Genomic structure and functional characterisation of the promoters of human and mouse nogo/rtn4

6-Methyl flavone inhibits Nogo-B expression and improves high fructose diet-induced liver injury in mice

Excessive fructose consumption increases hepatic de novo lipogenesis, resulting in cellular stress, inflammation and liver injury. Nogo-B is a resident protein of the endoplasmic reticulum that regulates its structure and function. Hepatic Nogo-B is a key protein in glycolipid metabolism, and inhibition of Nogo-B has protective effects against metabolic syndrome, thus small molecules that inhibit Nogo-B have therapeutic benefits for glycolipid metabolism disorders. In this study we tested 14 flavones/isoflavones in hepatocytes using dual luciferase reporter system based on the Nogo-B transcriptional response system, and found that 6-methyl flavone (6-MF) exerted the strongest inhibition on Nogo-B expression in hepatocytes with an IC50 value of 15.85 μM. Administration of 6-MF (50 mg· kg-1 ·d-1, i.g. for 3 weeks) significantly improved insulin resistance along with ameliorated liver injury and hypertriglyceridemia in high fructose diet-fed mice. In HepG2 cells cultured in a media containing an FA-fructose mixture, 6-MF (15 μM) significantly inhibited lipid synthesis, oxidative stress and inflammatory responses. Furthermore, we revealed that 6-MF inhibited Nogo-B/ChREBP-mediated fatty acid synthesis and reduced lipid accumulation in hepatocytes by restoring cellular autophagy and promoting fatty acid oxidation via the AMPKα-mTOR pathway. Thus, 6-MF may serve as a potential Nogo-B inhibitor to treat metabolic syndrome caused by glycolipid metabolism dysregulation.

The Reticulon-4 3-bp Deletion/Insertion Polymorphism Is Associated with Structural mRNA Changes and the Risk of Breast Cancer: A Population-Based Case-Control Study with Bioinformatics Analysis

Breast cancer (BC) is a complex disease caused by molecular events that disrupt cellular survival and death. Discovering novel biomarkers is still required to better understand and treat BC. The reticulon-4 (RTN4) gene, encoding Nogo proteins, plays a critical role in apoptosis and cancer development, with genetic variations affecting its function. We investigated the rs34917480 in RTN4 and its association with BC risk in an Iranian population sample. We also predicted the rs34917480 effect on RTN4 mRNA structure and explored the RTN4's protein-protein interaction network (PPIN) and related pathways. In this case-control study, 437 women (212 BC and 225 healthy) were recruited. The rs34917480 was genotyped using AS-PCR, mRNA secondary structure was predicted with RNAfold, and PPIN was constructed using the STRING database. Our findings revealed that this variant was associated with a decreased risk of BC in heterozygous (p = 0.012), dominant (p = 0.015), over-dominant (p = 0.017), and allelic (p = 0.035) models. Our prediction model showed that this variant could modify RTN4's mRNA thermodynamics and potentially its translation. RTN4's PPIN also revealed a strong association with apoptosis regulation and key signaling pathways highly implicated in BC. Consequently, our findings, for the first time, demonstrate that rs34917480 could be a protective factor against BC in our cohort, probably via preceding mechanisms.

Inhibition of miR-29b-1-5p Attenuates Inflammatory Response and Pulmonary Fibrosis in LPS-Induced Acute Lung Injury by Regulating RTN4 Expression

Objective

Acute lung injury (ALI) is a severe respiratory disorder causing alveolar-capillary barrier, leading to a high rate of morbidity and death in critically ill individuals. microRNAs (miRNAs)-mediated mechanism in the pathogenesis of ALI has attracted much interest. Herein, we attempt to characterize a candidate miRNA and its downstream target that is linked to the pathogenesis of ALI.

Methods

LPS-conditioned MH-S cells were treated with miR-29a-1-5p mimic, inhibitor, and RNT4 expression vector, and the ALI animal model was injected with agomir and antagomir of miR-29b-1-5p and RNT4 expression vector, in which the pro-inflammatory cytokine production, cell viability and apoptosis, myeloperoxidase (MPO) activity, wet/dry (W/D) ratio, and expression of TGF-β1, α-smooth muscle actin (α-SMA), E-cadherin, and vimentin were examined. miR-29a-1-5p inhibition of RTN4 translation was confirmed by luciferase activity assays.

Results

An elevated miR-29a-1-5p expression was demonstrated in LPS-conditioned MH-S cells. miR-29a-1-5p inhibitor transfection attenuated the production of pro-inflammatory cytokines and MH-S cell viability but enhanced the apoptosis. miR-29a-1-5p inhibition of RTN4 translation was demonstrated in the setting of LPS-induced ALI. LPS-induced murine models demonstrated upregulated miR-29a-1-5p. Intravenous injection of miR-29b-1-5p agomir attenuated mouse lung injury and pulmonary fibrosis. RTN4 overexpression resisting to miR-29a-1-5p overexpression was demonstrated in LPS-induced murine models.

Conclusion

The findings obtained from the study that disturbing the action of miR-29a-1-5p may be a novel therapeutic strategy for preventing ALI.

miR-182-5p Regulates Nogo-A Expression and Promotes Neurite Outgrowth of Hippocampal Neurons In Vitro

Nogo-A protein is a key myelin-associated inhibitor of axonal growth, regeneration, and plasticity in the central nervous system (CNS). Regulation of the Nogo-A/NgR1 pathway facilitates functional recovery and neural repair after spinal cord trauma and ischemic stroke. MicroRNAs are described as effective tools for the regulation of important processes in the CNS, such as neuronal differentiation, neuritogenesis, and plasticity. Our results show that miR-182-5p mimic specifically downregulates the expression of the luciferase reporter gene fused to the mouse Nogo-A 3′UTR, and Nogo-A protein expression in Neuro-2a and C6 cells. Finally, we observed that when rat primary hippocampal neurons are co-cultured with C6 cells transfected with miR-182-5p mimic, there is a promotion of the outgrowth of neuronal neurites in length. From all these data, we suggest that miR-182-5p may be a potential therapeutic tool for the promotion of axonal regeneration in different diseases of the CNS.

Silencing Nogo-B improves the integrity of blood-retinal barrier in diabetic retinopathy via regulating Src, PI3K/Akt and ERK pathways

OBJECTIVE

To examine the mechanisms of Nogo-B (RTN4B) in the protection of blood-retinal barrier in experimental diabetic retinopathy.

METHODS

The level of Nogo-B in vitreous and plasma samples was detected with ELISA. Diabetes was induced in Sprague-Dawley rats with intraperitoneal injection of streptozotocin. The rats were injected intravitreally with adeno-associated virus (AAV) for knockdown the expression of Nogo-B in retina or/and as AAV negative control. The permeability of blood-retinal barrier was detected with Rhodamine-B-dextran leakage assay. The expressions of Nogo-B, junctional proteins, inflammatory factors and signaling pathways were examined with Western blot and quantitative real-time PCR.

RESULTS

Nogo-B expression was significantly upregulated in clinical samples and experimental diabetic rat models. Under normal condition, Nogo-B knockdown resulted in the increased permeability of retinal blood vessels. In diabetic rat retinas, the vascular leakage was increased significantly, which was partially decreased by Nogo-B knockdown through increasing p/t-Src (Tyr529) and p/t-Akt (Ser473), and decreasing p/t-ERK1/2.

