NRAGE, a p75 neurotrophin receptor-interacting protein, induces caspase activation and cell death through a JNK-dependent mitochondrial pathway

RNA m6A methylation and regulatory proteins in pulmonary arterial hypertension

m6A (N6‑methyladenosine) is the most common and abundant apparent modification in mRNA of eukaryotes. The modification of m6A is regulated dynamically and reversibly by methyltransferase (writer), demethylase (eraser), and binding protein (reader). It plays a significant role in various processes of mRNA metabolism, including regulation of transcription, maturation, translation, degradation, and stability. Pulmonary arterial hypertension (PAH) is a malignant cardiopulmonary vascular disease characterized by abnormal proliferation of pulmonary artery smooth muscle cells. Despite the existence of several effective and targeted therapies, there is currently no cure for PAH and the prognosis remains poor. Recent studies have highlighted the crucial role of m6A modification in cardiovascular diseases. Investigating the role of RNA m6A methylation in PAH could provide valuable insights for drug development. This review aims to explore the mechanism and function of m6A in the pathogenesis of PAH and discuss the potential targeting of RNA m6A methylation modification as a treatment for PAH.

Immune activation of the p75 neurotrophin receptor: implications in neuroinflammation

Despite structural similarity with other tumor necrosis factor receptor superfamily (TNFRSF) members, the p75 neurotrophin receptor (p75NTR, TNFR16) mediates pleiotropic biological functions not shared with other TNFRs. The high level of p75NTR expression in the nervous system instead of immune cells, its utilization of co-receptors, and its interaction with soluble dimeric, rather than soluble or cell-tethered trimeric ligands are all characteristics which distinguish it from most other TNFRs. Here, we compare these attributes to other members of the TNFR superfamily. In addition, we describe the recent evolutionary adaptation in B7-1 (CD80), an immunoglobulin (Ig) superfamily member, which allows engagement to neuronally-expressed p75NTR. B7-1-mediated binding to p75NTR occurs in humans and other primates, but not lower mammals due to specific sequence changes that evolved recently in primate B7-1. This discovery highlights an additional mechanism by which p75NTR can respond to inflammatory cues and trigger synaptic elimination in the brain through engagement of B7-1, which was considered to be immune-restricted. These observations suggest p75NTR does share commonality with other immune co-modulatory TNFR family members, by responding to immunoregulatory cues. The evolution of primate B7-1 to bind and elicit p75NTR-mediated effects on neuronal morphology and function are discussed in relationship to immune-driven modulation of synaptic actions during injury or inflammation.

Dynamic expression of Mage-D1 in rat dental germs and potential role in mineralization of ectomesenchymal stem cells

Mage-D1 (MAGE family member D1) is involved in a variety of cell biological effects. Recent studies have shown that Mage-D1 is closely related to tooth development, but its specific regulatory mechanism is unclear. The purpose of this study was to investigate the expression pattern of Mage-D1 in rat dental germ development and its differential mineralization ability to ectomesenchymal stem cells (EMSCs), and to explore its potential mechanism. Results showed that the expression of Mage-D1 during rat dental germ development was temporally and spatially specific. Mage-D1 promotes the proliferation ability of EMSCs but inhibits their migration ability. Under induction by mineralized culture medium, Mage-D1 promotes osteogenesis and tooth-forming ability. Furthermore, the expression pattern of Mage-D1 at E19.5 d rat dental germ is similar to p75 neurotrophin receptor (p75NTR), distal-less homeobox 1 (Dlx1) and msh homeobox 1 (Msx1). In addition, Mage-D1 is binding to p75NTR, Dlx1, and Msx1 in vitro. These findings indicate that Mage-D1 is play an important regulatory role in normal mineralization of teeth. p75NTR, Dlx1, and Msx1 seem to be closely related to the underlying mechanism of Mage-D1 action.

A toolbox for class I HDACs reveals isoform specific roles in gene regulation and protein acetylation

The class I histone deacetylases are essential regulators of cell fate decisions in health and disease. While pan- and class-specific HDAC inhibitors are available, these drugs do not allow a comprehensive understanding of individual HDAC function, or the therapeutic potential of isoform-specific targeting. To systematically compare the impact of individual catalytic functions of HDAC1, HDAC2 and HDAC3, we generated human HAP1 cell lines expressing catalytically inactive HDAC enzymes. Using this genetic toolbox we compare the effect of individual HDAC inhibition with the effects of class I specific inhibitors on cell viability, protein acetylation and gene expression. Individual inactivation of HDAC1 or HDAC2 has only mild effects on cell viability, while HDAC3 inactivation or loss results in DNA damage and apoptosis. Inactivation of HDAC1/HDAC2 led to increased acetylation of components of the COREST co-repressor complex, reduced deacetylase activity associated with this complex and derepression of neuronal genes. HDAC3 controls the acetylation of nuclear hormone receptor associated proteins and the expression of nuclear hormone receptor regulated genes. Acetylation of specific histone acetyltransferases and HDACs is sensitive to inactivation of HDAC1/HDAC2. Over a wide range of assays, we determined that in particular HDAC1 or HDAC2 catalytic inactivation mimics class I specific HDAC inhibitors. Importantly, we further demonstrate that catalytic inactivation of HDAC1 or HDAC2 sensitizes cells to specific cancer drugs. In summary, our systematic study revealed isoform-specific roles of HDAC1/2/3 catalytic functions. We suggest that targeted genetic inactivation of particular isoforms effectively mimics pharmacological HDAC inhibition allowing the identification of relevant HDACs as targets for therapeutic intervention.

Integrated multi-omic characterization of congenital heart disease

The heart, the first organ to develop in the embryo, undergoes complex morphogenesis that when defective results in congenital heart disease (CHD). With current therapies, more than 90% of patients with CHD survive into adulthood, but many suffer premature death from heart failure and non-cardiac causes1. Here, to gain insight into this disease progression, we performed single-nucleus RNA sequencing on 157,273 nuclei from control hearts and hearts from patients with CHD, including those with hypoplastic left heart syndrome (HLHS) and tetralogy of Fallot, two common forms of cyanotic CHD lesions, as well as dilated and hypertrophic cardiomyopathies. We observed CHD-specific cell states in cardiomyocytes, which showed evidence of insulin resistance and increased expression of genes associated with FOXO signalling and CRIM1. Cardiac fibroblasts in HLHS were enriched in a low-Hippo and high-YAP cell state characteristic of activated cardiac fibroblasts. Imaging mass cytometry uncovered a spatially resolved perivascular microenvironment consistent with an immunodeficient state in CHD. Peripheral immune cell profiling suggested deficient monocytic immunity in CHD, in agreement with the predilection in CHD to infection and cancer2. Our comprehensive phenotyping of CHD provides a roadmap towards future personalized treatments for CHD.

Electroacupuncture promotes apoptosis and inhibits axonogenesis by activating p75 neurotrophin receptor for triple-negative breast xenograft in mice

PURPOSE

The aim of this study was to investigate the anti-tumor effect of electroacupuncture (EA) on mice bearing breast tumors by regulating p75 neurotrophin receptor (p75NTR) and remodelling intratumoral innervation.

METHODS

Female BALB/c mice were implanted with 4T1 breast tumor cells to establish a murine mammary cancer model. Tumor volume and weight were measured to evaluate tumor growth. Cell apoptosis was assessed by TUNEL assay. The relative expression of p75NTR, TrkA, TrkB, NGF and proNGF were detected by immunohistochemistry. Neurotransmitter and neurotrophin were detected by enzyme-linked immunosorbent assay. Intratumoral innervation was confirmed by β3-tubulin and TH labeling immunohistochemistry. The antagonist TAT-Pep5 was employed to determine if the effects of EA on tumor growth and cell apoptosis were mediated by p75NTR.

