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

Molecular profiling of a bladder cancer with very high tumour mutational burden

The increasing incidence of urothelial bladder cancer is a notable global concern, as evidenced by the epidemiological data in terms of frequency, distribution, as well as mortality rates. Although numerous molecular alterations have been linked to the occurrence and progression of bladder cancer, currently there is a limited knowledge on the molecular signature able of accurately predicting clinical outcomes. In this report, we present a case of a pT3b high-grade infiltrating urothelial carcinoma with areas of squamous differentiation characterized by very high tumor mutational burden (TMB), with up-regulations of immune checkpoints. The high TMB, along with elevated expressions of PD-L1, PD-L2, and PD1, underscores the rationale for developing a personalized immunotherapy focused on the use of immune-checkpoint inhibitors. Additionally, molecular analysis revealed somatic mutations in several other cancer-related genes, including TP53, TP63 and NOTCH3. Mutations of TP53 and TP63 genes provide mechanistic insights on the molecular mechanisms underlying disease development and progression. Notably, the above-mentioned mutations and the elevated hypoxia score make the targeting of p53 and/or hypoxia related pathways a plausible personalized medicine option for this bladder cancer, particularly in combination with immunotherapy. Our data suggest a requirement for molecular profiling in bladder cancer to possibly select appropriate immune-checkpoint therapy.

Genetically driven predisposition leads to an unusually genomic unstable renal cell carcinoma

Renal cell carcinoma originates from the lining of the proximal convoluted renal tubule and represents the most common type of kidney cancer. Risk factors and comorbidities might be associated to renal cell carcinoma, while a small fraction of 2-3% emerges from patients with predisposing cancer syndromes, typically associated to hereditary mutations in VHL, folliculin, fumarate hydratase or MET genes. Here, we report a case of renal cell carcinoma in patient with concurrent germline mutations in BRCA1 and RAD51 genes. This case displays an unusual high mutational burden and chromosomal aberrations compared to the typical profile of renal cell carcinoma. Mutational analysis on whole genome sequencing revealed an enrichment of the MMR2 mutational signature, which is indicative of impaired DNA repair capacity. Overall, the tumor displayed a profile of unusual high genomic instability which suggests a possible origin from germline predisposing mutations in the DNA repair genes BRCA1 and RAD51. While BRCA1 and RAD51 germline mutations are well-characterised in breast and ovarian cancer, their role in renal cell carcinoma is still largely unexplored. The genomic instability detected in this case of renal cell carcinoma, along with the presence of unusual mutations, might offer support to clinicians for the development of patient-tailored therapies.

Macrophage polarization and metabolism in atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of fatty deposits in the inner walls of vessels. These plaques restrict blood flow and lead to complications such as heart attack or stroke. The development of atherosclerosis is influenced by a variety of factors, including age, genetics, lifestyle, and underlying health conditions such as high blood pressure or diabetes. Atherosclerotic plaques in stable form are characterized by slow growth, which leads to luminal stenosis, with low embolic potential or in unstable form, which contributes to high risk for thrombotic and embolic complications with rapid clinical onset. In this complex scenario of atherosclerosis, macrophages participate in the whole process, including the initiation, growth and eventually rupture and wound healing stages of artery plaque formation. Macrophages in plaques exhibit high heterogeneity and plasticity, which affect the evolving plaque microenvironment, e.g., leading to excessive lipid accumulation, cytokine hyperactivation, hypoxia, apoptosis and necroptosis. The metabolic and functional transitions of plaque macrophages in response to plaque microenvironmental factors not only influence ongoing and imminent inflammatory responses within the lesions but also directly dictate atherosclerotic progression or regression. In this review, we discuss the origin of macrophages within plaques, their phenotypic diversity, metabolic shifts, and fate and the roles they play in the dynamic progression of atherosclerosis. It also describes how macrophages interact with other plaque cells, particularly T cells. Ultimately, targeting pathways involved in macrophage polarization may lead to innovative and promising approaches for precision medicine. Further insights into the landscape and biological features of macrophages within atherosclerotic plaques may offer valuable information for optimizing future clinical treatment for atherosclerosis by targeting macrophages.

Aged mesenchymal stem cells and inflammation: from pathology to potential therapeutic strategies

Natural ageing of organisms and corresponding age-related diseases result mainly from stem cell ageing and "inflammaging". Mesenchymal stem cells (MSCs) exhibit very high immune-regulating capacity and are promising candidates for immune-related disease treatment. However, the effect of MSC application is not satisfactory for some patients, especially in elderly individuals. With ageing, MSCs undergo many changes, including altered cell population reduction and differentiation ability, reduced migratory and homing capacity and, most important, defective immunosuppression. It is necessary to explore the relationship between the "inflammaging" and aged MSCs to prevent age-related diseases and increase the therapeutic effects of MSCs. In this review, we discuss changes in naturally ageing MSCs mainly from an inflammation perspective and propose some ideas for rejuvenating aged MSCs in future treatments.

