observing TrkA-GFP and fluorescently labeled NGF, Cy3.5-NGF. The velocity of TrkA-GFP dots associated with Cy3.5-NGF was remarkably higher than that of TrkA-GFP dots without Cy3.5-NGF. On the basis of these observations, we hypothesize that there is a signaling mechanism within a single vesicle that facilitates the intracellular transport of each vesicle containing the activated TrkA.
Collapse
|
28
|
Structure-Activity Relationships of Neuritogenic Gentiside Derivatives. ChemMedChem 2011; 6:1986-9. [DOI: 10.1002/cmdc.201100348] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Indexed: 11/06/2022]
|
29
|
Neurotrophin receptor TrkC is an entry receptor for Trypanosoma cruzi in neural, glial, and epithelial cells. Infect Immun 2011; 79:4081-7. [PMID: 21788388 DOI: 10.1128/iai.05403-11] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Trypanosoma cruzi, the agent of Chagas' disease, infects a variety of mammalian cells in a process that includes multiple cycles of intracellular division and differentiation starting with host receptor recognition by a parasite ligand(s). Earlier work in our laboratory showed that the neurotrophin-3 (NT-3) receptor TrkC is activated by T. cruzi surface trans-sialidase, also known as parasite-derived neurotrophic factor (PDNF). However, it has remained unclear whether TrkC is used by T. cruzi to enter host cells. Here, we show that a neuronal cell line (PC12-NNR5) relatively resistant to T. cruzi became highly susceptible to infection when overexpressing human TrkC but not human TrkB. Furthermore, trkC transfection conferred an ∼3.0-fold intracellular growth advantage. Sialylation-deficient Chinese hamster ovarian (CHO) epithelial cell lines Lec1 and Lec2 also became much more permissive to T. cruzi after transfection with the trkC gene. Additionally, NT-3 specifically blocked T. cruzi infection of the TrkC-NNR5 transfectants and of naturally permissive TrkC-bearing Schwann cells and astrocytes, as did recombinant PDNF. Two specific inhibitors of Trk autophosphorylation (K252a and AG879) and inhibitors of Trk-induced MAPK/Erk (U0126) and Akt kinase (LY294002) signaling, but not an inhibitor of insulin-like growth factor 1 receptor, abrogated TrkC-mediated cell invasion. Antibody to TrkC blocked T. cruzi infection of the TrkC-NNR5 transfectants and of cells that naturally express TrkC. The TrkC antibody also significantly and specifically reduced cutaneous infection in a mouse model of acute Chagas' disease. TrkC is ubiquitously expressed in the peripheral and central nervous systems, and in nonneural cells infected by T. cruzi, including cardiac and gastrointestinal muscle cells. Thus, TrkC is implicated as a functional PDNF receptor in cell entry, independently of sialic acid recognition, mediating broad T. cruzi infection both in vitro and in vivo.
Collapse
|
30
|
Nature and duration of growth factor signaling through receptor tyrosine kinases regulates HSV-1 latency in neurons. Cell Host Microbe 2011; 8:320-30. [PMID: 20951966 DOI: 10.1016/j.chom.2010.09.007] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Revised: 07/10/2010] [Accepted: 08/20/2010] [Indexed: 11/16/2022]
Abstract
Herpes simplex virus-1 (HSV-1) establishes life-long latency in peripheral neurons where productive replication is suppressed. While periodic reactivation results in virus production, the molecular basis of neuronal latency remains incompletely understood. Using a primary neuronal culture system of HSV-1 latency and reactivation, we show that continuous signaling through the phosphatidylinositol 3-kinase (PI3-K) pathway triggered by nerve growth factor (NGF)-binding to the TrkA receptor tyrosine kinase (RTK) is instrumental in maintaining latent HSV-1. The PI3-K p110α catalytic subunit, but not the β or δ isoforms, is specifically required to activate 3-phosphoinositide-dependent protein kinase-1 (PDK1) and sustain latency. Disrupting this pathway leads to virus reactivation. EGF and GDNF, two other growth factors capable of activating PI3-K and PDK1 but that differ from NGF in their ability to persistently activate Akt, do not fully support HSV-1 latency. Thus, the nature of RTK signaling is a critical host parameter that regulates the HSV-1 latent-lytic switch.