CONCLUSION

Nogo-B was increased in diabetic retinopathy and silencing Nogo-B is a promising therapy for diabetic retinopathy.

Genomic analysis unveils mechanisms of northward invasion and signatures of plateau adaptation in the Asian house rat

The Asian house rat (AHR), Rattus tanezumi, has recently invaded the northern half of China. The AHR is a highly adaptive rat species that has also successfully conquered the Qinghai-Tibet Plateau (QTP) and replaced the brown rat (BR), R. norvegicus, at the edge of the QTP. Here, we assembled a draft genome of the AHR and explored the mechanisms of its northward invasion and the genetic basis underlying plateau adaptation in this species. Population genomic analyses revealed that the northwardly invasive AHRs consisted of two independent and genetically distinct populations which might result from multiple independent primary invasion events. One invasive population exhibited reduced genetic diversity and distinct population structure compared with its source population, while the other displayed preserved genetic polymorphisms and little genetic differentiation from its source population. Genes involved in G-protein coupled receptors and carbohydrate metabolism may contribute to the local adaptation of northern AHRs. In particular, RTN4 was identified as a key gene for AHRs in the QTP that favours adaptation to high-altitude hypoxia. Coincidently, the physiological performance and transcriptome profiles of hypoxia-exposed rats both showed better hypoxia adaptation in AHRs than in BRs that failed to colonize the heart of the QTP, which may have facilitated the replacement of the BR population by the invading AHRs at the edge of the QTP. This study provides profound insights into the multiple origins of the northwardly invasive AHR and the great tolerance to hypoxia in this species.

Nogo-A Modulates the Synaptic Excitation of Hippocampal Neurons in a Ca2+-Dependent Manner

A tight regulation of the balance between inhibitory and excitatory synaptic transmission is a prerequisite for synaptic plasticity in neuronal networks. In this context, the neurite growth inhibitor membrane protein Nogo-A modulates synaptic plasticity, strength, and neurotransmitter receptor dynamics. However, the molecular mechanisms underlying these actions are unknown. We show that Nogo-A loss-of-function in primary mouse hippocampal cultures by application of a function-blocking antibody leads to higher excitation following a decrease in GABA_ARs at inhibitory and an increase in the GluA1, but not GluA2 AMPAR subunit at excitatory synapses. This unbalanced regulation of AMPAR subunits results in the incorporation of Ca²⁺-permeable GluA2-lacking AMPARs and increased intracellular Ca²⁺ levels due to a higher Ca²⁺ influx without affecting its release from the internal stores. Increased neuronal activation upon Nogo-A loss-of-function prompts the phosphorylation of the transcription factor CREB and the expression of c-Fos. These results contribute to the understanding of the molecular mechanisms underlying the regulation of the excitation/inhibition balance and thereby of plasticity in the brain.

Morphological Heterogeneity of the Endoplasmic Reticulum within Neurons and Its Implications in Neurodegeneration

The endoplasmic reticulum (ER) is a multipurpose organelle comprising dynamic structural subdomains, such as ER sheets and tubules, serving to maintain protein, calcium, and lipid homeostasis. In neurons, the single ER is compartmentalized with a careful segregation of the structural subdomains in somatic and neurite (axodendritic) regions. The distribution and arrangement of these ER subdomains varies between different neuronal types. Mutations in ER membrane shaping proteins and morphological changes in the ER are associated with various neurodegenerative diseases implying significance of ER morphology in maintaining neuronal integrity. Specific neurons, such as the highly arborized dopaminergic neurons, are prone to stress and neurodegeneration. Differences in morphology and functionality of ER between the neurons may account for their varied sensitivity to stress and neurodegenerative changes. In this review, we explore the neuronal ER and discuss its distinct morphological attributes and specific functions. We hypothesize that morphological heterogeneity of the ER in neurons is an important factor that accounts for their selective susceptibility to neurodegeneration.

Artesunate Regulates Neurite Outgrowth Inhibitor Protein B Receptor to Overcome Resistance to Sorafenib in Hepatocellular Carcinoma Cells

The multireceptor tyrosine kinase inhibitor sorafenib is a Food and Drug Administration-approved first-line drug for the treatment of advanced liver cancer that can reportedly extend overall survival in patients with advanced hepatocellular carcinoma (HCC). Primary and acquired resistance to sorafenib are gradually increasing however, leading to failure of HCC treatment with sorafenib. It is therefore crucial to study the potential mechanism of sorafenib resistance. The results of the current study indicate that neurite outgrowth inhibitor protein B receptor (NgBR) is overexpressed in cultured sorafenib-resistant cells, and that its expression is negatively correlated with the sensitivity of liver cancer cells to sorafenib. Artesunate can inhibit the expression of NgBR, and it may block sorafenib resistance. Herein we report that sorafenib treatment in combination with artesunate overcomes HCC resistance to sorafenib alone in a cell culture model.

Reduced Nogo expression inhibits diet-induced metabolic disorders by regulating ChREBP and insulin activity

BACKGROUND & AIMS

Chronic overconsumption of a high-carbohydrate diet leads to steatosis and its associated metabolic disorder and, eventually, to non-alcoholic fatty liver disease. Carbohydrate-responsive element binding protein (ChREBP) and insulin regulate de novo lipogenesis from glucose. Herein, we studied the effect of reticulon-4 (Nogo) expression on diet-induced metabolic disorders in mice.

METHODS

Nogo-deficient (Nogo^-/-) and littermate control [wild-type (WT)] mice were fed a high-glucose or high-fructose diet (HGD/HFrD) to induce metabolic disorders. The effects of Nogo small interfering (si) RNA (siRNA) on HFrD-induced metabolic disorders were investigated in C57BL/6J mice.

RESULTS

HGD/HFrD induced steatosis and its associated metabolic disorders in WT mice by activating ChREBP and impairing insulin sensitivity. They also activated Nogo-B expression, which in turn inhibited insulin activity. In response to HGD/HFrD feeding, Nogo deficiency enhanced insulin sensitivity and energy metabolism to reduce the expression of ChREBP and lipogenic molecules, activated AMP-activated catalytic subunit α, peroxisome proliferator activated receptor α and fibroblast growth factor 21, and reduced endoplasmic reticulum (ER) stress and inflammation, thereby blocking HGD/HFrD-induced hepatic lipid accumulation, insulin resistance and other metabolic disorders. Injection of Nogo siRNA protected C57BL/6J mice against HFrD-induced metabolic disorders by ameliorating insulin sensitivity, ChREBP activity, ER stress and inflammation.

CONCLUSIONS

Our study identified Nogo as an important mediator of insulin sensitivity and ChREBP activity. Reduction of Nogo expression is a potential strategy for the treatment of high-carbohydrate diet-induced metabolic complications.

LAY SUMMARY

Nogo deficiency blocks high-carbohydrate diet-induced glucose intolerance and insulin resistance, while increasing glucose/lipid utilisation and energy expenditure. Thus, reduction of Nogo expression protects against high-carbohydrate diet-induced body-weight gain, hepatic lipid accumulation and the associated metabolic disorders, indicating that approaches inhibiting Nogo expression can be applied for the treatment of diseases associated with metabolic disorders.