Programmed Cell Death Pathways in Cholangiocarcinoma: Opportunities for Targeted Therapy

Cholangiocarcinoma is a highly aggressive cancer arising from the bile ducts. The limited effectiveness of conventional therapies has prompted the search for new approaches to target this disease. Recent evidence suggests that distinct programmed cell death mechanisms, namely, apoptosis, ferroptosis, pyroptosis and necroptosis, play a critical role in the development and progression of cholangiocarcinoma. This review aims to summarize the current knowledge on the role of programmed cell death in cholangiocarcinoma and its potential implications for the development of novel therapies. Several studies have shown that the dysregulation of apoptotic signaling pathways contributes to cholangiocarcinoma tumorigenesis and resistance to treatment. Similarly, ferroptosis, pyroptosis and necroptosis, which are pro-inflammatory forms of cell death, have been implicated in promoting immune cell recruitment and activation, thus enhancing the antitumor immune response. Moreover, recent studies have suggested that targeting cell death pathways could sensitize cholangiocarcinoma cells to chemotherapy and immunotherapy. In conclusion, programmed cell death represents a relevant molecular mechanism of pathogenesis in cholangiocarcinoma, and further research is needed to fully elucidate the underlying details and possibly identify therapeutic strategies.

A regulatory circuit comprising the CBP and SIRT7 regulates FAM134B-mediated ER-phagy

Macroautophagy (autophagy) utilizes a serial of receptors to specifically recognize and degrade autophagy cargoes, including damaged organelles, to maintain cellular homeostasis. Upstream signals spatiotemporally regulate the biological functions of selective autophagy receptors through protein post-translational modifications (PTM) such as phosphorylation. However, it is unclear how acetylation directly controls autophagy receptors in selective autophagy. Here, we report that an ER-phagy receptor FAM134B is acetylated by CBP acetyltransferase, eliciting intense ER-phagy. Furthermore, FAM134B acetylation promoted CAMKII-mediated phosphorylation to sustain a mode of milder ER-phagy. Conversely, SIRT7 deacetylated FAM134B to temper its activities in ER-phagy to avoid excessive ER degradation. Together, this work provides further mechanistic insights into how ER-phagy receptor perceives environmental signals for fine-tuning of ER homeostasis and demonstrates how nucleus-derived factors are programmed to control ER stress by modulating ER-phagy.

ZNF750: A Novel Prognostic Biomarker in Metastatic Prostate Cancer

Prostate cancer is the most frequently diagnosed cancer and the fifth leading cause of cancer death among men in 2020. The clinical decision making for prostate cancer patients is based on the stratification of the patients according to both clinical and pathological parameters such as Gleason score and prostate-specific antigen levels. However, these tools still do not adequately predict patient outcome. The aim of this study was to investigate whether ZNF750 could have a role in better stratifying patients, identifying those with a higher risk of metastasis and with the poorest prognosis. The data reported here revealed that ZNF750 protein levels are reduced in human prostate cancer samples, and this reduction is even higher in metastatic samples. Interestingly, nuclear positivity is significantly reduced in patients with metastatic prostate cancer, regardless of both Gleason score and grade group. More importantly, the bioinformatics analysis indicates that ZNF750 expression is positively correlated with better prognosis. Overall, our findings suggest that nuclear expression of ZNF750 may be a reliable prognostic biomarker for metastatic prostate cancer, which lays the foundation for the development of new biological therapies.

Gene expression in organoids: an expanding horizon

Recent development of human three-dimensional organoid cultures has opened new doors and opportunities ranging from modelling human development in vitro to personalised cancer therapies. These new in vitro systems are opening new horizons to the classic understanding of human development and disease. However, the complexity and heterogeneity of these models requires cutting-edge techniques to capture and trace global changes in gene expression to enable identification of key players and uncover the underlying molecular mechanisms. Rapid development of sequencing approaches made possible global transcriptome analyses and epigenetic profiling. Despite challenges in organoid culture and handling, these techniques are now being adapted to embrace organoids derived from a wide range of human tissues. Here, we review current state-of-the-art multi-omics technologies, such as single-cell transcriptomics and chromatin accessibility assays, employed to study organoids as a model for development and a platform for precision medicine.

Dual Role of p73 in Cancer Microenvironment and DNA Damage Response

Understanding the mechanisms that regulate cancer progression is pivotal for the development of new therapies. Although p53 is mutated in half of human cancers, its family member p73 is not. At the same time, isoforms of p73 are often overexpressed in cancers and p73 can overtake many p53 functions to kill abnormal cells. According to the latest studies, while p73 represses epithelial–mesenchymal transition and metastasis, it can also promote tumour growth by modulating crosstalk between cancer and immune cells in the tumor microenvironment, M2 macrophage polarisation, Th2 T-cell differentiation, and angiogenesis. Thus, p73 likely plays a dual role as a tumor suppressor by regulating apoptosis in response to genotoxic stress or as an oncoprotein by promoting the immunosuppressive environment and immune cell differentiation.

Reticulon-1C Involvement in Muscle Regeneration

Skeletal muscle is a very dynamic and plastic tissue, being essential for posture, locomotion and respiratory movement. Muscle atrophy or genetic muscle disorders, such as muscular dystrophies, are characterized by myofiber degeneration and replacement with fibrotic tissue. Recent studies suggest that changes in muscle metabolism such as mitochondrial dysfunction and dysregulation of intracellular Ca²⁺ homeostasis are implicated in many adverse conditions affecting skeletal muscle. Accumulating evidence also suggests that ER stress may play an important part in the pathogenesis of inflammatory myopathies and genetic muscle disorders. Among the different known proteins regulating ER structure and function, we focused on RTN-1C, a member of the reticulon proteins family localized on the ER membrane. We previously demonstrated that RTN-1C expression modulates cytosolic calcium concentration and ER stress pathway. Moreover, we recently reported a role for the reticulon protein in autophagy regulation. In this study, we found that muscle differentiation process positively correlates with RTN-1C expression and UPR pathway up-regulation during myogenesis. To better characterize the role of the reticulon protein alongside myogenic and muscle regenerative processes, we performed in vivo experiments using either a model of muscle injury or a photogenic model for Duchenne muscular dystrophy. The obtained results revealed RTN-1C up-regulation in mice undergoing active regeneration and localization in the injured myofibers. The presented results strongly suggested that RTN-1C, as a protein involved in key aspects of muscle metabolism, may represent a new target to promote muscle regeneration and repair upon injury.