RESULTS

Peritumoral EA alleviated tumor growth especially after 14 days of intervention. Apoptosis index in the tumor tissue was obviously decreased after EA. Meanwhile, EA intervention significantly upregulated the expression of p75NTR and proNGF, along with a decline in the tumor growth and an increase in the cell apoptosis. Besides, EA reduced local sympathetic innervation and downregulated sympathetic neurotransmitter NE level in the local tumor. Furthermore, p75NTR antagonist alleviated EA-mediated cell apoptosis and intratumoral innervation.

CONCLUSIONS

One mechanism of EA intervention for alleviating tumor progression is mediated by p75NTR to promote apoptosis and decrease intratumoral axonogenesis in the tumor microenvironment.

p75NTR Ectodomain Ameliorates Cognitive Deficits and Pathologies in a Rapid Eye Movement Sleep Deprivation Mice Model

The neurotrophin receptor p75 (p75NTR) is a circadian rhythm regulator and mediates cognitive deficits induced by sleep deprivation (SD). The soluble extracellular domain of p75NTR (p75ECD) has been shown to exert a neuroprotective function in Alzheimer's disease (AD) and depression animal models. Nevertheless, the role of p75ECD in SD-induced cognitive dysfunction is unclear. In the present study we administrated p75ECD-Fc (10, 3 mg/kg), a recombinant fusion protein of human p75ECD and fragment C of immunoglobulin IgG₁, to treat mice via intraperitoneal injection. The results revealed that peripheral supplementation of high-dose p75ECD-Fc (10 mg/kg) recovered the balance between Aβ and p75ECD in the hippocampus and rescued the cognitive deficits in SD mice. We also found that p75ECD-Fc ameliorated other pathologies induced by SD, including neuronal apoptosis, synaptic plasticity impairment and neuroinflammation. The current study suggests that p75ECD-Fc is a potential candidate for SD and peripheral supplementation of p75ECD-Fc may be a prospective preventive measure for cognitive decline in SD.

Recent Advances in the Molecular and Cellular Mechanisms of gp120-Mediated Neurotoxicity

Axonal degeneration and loss of synapses are often seen in different brain areas of people living with human immunodeficiency virus (HIV). Nevertheless, the underlying causes of the pathological alterations observed in these individuals are poorly comprehended, considering that HIV does not infect neurons. Experimental data have shown that viral proteins, including the envelope protein gp120, cause synaptic pathology followed by neuronal cell death. These neurotoxic effects on synapses could be the result of a variety of mechanisms that decrease synaptic plasticity. In this paper, we will briefly present new emerging concepts connected with the ability of gp120 to promote the degeneration of synapses by either directly damaging the axonal cytoskeleton and/or the indirect activation of the p75 neurotrophin receptor death domain in dendrites.

CX3CR1-Expressing Myeloid Cells Regulate Host-Helminth Interaction and Lung Inflammation

Many helminth life cycles, including hookworm, involve a mandatory lung phase, where myeloid and granulocyte subsets interact with the helminth and respond to infection-induced lung injury. To evaluate these innate subsets in Nippostrongylus brasiliensis infection, reporter mice for myeloid cells (CX3CR1^GFP ) and granulocytes (PGRP^dsRED ) are employed. Nippostrongylus infection induces lung infiltration of reporter cells, including CX3CR1⁺ myeloid cells and PGRP⁺ eosinophils. Strikingly, CX3CR1^GFP/GFP mice, which are deficient in CX3CR1, are protected from Nippostrongylus infection with reduced weight loss, lung leukocyte infiltration, and worm burden compared to CX3CR1^+/+ mice. This protective effect is specific for CX3CR1 as CCR2-deficient mice do not exhibit reduced worm burdens. Nippostrongylus co-culture with lung Ly6C⁺ monocytes or CD11c⁺ cells demonstrates that CX3CR1^GFP/GFP monocytes secrete more pro-inflammatory cytokines and actively bind the parasites causing reduced motility. RNA sequencing of Ly6C⁺ or CD11c⁺ cells shows Nippostrongylus-induced gene expression changes, particularly in monocytes, associated with inflammation, chemotaxis, and extracellular matrix remodeling pathways. Analysis reveals cytotoxic and adhesion molecules as potential effectors against the parasite, such as Gzma and Gzmb, which are elevated in CX3CR1^GFP/GFP monocytes. These studies validate a dual innate cell reporter for lung helminth infection and demonstrate that CX3CR1 impairs monocyte-helminth interaction.

Regulatory Mechanism of Neurotrophin Receptor-Interacting Melanoma Antigen Coding Gene Homolog (NRAGE) Gene Methylation on Apoptosis of Breast Cancer Cell Under Tyrosine Kinases/Methyl Ethyl Ketone/Extracellular Regulated Protein Kinases Signaling Pathway

The aim of this study was to discover the influence of Neurotrophin receptor-interacting MAGE homolog (NRAGE) gene methylation on proliferation (Pro) and apoptosis (Apo) of breast cancer cell (BCC), and its influence on TrkA/MEK/ERK signaling. BCC lines MCF-7, MDA-MB-231, and normal mammary gland cell (MGC) MCF-10 were selected. Expression of NRAGE mRNA and methylation level in cells was analyzed via reverse transcription-polymerase chain reaction (RT-PCR) and methylation-specific PCR. Different concentrations (0, 5, 10 mol/L) of DNA methylase inhibitor 5-aza-2′-deoxycytidine (5-Aza-CdR) were adopted to treat the BCC cell line. With dimethyl sulfoxide (DMSO) treatment as control, cell count, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and Western blot were adopted to detect the Pro, Apo, relative expression (REP) of Apo-related proteins Bcl-2, Bax, and target proteins TrkA, MEK, and ERK1/2 after different treatments. The results showed that NRAGE mRNA level in MDA-MB-231 and MCF-7 was notably reduced versus MCF-10 (P < 0.05), and they could express methylated NRAGE specifically. 5-Aza-CdR can increase unmethylated NRAGE’s expression in BCC. Cell Pro level of the 5 and 10 mol/L treatments was greatly inhibited than DMSO and 0 mol/L treatments (P < 0.05). Apo rate and Apo-related proteins Bcl-2 and Bax increased obviously (P < 0.05). In addition, the phosphorylation levels of TrkA in the 5 and 10 mol/L treatments were considerably reduced (P < 0.05), while that in MEK and ERK1/2 was remarkably increased (P < 0.05). In short, NRAGE methylation can inhibit BCC’s Pro and regulate BCC’s Pro and Apo through TrkA/MEK/ERK signaling.

Valproic acid upregulates the expression of the p75NTR/sortilin receptor complex to induce neuronal apoptosis

The antiepileptic and mood stabilizer agent valproic acid (VPA) has been shown to exert anti-tumour effects and to cause neuronal damage in the developing brain through mechanisms not completely understood. In the present study we show that prolonged exposure of SH-SY5Y and LAN-1 human neuroblastoma cells to clinically relevant concentrations of VPA caused a marked induction of the protein and transcript levels of the common neurotrophin receptor p75NTR and its co-receptor sortilin, two promoters of apoptotic cell death in response to proneurotrophins. VPA induction of p75NTR and sortilin was associated with an increase in plasma membrane expression of the receptor proteins and was mimicked by cell treatment with several histone deacetylase (HDAC) inhibitors. VPA and HDAC1 knockdown decreased the level of EZH2, a core component of the polycomb repressive complex 2, and upregulated the transcription factor CASZ1, a positive regulator of p75NTR. CASZ1 knockdown attenuated VPA-induced p75NTR overexpression. Cell treatment with VPA favoured proNGF-induced p75NTR/sortilin interaction and the exposure to proNGF enhanced JNK activation and apoptotic cell death elicited by VPA. Depletion of p75NTR or addition of the sortilin agonist neurotensin to block proNGF/sortilin interaction reduced the apoptotic response to VPA and proNGF. Exposure of mouse cerebellar granule cells to VPA upregulated p75NTR and sortilin and induced apoptosis which was enhanced by proNGF. These results indicate that VPA upregulates p75NTR apoptotic cell signalling through an epigenetic mechanism involving HDAC inhibition and suggest that this effect may contribute to the anti-neuroblastoma and neurotoxic effects of VPA.