Identification of a new functional domain of Nogo-A that promotes inflammatory pain and inhibits neurite growth through binding to NgR1

Nogo-A is a key inhibitory molecule to axon regeneration, and plays diverse roles in other pathological conditions, such as stroke, schizophrenia, and neurodegenerative diseases. Nogo-66 and Nogo-Δ20 fragments are two known functional domains of Nogo-A, which act through the Nogo-66 receptor (NgR1) and sphingosine-1-phosphate receptor 2 (S1PR2), respectively. Here, we reported a new functional domain of Nogo-A, Nogo-A aa 846-861, was identified in the Nogo-A-specific segment that promotes complete Freund's adjuvant (CFA)-induced inflammatory pain. Intrathecal injection of its antagonist peptide 846-861PE or the specific antibody attenuated the CFA-induced inflammatory heat hyperalgesia. The 846-861 PE reduced the content of transient receptor potential vanilloid subfamily member 1 (TRPV1) in dorsal root ganglia (DRG) and decreased the response of DRG neurons to capsaicin. These effects were accompanied by a reduction in LIMK/cofilin phosphorylation and actin polymerization. GST pull-down and fluorescence resonance energy transfer (FRET) assays both showed that Nogo-A aa 846-861 bound to NgR1. Moreover, we demonstrated that Nogo-A aa 846-861 inhibited neurite outgrowth from cortical neurons and DRG explants. We concluded that Nogo-A aa 846-861 is a novel ligand of NgR1, which activates the downstream signaling pathways that inhibit axon growth and promote inflammatory pain.

Impact of RTN4 gene polymorphism and its plasma level on susceptibility to nasopharyngeal carcinoma: A case-control study

The RTN4 gene plays a role in the development and progression of cancer. This case-control study aimed to investigate the association between the RTN4 gene polymorphism and its plasma level with the risk of nasopharyngeal carcinoma (NPC) in a Chinese population.RTN4 gene polymorphisms (rs2920891, rs17046583, rs117465650, rs10496040, and rs2588519) in 220 patients with NPC and 300 healthy controls were analyzed using Snapshot single-nucleotide polymorphism genotyping assays. The plasma level of RTN4 was measured using the enzyme-linked immunosorbent assay.The allele frequencies of RTN4 gene polymorphisms showed no significant difference between the patients and controls (P > .05). Nevertheless, the rs2920891 polymorphism in a dominant model (A/C+C/C) and codominant model (A/C) was significantly associated with the susceptibility to NPC (P = .017, odds ratio [OR] = 1.54, 95% confidence interval [CI] = 1.08-2.21 and P = .034, OR = 1.64, 95% CI = 1.13-2.38, respectively). The plasma level of RTN4 was significantly higher in patients with NPC in comparison with the controls (P < .001). Furthermore, we observed that patients with NPC carrying the rs2920891 A/C+C/C genotype had a higher RTN4 level than those carrying the A/A genotype (P < .001).Our findings indicated that the rs2920891 polymorphism may be associated with increased susceptibility to NPC, possibly by increasing plasma RTN4.

Platelet procoagulant phenotype is modulated by a p38-MK2 axis that regulates RTN4/Nogo proximal to the endoplasmic reticulum: utility of pathway analysis

Upon encountering physiological cues associated with damaged or inflamed endothelium, blood platelets set forth intracellular responses to ultimately support hemostatic plug formation and vascular repair. To gain insights into the molecular events underlying platelet function, we used a combination of interactome, pathway analysis, and other systems biology tools to analyze associations among proteins functionally modified by reversible phosphorylation upon platelet activation. While an interaction analysis mapped out a relative organization of intracellular mediators in platelet signaling, pathway analysis revealed directional signaling relations around protein kinase C (PKC) isoforms and mitogen-activated protein kinases (MAPKs) associated with platelet cytoskeletal dynamics, inflammatory responses, and hemostatic function. Pathway and causality analysis further suggested that platelets activate a specific p38-MK2 axis to phosphorylate RTN4 (reticulon-4, also known as Nogo), a Bcl-xl sequestration protein and critical regulator of endoplasmic reticulum (ER) physiology. In vitro, we find that platelets drive a p38-MK2-RTN4-Bcl-xl pathway associated with the regulation of the ER and platelet phosphatidylserine exposure. Together, our results support the use of pathway tools in the analysis of omics data sets as a means to help generate novel, mechanistic, and testable hypotheses for platelet studies while uncovering RTN4 as a putative regulator of platelet cell physiological responses.

Effects of altered RTN3 expression on BACE1 activity and Alzheimer's neuritic plaques

Reticulon 3 (RTN3), which is a member of the reticulon family of proteins, has a biochemical function of shaping tubular endoplasmic reticulum. RTN3 has also been found to interact with β-site amyloid precursor protein cleaving enzyme 1 (BACE1), which initiates the generation of β-amyloid peptides (Aβ) from amyloid precursor protein. Aβ is the major proteinaceous component in neuritic plaques, which constitute one of the major pathological features in brains of Alzheimer's disease (AD) patients. Mice deficient in or overexpressing RTN3 have altered amyloid deposition through effects on BACE1 expression and activity. In this review, we will summarize the current findings concerning the role of RTN3 in AD pathogenesis and demonstrate that RTN3 protein levels act as age-dependent modulators of BACE1 activity and Aβ deposition during the pathogenic progression of AD.

Sarcoplasmic reticulum-mitochondria communication in cardiovascular pathophysiology

Repetitive, calcium-mediated contractile activity renders cardiomyocytes critically dependent on a sustained energy supply and adequate calcium buffering, both of which are provided by mitochondria. Moreover, in vascular smooth muscle cells, mitochondrial metabolism modulates cell growth and proliferation, whereas cytosolic calcium levels regulate the arterial vascular tone. Physical and functional communication between mitochondria and sarco/endoplasmic reticulum and balanced mitochondrial dynamics seem to have a critical role for optimal calcium transfer to mitochondria, which is crucial in calcium homeostasis and mitochondrial metabolism in both types of muscle cells. Moreover, mitochondrial dysfunction has been associated with myocardial damage and dysregulation of vascular smooth muscle proliferation. Therefore, sarco/endoplasmic reticulum-mitochondria coupling and mitochondrial dynamics are now viewed as relevant factors in the pathogenesis of cardiac and vascular diseases, including coronary artery disease, heart failure, and pulmonary arterial hypertension. In this Review, we summarize the evidence related to the role of sarco/endoplasmic reticulum-mitochondria communication in cardiac and vascular muscle physiology, with a focus on how perturbations contribute to the pathogenesis of cardiovascular disorders.