The Regulatory Role of Reticulons in Neurodegeneration: Insights Underpinning Therapeutic Potential for Neurodegenerative Diseases

In the last few decades, cytoplasmic organellar dysfunction, such as that of the endoplasmic reticulum (ER), has created a new area of research interest towards the development of serious health maladies including neurodegenerative diseases. In this context, the extensively dispersed family of ER-localized proteins, i.e. reticulons (RTNs), is gaining interest because of its regulative control over neural regeneration. As most neurodegenerative diseases are pathologically manifested with the accretion of misfolded proteins with subsequent induction of ER stress, the regulatory role of RTNs in neural dysfunction cannot be ignored. With the limited information available in the literature, delineation of the functional connection between rising consequences of neurodegenerative diseases and RTNs need to be elucidated. In this review, we provide a broad overview on the recently revealed regulatory roles of reticulons in the pathophysiology of several health maladies, with special emphasis on neurodegeneration. Additionally, we have also recapitulated the decisive role of RTN4 in neurite regeneration and highlighted how neurodegeneration and proteinopathies are mechanistically linked with each other through specific RTN paralogues. With the recent findings advocating zebrafish Rtn4b (a mammalian Nogo-A homologue) downregulation following central nervous system (CNS) lesion, RTNs provides new insight into the CNS regeneration. However, there are controversies with respect to the role of Rtn4b in zebrafish CNS regeneration. Given these controversies, the connection between the unique regenerative capabilities of zebrafish CNS by distinct compensatory mechanisms and Rtn4b signalling pathway could shed light on the development of new therapeutic strategies against serious neurodegenerative diseases.

Modulation of autophagy by RTN-1C: role in autophagosome biogenesis

The endoplasmic reticulum (ER) is a key organelle fundamental for the maintenance of cellular homeostasis and to determine the cell’s fate under stress conditions. Among the known proteins that regulate ER structure and function there is Reticulon-1C (RTN-1C), a member of the reticulon family localized primarily on the ER membrane. We previously demonstrated that RTN-1C expression affects ER function and stress condition. ER is an essential site for the regulation of apoptotic pathways and it has also been recently recognized as an important component of autophagic signaling. Based on these evidences, we have investigated the impact of RTN-1C modulation on autophagy induction. Interestingly we found that reticulon overexpression is able to activate autophagic machinery and its silencing results in a significative inhibition of both basal and induced autophagic response. Using different experimental approaches we demonstrated that RTN-1C colocalizes with ATG16L and LC3II on the autophagosomes. Considering the key role of reticulon proteins in the control of ER membrane shaping and homeostasis, our data suggest the participation of RTN-1C in the autophagic vesicle biogenesis at the level of the ER compartment. Our data indicate a new mechanism by which this structural ER protein modulates cellular stress, that is at the basis of different autophagy-related pathologies.

Knockdown of RTN1-C attenuates traumatic neuronal injury through regulating intracellular Ca2+ homeostasis

Reticulons (RTNs) are a family of membrane-bound proteins that are dominantly localized to the endoplasmic reticulum (ER) membrane. RTN1-C is one member of RTNs abundantly expressed in the brain and has been shown to mediate neuronal injury in cerebral ischemia models. In the present study, we investigated the role of RTN1-C in an in vitro brain trauma model mimicked by traumatic neuronal injury (TNI) in primary cultured cortical neurons. TNI increased the expression of RTN1-C in cortical neurons but had no effect on RTN1-A and RTN1-B. Knockdown of RTN1-C with specific siRNA (Si-RTN1-C) significantly decreased cytotoxicity and apoptosis after TNI. The results of Ca²⁺ imaging showed that intracellular Ca²⁺ overload induced by TNI was attenuated by RTN1-C knockdown. Furthermore, the activation of metabotropic glutamate receptor 1 (mGluR1)-induced Ca²⁺ response was partially prevented by Si-RTN1-C transfection. We also evaluated the role of RTN1-C in store-operated Ca²⁺ entry (SOCE) in cortical neurons using the ER Ca²⁺ inducer thapsigargin (Tg). The results showed that knockdown of RTN1-C alleviated the SOCE-mediated Ca²⁺ influx and decreased the expression of stromal interactive molecule 1 (STIM1). In summary, the present study found that knockdown of RTN1-C protected neurons against TNI via preservation of intracellular Ca²⁺ homeostasis, which was associated with the inhibition of mGluR1-mediated ER Ca²⁺ release and suppression of STIM1-related SOCE. Thus, RTN1-C might represent a therapeutic target for traumatic brain injury (TBI) research.