Collapse
|
31
|
Neurotrophic effects of a cyanine dye via the PI3K-Akt pathway: attenuation of motor discoordination and neurodegeneration in an ataxic animal model. PLoS One 2011; 6:e17137. [PMID: 21347252 PMCID: PMC3037960 DOI: 10.1371/journal.pone.0017137] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Accepted: 01/21/2011] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND Neurotrophic factors may be future therapeutic agents for neurodegenerative disease. In the screening of biologically active molecules for neurotrophic potency, we found that a photosensitizing cyanine dye, NK-4, had remarkable neurotrophic activities and was a potent radical scavenger. METHODOLOGY/PRINCIPAL FINDINGS In this study, we evaluated the effect of NK-4 on the protection of neurons against oxidative damage and investigated the associated intracellular signaling pathways. Subsequently, we evaluated the effect of NK-4 in an animal model of neurodegeneration. In vitro, NK-4 showed dose-dependent protection of PC12 cells from toxicity induced by oxidative stress caused by hydrogen peroxide (H(2)O(2)) or 6-hydroxydopamine (6-OHDA). Comparison of extracellular signal-regulated kinase signaling pathways between treatment with NK-4 and nerve growth factor (NGF) using K252a, an inhibitor of the NGF receptor TrkA, revealed that NK-4 activity occurs independently of NGF receptors. LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, blocked the protective effect of NK-4, and NK-4 caused activation of Akt/protein kinase B, a downstream effector of PI3K. These results suggest that the neuroprotective effects of NK-4 are mediated by the PI3K-Akt signaling pathway. NK-4 treatment also attenuated stress-induced activation of SAPK/JNK, which suggests that NK-4 activates a survival signaling pathway and inhibits stress-activated apoptotic pathways independently of the TrkA receptor in neuronal cells. In vivo, administration of NK-4 improved motor coordination in genetic ataxic hamsters, as assessed by rota-rod testing. Histological analysis showed that cerebellar atrophy was significantly attenuated by NK-4 treatment. Notably, the Purkinje cell count in the treated group was threefold higher than that in the vehicle group. CONCLUSIONS/SIGNIFICANCE These results suggest that NK-4 is a potential agent for therapy for neurodegenerative disorders based on the activation of survival signaling pathways.
Collapse
|
32
|
Exogenous gangliosides increase the release of brain-derived neurotrophic factor. Neuropharmacology 2010; 60:1160-7. [PMID: 20971126 DOI: 10.1016/j.neuropharm.2010.10.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 09/24/2010] [Accepted: 10/14/2010] [Indexed: 11/18/2022]
Abstract
Gangliosides are lipophilic compounds found in cell plasma membranes throughout the brain that play a role in neuronal plasticity and regeneration. Indeed, absence or abnormal accumulation of gangliosides has been shown to lead to neurological disorders. Experimental data have shown that exogenous gangliosides exhibit properties similar to the neurotrophins, a family of neurotrophic factors that are important in the survival and maintenance of neurons and prevention of neurological diseases. Brain-derived neurotrophic factor (BDNF) is the most abundant of the neurotrophins. This work was done to reveal the neurotrophic mechanism of exogenous gangliosides. In particular, we examined whether gangliosides promote the release of BDNF. Rat hippocampal neurons or human neuroblastoma cells were transduced with a recombinant adenovirus expressing BDNF-flag to facilitate detection of BDNF. Release of BDNF was then determined by Western blot analysis and a two-site immunoassay of culture medium. The depolarizing agent KCl was used as a comparison. In hippocampal neurons, both GM1 ganglioside and KCl evoked within minutes the release of mature BDNF. In human cells, GM1 and other gangliosides released both mature BDNF and pro-BDNF. The effect of gangliosides was structure-dependent. In fact, GT1b preferentially released mature BDNF whereas GM1 released both mature and pro-BDNF. Ceramide and sphingosine did not modify the release of BDNF. This work provides additional experimental evidence that exogenous gangliosides can be used to enhance the neurotrophic factor environment and promote neuronal survival in neurological diseases. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.