Is there a role for the p75 neurotrophin receptor in mediating degeneration during oxidative stress and after hypoxia?

Cholinergic basal forebrain (cBF) neurons are particularly vulnerable to degeneration following trauma and in neurodegenerative conditions. One reason for this is their characteristic expression of the p75 neurotrophin receptor (p75^NTR ), which is up-regulated and mediates neuronal death in a range of neurological and neurodegenerative conditions, including dementia, stroke and ischaemia. The signalling pathway by which p75^NTR signals cell death is incompletely characterised, but typically involves activation by neurotrophic ligands and signalling through c-Jun kinase, resulting in caspase activation via mitochondrial apoptotic signalling pathways. Less well appreciated is the link between conditions of oxidative stress and p75^NTR death signalling. Here, we review the literature describing what is currently known regarding p75^NTR death signalling in environments of oxidative stress and hypoxia to highlight the overlap in signalling pathways and the implications for p75^NTR signalling in cBF neurons. We propose that there is a causal relationship and define key questions to test this assertion.

Small molecule modulation of the p75 neurotrophin receptor inhibits multiple amyloid beta-induced tau pathologies

Longitudinal preclinical and clinical studies suggest that Aβ drives neurite and synapse degeneration through an array of tau-dependent and independent mechanisms. The intracellular signaling networks regulated by the p75 neurotrophin receptor (p75NTR) substantially overlap with those linked to Aβ and to tau. Here we examine the hypothesis that modulation of p75NTR will suppress the generation of multiple potentially pathogenic tau species and related signaling to protect dendritic spines and processes from Aβ-induced injury. In neurons exposed to oligomeric Aβ in vitro and APP mutant mouse models, modulation of p75NTR signaling using the small-molecule LM11A-31 was found to inhibit Aβ-associated degeneration of neurites and spines; and tau phosphorylation, cleavage, oligomerization and missorting. In line with these effects on tau, LM11A-31 inhibited excess activation of Fyn kinase and its targets, tau and NMDA-NR2B, and decreased Rho kinase signaling changes and downstream aberrant cofilin phosphorylation. In vitro studies with pseudohyperphosphorylated tau and constitutively active RhoA revealed that LM11A-31 likely acts principally upstream of tau phosphorylation, and has effects preventing spine loss both up and downstream of RhoA activation. These findings support the hypothesis that modulation of p75NTR signaling inhibits a broad spectrum of Aβ-triggered, tau-related molecular pathology thereby contributing to synaptic resilience.

Emerging roles of the MAGE protein family in stress response pathways

The melanoma antigen (MAGE) proteins all contain a MAGE homology domain. MAGE genes are conserved in all eukaryotes and have expanded from a single gene in lower eukaryotes to ∼40 genes in humans and mice. Whereas some MAGEs are ubiquitously expressed in tissues, others are expressed in only germ cells with aberrant reactivation in multiple cancers. Much of the initial research on MAGEs focused on exploiting their antigenicity and restricted expression pattern to target them with cancer immunotherapy. Beyond their potential clinical application and role in tumorigenesis, recent studies have shown that MAGE proteins regulate diverse cellular and developmental pathways, implicating them in many diseases besides cancer, including lung, renal, and neurodevelopmental disorders. At the molecular level, many MAGEs bind to E3 RING ubiquitin ligases and, thus, regulate their substrate specificity, ligase activity, and subcellular localization. On a broader scale, the MAGE genes likely expanded in eutherian mammals to protect the germline from environmental stress and aid in stress adaptation, and this stress tolerance may explain why many cancers aberrantly express MAGEs Here, we present an updated, comprehensive review on the MAGE family that highlights general characteristics, emphasizes recent comparative studies in mice, and describes the diverse functions exerted by individual MAGEs.

Cellular Prion Protein (PrPc): Putative Interacting Partners and Consequences of the Interaction

Cellular prion protein (PrPc) is a small glycosylphosphatidylinositol (GPI) anchored protein most abundantly found in the outer leaflet of the plasma membrane (PM) in the central nervous system (CNS). PrPc misfolding causes neurodegenerative prion diseases in the CNS. PrPc interacts with a wide range of protein partners because of the intrinsically disordered nature of the protein’s N-terminus. Numerous studies have attempted to decipher the physiological role of the prion protein by searching for proteins which interact with PrPc. Biochemical characteristics and biological functions both appear to be affected by interacting protein partners. The key challenge in identifying a potential interacting partner is to demonstrate that binding to a specific ligand is necessary for cellular physiological function or malfunction. In this review, we have summarized the intracellular and extracellular interacting partners of PrPc and potential consequences of their binding. We also briefly describe prion disease-related mutations at the end of this review.

Small-molecule modulation of the p75 neurotrophin receptor inhibits a wide range of tau molecular pathologies and their sequelae in P301S tauopathy mice

In tauopathies, phosphorylation, acetylation, cleavage and other modifications of tau drive intracellular generation of diverse forms of toxic tau aggregates and associated seeding activity, which have been implicated in subsequent synaptic failure and neurodegeneration. Suppression of this wide range of pathogenic species, seeding and toxicity mechanisms, while preserving the physiological roles of tau, presents a key therapeutic goal. Identification and targeting of signaling networks that influence a broad spectrum of tau pathogenic mechanisms might prevent or reverse synaptic degeneration and modify disease outcomes. The p75 neurotrophin receptor (p75NTR) modulates such networks, including activation of multiple tau kinases, calpain and rhoA-cofilin activity. The orally bioavailable small-molecule p75NTR modulator, LM11A-31, was administered to tauP301S mice for 3 months starting at 6 months of age, when tau pathology was well established. LM11A-31 was found to reduce: excess activation of hippocampal cdk5 and JNK kinases and calpain; excess cofilin phosphorylation, tau phosphorylation, acetylation and cleavage; accumulation of multiple forms of insoluble tau aggregates and filaments; and, microglial activation. Hippocampal extracts from treated mice had substantially reduced tau seeding activity. LM11A-31 treatment also led to a reversal of pyramidal neuron dendritic spine loss, decreased loss of dendritic complexity and improvement in performance of hippocampal behaviors. These studies identify a therapeutically tractable upstream signaling module regulating a wide spectrum of basic mechanisms underlying tauopathies.

Mouse Nerve Growth Factor Facilitates the Growth of Interspinal Schwannoma Cells by Activating NGF Receptors

Objective

Nerve growth factor (NGF) is a member of the neurotrophic factor family and plays a vital role in the physiological processes of organisms, especially in the nervous system. Many recent studies have reported that NGF is also involved in the regulation of tumourigenesis by either promoting or suppressing tumor growth, which depends on the location and type of tumor. However, little is known regarding the effect of NGF on interspinal schwannoma (IS). In the present study, we aimed to explored whether mouse nerve growth factor (mNGF), which is widely used in the clinic, can influence the growth of interspinal schwannoma cells (ISCs) isolated from IS in vitro.

Methods

ISCs were isolated, cultured and identified by S-100 with immunofluorescence analysis. S-100-positive cells were divided into five groups, and separately cultured with various concentrations of mNGF (0 [phosphate buffered saline, PBS], 40, 80, 160, and 320 ng/mL) for 24 hours. Western blot and quantantive real time polymerase chain reaction (PCR) were applied to detect tyrosine kinase A (TrkA) receptor and p75 neurotrophin receptor (p75^NTR) in each group. Crystal violet staining was selected to assess the effect of mNGF (160 ng/mL) on ISCs growth.