Association of CAA and TATC Insertion/Deletion Genetic Polymorphisms in RTN4 3'-UTR with Hepatocellular Carcinoma Risk

Evidence from recent researchers suggested that RTN4 is a multifunctional gene, including tumor suppression, apoptosis, vascular remodeling, and inhibition of axonal regeneration. The CAA and TATC insertion/deletion polymorphisms (CAA/TATC polymorphisms) of RTN4 3″-untranslated regions (UTRs) have been linked to cervical squamous cell carcinoma (CSCC), uterine leiomyomas (UL) and non-small cell lung cancer (NSCLC). However, the association between these two polymorphisms sites with Hepatocellular Carcinoma (HCC) risk was not carry out before. A total of 284 HCC patients and 484 control subjects were recruited for this study. The RTN4 CAA/TATC insertion/deletion genotypes were determined using polymerase chain reaction (PCR) assay. The ID/DD genotypes of CAA were significantly associated with an increased risk of HCC compared with the II genotype (ID vs. II: OR = 1.50, 95% CI: 1.10-2.04; DD vs. II: OR = 2.00, 95%CI: 1.15-3.46). Meanwhile, the frequency of D allele of CAA was significantly related with an increased risk of HCC compared with the I allele (D vs. I: OR = 1.39, 95% CI: 1.12-1.73). The ID genotypes of TATC was significantly associated with an increased risk of HCC compared with the DD genotype (ID vs. DD: OR = 1.70, 95% CI: 1.23-2.33). The present study provided evidence that RTN4 CAA/TATC polymorphisms were associated with HCC development in Chinese Han population.

Endoplasmic Reticulum: The Favorite Intracellular Niche for Viral Replication and Assembly

The endoplasmic reticulum (ER) is the largest intracellular organelle. It forms a complex network of continuous sheets and tubules, extending from the nuclear envelope (NE) to the plasma membrane. This network is frequently perturbed by positive-strand RNA viruses utilizing the ER to create membranous replication factories (RFs), where amplification of their genomes occurs. In addition, many enveloped viruses assemble progeny virions in association with ER membranes, and viruses replicating in the nucleus need to overcome the NE barrier, requiring transient changes of the NE morphology. This review first summarizes some key aspects of ER morphology and then focuses on the exploitation of the ER by viruses for the sake of promoting the different steps of their replication cycles.

Integrative functional transcriptomic analyses implicate specific molecular pathways in pulmonary toxicity from exposure to aluminum oxide nanoparticles

Gene expression profiling has developed rapidly in recent years and it can predict and define mechanisms underlying chemical toxicity. Here, RNA microarray and computational technology were used to show that aluminum oxide nanoparticles (Al2O3 NPs) were capable of triggering up-regulation of genes related to the cell cycle and cell death in a human A549 lung adenocarcinoma cell line. Gene expression levels were validated in Al2O3 NPs exposed A549 cells and mice lung tissues, most of which showed consistent trends in regulation. Gene-transcription factor network analysis coupled with cell- and animal-based assays demonstrated that the genes encoding PTPN6, RTN4, BAX and IER play a role in the biological responses induced by the nanoparticle exposure, which caused cell death and cell cycle arrest in the G2/S phase. Further, down-regulated PTPN6 expression demonstrated a core role in the network, thus expression level of PTPN6 was rescued by plasmid transfection, which showed ameliorative effects of A549 cells against cell death and cell cycle arrest. These results demonstrate the feasibility of using gene expression profiling to predict cellular responses induced by nanomaterials, which could be used to develop a comprehensive knowledge of nanotoxicity.

Endoplasmic Protein Nogo-B (RTN4-B) Interacts with GRAMD4 and Regulates TLR9-Mediated Innate Immune Responses

TLRs are distributed in their characteristic cellular or subcellular compartments to efficiently recognize specific ligands and to initiate intracellular signaling. Whereas TLRs recognizing pathogen-associated lipids or proteins are localized to the cell surface, nucleic acid-sensing TLRs are expressed in endosomes and lysosomes. Several endoplasmic reticulum (ER)-resident proteins are known to regulate the trafficking of TLRs to the specific cellular compartments, thus playing important roles in the initiation of innate immune responses. In this study, we show that an ER-resident protein, Nogo-B (or RTN4-B), is necessary for immune responses triggered by nucleic acid-sensing TLRs, and that a newly identified Nogo-B-binding protein (glucosyltransferases, Rab-like GTPase activators and myotubularins [GRAM] domain containing 4 [GRAMD4]) negatively regulates the responses. Production of inflammatory cytokines in vitro by macrophages stimulated with CpG-B oligonucleotides or polyinosinic:polycytidylic acid was attenuated in the absence of Nogo-B, which was also confirmed in serum samples from Nogo-deficient mice injected with polyinosinic:polycytidylic acid. Although a deficiency of Nogo-B did not change the incorporation or delivery of CpG to endosomes, the localization of TLR9 to endolysosomes was found to be impaired. We identified GRAMD4 as a downmodulator for TLR9 response with a Nogo-B binding ability in ER, because our knockdown and overexpression experiments indicated that GRAMD4 suppresses the TLR9 response and knockdown of Gramd4 strongly enhanced the response in the absence of Nogo-B. Our findings indicate a critical role of Nogo-B and GRAMD4 in trafficking of TLR9.

RTN4 3'-UTR insertion/deletion polymorphism and susceptibility to non-small cell lung cancer in Chinese Han population

Nogo protein, encoded by gene reticulon-4 (RTN4), includes three major isoforms by different splicing, named Nogo-A Nogo-B and Nogo-C. Nogo proteins play an important role in the apoptosis of cells, especially in tumor cells. RTN4 single nucleotide polymorphisms (SNPs) can influence the efficiency of transcription and translation thus being related with an individual's predisposition to cancer. The CAA insertion/deletion polymorphism (rs34917480) within RTN4 3'-UTR has been reported to be associated with many cancer types. In order to investigate the relationship between this polymorphism and susceptibility to non-small cell lung cancer (NSCLC) in the Chinese population, we conducted the present case-control study including 411 NSCLC patients and 471 unrelated healthy controls. The genotype distributions were significantly different between cases and controls (p=0.014). We found that the del allele could significantly increase NSCLC risk (ins/ins vs ins/del: p=0.007, OR 1.46, 95%CI=1.11-1.93; dominant model: p=0.004, OR 1.47, 95%CI=1.13-1.92 and allele model: p=0.008, OR 1.35, 95%CI=1.08-1.67). This association was stronger in participants over 60 years old, males and smokers. We therefore conclude that the CAA insertion/deletion polymorphism (rs34917480) contributes to non-small cell lung cancer risk in Chinese population. Age, sex and environmental exposure are also related to carcinogenic effects of rs34917480.

Identification of MANF as a protein interacting with RTN1-C

Reticulons (RTNs) constitute a family of endoplasmic reticulum (ER)-associated proteins with a reticular distribution. Recently, evidence has shown that they exert a cancer-specific proapoptotic function via interaction or modulation of specific proteins. Such evidence is particularly associated with the RTN1-C family members. In order to explore proteins that interact with RTN1-C, the yeast two-hybrid system and regular molecular biological techniques were used to screen the human fetal brain cDNA library. As a result, seven RTN1-C interacting proteins including Homo sapiens mesencephalic astrocyte-derived neurotrophic factor (MANF) were obtained. The interactions between RTN1-C and its interacting proteins were confirmed by β-galactosidase assay and growth test in selective media. Moreover, the MANF/RTN1-C interaction was verified in vitro by glutathione S-transferase pull-down assay and in vivo by immunoprecipitation assay. By immunofluorescence assay, it was found that MANF co-localized with RTN1-C in the ER. Knockdown of RTN1-C reduced the localization of MANF in the ER. These results provide clues to further explore the function of RTN1-C and MANF in neurodegenerative diseases and cancer.