Collapse
|
33
|
Green tea polyphenols potentiate the action of nerve growth factor to induce neuritogenesis: possible role of reactive oxygen species. J Neurosci Res 2010; 88:3644-55. [PMID: 20936703 DOI: 10.1002/jnr.22519] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 08/11/2010] [Accepted: 08/20/2010] [Indexed: 12/21/2022]
Abstract
Exogenously administered nerve growth factor (NGF) repairs injured axons, but it does not cross the blood-brain barrier. Thus, agents that could potentiate the neuritogenic ability of endogenous NGF would be of great utility in treating neurological injuries. Using the PC12 cell model, we show here that unfractionated green tea polyphenols (GTPP) at low concentrations (0.1 μg/ml) potentiate the ability of low concentrations of NGF (2 ng/ml) to induce neuritogenesis at a level comparable to that induced by optimally high concentrations of NGF (50 ng/ml) alone. In our experiments, GTPP by itself did not induce neuritogenesis or increase immunofluorescent staining for β-tubulin III; however, it increased expression of mRNA and proteins for the neuronal markers neurofilament-L and GAP-43. Among the polyphenols present in GTPP, epigallocatechin-3-gallate (EGCG) alone appreciably potentiated NGF-induced neurite outgrowth. Although other polyphenols present in GTPP, particularly epigallocatechin and epicatechin, lack this activity, they synergistically promoted this action of EGCG. GTPP also induced an activation of extracellular signal-regulated kinases (ERKs). PD98059, an inhibitor of the ERK pathway, blocked the expression of GAP-43. K252a, an inhibitor of TrkA-associated tyrosine kinase, partially blocked the expression of these genes and ERK activation. Antioxidants, catalase (cell-permeable form), and N-acetylcysteine (both L and D-forms) inhibited these events and abolished the GTPP potentiation of NGF-induced neuritogenesis. Taken together, these results show for the first time that GTPP potentiates NGF-induced neuritogenesis, likely through the involvement of sublethal levels of reactive oxygen species, and suggest that unfractionated GTPP is more effective in this respect than its fractionated polyphenols.
Collapse
|
34
|
BDNF evokes release of endogenous cannabinoids at layer 2/3 inhibitory synapses in the neocortex. J Neurophysiol 2010; 104:1923-32. [PMID: 20719932 DOI: 10.1152/jn.00472.2010] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The neurotrophin brain-derived neurotrophic factor (BDNF) is a potent regulator of inhibitory synaptic transmission, although the locus of this effect and the underlying mechanisms are controversial. We explored a potential interaction between BDNF and endogenous cannabinoid (endocannabinoid) signaling because activation of type 1 cannabinoid (CB1) receptors potently regulates γ-aminobutyric acid (GABA) release and both trkB tyrosine kinase receptors and CB1 receptors are highly expressed at synapses in neocortical layer 2/3. Here, we found that the effects of BDNF at inhibitory cortical synapses are mediated by the release of endocannabinoids acting retrogradely at presynaptic CB1 receptors. Specifically, acute application of BDNF rapidly reduced the amplitude of inhibitory postsynaptic currents (IPSCs) via postsynaptic trkB receptor activation because intracellular delivery of the tyrosine kinase inhibitor K252a completely blocked the BDNF effect. Although triggered by postsynaptic trkB activation, BDNF exposure decreased presynaptic release probability, as evidenced by increases in the paired-pulse ratio and coefficient of variation of evoked responses. In addition, BDNF decreased the frequency but not the amplitude of action potential-independent miniature IPSCs and BDNF did not alter the postsynaptic response to locally applied GABA. These results suggest that BDNF induces the release of a retrograde messenger from the postsynaptic cell that regulates presynaptic neurotransmitter release. Consistent with a role for endocannabinoids as the retrograde signal, the effect of BDNF on IPSCs was blocked by CB1 receptor antagonists and was occluded by a cannabinoid receptor agonist. Furthermore, inhibiting endocannabinoid synthesis or transport also disrupted the BDNF effect, implicating postsynaptic endocannabinoid release triggered by BDNF.
Collapse
|
35
|
Heat shock protein 90 inhibition depletes TrkA levels and signaling in human acute leukemia cells. Mol Cancer Ther 2010; 9:2232-42. [PMID: 20663926 DOI: 10.1158/1535-7163.mct-10-0336] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nerve growth factor (NGF) induces autophosphorylation and downstream progrowth and prosurvival signaling from the receptor tyrosine kinase TrkA. Overexpression or activating mutation of TrkA has been described in human acute myeloid leukemia cells. In the present study, we show the chaperone association of TrkA with heat shock protein 90 (hsp90) and the inhibitory effect of the hsp90 inhibitor, 17-DMAG, on TrkA levels and signaling in cultured and primary myeloid leukemia cells. Treatment with 17-DMAG disrupted the binding of TrkA with hsp90 and the cochaperone cdc37, resulting in polyubiquitylation, proteasomal degradation, and depletion of TrkA. Exposure to 17-DMAG inhibited NGF-induced p-TrkA, p-AKT, and p-ERK1/2 levels, as well as induced apoptosis of K562, 32D cells with ectopic expression of wild-type TrkA or the constitutively active mutant Delta TrkA, and of primary myeloid leukemia cells. Additionally, 17-DMAG treatment inhibited NGF-induced neurite formation in the rat pheochromocytoma PC-12 cells. Cotreatment with 17-DMAG and K-252a, an inhibitor of TrkA-mediated signaling, induced synergistic loss of viability of cultured and primary myeloid leukemia cells. These findings show that TrkA is an hsp90 client protein, and inhibition of hsp90 depletes TrkA and its progrowth and prosurvival signaling in myeloid leukemia cells. These findings also support further evaluation of the combined activity of an hsp90 inhibitor and TrkA antagonist against myeloid leukemia cells.