Results

ISCs growth was enhanced by mNGF in a dose-dependent manner. The result of crystal violet staining revealed that it was significantly strengthened the cells growth kinetics when cultured with 160 ng/mL mNGF compared to PBS group. Western blot and quantantive real time PCR discovered that TrkA receptor and mRNA expression were both up-regualated under the condition of mNGF, expecially in 160 ng/mL, while the exoression of p75^NTR demonstrated no difference among groups.

Conclusion

From these data, we conclude that exogenous mNGF can facilitate ISC growth by activating both TrkA receptor and p75^NTR. In addition, patients who are suffering from IS should not be administered mNGF in the clinic.

Reversal of Cognitive Impairment in gp120 Transgenic Mice by the Removal of the p75 Neurotrophin Receptor

Activation of the p75 neurotrophin receptor (p75NTR), by the proneurotrophin brain-derived neurotrophic factor (proBDNF), triggers loss of synapses and promotes neuronal death. These pathological features are also caused by the human immunodeficiency virus-1 (HIV) envelope protein gp120, which increases the levels of proBDNF. To establish whether p75NTR plays a role in gp120-mediated neurite pruning, we exposed primary cultures of cortical neurons from p75NTR^–/– mice to gp120. We found that the lack of p75NTR expression significantly reduced gp120-mediated neuronal cell death. To determine whether knocking down p75NTR is neuroprotective in vivo, we intercrossed gp120 transgenic (tg) mice with p75NTR heterozygous mice to obtain gp120tg mice lacking one or two p75NTR alleles. The removal of p75NTR alleles inhibited gp120-mediated decrease of excitatory synapses in the hippocampus, as measured by the levels of PSD95 and subunits of the N-methyl-D-Aspartate receptor in synaptosomes. Moreover, the deletion of only one copy of the p75NTR gene was sufficient to restore the cognitive impairment observed in gp120tg mice. Our data suggest that activation of p75NTR is one of the mechanisms crucial for the neurotoxic effect of gp120. These data indicate that p75NTR antagonists could provide an adjunct therapy against synaptic simplification caused by HIV.

Brain-Derived Neurotrophic Factor (BDNF): Novel Insights into Regulation and Genetic Variation

Since its discovery, brain-derived neurotrophic factor (BDNF) has spawned a literature that now spans 35 years of research. While all neurotrophins share considerable overlap in sequence homology and their processing, BDNF has become the most widely studied neurotrophin because of its broad roles in brain homeostasis, health, and disease. Although research on BDNF has produced thousands of articles, there remain numerous long-standing questions on aspects of BDNF molecular biology and signaling. Here we provide a comprehensive review, including both a historical narrative and a forward-looking perspective on advances in the actions of BDNF within the brain. We specifically review BDNF’s gene structure, peptide composition (including domains, posttranslational modifications and putative motif sites), mechanisms of transport, signaling pathway recruitment, and other recent developments including the functional effects of genetic variation and the discovery of a new BDNF prodomain ligand. This body of knowledge illustrates a highly conserved and complex role for BDNF within the brain, that promotes the idea that the neurotrophin biology of BDNF is diverse and that any disease involvement is likely to be equally multifarious.

The role of TrkA in the promoting wounding-healing effect of CD271 on epidermal stem cells

CD271, a receptor of nerve growth factor (NGF), affects the biological properties of epidermal stem cells (eSCs) which are essential for skin wound closure. Tropomyosin-receptor kinase A (TrkA), another receptor of NGF, combined with CD271 has been involved with nervous system and skin keratinocytes. However, the exact role of TrkA combined with CD271 in eSCs during skin wound closure is still unclear. This study aimed to reveal the role of TrkA in the promoting wounding-healing effect of CD271 on eSCs. We obtained CD271-vo (over-expression of CD271) eSCs by lentiviral infection. K252a was used to inhibit TrkA expression. Full-thickness skin mouse wound closure model (5 mm in diameter) was used to detect the ability of CD271 over-expressed/TrkA-deficient during wound healing. The biological characteristics of eSCs and their proliferation and apoptosis were detected using immunohistochemistry and western blot. The expressions of protein kinase B (pAkt)/Akt, phosphorylated extracellular-signal-related kinase (pERK)/ERK1/2, and c-Jun N-terminal kinase (pJNK)/JNK were also detected by western blot. We found that over-expression of CD271 promoted the biological functions of eSCs. Interestingly, over-expression of CD271 in the absence of TrkA neither promoted eSCs' migration and proliferation nor promoted wound healing in a mouse model. In addition, we observed the reduced expression of pAkt/Akt and pERK/ERK1/2 following TrkA inhibition in vitro. Our studies demonstrated that the role of TrkA in the promoting wounding-healing effect of CD271 on eSCs.

Modulating Neurotrophin Receptor Signaling as a Therapeutic Strategy for Huntington's Disease

Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder caused by CAG repeat expansions in the IT15 gene which encodes the huntingtin (HTT) protein. Currently, no treatments capable of preventing or slowing disease progression exist. Disease modifying therapeutics for HD would be expected to target a comprehensive set of degenerative processes given the diverse mechanisms contributing to HD pathogenesis including neuroinflammation, excitotoxicity, and transcription dysregulation. A major contributor to HD-related degeneration is mutant HTT-induced loss of neurotrophic support. Thus, neurotrophin (NT) receptors have emerged as therapeutic targets in HD. The considerable overlap between NT signaling networks and those dysregulated by mutant HTT provides strong theoretical support for this approach. This review will focus on the contributions of disrupted NT signaling in HD-related neurodegeneration and how targeting NT receptors to augment pro-survival signaling and/or to inhibit degenerative signaling may combat HD pathologies. Therapeutic strategies involving NT delivery, peptidomimetics, and the targeting of specific NT receptors (e.g., Trks or p75^NTR), particularly with small molecule ligands, are discussed.

Subclinical hypothyroidism in pregnant rats impaired learning and memory of their offspring by promoting the p75NTR signal pathway

OBJECTIVE

Maternal hypothyroidism during pregnancy can affect the neurodevelopment of their offspring. This study aimed to investigate the effects of maternal subclinical hypothyroidism (SCH) on spatial learning and memory, and its relationship with the apoptotic factors in cerebral cortex of the offspring.

METHODS

Female adult Wistar rats were randomly divided into three groups (n = 15 per group): control (CON) group, SCH group and overt hypothyroidism (OH) group. Spatial learning and memory in the offspring were evaluated by long-term potentiation (LTP) and Morris water-maze (MWM) test. The protein expression of the p75 neurotrophin receptor (p75^NTR), phospho-c-Jun N-terminal kinase (p-JNK), the pro-apoptotic protein p53 and Bax were detected by Western blotting.

RESULTS

The Pups in the SCH and OH groups showed longer escape latencies in the MWM and decreased field-excitatory post synaptic potentials in LTP tests compared with those in the CON group. p75^NTR, p-JNK, p53 and Bax expression levels in the cerebral cortex increased in pups in the SCH and OH groups compared with those in the CON group.

CONCLUSIONS

Maternal SCH during pregnancy may impair spatial learning and memory in the offspring and may be associated with the increased apoptosis in the cerebral cortex.