Form follows function: the importance of endoplasmic reticulum shape

The endoplasmic reticulum (ER) has a remarkably complex structure, composed of a single bilayer that forms the nuclear envelope, along with a network of sheets and dynamic tubules. Our understanding of the biological significance of the complex architecture of the ER has improved dramatically in the last few years. The identification of proteins and forces required for maintaining ER shape, as well as more advanced imaging techniques, has allowed the relationship between ER shape and function to come into focus. These studies have also revealed unexpected new functions of the ER and novel ER domains regulating alterations in ER dynamics. The importance of ER structure has become evident as recent research has identified diseases linked to mutations in ER-shaping proteins. In this review, we discuss what is known about the maintenance of ER architecture, the relationship between ER structure and function, and diseases associated with defects in ER structure.

Nogo-B expression, in arterial intima, is impeded in the early stages of atherosclerosis in humans

Nogo-B (Reticulon 4B) is considered to be a novel vascular marker, which may have a protective role in injury-induced neointima formation and atherosclerosis. Nogo A/B is found to be crucial for monocyte/macrophage recruitment in acute inflammation and it is expressed in CD68 + macrophages. We hypothesize that macrophage infiltration in atherosclerosis is not dependent on Nogo-B expression in arterial wall. We have assessed Nogo-B expression and macrophage accumulation in the iliac arteries of healthy organ donors and organ donors with cardiovascular risk factors. Paraffin sections of 66 iliac arteries, from 44 deceased organ donors (17 women and 27 men), were studied. The healthy and cardiovascular risk (CVR) subgroups were created. With regard to staging of the atherosclerotic process, the thickness of arterial intima was measured in digitalized images of H+E stained tissue sections. Immunohistochemical reactions (Nogo-B and CD68) were carried out in all arteries (66 samples). Western blotting (WB-19 samples) and real-time PCR (27 samples) were performed on selected arteries. Significantly higher Nogo-B expression was demonstrated in the intima of the healthy subjects' subgroup, using immunohistochemistry. WB and real-time PCR revealed a trend toward lower Nogo-B expression in the adventitia of the CVR subgroup. Furthermore, the thickness of the intima was found to negatively correlate with the expression of Nogo-B in the intima and media (r = -0.32; p < 0.05; r = -0.32; p < 0.05). Macrophage infiltrates were more prominent in intima of CVR subjects (0.65 vs 3.52 a.u.; p < 0.01). Macrophage density in intima increased with atherosclerosis progression (r = 0.37; p < 0.01). CD68 macrophages density in adventitia was lower in CVR arteries than in healthy arteries. The expression of Nogo-B, in arterial intima, is impeded in the early stages of atherosclerosis. Accumulation of arterial intimal CD68 macrophages has been shown to progress; however, the overall macrophage density in the adventitia is reduced in arteries shown to have intimal thickening. Macrophage infiltration is not accompanied by Nogo-B expression in atherosclerotic arteries.

Nogo-A couples with Apg-1 through interaction and co-ordinate expression under hypoxic and oxidative stress

Nogo-A is the largest isoform of the Nogo/RTN4 (reticulon 4) proteins and has been characterized as a major myelin-associated inhibitor of regenerative nerve growth in the adult CNS (central nervous system). Apart from the myelin sheath, Nogo-A is expressed at high levels in principal neurons of the CNS. The specificity of Nogo-A resides in its central domain, NiG. We identified Apg-1, a member of the stress-induced Hsp110 (heat-shock protein of 110 kDa) family, as a novel interactor of NiG/Nogo-A. The interaction is selective because Apg-1 interacts with Nogo-A/RTN4-A, but not with RTN1-A, the closest paralogue of Nogo-A. Conversely, Nogo-A binds to Apg-1, but not to Apg-2 or Hsp105, two other members of the Hsp110 family. We characterized the Nogo-A–Apg-1 interaction by affinity precipitation, co-immunoprecipitation and proximity ligation assay, using primary hippocampal neurons derived from Nogo-deficient mice. Under conditions of hypoxic and oxidative stress we found that Nogo-A and Apg-1 were tightly co-regulated in hippocampal neurons. Although both proteins were up-regulated under hypoxic conditions, their expression levels were reduced upon the addition of hydrogen peroxide. Taken together, we suggest that Nogo-A is closely involved in the neuronal response to hypoxic and oxidative stress, an observation that may be of relevance not only in stroke-induced ischaemia, but also in neuroblastoma formation.

The nerve growth inhibitor Nogo-A selectively binds to the heat-shock protein Apg-1 and the expression levels of these two interactors are co-regulated under different forms of stress in neurons.

Nogo-A Represses Anatomical and Synaptic Plasticity in the Central Nervous System

Nogo-A was initially discovered as a myelin-associated growth inhibitory protein limiting axonal regeneration after central nervous system (CNS) injury. This review summarizes current knowledge on how myelin and neuronal Nogo-A and its receptors exert physiological functions ranging from the regulation of growth suppression to synaptic plasticity in the developing and adult intact CNS.

Reticulon1-C modulates protein disulphide isomerase function

Endoplasmic reticulum (ER) is the primary site for the synthesis and folding of secreted and membrane-bound proteins. Accumulation of unfolded and misfolded proteins in ER underlies a wide range of human neurodegenerative disorders. Hence, molecules regulating the ER stress response represent potential candidates as drug targets for tackling these diseases. Protein disulphide isomerase (PDI) is a chaperone involved in ER stress pathway, its activity being an important cellular defense against protein misfolding. Here, we demonstrate that human neuroblastoma SH-SY5Y cells overexpressing the reticulon protein 1-C (RTN1-C) reticulon family member show a PDI punctuate subcellular distribution identified as ER vesicles. This represents an event associated with a significant increase of PDI enzymatic activity. We provide evidence that the modulation of PDI localization and activity does not only rely upon ER stress induction or upregulation of its synthesis, but tightly correlates to an alteration in its nitrosylation status. By using different RTN1-C mutants, we demonstrate that the observed effects depend on RTN1-C N-terminal region and on the integrity of the microtubule network. Overall, our results indicate that RTN1-C induces PDI redistribution in ER vesicles, and concomitantly modulates its activity by decreasing the levels of its S-nitrosylated form. Thus RTN1-C represents a promising candidate to modulate PDI function.

Association of genetic variations in RTN4 3'-UTR with risk of uterine leiomyomas

This pilot case-control study was conducted to test the hypothesis that the TATC (rs71682890) and CAA (rs34917480) insertion/deletion polymorphisms of RTN4 3'-UTR are associated with the susceptibility to uterine leiomyoma (UL). The study recruited 286 premenopausal women with UL and 450 unrelated postmenopausal women not presenting the disease as control subjects. The polymorphisms of rs71682890 and rs34917480 were genotyped with the method of polymerase chain reaction polyacrylamide gel electrophoresis (PCR - PAGE). No statistically significant association was observed between the TATC insertion/deletion polymorphism and UL risk. However, increased UL risk was identified to be significantly associated with CAA insertion/deletion polymorphism in the recessive and codominant model. The present study provided evidence for the first time that CAA polymorphism in RTN4 3'-UTR, but not TATC polymorphism may be involved in susceptibility to UL.