Collapse
|
36
|
Synergistic effects of osteonectin and brain-derived neurotrophic factor on axotomized retinal ganglion cells neurite outgrowth via the mitogen-activated protein kinase-extracellular signal-regulated kinase 1/2 pathways. Neuroscience 2010; 165:463-74. [PMID: 19837135 DOI: 10.1016/j.neuroscience.2009.10.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 10/06/2009] [Accepted: 10/13/2009] [Indexed: 11/19/2022]
Abstract
Our previous study identified osteonectin (ON) in a screen of factors made by Schwann cells (SCs) which promoted peripheral and central neurons survival and neuritogenesis, however, the mechanisms of ON promoting effects are largely unknown. In the present study, we investigated the effects of ON-deficient SC-conditioned medium (SCCM) and molecular mechanisms of ON, in regulating retinal ganglion cells (RGCs) survival and neurite outgrowth. Neonatal rat RGCs and SCs were purified by immunopanning technique. RGC survival and neuritogenesis reduced significantly when treated with either ON-null mice SCCM or ON-immunodepleted (IP) SCCM (P<0.05). In contrast to wild type SCCM, in the presence of a tyrosine kinase receptor (Trk) inhibitor (K252a), ON-null mice SCCM-induced neuritogenesis were further reduced by 24%. The Trk-mediated signaling pathways became more sensitive to K252a inhibition in the absence of ON. We also showed the synergistic effects of ON and brain-derived neurotrophic factor (BDNF) in promoting RGCs growth and the involvement of ON in two major neurotrophin-mediated signaling pathways, PI-3K-Akt and MAPK-Erk1/2. ON alone activated Akt phosphorylation and increased survival. Blockage of TrkB signalling pathway by TrkB-Fc chimera (BDNF scavenger) or K252a in ON-treated cultures reduced Akt-P level significantly. This suggests that ON induces BDNF synthesis and secretion from RGCs. The enhancement of neuritogenesis and Erk1/2 phosphorylation by ON in BDNF-treated cultures further demonstrate the signaling pathways responsible for the synergistic effect of ON on BDNF-induced neurite outgrowth. To the best of our knowledge, this is the first report showing the synergistic effects of ON on classical neurotrophins which participate in the same signalling pathways in regulating RGC neurite outgrowth.
Collapse
|
37
|
Chemical genetics identifies small-molecule modulators of neuritogenesis involving neuregulin-1/ErbB4 signaling. ACS Chem Neurosci 2010; 1:325-342. [PMID: 20495671 DOI: 10.1021/cn900046a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Genetic findings have suggested that neuregulin-1 (Nrg1) and its receptor v-erb-a erythroblastic leukemia viral oncogene homolog 4 (ErbB4) may play a role in neuropsychiatric diseases. However, the downstream signaling events and relevant phenotypic consequences of altered Nrg1 signaling in the nervous system remain poorly understood. To identify small molecules for probing Nrg1-ErbB4 signaling, a PC12-cell model was developed and used to perform a live-cell, image-based screen of the effects of small molecules on Nrg1-induced neuritogenesis. By comparing the resulting phenotypic data to that of a similar screening performed with nerve growth factor (NGF), this multidimensional screen identified compounds that directly inhibit Nrg1-ErbB4 signaling, such as the 4-anilino-quinazoline Iressa (gefitinib), as well as compounds that potentiate Nrg1-ErbB4 signaling, such as the indolocarbazole K-252a. These findings provide new insights into the regulation of Nrg1-ErbB4 signaling events and demonstrate the feasibility of using such a multidimensional, chemical-genetic approach for discovering probes of pathways implicated in neuropsychiatric diseases.