Reduced inflammatory factor expression facilitates recovery after sciatic nerve injury in TLR4 mutant mice

Toll-like receptors (TLRs) are extremely significant pattern recognition receptors. When nerve injury occurs, a variety of inflammatory factors are generated, leading to an exceedingly complex micro-environment. TLRs recognize damage-associated molecular patterns. To investigate the correlation between TLR4 and recovery after sciatic nerve injury, the model of sciatic nerve injury was conducted using TLR4-mutated mice (C3H/HeJ) and wild mice (C3H/HeN). Our goal was to identify short-stage and long-stage changes after sciatic nerve injury, mainly by checking the expression changes of inflammation factors in the short-stage and the differences in the recovery of the injured sciatic nerve in the long-stage. The results show that the increase of changes in the HeN group of IL-1β, IL-6, TNF-α and MCP-1 are more obvious than in the HeJ group, with caspase1 expression higher and Nlrp3 expression lower in the former group. Further results reveal intense inflammation occurred in the HeN group showing more neutrophils and macrophages. Nlrp3 and caspase1 showed little difference by Immunohistochemistry, with Nlrp6 expression differing between the HeJ group and the HeN group. The results led us to conclude that better recovery of the injured sciatic nerve occurred in the HeJ group because the expression of GAP-43 and p75NTR was higher and had a better SFI figure. TLR4 mutation can decrease the expression of inflammatory factors and enhance the speed of recovery after sciatic nerve injury. The changes in the expression of Nlrp6, which are related to the TLR4 mutation, may influence recovery of the injured sciatic nerve. Further studies will be conducted to confirm these results.

Generation and characterization of a human oral squamous carcinoma cell line SCC-9 with CRISPR/Cas9-mediated deletion of the p75 neurotrophin receptor

OBJECTIVE

To investigate the importance of the p75 neurotrophin receptor (p75^NTR) in human tongue squamous carcinoma cells, we exploited the CRISPR/Cas9 technology to establish a p75^NTR-knockout SCC-9 cell line and to explore the effect on biological functions.

MATERIALS AND METHODS

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated endonuclease (Cas9) system was used to generate genomic deletion mutants of p75^NTR in the tongue squamous carcinoma cell lines SCC-9. Single-guide RNA (sgRNA) sequences were designed to target the p75^NTR genomic sequence and were cloned into plasmid pGK1.1. The linearized vector was electroporated into SCC-9 cells and p75^NTR deletion was confirmed using Cruiser™ enzyme digestion and PCR amplification. SCC-9 clones with successful deletion of p75^NTR were identified and verified by sequencing and selected for functional testing in cell proliferation, invasion, migration, and colony-forming assays.

RESULTS

Compared with control cells, p75^NTR-knockout SCC-9 cells showed significantly diminished abilities to proliferate, invade, migrate, and form colonies, indicating a reduction in pro-tumorigenic behavior.

CONCLUSION

These data demonstrate, first, that the CRISPR/Cas9 system is a simplified method for generating p75^NTR knockouts with relatively high efficiency, and second, that deletion of p75^NTR suppresses several tumor-promoting properties of SCC-9 cells, suggesting that p75^NTR is a potential target for the development of novel therapies for tongue cancer.

NRAGE induces β-catenin/Arm O-GlcNAcylation and negatively regulates Wnt signaling

The Wnt pathway is crucial for animal development, as well as tumor formation. Understanding the regulation of Wnt signaling will help to elucidate the mechanism of the cell cycle, cell differentiation and tumorigenesis. It is generally accepted that in response to Wnt signals, β-catenin accumulates in the cytoplasm and is imported into the nucleus where it recruits LEF/TCF transcription factors to activate the expression of target genes. In this study, we report that human NRAGE, a neurotrophin receptor p75 (p75NTR) binding protein, markedly suppresses the expression of genes activated by the Wnt pathway. Consistent with this finding, loss of function of NRAGE by RNA interference (RNAi) activates the Wnt pathway. Moreover, NRAGE suppresses the induction of axis duplication by microinjected β-catenin in Xenopus embryos. To our surprise, NRAGE induces nuclear localization of β-catenin and increases its DNA binding ability. Further studies reveal that NRAGE leads to the modification of β-catenin/Arm with O-linked beta-N-acetylglucosamine (O-GlcNAc), and failure of the association between β-catenin/Arm and pygopus(pygo) protein, which is required for transcriptional activation of Wnt target genes. Therefore, our findings suggest a novel mechanism for regulating Wnt signaling.

Prediction of years of life after diagnosis of breast cancer using omics and omic-by-treatment interactions

Breast cancer (BC) is the second most common type of cancer and a major cause of death for women. Commonly, BC patients are assigned to risk groups based on the combination of prognostic and prediction factors (eg, patient age, tumor size, tumor grade, hormone receptor status, etc). Although this approach is able to identify risk groups with different prognosis, patients are highly heterogeneous in their response to treatments. To improve the prediction of BC patients, we extended clinical models (including prognostic and prediction factors with whole-omic data) to integrate omics profiles for gene expression and copy number variants (CNVs). We describe a modeling framework that is able to incorporate clinical risk factors, high-dimensional omics profiles, and interactions between omics and non-omic factors (eg, treatment). We used the proposed modeling framework and data from METABRIC (Molecular Taxonomy of Breast Cancer Consortium) to assess the impact on the accuracy of BC patient survival predictions when omics and omic-by-treatment interactions are being considered. Our analysis shows that omics and omic-by-treatment interactions explain a sizable fraction of the variance on survival time that is not explained by commonly used clinical covariates. The sizable interaction effects observed, together with the increase in prediction accuracy, suggest that whole-omic profiles could be used to improve prognosis prediction among BC patients.

p75 Neurotrophin Receptor in the Skin: Beyond Its Neurotrophic Function

p75 neurotrophin receptor (p75^NTR), also known as CD271, is the low-affinity receptor that, together with the tyrosine kinase receptor tropomyosin-receptor kinase (Trk), mediate neurotrophin (NT) functions. Beside their classic role in skin innervation, NT and their receptors constitute a complex cutaneous network associated with a number of autocrine and paracrine activities. In this context, the role of p75^NTR is becoming more and more important. This review will focus on the intriguing functions of p75^NTR in healthy and diseased skin. First, p75^NTR counterbalances the proliferative and survival activities of its cognate receptor Trk by inducing keratinocyte apoptosis. In addition, p75^NTR identifies an early transit-amplifying (TA) keratinocyte population and plays a critical role in keratinocyte stem cell transition to its progeny as well as in epidermal differentiation. p75^NTR is absent in psoriatic TA cells, thus rendering these cells resistant to apoptosis. On the other hand, p75^NTR infection restores NT-induced apoptosis in psoriatic keratinocytes. Taken together, these results provide evidence for a critical role of p75^NTR in epidermal homeostasis, while its lack may account for the TA defect in psoriasis. While the issue of p75^NTR as a marker of melanoma initiating cells is still to be solved, there is strong evidence that downregulation of this receptor is a precondition to melanoma invasion and metastasis in vitro and in vivo. All in all, this review points to p75^NTR as a major actor in both physiologic and pathologic conditions at the skin level.

p75 neurotrophin receptor: A potential surface marker of tongue squamous cell carcinoma stem cells

The present study detected p75 neurotrophin receptor (p75^NTR) expression in tongue squamous cell carcinoma (TSCC) cell lines, in order to define the biological properties of p75^NTR+ cells and to confirm the use of p75^NTR+ as a surface marker for TSCC stem cells. p75^NTR+ cells were separated from Tca-8113 and CAL-27 TSCC cells by fluorescence-activated cell sorting. Colony formation, MTT and scratch assays, and a tumorigenicity analysis were performed to measure self-renewal and proliferation, multidirectional differentiation, and tumorigenicity of p75^NTR+ cells. p75^NTR+ cells comprised 3.1 and 1.9% of Tca-8113 and CAL-27 cells (mean of three experiments), respectively, and were more able to form colonies compared with non-sorted cells (P<0.01). In addition, the proportion of p75^NTR+ cells generated from monoclonal p75^NTR+ cells decreased to 14.5 (Tca-8113) and 5.8% (CAL-27) of cells within 2 weeks, thus suggesting that p75^NTR+ cells are able to generate p75^NTR+ and p75^NTR− cells. Furthermore, p75^NTR+ cells exhibited increased proliferation, as evidenced by MTT assay (P<0.01) and had greater metastatic ability according to the scratch assay (P<0.01), compared with non-sorted cells. p75^NTR+ cells also exhibited a greater tumorigenic capacity compared with non-sorted cells. In conclusion, p75^NTR+ cells isolated from TSCC cell lines possess the characteristics of cancer stem cells; therefore, p75^NTR may be considered a useful surface marker for the identification of TSCC stem cells.