Time course and spatial profile of Nogo-A expression in experimental autoimmune encephalomyelitis in C57BL/6 mice

Inhibition of the myelin-associated neurite outgrowth inhibitor Nogo-A has been found to be beneficial in experimental autoimmune encephalomyelitis (EAE), but there are little data on its expression dynamics during the disease course. We analyzed Nogo-A mRNA and protein during the course of EAE in 27 C57BL/6 mice and in 8 controls. Histopathologic and molecular analyses were performed on Day 0 (naive), preclinical (Day 10), acute (Days 18-22) and chronic (Day 50) time points. In situ hybridization and real-time polymerase chain reaction analyses revealed reduced Nogo-A mRNA expression at preclinical (p < 0.0001) and acute phases (p < 0.0001), followed by upregulation during the chronic phase (p < 0.0001). Nogo-A mRNA was expressed in neurons and oligodendrocytes. By immunohistochemistry and Western blot, there was increased Nogo-A protein expression (p < 0.001) in the chronic phase. Moreover, spatial differences were observed within EAE lesions. The pattern of Nogo-A protein expression inversely correlated with axonal regeneration growth-associated protein 43-positive axons (60% of which were Nogo-A contact-free during the acute phase) and axonal injury (β-amyloid precursor protein-positive axons). Cortical Nogo-66 receptor protein and mRNA levels increased during the chronic phase. The results indicate that Nogo-A and Nogo receptor are actively regulated in EAE lesions; this may indicate a specific time window for localized axonal regeneration in the acute phase of EAE.

Reticulon Protein-1C: A New Hope in the Treatment of Different Neuronal Diseases

Reticulons (RTNs) are a group of membrane proteins localized on the ER and known to regulate ER structure and functions. Several studies have suggested that RTNs are involved in different important cellular functions such as changes in calcium homeostasis, ER-stress-mediated cell death, and autophagy. RTNs have been demonstrated to exert a cancer specific proapoptotic function via the interaction or the modulation of specific proteins. Reticulons have also been implicated in different signaling pathways which are at the basis of the pathogenesis of several neurodegenerative diseases. In this paper we discuss the accumulating evidence identifying RTN-1C protein as a promising target in the treatment of different pathologies such as cancer or neurodegenerative disorders.

Novel extraneural role of neurite outgrowth inhibitor A: modulation of osteoclastogenesis via positive feedback regulation of nuclear factor of activated T cell cytoplasmic 1

Osteoclasts are bone-resorbing cells differentiated from macrophage/monocyte lineage precursors upon receptor activator of NF-κB ligand (RANKL) stimulation. In a proteomic approach to identify proteins involved in osteoclastogenesis, we observed a dramatic increase in the expression of neurite outgrowth inhibitor A (Nogo-A) upon RANKL stimulation of mouse bone marrow macrophages (BMMs) in a nuclear factor of activated T cell cytoplasmic 1 (NFATc1)-dependent manner. The knockdown of Nogo-A in BMMs significantly reduced RANKL-dependent osteoclast differentiation accompanied by diminished NFATc1 induction, suggesting that a positive feedback mechanism is involved. Conversely, Nogo-A overexpression in BMMs as well as in RAW264.7 macrophages greatly augmented osteoclastogenesis, with concomitant increase in the NFATc1 induction. Both the mitogen-activated protein kinase (MAPK) pathway and calcium oscillation, which are central to RANKL-dependent NFATc1 activation and induction, were enhanced by Nogo-A. Finally, Nogo-A knockdown in mouse calvariae prevented interleukin 1 (IL-1)-induced bone loss. These findings not only reveal an unprecedented extraneural role of Nogo-A in osteoclastogenesis but also suggest a novel drug target against bone-lytic diseases.

Genetic variation in RTN4 3'-UTR and susceptibility to cervical squamous cell carcinoma

Recent studies have suggested that RTN4 is a multifunctional gene, including inhibition of axonal regeneration, vascular remodeling, apoptosis, and tumor suppression. The TATC and CAA insertion/deletion polymorphisms of RTN4 3'-UTR have been linked to schizophrenia, depression, and dilated cardiomyopathy. To test whether these two polymorphisms are associated with cervical squamous cell carcinoma (CSCC), in this research, by using polymerase chain reaction-polyacrylamide gel electrophoresis, we determined the genotypes of the TATC and CAA polymorphisms in 336 CSCC patients and 450 unrelated control subjects. Allele frequencies of TATC and CAA polymorphisms were not significantly different between CSCC patients and control subjects (odds ratio [OR]=1.22, 95% confidence interval [CI]=0.98-1.50 for TATC; OR=0.95, 95% CI=0.76-1.18 for CAA). Decreased CSCC risk was associated with TATC polymorphism in a recessive model (OR=0.49, 95% CI=0.30-0.77), while no significant association was observed between CAA polymorphism and CSCC in different genetic models. Results of stratified analysis revealed that both TATC and CAA polymorphisms were associated with high clinical stage, and CAA polymorphism was also associated with positive parametrial invasion (OR=0.69, 95% CI=0.48-0.98). The present study provides evidence that TATC and CAA insertion/deletion polymorphisms are associated with CSCC, indicating that genetic variation in RTN4 3'-UTR contributes to the susceptibility to CSCC. It is necessary to confirm these findings in ethnically different populations and with a larger sample.

RNT4 3'-UTR insertion/deletion polymorphisms are not associated with atrial septal defect in Chinese Han population: a brief communication

Atrial septal defect (ASD) is a common type of congenital heart disease, which is defined as any communication through atrial septum. Several studies have revealed that genetic factors may influence the susceptibility of ASD. Recent studies have shown that reticulon 4 (RTN4) gene might be involved in some processes relevant to heart development, such as regulation of cell migration and vascular remodeling. This study aimed to evaluate RTN4 gene polymorphisms of CAA and TATC insertion/deletion in relation to the risk of ASD in Chinese Han population. A total of 175 ASD patients and 308 unrelated healthy controls were successfully investigated. The polymorphisms of patients were determined by polymerase chain reaction-polyacrylamide gel electrophoresis. There was no significant difference in the allele frequencies of CAA and TATC insertion/deletion in RNT4 gene between ASD patients and controls. The same results were seen in their genotypes. The present study suggests that CAA and TATC insertion/deletion polymorphisms of RNT4 gene may not be a useful marker to predict the susceptibility of ASD in Chinese Han population.

Chinese Medicine's Intervention Effect on Nogo-A/NgR

Cerebral vascular disease is very common in the elderly and is one of the most dangerous diseases which is hazardous to the body's health, and it is the medical specialists' study hot spot not only in the clinical field but also in the medical basic research field. Neural regeneration has been paid more and more attention in recent years. Nogo's function in the process of neural regeneration has become the focal point since it was discovered in the year 2000. Many studies elucidate that Nogo negatively affects the neural regeneration and plasticity. Chinese medicine plays an important role in the prevention and treatment of neural diseases, and recently some researches about the Chinese medicine's intervention effect on Nogo-A/NgR sprang up, so it is necessary to make a review on this aspect.