Collapse
|
38
|
Adrenergic stimulation mediates visceral hypersensitivity to colorectal distension following heterotypic chronic stress. Gastroenterology 2010; 138:294-304.e3. [PMID: 19800336 PMCID: PMC2813397 DOI: 10.1053/j.gastro.2009.09.054] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 09/11/2009] [Accepted: 09/18/2009] [Indexed: 01/27/2023]
Abstract
BACKGROUND & AIMS Chronic stress exacerbates or causes relapse of symptoms such as abdominal pain and cramping in patients with irritable bowel syndrome. We investigated whether chronic stress increases plasma norepinephrine and sensitizes colon-specific dorsal root ganglion (DRG) neurons by increasing expression of nerve growth factor (NGF) in the colon wall. METHODS Heterotypic chronic stress (HeCS) was applied to male Wistar rats and neurologic and molecular responses were analyzed. Tissues were analyzed for NGF expression. RESULTS HeCS significantly increased visceromoter response to colorectal distension; expression of NGF increased in colonic muscularis externa and mucosa/submucosa. Rheobase decreased, resting membrane potential was depolarized, and electrogenesis of action potentials increased in colon-specific thoracolumbar DRG neurons. Luminal administration of resiniferatoxin in distal colon, systemic administration of anti-NGF antibody, or inhibition of the NGF receptor trkA by k252a or antisense oligonucleotides in thoracolumbar DRG blocked the chronic stress-induced visceral hypersensitivity to colorectal distension. Blockade of alpha1/alpha2- and beta1/beta2-adrenergic receptors prevented the stress-induced visceral hypersensitivity and increased expression of NGF in the colon wall. HeCS did not induce any inflammatory response in the colon wall. CONCLUSIONS The peripheral stress mediator norepinephrine induces visceral hypersensitivity to colorectal distension in response to HeCS by increasing the expression of NGF in the colon wall, which sensitizes primary afferents in the absence of an inflammatory response.
Collapse
|
39
|
The semaphorin 4D-plexin-B signalling complex regulates dendritic and axonal complexity in developing neurons via diverse pathways. Eur J Neurosci 2009; 30:1193-208. [PMID: 19788569 DOI: 10.1111/j.1460-9568.2009.06934.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Semaphorins and their receptors, plexins, have emerged as key regulators of various aspects of neuronal development. In contrast to the Plexin-A family, the cellular functions of Plexin-B family proteins in developing neurons are only poorly understood. An activation of Plexin-B1 via its ligand, semaphorin 4D (Sema4D), produces an acute collapse of axonal growth cones in hippocampal and retinal neurons over the early stages of neurite outgrowth. However, the functional role of Sema4D-Plexin-B interactions over subsequent stages of neurite development, differentiation and maturation has not been characterized. Here we addressed this question using morphogenetic assays and time-lapse imaging on developing rat hippocampal neurons as a model system. Interestingly, Sema4D treatment over several hours was observed to promote branching and complexity in hippocampal neurons via the activation of Plexin-B1. The activation of receptor tyrosine kinases and the Rho kinase following Sema4D treatment was found to control dendritic and axonal morphogenesis by differentially regulating branching and extension. Phosphoinositide-3-kinase, but not extracellular signal-regulated kinase 1/2, was observed to be important for the stimulatory effects of Sema4D on dendritic branching. Furthermore, we observed that the mammalian target of rapamycin is activated downstream of Plexin-B1 and contributes to Sema4D-induced effects on dendritic branching. In contrast, glycogen synthase kinase-3 beta, another effector of phosphoinositide-3-kinase signalling, was not involved. Thus, our results show that Sema4D-Plexin-B interactions modulate dendritic and axonal arborizations of developing neurons by co-ordinated and concerted activation of diverse signalling pathways.
Collapse
|
40
|
Neurotrophin signaling through tropomyosin receptor kinases contributes to survival and proliferation of non-Hodgkin lymphoma. Exp Hematol 2009; 37:1295-309. [PMID: 19716854 DOI: 10.1016/j.exphem.2009.08.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Revised: 07/14/2009] [Accepted: 08/24/2009] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Neurotrophin receptor signaling has been increasingly recognized as an important factor in the development and progression of a variety of malignancies. In order to analyze the potential contribution of neurotrophin signaling to lymphoma cell survival, we investigated the role of a neurotrophin axis in promoting survival and proliferation of non-Hodgkin lymphoma (NHL) cells. MATERIALS AND METHODS The role of neurotrophins in the survival and proliferation of NHL cells was determined by exposing cells to the Trk-specific inhibitor, K252a, and then performing (3)H-thymidine incorporation and Annexin-V/propidium iodide staining. The involvement of nuclear factor-kappaB (NF-kappaB) in this process was studied using Western blot, electrophoretic mobility shift assay, and immunofluorescence assays. RESULTS Here we demonstrate that both primary NHL cells and diffuse large B-cell lymphoma cell lines express Trk receptors and their neurotrophin ligands. Furthermore, these cells are sensitive to the Trk-specific inhibitor, K252a, as evidenced by the inhibition of proliferation and/or induction of apoptosis. Analysis of the mechanism into the effects of K252a revealed that, in the OCI-LY3 cell line, K252a induced a subnuclear distribution of NF-kappaB resulting in the sequestration of RelA in the nucleolus, thereby inhibiting NF-kappaB-dependent gene transcription. This results in the loss of interleukin-6 production; a known survival-promoting signal for OCI-LY3, as well as many primary diffuse large B-cell lymphomas. CONCLUSION Thus, Trk receptors represent a novel therapeutic target for the treatment of NHL.