Encephalitis is mediated by ROP18 of Toxoplasma gondii, a severe pathogen in AIDS patients

The neurotropic parasite Toxoplasma gondii is a globally distributed parasitic protozoan among mammalian hosts, including humans. During the course of infection, the CNS is the most commonly damaged organ among invaded tissues. The polymorphic rhoptry protein 18 (ROP18) is a key serine (Ser)/threonine (Thr) kinase that phosphorylates host proteins to modulate acute virulence. However, the basis of neurotropism and the specific substrates through which ROP18 exerts neuropathogenesis remain unknown. Using mass spectrometry, we performed proteomic analysis of proteins that selectively bind to active ROP18 and identified RTN1-C, an endoplasmic reticulum (ER) protein that is preferentially expressed in the CNS. We demonstrated that ROP18 is associated with the N-terminal portion of RTN1-C and specifically phosphorylates RTN1-C at Ser7/134 and Thr4/8/118. ROP18 phosphorylation of RTN1-C triggers ER stress-mediated apoptosis in neural cells. Remarkably, ROP18 phosphorylation of RTN1-C enhances glucose-regulated protein 78 (GRP78) acetylation by attenuating the activity of histone deacetylase (HDAC), and this event is associated with an increase of neural apoptosis. These results clearly demonstrate that both RTN1-C and HDACs are involved in T. gondii ROP18-mediated pathogenesis of encephalitis during Toxoplasma infection.

The Reticulum-Associated Protein RTN1A Specifically Identifies Human Dendritic Cells

RTN1 is an endoplasmic reticulum-associated protein that was initially identified in neuronal tissues. Here we show that the main isoform RTN1A is a marker for dendritic cells. In the skin, HLA-DR⁺CD1a^highCD207⁺CD11c^weak Langerhans cells were the only cells in the epidermis, and HLA-DR⁺CD11c⁺ dendritic cells were the main cells in the dermis, expressing this protein. RTN1A⁺ dendritic cells were also found in gingiva, trachea, tonsil, thymus, and peripheral blood. During differentiation of MUTZ-3 cells into Langerhans cells, expression of RTN1A mRNA and protein preceded established Langerhans cell markers CD1a and CD207, and RTN1A protein partially co-localized with the endoplasmic reticulum marker protein disulfide isomerase. In line with this observation, we found that RTN1A was expressed by around 80% of Langerhans cell precursors in human embryonic skin. Our findings show that RTN1A is a marker for cells of the dendritic lineage, including Langerhans cells and dermal dendritic cells. This unexpected finding will serve as a starting point for the elucidation of the, until now, elusive functional roles of RTN1A in both the immune and the nervous system.

RTN1 and RTN3 protein are differentially associated with senile plaques in Alzheimer's brains

Reticulon proteins (RTNs), consisting of RTN1 to RTN4, were previously shown to interact with BACE1 by negatively modulating its secretase activity. In RTN3-null mice, RTN1 expression was slightly elevated. To understand the in vivo role of RTN1, we generated RTN1-null mice and compared the effects of RTN1 and RTN3 on BACE1 modulation. We show that RTN1 is mostly expressed by neurons and not by glial cells under normal conditions, similar to the expression of RTN3. However, RTN1 is more localized in dendrites and is an excellent marker for dendrites of Purkinje cells, while RTN3 expression is less evident in dendrites. This differential localization also correlates with their associations with amyloid plaques in Alzheimer's brains: RTN3, but not RTN1, is abundantly enriched in dystrophic neurites. RTN3 deficiency causes elevation of BACE1 protein levels, while RTN1 deficiency shows no obvious effects on BACE1 activity due to compensation by RTN3, as RTN1 deficiency causes elevation of RTN3 expression. Hence, expression of RTN1 and RTN3 is tightly regulated in mouse brains. Together, our data show that RTN1 and RTN3 have differential effects on the formation of senile plaques in Alzheimer's brains and that RTN3 has a more prominent role in Alzheimer's pathogenesis.

Gene networks in neurodegenerative disorders

Three neurodegenerative diseases [Amyotrophic Lateral Sclerosis (ALS), Parkinson's disease (PD) and Alzheimer's disease (AD)] have many characteristics like pathological mechanisms and genes. In this sense some researchers postulate that these diseases share the same alterations and that one alteration in a specific protein triggers one of these diseases. Analyses of gene expression may shed more light on how to discover pathways, pathologic mechanisms associated with the disease, biomarkers and potential therapeutic targets. In this review, we analyze four microarrays related to three neurodegenerative diseases. We will systematically examine seven genes (CHN1, MDH1, PCP4, RTN1, SLC14A1, SNAP25 and VSNL1) that are altered in the three neurodegenerative diseases. A network was built and used to identify pathways, miRNA and drugs associated with ALS, AD and PD using Cytoscape software an interaction network based on the protein interactions of these genes. The most important affected pathway is PI3K-Akt signalling. Thirteen microRNAs (miRNA-19B1, miRNA-107, miRNA-124-1, miRNA-124-2, miRNA-9-2, miRNA-29A, miRNA-9-3, miRNA-328, miRNA-19B2, miRNA-29B2, miRNA-124-3, miRNA-15A and miRNA-9-1) and four drugs (Estradiol, Acetaminophen, Resveratrol and Progesterone) for new possible treatments were identified.