Implication of the neurotrophin receptor p75NTR in vascular diseases: beyond the eye

INTRODUCTION

The p75 neurotrophin receptor (p75^NTR) is a member of TNF-α receptor superfamily that bind all neurotrophins, mainly regulating their pro-apoptotic actions. Ischemia is a common pathology in different cardiovascular diseases affecting multiple organs, however the contribution of p75^NTR remains not fully addressed. The aim of this work is to review the current evidence through published literature studying the impact of p75^NTR receptor in ischemic vascular diseases.

AREAS COVERED

In the eye, several ischemic ocular diseases are associated with enhanced p75^NTR expression. Ischemic retinopathy including diabetic retinopathy, retinopathy of prematurity and retinal vein occlusion are characterized initially by ischemia followed by excessive neovascularization. Beyond the eye, cerebral ischemia, myocardial infarction and critical limb ischemia are ischemic cardiovascular diseases that are characterized by altered expression of neurotrophins and p75^NTR expression. We surveyed both clinical and experimental studies that examined the impact of p75^NTR receptor in ischemic diseases of eye, heart, brain and peripheral limbs.

EXPERT COMMENTARY

p75^NTR receptor is a major player in multiple ischemic vascular diseases affecting the eye, brain, heart and peripheral limbs with significant increases in its expression accompanying neuro-vascular injury. This has been addressed in the current review along with the beneficial vascular outcomes of p75^NTR inhibition.

Neurotrophin Signaling and Stem Cells-Implications for Neurodegenerative Diseases and Stem Cell Therapy

Neurotrophins (NTs) are members of a neuronal growth factor protein family whose action is mediated by the tropomyosin receptor kinase (TRK) receptor family receptors and the p75 NT receptor (p75NTR), a member of the tumor necrosis factor (TNF) receptor family. Although NTs were first discovered in neurons, recent studies have suggested that NTs and their receptors are expressed in various types of stem cells mediating pivotal signaling events in stem cell biology. The concept of stem cell therapy has already attracted much attention as a potential strategy for the treatment of neurodegenerative diseases (NDs). Strikingly, NTs, proNTs, and their receptors are gaining interest as key regulators of stem cells differentiation, survival, self-renewal, plasticity, and migration. In this review, we elaborate the recent progress in understanding of NTs and their action on various stem cells. First, we provide current knowledge of NTs, proNTs, and their receptor isoforms and signaling pathways. Subsequently, we describe recent advances in the understanding of NT activities in various stem cells and their role in NDs, particularly Alzheimer's disease (AD) and Parkinson's disease (PD). Finally, we compile the implications of NTs and stem cells from a clinical perspective and discuss the challenges with regard to transplantation therapy for treatment of AD and PD.

p75 neurotrophin receptor regulates differential mineralization of rat ectomesenchymal stem cells

OBJECTIVES

The aim of this study was to investigate whether p75NTR (p75 neurotrophin receptor) regulates differential mineralization capacity of rEMSCs (rat ectomesenchymal stem cells) and underlying mechanisms associated with Mage-D1 (melanoma-associated antigens-D1).

MATERIALS AND METHODS

Immunohistochemical staining of p75NTR in developing tooth germs was performed on E12.5d (embryonic 12.5 days) and E19.5d (embryonic 19.5 days). E12.5d EMSCs and E19.5d EMSCs were isolated in the same pregnant Sprague-Dawley rats from embryonic maxillofacial processes and tooth germs. p75NTR small-interfering RNA, p75NTR overexpression plasmid, Mage-D1 small-interfering RNA and recombined rat NGF were used to transfect cells.

RESULTS

p75NTR was expressed in epithelial-mesenchymal interaction areas at E12.5d and E19.5d tooth germ development stages. E19.5d EMSCs had higher p75NTR expression levels and differential mineralization capacity but lower levels of cell proliferation. Under induction by mineralized culture medium, the potential of differential mineralization had identical trends in regulation of p75NTR in EMSCs; Mage-D1 did not fluctuate and TrkA was not expressed. Binding of p75NTR and Mage-D1 were detected. Mage-D1 knockdown significantly down-regulated expression of related genes, which NGF could not rescue.

CONCLUSION

p75NTR participated in tooth germ development stages and mediated differential mineralization of EMSCs. p75NTR played a critical role in regulating the potential of differential mineralization of EMSCs. Mage-D1 seemed to act as a bridge in the underlying mechanism of effects of p75NTR.

MAGED1 is a novel regulator of a select subset of bHLH PAS transcription factors

Transcription factors of the basic helix-loop-helix (bHLH) PER-ARNT-SIM (PAS) family generally have critical and nonredundant biological roles, but some bHLH PAS proteins compete for common cofactors or recognise similar DNA elements. Identifying factors that regulate function of bHLH PAS proteins, particularly in cells where multiple family members are coexpressed, is important for understanding bHLH PAS factor biology. This study identifies and characterises a novel interaction between melanoma-associated antigen D1 (MAGED1) and select members of the bHLH PAS transcription factor family. MAGED1 binds and positively regulates the transcriptional activity of family members SIM1, SIM2, NPAS4 and ARNT2, but does not interact with AhR, HIF1α and ARNT. This interaction is mediated by PAS repeat regions which also form the interface for bHLH PAS dimerisation, and accordingly MAGED1 is not found in complex with bHLH PAS dimers. We show that MAGED1 does not affect bHLH PAS protein levels and cannot be acting as a coactivator of transcriptionally active heterodimers, but rather appears to interact with nascent bHLH PAS proteins in the cytoplasm to enhance their function prior to nuclear import. As a selective regulator, MAGED1 may play an important role in the biology of these specific factors and in general bHLH PAS protein dynamics.

The effects of short-term JNK inhibition on the survival and growth of aged sympathetic neurons

During the course of normal aging, certain populations of nerve growth factor (NGF)-responsive neurons become selectively vulnerable to cell death. Studies using dissociated neurons isolated from neonates have shown that c-Jun N-terminal kinases (JNKs) are important in regulating the survival and neurite outgrowth of NGF-responsive sympathetic neurons. Unlike neonatal neurons, adult sympathetic neurons are not dependent on NGF for their survival. Moreover, the NGF precursor, proNGF, is neurotoxic for aging but not young adult NGF-responsive neurons. Because of these age-related differences, the effects of JNK inhibition on the survival and growth of sympathetic neurons isolated from aged mice were studied. Aged neurons, as well as glia, were found to be dependent on JNK for their growth but not their survival. Conversely, proNGF neurotoxicity was JNK-dependent and mediated by the p75-interacting protein NRAGE, whereas neurite outgrowth was independent of NRAGE. These results have implications for the potential use of JNK inhibitors as therapies for ameliorating age-related neurodegenerative disease.

Complex roles of NRAGE on tumor

NRAGE, also known as Dlxin-1or MAGE-D1, is a member of type II melanoma-associated antigen (MAGE) and plays an essential role in life activities, including differentiation, apoptosis, and cell cycle. Studies increasingly found that NRAGE is closely related to the tumor events, such as tumor occurrence, invasion, and metastasis. However, complex and contradictory functions of NRAGE in different circumstances are observed, suggesting that NRAGE is unique from other MAGE gene family members. This review summarizes recent findings concerning the structure and biological functions of NRAGE, which may provide a basis for a more comprehensive understanding of and further research on NRAGE.

p75NTR-dependent Rac1 activation requires receptor cleavage and activation of an NRAGE and NEDD9 signaling cascade

The p75 neurotrophin receptor (p75NTR, also known as tumor necrosis factor receptor superfamily member 16) is implicated in diverse cellular events, but fundamental aspects of its signaling mechanisms remain unclear. To address this, we have established a novel bioassay to characterize signaling cascades activated by p75NTR. We show that in COS7 cells, p75NTR expression causes a large increase in cell surface area that relies on the activation of Rac1, and we demonstrate that the p75NTR-dependent COS7 phenotype is dependent on ADAM17- and c-secretase-dependent cleavage of p75NTR and generation of the p75NTR intracellular domain (p75NTRICD). We show that the p75NTR adaptor protein NRAGE (also known as MAGED1) acts downstream of the p75NTRICD in this cascade and, through a yeast two-hybrid screen, identify NEDD9, a Cas family adaptor protein, as a novel NRAGE-binding partner that mediates p75NTR-dependent Rac1 activation and cell spreading. Our results demonstrate a crucial role for p75NTR cleavage in small GTPase activation and define a novel Rac1 activation pathway involving the p75NTRICD, NRAGE andNEDD9.