Collapse
|
41
|
The regulatory role of nerve growth factor and its receptor system in fibroblast-like synovial cells. Scand J Rheumatol 2009; 38:207-15. [PMID: 19177265 DOI: 10.1080/03009740802448866] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
OBJECTIVES Investigating the role of nerve growth factor (NGF) and its receptors (NGF-R) in inflammatory diseases is an active field of research. Inflammatory diseases of the joint are the commonest cause of human morbidity but very little is known about the effect of NGF on synovial tissue biology. Here we have studied NGF/NGF-R and their functional significance on cultured fibroblast-like synovial cells (FLS) collected from the synovial tissue of five healthy subjects. METHODS NGF/NGF-R expression was determined in the basal condition and after stimulation with tumour necrosis factor (TNF)alpha and interleukin (IL)-1beta by enzyme-linked immunosorbent assay (ELISA) and fluorescence-activated cell sorting (FACS). Proliferation studies were performed by cell count, hexosaminidase assay, and the MTT assay. The synovial fluid (SF) NGF level was studied by ELISA in 12 psoriatic arthritis (PsA), 14 rheumatoid arthritis (RA), and 10 osteoarthritis (OA) patients. RESULTS FACS studies showed that unstimulated FLS expressed low levels of NGF and the high-affinity NGF-tyrosine kinase receptor TrkA, and TNFalpha and IL-1beta increased NGF and TrkA expression in FLS. NGF (100 ng/mL) increased FLS proliferation by 400% compared to the control (medium only). The NGF level was significantly higher in the PsA group (365.5+/-85.2 pg/mL) than in the RA (120+/-35 pg/mL) and OA groups (30+/-6 pg/mL). CONCLUSIONS Upregulation of NGF/TrkA in proinflammatory cytokine-activated FLS, the mitogenic effect of NGF on FLS, and the increased NGF level in SF of inflammatory arthritis suggest that there is cross-talk between NGF/NGF-R and FLS. These results also suggest that dysregulated production of NGF may lead to synovial cell proliferation and thus could influence the inflammatory and proliferative cascades of inflammatory arthritis.
Collapse
|
42
|
Different protection of K252a and N-acetyl-L-cysteine against amyloid-beta peptide-induced cortical neuron apoptosis involving inhibition of MLK3-MKK7-JNK3 signal cascades. J Neurosci Res 2009; 87:918-27. [PMID: 18951497 DOI: 10.1002/jnr.21909] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Amyloid-beta peptide (Abeta) has been implicated in the etiopathogenesis of Alzheimer's disease (AD). However, the molecular mechanisms underlying Abeta neurotoxicity remain to be elucidated. This study showed that Abeta treatment resulted in the increased phosphorylation (activation) of MLK3, MKK7, and JNK3 in cultured cortical neurons, which characterized as biphasic activation (first peaked at 1 hr and second peaked at 12 hr after Abeta treatment). K252a blocked Abeta-induced neuronal apoptosis, both early and late phases of MLK3-MKK7-JNK3 activation, as well as downstream signal events involving p-JNKs nuclear translocation, c-Jun phosphorylation, and Bad translocation to the mitochondria. The neuroprotective effect of K252a on Abeta-induced apoptosis was partially dependent on Akt activation. In contrast, antioxidant N-acetyl-L-cysteine (NAC) reduced early, but not late, MLK3-MKK7-JNK3 activation by Abeta treatment and provided a weak neuroprotective ability in Abeta-induced apoptosis. Taken together, Abeta neurotoxicity is mainly due to MLK3-MKK7-JNK3 signal cascades. The late signal events of MLK3 activation after Abeta treatment may play an important role in AD neuronal loss and will be a promising pharmacological target for AD therapeutic intervention.