The Histone-Deacetylase-Inhibitor Suberoylanilide Hydroxamic Acid Promotes Dental Pulp Repair Mechanisms Through Modulation of Matrix Metalloproteinase-13 Activity

Direct application of histone-deacetylase-inhibitors (HDACis) to dental pulp cells (DPCs) induces chromatin changes, promoting gene expression and cellular-reparative events. We have previously demonstrated that HDACis (valproic acid, trichostatin A) increase mineralization in dental papillae-derived cell-lines and primary DPCs by stimulation of dentinogenic gene expression. Here, we investigated novel genes regulated by the HDACi, suberoylanilide hydroxamic acid (SAHA), to identify new pathways contributing to DPC differentiation. SAHA significantly compromised DPC viability only at relatively high concentrations (5 μM); while low concentrations (1 μM) SAHA did not increase apoptosis. HDACi-exposure for 24 h induced mineralization-per-cell dose-dependently after 2 weeks; however, constant 14d SAHA-exposure inhibited mineralization. Microarray analysis (24 h and 14 days) of SAHA exposed cultures highlighted that 764 transcripts showed a significant >2.0-fold change at 24 h, which reduced to 36 genes at 14 days. 59% of genes were down-regulated at 24 h and 36% at 14 days, respectively. Pathway analysis indicated SAHA increased expression of members of the matrix metalloproteinase (MMP) family. Furthermore, SAHA-supplementation increased MMP-13 protein expression (7 d, 14 days) and enzyme activity (48 h, 14 days). Selective MMP-13-inhibition (MMP-13i) dose-dependently accelerated mineralization in both SAHA-treated and non-treated cultures. MMP-13i-supplementation promoted expression of several mineralization-associated markers, however, HDACi-induced cell migration and wound healing were impaired. Data demonstrate that short-term low-dose SAHA-exposure promotes mineralization in DPCs by modulating gene pathways and tissue proteases. MMP-13i further increased mineralization-associated events, but decreased HDACi cell migration indicating a specific role for MMP-13 in pulpal repair processes. Pharmacological inhibition of HDAC and MMP may provide novel insights into pulpal repair processes with significant translational benefit. J. Cell. Physiol. 231: 798-816, 2016. © 2015 Wiley Periodicals, Inc.

A genome-wide association study for colorectal cancer identifies a risk locus in 14q23.1

Over 50 loci associated with colorectal cancer (CRC) have been uncovered by genome-wide association studies (GWAS). Identifying additional loci has the potential to help elucidate aspects of the underlying biological processes leading to better understanding of the pathogenesis of the disease. We re-evaluated a GWAS by excluding controls that have family history of CRC or personal history of colorectal polyps, as we hypothesized that their inclusion reduces power to detect associations. This is supported empirically and through simulations. Two-phase GWAS analysis was performed in a total of 16,517 cases and 14,487 controls. We identified rs17094983, a SNP associated with risk of CRC [p = 2.5 × 10(-10); odds ratio estimated by re-including all controls (OR) = 0.87, 95% confidence interval (CI) 0.83-0.91; minor allele frequency (MAF) = 13%]. Results were replicated in samples of African descent (1894 cases and 4703 controls; p = 0.01; OR = 0.86, 95% CI 0.77-0.97; MAF = 16 %). Gene expression data in 195 colon adenocarcinomas and 59 normal colon tissues from two different studies revealed that this locus has genotypes that are associated with RTN1 (Reticulon 1) expression (p = 0.001), a protein-coding gene involved in survival and proliferation of cancer cells which is highly expressed in normal colon tissues but has significantly reduced expression in tumor cells (p = 1.3 × 10(-8)).

Aberrantly Expressed OTX Homeobox Genes Deregulate B-Cell Differentiation in Hodgkin Lymphoma

In Hodgkin lymphoma (HL) we recently reported that deregulated homeobox gene MSX1 mediates repression of the B-cell specific transcription factor ZHX2. In this study we investigated regulation of MSX1 in this B-cell malignancy. Accordingly, we analyzed expression and function of OTX homeobox genes which activate MSX1 transcription during embryonal development in the neural plate border region. Our data demonstrate that OTX1 and OTX2 are aberrantly expressed in both HL patients and cell lines. Moreover, both OTX loci are targeted by genomic gains in overexpressing cell lines. Comparative expression profiling and subsequent pathway modulations in HL cell lines indicated that aberrantly enhanced FGF2-signalling activates the expression of OTX2. Downstream analyses of OTX2 demonstrated transcriptional activation of genes encoding transcription factors MSX1, FOXC1 and ZHX1. Interestingly, examination of the physiological expression profile of ZHX1 in normal hematopoietic cells revealed elevated levels in T-cells and reduced expression in B-cells, indicating a discriminatory role in lymphopoiesis. Furthermore, two OTX-negative HL cell lines overexpressed ZHX1 in correlation with genomic amplification of its locus at chromosomal band 8q24, supporting the oncogenic potential of this gene in HL. Taken together, our data demonstrate that deregulated homeobox genes MSX1 and OTX2 respectively impact transcriptional inhibition of (B-cell specific) ZHX2 and activation of (T-cell specific) ZHX1. Thus, we show how reactivation of a specific embryonal gene regulatory network promotes disturbed B-cell differentiation in HL.