Genetic and pharmacological intervention of the p75NTR pathway alters morphological and behavioural recovery following traumatic brain injury in mice

PRIMARY OBJECTIVE

Neurotrophin levels are elevated after TBI, yet there is minimal regeneration. It was hypothesized that the pro-neurotrophin/p75NTR pathway is induced more than the mature neurotrophin/Trk pathway and that interfering with p75 signalling improves recovery following TBI.

RESEARCH DESIGN

Lateral Fluid Percussion (LFP) injury was performed on wildtype and p75 mutant mice. In addition, TrkB agonist 7,8 Dihydroxyflavone or p75 antagonist TAT-Pep5 were tested. Western blot and immunohistochemistry revealed biochemical and cellular changes. Morris Water Maze and Rotarod tests demonstrated cognitive and vestibulomotor function.

MAIN OUTCOMES AND RESULTS

p75 was up-regulated and TrkB was down-regulated 1 day post-LFP. p75 mutant mice as well as mice treated with the p75 antagonist or the TrkB agonist exhibited reduced neuronal death and degeneration and less astrocytosis. The cells undergoing apoptosis appear to be neurons rather than glia. There was improved motor function and spatial learning in p75 mutant mice and mice treated with the p75 antagonist.

CONCLUSIONS

Many of the pathological and behavioural consequences of TBI might be due to activation of the pro-neurotrophin/p75 toxic pathway overriding the protective mechanisms of the mature neurotrophin/Trk pathway. Targeting p75 can be a novel strategy to counteract the damaging effects of TBI.

MAGED1 is a negative regulator of bone remodeling in mice

Melanoma antigen family D1 (MAGED1), an important adaptor protein, has been shown to ubiquitously express and play critical roles in many aspects of cellular events and physiological functions. However, its role in bone remodeling remains unknown. We, therefore, analyzed the bone phenotype of Maged1-deficient mice. Maged1-deficient mice displayed a significant osteoporotic phenotype with a marked decrease in bone density and deterioration of trabecular architecture. Histomorphometric analysis demonstrated an increased mineral apposition rate as well as increased osteoclast number and surface in Maged1 knockout mice. At the cellular level, Maged1-deficient osteoblasts exhibited an increased proliferation rate and accelerated differentiation. MAGED1 deficiency also caused a promotion in osteoclastogenesis, and that was attributed to the cell autonomous acceleration of differentiation in osteoclasts and an increased receptor activator of NF-κB ligand/osteoprotegerin ratio, a major index of osteoclastogenesis, in osteoblasts. Thus, we identified MAGED1 as a novel regulator of osteoblastogenesis, osteoclastogenesis, and bone remodeling in a mouse model.

Anti-parkinsonian effects of octacosanol in 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine-treated mice

Our previous research showed that octacosanol exerted its protective effects in 6-hydroxydopamine-induced Parkinsonian rats. The goal of this study was to investigate whether octacosanol would attenuate neurotoxicity in 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP)-treated C57BL/6N mice and its potential mechanism. Behavioral tests, tyrosine hydroxylase immunohistochemistry and western blot were used to investigate the effects of octacosanol in a mouse model of Parkinson's disease. Oral administration of octacosanol (100 mg/kg) significantly improved behavioral impairments in mice treated by MPTP and markedly ameliorated morphological appearances of tyrosine hydroxylase-positive neuronal cells in the substantia nigra. Furthermore, octacosanol blocked MPTP-induced phosphorylation of p38MAPK and JNK, but not ERK1/2. These findings implicated that the protective effects afforded by octacosanol might be mediated by blocking the phosphorylation of p38MAPK and JNK on the signal transduction in vivo. Considering its excellent tolerability, octacosanol might be considered as a candidate agent for clinical application in treating Parkinson's disease.

Modulation of p75 neurotrophin receptor under hypoxic conditions induces migration and invasion of C6 glioma cells

p75 neurotrophin receptor (p75NTR) has been reported to play important roles in various cancer types. However, the exact mechanism of tumorigenesis involving p75NTR is unknown. In this study, we investigated the relationship between the expression of p75NTR in malignant glioma and the impact on tumor cell migration and invasion. p75NTR and hypoxia-inducible factor-1α (HIF-1α) expression was down-regulated by short-hairpin RNA and up-regulated with expression vectors. By immunohistochemical staining and Western blot analysis, we found that p75NTR was expressed in both human and rat malignant gliomas. Knockdown of p75NTR increased the expression of vimentin, vascular endothelial growth factor, Matrix metalloproteinase 9, and TWIST, and enhanced the invasion and migration abilities assessed by transwell assay in the C6 tumor cells. Inverse expressions of p75NTR and HIF-1α were detected in glioma cell lines under hypoxic conditions, while increased HIF-1α significantly downregulated the expression of p75NTR, suggesting a HIF-1α-p75NTR-EMT pathway that may regulate glioma cells invasion and migration. Downregulation of p75NTR increased phosphorylation of Src, focal adhesion kinase (FAK) and paxillin. Knockdown of p75NTR also dysregulated β-catenin-mediated cell junctions, and up-regulated the expressions of fibronectin and L1CAM in the cell-cell junctions, thus suggesting that p75NTR knockdown contributed to a more aggressive migration phenotype via FAK signaling pathway. Our studies suggested that modulation of p75NTR under hypoxic condition could enhance C6 cells migration and invasion by induction of EMT, and activation of the FAK pathway. The HIF-1α-p75NTR-EMT axis may play a central role in glioma tumorigenesis.

VGF (TLQP-62)-induced neurogenesis targets early phase neural progenitor cells in the adult hippocampus and requires glutamate and BDNF signaling

The neuropeptide VGF (non-acronymic), which has antidepressant-like effects, enhances adult hippocampal neurogenesis as well as synaptic activity and plasticity in the hippocampus, however the interaction between these processes and the mechanism underlying this regulation remain unclear. In this study, we demonstrate that VGF-derived peptide TLQP-62 specifically enhances the generation of early progenitor cells in nestin-GFP mice. Specifically, TLQP-62 significantly increases the number of Type 2a neural progenitor cells (NPCs) while reducing the number of more differentiated Type 3 cells. The effect of TLQP-62 on proliferation rather than differentiation was confirmed using NPCs in vitro; TLQP-62 but not scrambled peptide PEHN-62 increases proliferation in a cell line as well as in primary progenitors from adult hippocampus. Moreover, TLQP-62 but not scrambled peptide increases Cyclin D mRNA expression. The proliferation of NPCs induced by TLQP-62 requires synaptic activity, in particular through NMDA and metabotropic glutamate receptors. The activation of glutamate receptors by TLQP-62 activation induces phosphorylation of CaMKII through NMDA receptors and protein kinase D through metabotropic glutamate receptor 5 (mGluR5). Furthermore, pharmacological antagonists to CaMKII and PKD inhibit TLQP-62-induced proliferation of NPCs indicating that these signaling molecules downstream of glutamate receptors are essential for the actions of TLQP-62 on neurogenesis. We also show that TLQP-62 gradually activates Brain-Derived Neurotrophic Factor (BDNF)-receptor TrkB in vitro and that Trk signaling is required for TLQP-62-induced proliferation of NPCs. Understanding the precise molecular mechanism of how TLQP-62 influences neurogenesis may reveal mechanisms by which VGF-derived peptides act as antidepressant-like agents.