Defeating inhibition of regeneration by scar and myelin components

Axon regeneration and the sprouting processes that underlie plasticity are blocked by inhibitory factors in the central nervous system (CNS) environment, several of which are upregulated after injury. The major inhibitory molecules are those associated with myelin and those associated with the glial scar. In myelin, NogoA, MAG, and OMgp are present on normal oligodendrocytes and on myelin debris. They act partly via the Nogo receptor, partly via an unidentified amino-Nogo receptor. In the glial scar, chondroitin sulphate proteoglycans, semaphorins, and the formation of a collagen-based membrane are all inhibitory. Methods to counteract these forms of inhibition have been identified, and these treatments promote axon regeneration in the damaged spinal cord, and in some cases recovery of function through enhanced plasticity.

Nogo-B regulates migration and contraction of airway smooth muscle cells by decreasing ARPC 2/3 and increasing MYL-9 expression

BACKGROUND

Abnormal proliferation, apoptosis, migration and contraction of airway smooth muscle (ASM) cells in airway remodeling in asthma are basically excessive repair responses to a network of inflammatory mediators such as PDGF, but the mechanisms of such responses remain unclear. Nogo-B, a member of the reticulum family 4(RTN4), is known to play a key role in arteriogenesis and tissue repair. Further studies are needed to elucidate the role of Nogo-B in airway smooth muscle abnormalities.

METHODS

A mouse model of chronic asthma was established by repeated OVA inhalation and subjected to Nogo-B expression analysis using immunohistochemistry and Western Blotting. Then, primary human bronchial smooth muscle cells (HBSMCs) were cultured in vitro and a siRNA interference was performed to knockdown the expression of Nogo-B in the cells. The effects of Nogo-B inhibition on PDGF-induced HBSMCs proliferation, migration and contraction were evaluated. Finally, a proteomic analysis was conducted to unveil the underlying mechanisms responsible for the function of Nogo-B.

RESULTS

Total Nogo-B expression was approximately 3.08-fold lower in chronic asthmatic mice compared to naïve mice, which was obvious in the smooth muscle layer of the airways. Interference of Nogo-B expression by siRNA resulted nearly 96% reduction in mRNA in cultured HBSMCs. In addition, knockdown of Nogo-B using specific siRNA significantly decreased PDGF-induced migration of HBSMCs by 2.3-fold, and increased the cellular contraction by 16% compared to negative controls, but had limited effects on PDGF-induced proliferation. Furthermore, using proteomic analysis, we demonstrate that the expression of actin related protein 2/3 complex subunit 5 (ARPC 2/3) decreased and, myosin regulatory light chain 9 isoform a (MYL-9) increased after Nogo-B knockdown.

CONCLUSIONS

These data define a novel role for Nogo-B in airway remodeling in chronic asthma. Endogenous Nogo-B, which may exert its effects through ARPC 2/3 and MYL-9, is necessary for the migration and contraction of airway smooth muscle cells.

Endothelial reticulon-4B (Nogo-B) regulates ICAM-1-mediated leukocyte transmigration and acute inflammation

The reticulon (Rtn) family of proteins are localized primarily to the endoplasmic reticulum (ER) of most cells. The Rtn-4 family, (aka Nogo) consists of 3 splice variants of a common gene called Rtn-4A, Rtn-4B, and Rtn-4C. Recently, we identified the Rtn-4B (Nogo-B) protein in endothelial and smooth muscle cells of the vessel wall, and showed that Nogo-B is a regulator of cell migration in vitro and vascular remodeling and angiogenesis in vivo. However, the role of Nogo-B in inflammation is still largely unknown. In the present study, we use 2 models of inflammation to show that endothelial Nogo-B regulates leukocyte transmigration and intercellular adhesion molecule-1 (ICAM-1)-dependent signaling. Mice lacking Nogo-A/B have a marked reduction in neutrophil and monocyte recruitment to sites of inflammation, while Nogo-A/B(-/-) mice engrafted with wild-type (WT) bone marrow still exhibit impaired inflammation compared with WT mice engrafted with Nogo-A/B(-/-) bone marrow, arguing for a critical role of host Nogo in this response. Using human leukocytes and endothelial cells, we show mechanistically that the silencing of Nogo-B with small interfering RNA (siRNA) impairs the transmigration of neutrophils and reduces ICAM-1-stimulated phosphorylation of vascular endothelial-cell cadherin (VE-cadherin). Our results reveal a novel role of endothelial Nogo-B in basic immune functions and provide a key link in the molecular network governing endothelial-cell regulation of diapedesis.

Analysis of RTN4 3'UTR insertion/deletion polymorphisms in ventricular septal defect in a Chinese Han population

Congenital heart disease is the most common type of birth defect and the leading cause of infant mortality in the first year of life. Ventricular septal defect (VSD) is one of the most general congenital heart defects and is a defect in the wall between the right and left ventricles of the heart. The pathogenesis of VSD has been extensively investigated for many years, but it remains uncertain. To determine whether reticulon 4 gene (RTN4) 3'UTR insertion/deletion polymorphisms are associated with VSD, we genotyped the TATC and CAA insertion/deletion polymorphisms of RTN4 by polymerase chain reaction-polyacrylamide gel electrophoresis in 151 VSD patients and 308 unrelated healthy subjects in a Chinese Han population. No significant differences in 3'UTR TATC and CAA insertion/deletion polymorphisms genotype and allele frequencies were observed between the VSD and controls. These data indicate that, for the first time, RTN4 3'UTR insertion/deletion polymorphisms may not appear to play a role in the susceptibility of VSD in Chinese Han population.

The age- and amyloid-β-related increases in Nogo B contribute to microglial activation

The family of reticulons include three isoforms of the Nogo protein, Nogo A, Nogo B and Nogo C. Nogo A is expressed on neuronal tissue and its primary effect is widely acknowledged to be inhibition of neurite outgrowth. Although both Nogo B and Nogo C are also expressed in neuronal tissue, their roles in the CNS remain to be identified. In this study, we set out to assess whether expression of Nogo A or Nogo B was altered in tissue prepared from aged rats in which increased microglial activation is accompanied by decreased synaptic plasticity. The data indicate that Nogo B, but not Nogo A, was markedly increased in hippocampal tissue prepared from aged rats and that, at least in vitro, Nogo B increased several markers of microglial activation. In a striking parallel with the age-related changes, we demonstrate that intracerebroventricular delivery of amyloid-β (Aβ)(1-40)+Aβ(1-42) for 8 days was associated with a depression of long-term potentiation (LTP) and an increase in markers of microglial activation and Nogo B. In both models, evidence of cell stress was identified by increased activity of caspases 8 and 3 and importantly, incubation of cultured neurons in the presence of Nogo B increased activity of both enzymes. The data identify, for the first time, an effect of Nogo B in the brain and specifically show that its expression is increased in conditions where synaptic plasticity is compromised.

Functions of Nogo proteins and their receptors in the nervous system

The membrane protein Nogo-A was initially characterized as a CNS-specific inhibitor of axonal regeneration. Recent studies have uncovered regulatory roles of Nogo proteins and their receptors--in precursor migration, neurite growth and branching in the developing nervous system--as well as a growth-restricting function during CNS maturation. The function of Nogo in the adult CNS is now understood to be that of a negative regulator of neuronal growth, leading to stabilization of the CNS wiring at the expense of extensive plastic rearrangements and regeneration after injury. In addition, Nogo proteins interact with various intracellular components and may have roles in the regulation of endoplasmic reticulum (ER) structure, processing of amyloid precursor protein and cell survival.