RTN1 mediates progression of kidney disease by inducing ER stress

Identification of new biomarkers and drug targets for chronic kidney disease (CKD) is required for the development of more effective therapy. Here we report an association between expression of reticulon 1 (RTN1) and severity of CKD. An isoform-specific increase in the expression of RTN1A is detected in the diseased kidneys from mice and humans, and correlates inversely with renal function in patients with diabetic nephropathy. RTN1 overexpression in renal cells induces ER stress and apoptosis, whereas RTN1 knockdown attenuates tunicamycin-induced and hyperglycaemia-induced ER stress and apoptosis. RTN1A interacts with PERK through its N-terminal and C-terminal domains, and mutation of these domains prevents this effect on ER stress. Knockdown of Rtn1a expression in vivo attenuates ER stress and renal fibrosis in mice with unilateral ureteral obstruction, and also attenuates ER stress, proteinuria, glomerular hypertrophy and mesangial expansion in diabetic mice. Together, these data indicate that RTN1A contributes to progression of kidney disease by inducing ER stress.

ER stress is associated with the pathogenesis of chronic kidney disease (CKD) and new CKD therapies are needed. Here the authors show that expression of Rtn1 can control severity of renal disease and that inhibition of its expression can attenuate ER stress and CKD.

Stress signaling in mammalian oocytes and embryos: a basis for intervention and improvement of outcomes

Oocytes and early stage embryos are highly sensitive to variation in diverse exogenous factors such as temperature, osmolarity, oxygen, nutrient restriction, pH, shear stress, toxins, amino acid availability, and lipids. It is becoming increasingly apparent that many such factors negatively affect the endoplasmic reticulum, protein synthesis and protein processing, initiating ER stress and unfolded protein responses. As a result, ER stress signaling serves as a common mediator of cellular responses to diverse stressors. In oocytes and embryos, this leads to developmental arrest and epigenetic changes. Recent studies have revealed that preventing ER stress or inhibiting ER stress signaling can preserve or even enhance oocyte and embryo developmental potential. This review examines ER stress signaling, how it arises, how it affects oocytes and embryos, and how its occurrence can be managed or prevented.

Endoplasmic reticulum stress signaling in mammalian oocytes and embryos: life in balance

Mammalian oocytes and embryos are exquisitely sensitive to a wide range of insults related to physical stress, chemical exposure, and exposures to adverse maternal nutrition or health status. Although cells manifest specific responses to various stressors, many of these stressors intersect at the endoplasmic reticulum (ER), where disruptions in protein folding and production of reactive oxygen species initiate downstream signaling events. These signals modulate mRNA translation and gene transcription, leading to recovery, activation of autophagy, or with severe and prolonged stress, apoptosis. ER stress signaling has recently come to the fore as a major contributor to embryo demise. Accordingly, agents that modulate or inhibit ER stress signaling have yielded beneficial effects on embryo survival and long-term developmental potential. We review here the mechanisms of ER stress signaling, their connections to mammalian oocytes and embryos, and the promising indications that interventions in this pathway may provide new opportunities for improving mammalian reproduction and health.

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.

Neuroprotective effect of water extract of Panax ginseng on corticosterone-induced apoptosis in PC12 cells and its underlying molecule mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Panax ginseng C.A. Meyer (Family Araliaceae) is an important medicinal plant which has been employed as a panacea for more than 2,000 years in China. It has the actions of invigorating primordial qi, recovering pulse and desertion, engendering liquid, and calming spirit. The water extract of Panax ginseng (WEG) has been used to treat kinds of central nervous system disorders, such as depression, insomnia, Alzheimer׳s disease and Parkinson׳s disease. Our previous work has demonstrated that WEG possessed antidepressant-like activities in both acute and chronic stress models of depression. Nevertheless, there are no studies on the cytoprotection and potential mechanisms of WEG on corticosterone-induced apoptosis. The present study focuses on cytoprotection against corticosterone-induced neurotoxicity in PC12 cells and its underlying molecule mechanisms of the antidepressant-like effect of WEG.

MATERIALS AND METHODS

The PC12 cells were treated with 250 μmol/L corticosterone in the absence or presence of WEG for 24h, then 3-(4,5-dimethy thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) detection, Hoechst33342 staining and TUNEL staining were investigated to confirm the neuroprotection of WEG. Then, mitochondrial permeability transition pore (mPTP), mitochondrial membrane potential (MMP), intracellular Ca(2+) ([Ca(2+)]i), reactive oxygen species (ROS) concentration, and the expression level of glucocorticoid receptor (GR), heat shock protein 90 (Hsp90), histone deactylase 6 (HDAC6), glucose-regulated protein 78 (GRP78), growth arrest and DNA damage inducible protein 153 (GADD153), X-box DNA-binding protein-1 (XBP-1), caspase-12, cytochrome C, inhibitor of caspase-activated deoxyribonuclease (ICAD), caspase-3 and caspase-9 were assessed by Western Blot analysis to understand the molecule mechanisms of neuroprotection of WEG.

RESULTS

WEG partly reversed corticosterone-induced damage in PC12 cells, which increased cell viability, decreased LDH release, and attenuated corticosterone-induced apoptosis as compared with the corticosterone-treated group. Mechanistically, compared with the corticosterone-treated group, WEG strongly attenuated [Ca(2+)]i overload and ROS level, and restored mitochondrial function, including mPTP and MMP. Furthermore, WEG strongly up-regulated the expression of GR and HDAC6, and down-regulated the expression of Hsp90, cytochrome C, ICAD, caspase-3, caspase-9 as well as endoplasmic reticulum (ER) stress-related proteins, such as GADD153, GRP78, XBP-1, and caspase-12.

CONCLUSION

WEG possessed neuroprotection against corticosterone-induced damage in PC12 cells, and the underlying molecule mechanisms was depended on the intervening of HDAC6 and HSP90 of the GR-related function proteins, and subsequent restoration of ER and mitochondria functions.