Collapse
|
43
|
Trypanosoma cruzi promotes neuronal and glial cell survival through the neurotrophic receptor TrkC. Infect Immun 2009; 77:1368-75. [PMID: 19179422 DOI: 10.1128/iai.01450-08] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Trypanosoma cruzi, the agent of Chagas' disease, promotes neuron survival through receptor tyrosine kinase TrkA and glycosylphosphatidylinositol-anchored glial cell-derived family ligand receptors (GFRalpha). However, these receptors are expressed by only a subset of neurons and at low levels or not at all in glial cells. Thus, T. cruzi might exploit an additional neurotrophic receptor(s) to maximize host-parasite equilibrium in the nervous system. We show here that T. cruzi binds TrkC, a neurotrophic receptor expressed by glial cells and many types of neurons, and that the binding is specifically inhibited by neurotrophin-3, the natural TrkC ligand. Coimmunoprecipitation and competition assays show that the trans-sialidase/parasite-derived neurotrophic factor (PDNF), previously identified as a TrkA ligand, mediates the T. cruzi-TrkC interaction. PDNF promotes TrkC-dependent mitogen-activated protein kinase signaling, neurite outgrowth, and survival of genetically engineered PC12 neuronal cells and glial Schwann cells in a TrkC-dependent manner. Thus, TrkC is a new neurotrophic receptor that T. cruzi engages to promote the survival of neuronal and glial cells. The results raise the possibility that T. cruzi recognition of TrkC underlies regenerative events in nervous tissues of patients with Chagas' disease.
Collapse
|
44
|
Sall2 is a novel p75NTR-interacting protein that links NGF signalling to cell cycle progression and neurite outgrowth. EMBO J 2009; 28:261-73. [PMID: 19131967 DOI: 10.1038/emboj.2008.274] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Accepted: 12/03/2008] [Indexed: 01/08/2023] Open
Abstract
By screening a fetal brain two-hybrid library with the death domain of the p75 neurotrophin receptor (NTR), we identified the Sall2 transcription factor as a novel interacting protein. Sall2 is a unique member of the Sall gene family, which is believed to be a tumour suppressor. Here, we show that Sall2 contains a p75NTR interaction domain not found in other Sall proteins and that p75NTR/Sall2 complexes co-immunoprecipitate from brain lysates. NGF dissociates p75NTR/Sall2 complexes and activates TrkA, which has an obligate function in the nuclear translocation of Sall2. NGF also increases Sall2 expression and this is mediated by p75NTR, but may not require TrkA. Depletion of Sall2 from cells decreases the expression and activity of p21(WAF1/CIP1), as well as the ability of NGF to induce growth arrest and the development of neurites. Overexpression of Sall2 activates p21(WAF1/CIP1), induces growth arrest, and promotes neurite outgrowth independently of NGF. These data establish Sall2 as a link between NTRs and transcriptional events that regulate the growth and development of neuronal cells.
Collapse
|
45
|
Molecular cloning, sequence analysis and functional characterization of the gene cluster for biosynthesis of K-252a and its analogs. MOLECULAR BIOSYSTEMS 2009; 5:1180-91. [DOI: 10.1039/b905293c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
46
|
Nerve growth factor and brain-derived neurotrophic factor attenuate angiotensin-II-induced facilitation of calcium channels in acutely dissociated nucleus tractus solitarii neurons of the rat. Arch Oral Biol 2008; 53:1192-201. [DOI: 10.1016/j.archoralbio.2008.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Revised: 06/03/2008] [Accepted: 07/25/2008] [Indexed: 02/05/2023]
|
47
|
Presynaptic and postsynaptic NMDA receptors mediate distinct effects of brain-derived neurotrophic factor on synaptic transmission. J Neurophysiol 2008; 100:3175-84. [PMID: 18922945 DOI: 10.1152/jn.90880.2008] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In addition to its effects on neuronal survival and differentiation, brain-derived neurotrophic factor (BDNF) plays an important role in modulating synaptic transmission and plasticity in many brain areas, most notably the neocortex and hippocampus. These effects may underlie a role for BDNF in learning and memory as well as developmental plasticity. Consistent with localization of the tropomyosin-related kinase B receptor to both sides of the synapse, BDNF appears to have pre- and postsynaptic effects, but the underlying cellular mechanisms are unclear and it is not known whether pre- and postsynaptic modulations by BDNF occur simultaneously. To address these issues, we recorded dual-component (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid [AMPA] and N-methyl-D-aspartate [NMDA]) miniature excitatory postsynaptic currents (mEPSCs) from cortical and hippocampal pyramidal neurons and dentate gyrus granule cells from acute brain slices. BDNF had no effect on the fast component of mEPSC decay or on the peak amplitude, suggesting that BDNF did not modulate postsynaptic AMPA receptors, although BDNF rapidly modulated NMDA receptors, as seen by an enhancement of the slow component of mEPSC decay that was prevented by blocking postsynaptic NMDA receptors. At the same time, BDNF acted presynaptically to enhance mEPSC frequency. Surprisingly, the effect on frequency was also NMDA receptor dependent, but required activation of presynaptic, not postsynaptic, NMDA receptors. BDNF also enhanced action potential-dependent glutamate release via presynaptic NMDA receptors, an effect that was unmasked when voltage-gated calcium channels were partially inhibited. Our results indicate that BDNF acutely modulates presynaptic release and postsynaptic responsiveness through simultaneous effects on pre- and postsynaptic NMDA receptors.