Genomic imprinting in development, growth, behavior and stem cells

Genes that are subject to genomic imprinting in mammals are preferentially expressed from a single parental allele. This imprinted expression of a small number of genes is crucial for normal development, as these genes often directly regulate fetal growth. Recent work has also demonstrated intricate roles for imprinted genes in the brain, with important consequences on behavior and neuronal function. Finally, new studies have revealed the importance of proper expression of specific imprinted genes in induced pluripotent stem cells and in adult stem cells. As we review here, these findings highlight the complex nature and developmental importance of imprinted genes.

NRAGE promotes cell proliferation by stabilizing PCNA in a ubiquitin-proteasome pathway in esophageal carcinomas

Neurotrophin receptor-interacting melanoma antigen-encoding gene homolog (NRAGE) is generally recognized as a tumor suppressor as it induces cell apoptosis and suppresses cell metastasis. However, it has recently been reported that NRAGE is overexpressed in lung cancer, melanoma and colon cancer, implicating a complicated role of NRAGE as we have expected. In the study, we aim to elucidate the functional roles and molecular mechanisms of NRAGE in esophageal carcinoma. We found that both NRAGE mRNA and protein were significantly overexpressed in esophageal tumor tissues. Consistently, both in vivo and in vitro analyses demonstrated that knockdown of NRAGE apparently inhibited cell growth, and cell cycle analysis further demonstrated that NRAGE knockdown cells were mainly arrested in G2M cell phase, accompanied with an apparent reduction of S phase. In the process of exploring molecular mechanisms, we found that either knockdown in vitro or knockout in vivo of NRAGE reduced proliferating cell nuclear antigen (PCNA) protein, expression of which could completely rescue the inhibited proliferation in NRAGE defective cells. Furthermore, NRAGE physically interacted with PCNA in esophageal cancer cells through DNA polymerase III subunit, and knockdown of NRAGE facilitated PCNA K48-linked polyubiquitination, leading PCNA to the proteasome-dependent degradation and a ubiquitin-specific protease USP10 was identified to be a key regulator in the process of K48 polyubiquitination in NRAGE-deleted cells. In conclusion, our study highlights a unique role of NRAGE and implies that NRAGE is likely to be an attractive oncotarget in developing novel genetic anticancer therapeutic strategies for esophageal squamous cell carcinomas.

Maged1 co-interacting with CREB through a hexapeptide repeat domain regulates learning and memory in mice

Maged1 is a member of the type II melanoma antigen (MAGE) family of proteins, which is highly conserved in the brain between mouse and human. Recently, Maged1 has been reported to be involved in depression and impaired sexual behavior. However, the role of Maged1 in learning and memory remains unknown. The aim of the present study was therefore to investigate whether Maged1 deficiency can impair learning and memory formation. By behavioral tests and electrophysiological recording, we observed that 5-6-month-old Maged1 knockout mice displayed the reduced basal synaptic transmission, pronounced hippocampal dysfunction, impaired spatial learning, and a deficit in long-term potentiation induction. Data from immunohistochemical and Western blot showed the reduced dendritic spine density and the number of synapses in the hippocampus of the Maged1 knockout mice, and Maged1 deficiency prevented the interaction of Maged1 with cAMP response element-binding protein (CREB). Furthermore, by chromatin immunoprecipitation and luciferase assay, we observed the downregulated activity of CREB and the suppressed CREB-dependent transcription after deficiency of Maged1, which lead to the decreased levels of brain-derived neurotrophic factor. Taken together, our results provide the evidence that Maged1 is involved in synaptic transmission and hippocampus-dependent learning and memory formation.

Arrestins in apoptosis

Programmed cell death (apoptosis) is a coordinated set of events eventually leading to the massive activation of specialized proteases (caspases) that cleave numerous substrates, orchestrating fairly uniform biochemical changes than culminate in cellular suicide. Apoptosis can be triggered by a variety of stimuli, from external signals or growth factor withdrawal to intracellular conditions, such as DNA damage or ER stress. Arrestins regulate many signaling cascades involved in life-or-death decisions in the cell, so it is hardly surprising that numerous reports document the effects of ubiquitous nonvisual arrestins on apoptosis under various conditions. Although these findings hardly constitute a coherent picture, with the same arrestin subtypes, sometimes via the same signaling pathways, reported to promote or inhibit cell death, this might reflect real differences in pro- and antiapoptotic signaling in different cells under a variety of conditions. Recent finding suggests that one of the nonvisual subtypes, arrestin-2, is specifically cleaved by caspases. Generated fragment actively participates in the core mechanism of apoptosis: it assists another product of caspase activity, tBID, in releasing cytochrome C from mitochondria. This is the point of no return in committing vertebrate cells to death, and the aspartate where caspases cleave arrestin-2 is evolutionary conserved in vertebrate, but not in invertebrate arrestins. In contrast to wild-type arrestin-2, its caspase-resistant mutant does not facilitate cell death.

The biological functions and signaling mechanisms of the p75 neurotrophin receptor

The p75 neurotrophin receptor (p75(NTR)) regulates a wide range of cellular functions, including programmed cell death, axonal growth and degeneration, cell proliferation, myelination, and synaptic plasticity. The multiplicity of cellular functions governed by the receptor arises from the variety of ligands and co-receptors which associate with p75(NTR) and regulate its signaling. P75(NTR) promotes survival through interactions with Trk receptors, inhibits axonal regeneration via partnerships with Nogo receptor (Nogo-R) and Lingo-1, and promotes apoptosis through association with Sortilin. Signals downstream of these interactions are further modulated through regulated intramembrane proteolysis (RIP) of p75(NTR) and by interactions with numerous cytosolic partners. In this chapter, we discuss the intricate signaling mechanisms of p75(NTR), emphasizing how these signals are differentially regulated to mediate these diverse cellular functions.

Neurotrophins in the regulation of cellular survival and death

The neurotrophins play crucial roles regulating survival and apoptosis in the developing and injured nervous system. The four neurotrophins exert profound and crucial survival effects on developing peripheral neurons, and their expression and action is intimately tied to successful innervation of peripheral targets. In the central nervous system, they are dispensable for neuronal survival during development but support neuronal survival after lesion or other forms of injury. Neurotrophins also regulate apoptosis of both peripheral and central neurons, and we now recognize that there are regulatory advantages to having the same molecules regulate life and death decisions. This chapter examines the biological contexts in which these events take place and highlights the specific ligands, receptors, and signaling mechanisms that allow them to occur.

The ubiquitin ligase Praja1 reduces NRAGE expression and inhibits neuronal differentiation of PC12 cells

Evidence suggests that regulated ubiquitination of proteins plays a critical role in the development and plasticity of the central nervous system. We have previously identified the ubiquitin ligase Praja1 as a gene product induced during fear memory consolidation. However, the neuronal function of this enzyme still needs to be clarified. Here, we investigate its involvement in the nerve growth factor (NGF)-induced differentiation of rat pheochromocytoma (PC12) cells. Praja1 co-localizes with cytoskeleton components and the neurotrophin receptor interacting MAGE homologue (NRAGE). We observed an enhanced expression of Praja1 after 3 days of NGF treatment and a suppression of neurite formation upon Praja1 overexpression in stably transfected PC12 cell lines, which was associated with a proteasome-dependent reduction of NRAGE levels. Our data suggest that Praja1, through ubiquitination and degradation of NRAGE, inhibits neuronal differentiation. The two murine isoforms, Praja1.1 and Praja1.2, appear to be functionally homologous in this respect.