A novel centrosome and microtubules associated subcellular localization of Nogo-A: implications for neuronal development

Oligodendrocyte-derived neurite-outgrowth inhibitor Nogo-A and its restriction mechanism are well-known. Recently, Nogo-A is reported to be abundantly expressed in neurons, however, the concrete link between neuronal Nogo-A and neuronal development is poorly understood. In the present study, we used Neuro2A and COS7 cell lines to clarify that Nogo-A largely distributed in the centrosome and microtubules-rich regions. When endogenous Nogo-A was down-regulated with RNA interference, the percentage of cell differentiation and the total neurite length of Neuro2A exposed to valproic acid (VPA) decreased sharply. Furthermore, in primary neurons, acetylated α-tubulin decreased at the tips of neurites where endogenous Nogo-A was still highly expressed. In HEK293FT cell lines, Nogo-A overexpression could redistribute acetylated α-tubulin but not change the level of α-tubulin. Together, our data discovered that centrosome- and microtubules-localized Nogo-A positively regulates neuronal differentiation and neurite outgrowth of Neuro2A cell lines, implicating the essential roles of subcellular Nogo-A in neuronal development.

The role of reticulons in neurodegenerative diseases

Reticulons (RTNs) are a group of membrane-associated proteins mainly responsible for shaping the tubular endoplasmic reticulum network, membrane trafficking, inhibition of axonal growth, and apoptosis. These proteins share a common sequence feature, the reticulon homology domain, which consists of paired hydrophobic stretches that are believed to induce membrane curvature by acting as a wedge in bilayer membranes. RTNs are ubiquitously expressed in all tissues, but each RTN member exhibits a unique expression pattern that prefers certain tissues or even cell types. Recently, accumulated evidence has suggested additional and unexpected roles for RTNs, including those on DNA binding, autophagy, and several inflammatory-related functions. These manifold actions of RTNs account for their ever-growing recognition of their involvement in neurodegenerative diseases like Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis, as well as hereditary spastic paraplegia. This review summarizes the latest discoveries on RTNs in human pathophysiology, and the engagement of these in neurodegeneration, along with the implications of these findings for a better understanding of the molecular events triggered by RTNs and their potential exploitation as next-generation therapeutics.

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.

An involvement of oxidative stress in endoplasmic reticulum stress and its associated diseases

The endoplasmic reticulum (ER) is the major site of calcium storage and protein folding. It has a unique oxidizing-folding environment due to the predominant disulfide bond formation during the process of protein folding. Alterations in the oxidative environment of the ER and also intra-ER Ca²⁺ cause the production of ER stress-induced reactive oxygen species (ROS). Protein disulfide isomerases, endoplasmic reticulum oxidoreductin-1, reduced glutathione and mitochondrial electron transport chain proteins also play crucial roles in ER stress-induced production of ROS. In this article, we discuss ER stress-associated ROS and related diseases, and the current understanding of the signaling transduction involved in ER stress.

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.

A metal-binding site in the RTN1-C protein: new perspectives on the physiological role of a neuronal protein

Reticulon 1-C (RTN1-C) is an ER-associated neuronal protein characterized by horse-shoe-like topology with two transmembrane helices and the N- and C-terminal regions which are supposed in the cytosolic side of ER. The physiological role of this protein is not completely clarified, but several studies have suggested its involvement in the neuronal differentiation, membrane vesicle trafficking and induction of apoptosis. The C-terminal region of RTN1-C is characterized by the presence of a H4 histone consensus sequence that makes it able to interact with nucleic acids and HDAC enzymes both in vitro and in vivo. In the present study a potential metal ion binding motif (HxE/D) at the C-terminal of the RTN1-C has been identified and its capability to bind metals investigated by UV-vis, CD, multidimensional NMR spectroscopy and biological assays. The results suggest a possible implication of the metal ions in the mechanisms of formation of the recently observed RTNs multiprotein complexes contributing to understand the structure and function of this neuronal membrane protein, suggesting a possible effect of the metal binding property on its biological function.

The reticulons: guardians of the structure and function of the endoplasmic reticulum

The endoplasmic reticulum (ER) consists of the nuclear envelope and a peripheral network of tubules and membrane sheets. The tubules are shaped by a specific class of curvature stabilizing proteins, the reticulons and DP1; however it is still unclear how the sheets are assembled. The ER is the cellular compartment responsible for secretory and membrane protein synthesis. The reducing conditions of ER lead to the intra/inter-chain formation of new disulphide bonds into polypeptides during protein folding assessed by enzymatic or spontaneous reactions. Moreover, ER represents the main intracellular calcium storage site and it plays an important role in calcium signaling that impacts many cellular processes. Accordingly, the maintenance of ER function represents an essential condition for the cell, and ER morphology constitutes an important prerogative of it. Furthermore, it is well known that ER undergoes prominent shape transitions during events such as cell division and differentiation. Thus, maintaining the correct ER structure is an essential feature for cellular physiology. Now, it is known that proper ER-associated proteins play a fundamental role in ER tubules formation. Among these ER-shaping proteins are the reticulons (RTN), which are acquiring a relevant position. In fact, beyond the structural role of reticulons, in very recent years new and deeper functional implications of these proteins are emerging in relation to their involvement in several cellular processes.