Collapse
|
48
|
Effects of axotomy on cultured sensory neurons of Aplysia: long-term injury-induced changes in excitability and morphology are mediated by different signaling pathways. J Neurophysiol 2008; 100:3209-24. [PMID: 18842953 DOI: 10.1152/jn.90539.2008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
To facilitate an understanding of injury-induced changes within the nervous system, we used a single-cell, in vitro model of axonal injury. Sensory neurons were individually dissociated from the CNS of Aplysia and placed into cell culture. The major neurite of some neurons was then transected (axotomized neurons). Axotomy in hemolymph-containing culture medium produced long-term hyperexcitability (LTH-E) and enhanced neuritic sprouting (long-term hypermorphogenesis [LTH-M]). Axotomy in the absence of hemolymph induced LTH-E, but not LTH-M. Hemolymph-derived growth factors may activate tyrosine receptor kinase (Trk) receptors in sensory neurons. To examine this possibility, we treated uninjured (control) and axotomized sensory neurons with K252a, an inhibitor of Trk receptor activity. K252a depressed the excitability of both axotomized and control neurons. K252a also produced a distinct pattern of arborizing outgrowth of neurites in both axotomized and control neurons. Protein kinase C (PKC) is an intracellular signal downstream of Trk; accordingly, we tested the effects of bisindolylmaleimide I (Bis-I), a specific inhibitor of PKC, on the axotomy-induced cellular changes. Bis-I blocked LTH-E, but did not disrupt LTH-M. Finally, because Trk activates the extracellular signal regulated kinase pathway in Aplysia sensory neurons, we examined whether this pathway mediates the injury-induced changes. Sensory neurons were axotomized in the presence of U0126, an inhibitor of mitogen-activated/extracellular receptor-regulated kinase. U0126 blocked the LTH-M due to axotomy, but did not impair LTH-E. Therefore distinct cellular signaling pathways mediate the induction of LTH-E and LTH-M in the sensory neurons.
Collapse
|
49
|
Abstract
BACKGROUND The tropomyosin-related kinase A (TrkA) proto-oncogene encodes for a receptor that binds with high affinity to the neurotrophin ligand, nerve growth factor (NGF). Intracellular signaling mediated by the TrkA/NGF axis orchestrates neuronal cell differentiation, mitogenesis, and survival. Interestingly, TrkA also is expressed by bone forming cells, and its signaling promotes antiapoptotic effects in actively dividing osteoblasts. HYPOTHESIS In canine immortalized cell lines and naturally occurring tumor samples, osteosarcoma (OSA) cells will express TrkA. In canine OSA cell lines, TrkA signaling will promote cell mitogenesis and survival. METHODS In vitro, TrkA expression in canine OSA cell lines was assessed by reverse transcriptase-polymerase chain reaction, flow cytometry, and immunocytochemistry. In vitro, the involvement of TrkA-mediated signaling for cell mitogenesis and survival were investigated with commercially available assays. In vivo, TrkA expression was evaluated in primary tumors and pulmonary metastases with immunocytochemistry and immunohistochemistry, respectively. RESULTS In vitro, canine OSA cells expressed TrkA mRNA and protein. Ligation of TrkA with exogenous NGF did not induce mitogenesis. Blockade of TrkA signaling with either a protein kinase inhibitor or NGF-neutralizing antibody induced apoptosis of canine OSA cell lines. In vivo, the majority (10/15) of canine OSA primary tumors and pulmonary metastases (9/12) expressed TrkA protein. CONCLUSIONS AND CLINICAL IMPORTANCE Canine OSA cells express TrkA, and its signaling protects against apoptosis. Most dogs with spontaneously arising OSA express TrkA within their primary tumors and pulmonary metastatic lesions, warranting further investigations with TrkA antagonists as a novel treatment option for canine OSA.
Collapse
|
50
|
TrkA pathway(s) is involved in regulation of TRPM7 expression in hippocampal neurons subjected to ischemic-reperfusion and oxygen–glucose deprivation. Brain Res Bull 2008; 76:124-30. [DOI: 10.1016/j.brainresbull.2008.01.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 01/15/2008] [Accepted: 01/16/2008] [Indexed: 01/09/2023]
|