Epithelial reticulon 4B (Nogo-B) is an endogenous regulator of Th2-driven lung inflammation

The reticulon protein Nogo-B is highly expressed in the lungs, and its loss augments lung inflammation in part as a result of decreased expression of the antiinflammatory protein PLUNC.

Nogo-B is a member of the reticulon family of proteins (RTN-4B) that is highly expressed in lung tissue; however, its function remains unknown. We show that mice with Th2-driven lung inflammation results in a loss of Nogo expression in airway epithelium and smooth muscle compared with nonallergic mice, a finding which is replicated in severe human asthma. Mice lacking Nogo-A/B (Nogo-KO) display an exaggerated asthma-like phenotype, and epithelial reconstitution of Nogo-B in transgenic mice blunts Th2-mediated lung inflammation. Microarray analysis of lungs from Nogo-KO mice reveals a marked reduction in palate lung and nasal clone (PLUNC) gene expression, and the levels of PLUNC are enhanced in epithelial Nogo-B transgenic mice. Finally, transgenic expression of PLUNC into Nogo-KO mice rescues the enhanced asthmatic-like responsiveness in these KO mice. These data identify Nogo-B as a novel protective gene expressed in lung epithelia, and its expression regulates the levels of the antibacterial antiinflammatory protein PLUNC.

Identification and characterization of alternative promoters of zebrafish Rtn-4/Nogo genes in cultured cells and zebrafish embryos

In mammals, the Nogo family consists of Nogo-A, Nogo-B and Nogo-C. However, there are three Rtn-4/Nogo-related transcripts were identified in zebrafish. In addition to the common C-terminal region, the N-terminal regions of Rtn4-n/Nogo-C1, Rtn4-m/Nogo-C2 and Rtn4-l/Nogo-B, respectively, contain 9, 25 and 132 amino acid residues. In this study, we isolated the 5'-upstream region of each gene from a BAC clone and demonstrated that the putative promoter regions, P1-P3, are functional in cultured cells and zebrafish embryos. A transgenic zebrafish Tg(Nogo-B:GFP) line was generated using P1 promoter region to drive green fluorescent protein (GFP) expression through Tol2-mediated transgenesis. This line recapitulates the endogenous expression pattern of Rtn4-l/Nogo-B mRNA in the brain, brachial arches, eyes, muscle, liver and intestines. In contrast, GFP expressions by P2 and P3 promoters were localized to skeletal muscles of zebrafish embryos. Several GATA and E-box motifs are found in these promoter regions. Using morpholino knockdown experiments, GATA4 and GATA6 were involved in the control of P1 promoter activity in the liver and intestine, while Myf5 and MyoD for the control of P1 and P3 promoter activities in muscles. These data demonstrate that zebrafish Rtn4/Nogo transcripts might be generated by coupling mechanisms of alternative first exons and alternative promoter usage.

Expression of Nogo-A on the retina in rat model with chronic ocular hypertension

AIM

To study the expressive variation of Nogo-A on rat retina in the process of chronic ocular hypertension.

METHODS

Thirty-six healthy adult male Wistars were randomly divided into control group (6 rats) and chronic hypertension group (30 rats). Chronic hypertension was created by cauterizing the superficial scleral veins. Immunohistochemistry technique was used to evaluate the expressive varieties of Nogo-A at different time points during the course of chronic ocular hypertension.

RESULTS

The success of the model was indicated by over 40% of increase in the IOP as compared with normal rats. Compared with control group, as time passed chronic hypertension group gradually had detectable morphology changes in the retina. At the 21st day of chronic ocular hypertension, retinas became thinner and the quantity of retinal ganglion cells (RGC) decreased (P<0.05). Assoicated with the morphological changes, the expression of Nogo-A was strongly increased (P<0.05).

CONCLUSION

Myelin associated protein Nogo-A plays a part in the process of chronic ocular hypertension.

The natural history of the myelin-derived nerve growth inhibitor Nogo-A

Nogo-A is possibly the best characterized myelin-derived inhibitor of nerve growth in the adult central nervous system (CNS). It is a member of the ancient reticulon family of mainly endoplasmic reticulum resident proteins with representatives found throughout the eukaryotic domain. Orthologs of the nogo gene were identified in tetrapods and teleost fish but none have been detected in invertebrates. Evolution of the nogo gene has been non-homogeneous. The exon-intron arrangement is conserved from amphibians (Xenopus) to mammals, but partly deviates from that found in several teleost fish species, indicating that the recruitment of nogo exons proceeded along at least two independent lines during early vertebrate evolution. This might have far-reaching consequences. Tetrapod nogo orthologs encode two neurite growth inhibitory domains whereas in fish nogo only one of the inhibitory domains is present. These distinct paths in nogo evolution have potentially contributed to the regeneration permissive CNS in fish as opposed to the non-regenerating CNS in higher vertebrates.

Acetylation of RTN-1C regulates the induction of ER stress by the inhibition of HDAC activity in neuroectodermal tumors

Reticulons are a family of highly conserved proteins, localized in the endoplasmic reticulum (ER) and involved in different cellular functions, such as intracellular membrane trafficking, apoptosis and nuclear envelope formation. The reticulon protein family consists of four members, but their specific functions are presently poorly understood. RTN-1C overexpression triggers apoptosis, regulating ER stress versus DNA damage-induced cell death in a mutually exclusive way. The different RTN isoforms share a C-terminal reticulon homology domain containing two hydrophobic segments and a 66-amino acid hydrophilic loop. In the C-terminal region of RTN-1C, a unique consensus sequence (GAKRH) has recently been identified, showing 100% identity with the DNA-binding domain of histone H4. In this study, we show that this sequence is essential for RTN-1C-mediated apoptosis. It is noteworthy that the lysine 204 present in this region is post-translationally modified by acetylation and that this event is associated with a significant decrease in histone deacetylase activity and contributes to RTN-1C binding to DNA. These data demonstrate a molecular mechanism by which RTN-1C controls apoptosis and indicate this protein to be a novel potential target for cancer therapy.

Receptors for myelin inhibitors: Structures and therapeutic opportunities

Many studies have indicated that the inability of adult mammalian central nervous system (CNS) to regenerate after injury is partly due to the existence of growth-inhibitory molecules associated with CNS myelin. Studies over the years have led to the identification of multiple myelin-associated inhibitors, among which Nogo, myelin-associated glycoprotein (MAG) and oligodendrocyte-myelin glycoprotein (Omgp) represent potentially major contributors to CNS axon regeneration failure. Here we review in vitro and in vivo investigations into these inhibitory ligands and their functional mechanisms, focusing particularly on the neuronal receptors that mediate the inhibitory signals from these myelin molecules. A better understanding of the receptors for myelin-associated inhibitors could provide opportunities to decipher the mechanism of restriction in CNS regeneration, and lead to the development of potential therapeutic targets in neurodegenerative diseases and neurological injury. We will discuss the structures of the receptors and therapeutic opportunities that might arise based on this information.