Transcriptional analysis implicates endoplasmic reticulum stress in bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE) is a fatal, transmissible, neurodegenerative disease of cattle. To date, the disease process is still poorly understood. In this study, brain tissue samples from animals naturally infected with BSE were analysed to identify differentially regulated genes using Affymetrix GeneChip Bovine Genome Arrays. A total of 230 genes were shown to be differentially regulated and many of these genes encode proteins involved in immune response, apoptosis, cell adhesion, stress response and transcription. Seventeen genes are associated with the endoplasmic reticulum (ER) and 10 of these 17 genes are involved in stress related responses including ER chaperones, Grp94 and Grp170. Western blotting analysis showed that another ER chaperone, Grp78, was up-regulated in BSE. Up-regulation of these three chaperones strongly suggests the presence of ER stress and the activation of the unfolded protein response (UPR) in BSE. The occurrence of ER stress was also supported by changes in gene expression for cytosolic proteins, such as the chaperone pair of Hsp70 and DnaJ. Many genes associated with the ubiquitin-proteasome pathway and the autophagy-lysosome system were differentially regulated, indicating that both pathways might be activated in response to ER stress. A model is presented to explain the mechanisms of prion neurotoxicity using these ER stress related responses. Clustering analysis showed that the differently regulated genes found from the naturally infected BSE cases could be used to predict the infectious status of the samples experimentally infected with BSE from the previous study and vice versa. Proof-of-principle gene expression biomarkers were found to represent BSE using 10 genes with 94% sensitivity and 87% specificity.

Emerging functions of myelin-associated proteins during development, neuronal plasticity, and neurodegeneration

Adult mammalian central nervous system (CNS) axons have a limited regrowth capacity following injury. Myelin-associated inhibitors (MAIs) limit axonal outgrowth, and their blockage improves the regeneration of damaged fiber tracts. Three of these proteins, Nogo-A, MAG, and OMgp, share two common neuronal receptors: NgR1, together with its coreceptors [p75(NTR), TROY, and Lingo-1]; and the recently described paired immunoglobulin-like receptor B (PirB). These proteins impair neuronal regeneration by limiting axonal sprouting. Some of the elements involved in the myelin inhibitory pathways may still be unknown, but the discovery that blocking both PirB and NgR1 activities leads to near-complete release from myelin inhibition, sheds light on one of the most competitive and intense fields of neuroregeneration study in recent decades. In parallel with the identification and characterization of the roles and functions of these inhibitory molecules in axonal regeneration, data gathered in the field strongly suggest that most of these proteins have roles other than axonal growth inhibition. The discovery of a new group of interacting partners for myelin-associated receptors and ligands, as well as functional studies within or outside the CNS environment, highlights the potential new physiological roles for these proteins in processes, such as development, neuronal homeostasis, plasticity, and neurodegeneration.

A molecular portrait of gastrointestinal stromal tumors: an integrative analysis of gene expression profiling and high-resolution genomic copy number

In addition to KIT and PDGFRA mutations, sequential accumulation of other genetic events is involved in the development and progression of gastrointestinal stromal tumors (GISTs). Until recently, the significance of these other alterations has not been thoroughly investigated. We report the first study that integrates gene expression profiling and high-resolution genomic copy number analyses in GIST. Fresh tissue specimens from 25 patients with GIST were collected, and gene expression profiling and high-resolution genomic copy number analyses were performed, using Affymetrix U133Plus and SNP array 6.0. We found that all 21 mutant GIST patients showed both macroscopic cytogenetic alterations and cryptic microdeletions or amplifications, whereas 75% (three of four) of wild-type patients with GIST did not show genomic imbalances. The most frequently observed chromosomal alterations in patients with mutant GIST included 14q complete or partial deletion (17 of 25), 1p deletion (14 of 25) and 22q deletion (10 of 25). Genetic targets of the chromosomal aberrations were selected by integrated analysis of copy number and gene expression data. We detected the involvement of known oncogenes and tumor suppressors including KRAS in chr 12p amplification and KIF1B, PPM1A, NF2 in chr 1p, 14q and 22p deletions, respectively. The genomic segment most frequently altered in mutated samples was the 14q23.1 region, which contains potentially novel tumor suppressors, including DAAM1, RTN1 and DACT1. siRNA-mediated RTN1 downregulation showed evidence for the potential role in GIST pathogenesis. The combination of gene expression profiling and high-resolution genomic copy number analysis offers a detailed molecular portrait of GISTs, providing an essential comprehensive knowledge necessary to guide the discovery of novel target genes involved in tumor development and progression.

Characterization of gene expression induced by RTN-1C in human neuroblastoma cells and in mouse brain

The endoplasmic reticulum (ER) stress-mediated pathway is involved in a wide range of human neurodegenerative disorders. Hence, molecules that regulate the ER stress response represent potential candidates as drug targets to tackle these diseases. In previous studies we demonstrated that upon acetylation the reticulon-1C (RTN-1C) variant of the reticulon family leads to inhibition of histone deacetylase (HDAC) enzymatic activity and endoplasmic reticulum stress-dependent apoptosis. Here, by microarray analysis of the whole human genome we found that RTN-1C is able to specifically regulate gene expression, modulating transcript clusters which have been implicated in the onset of neurodegenerative disorders. Interestingly, we show that some of the identified genes were also modulated in vivo in a brain-specific mouse model overexpressing RTN-1C. These data provide a basis for further investigation of RTN-1C as a potential molecular target for use in therapy and as a specific marker for neurological diseases.