Nischarin, a novel protein that interacts with the integrin alpha5 subunit and inhibits cell migration

Clinical significance of downregulated NISCH expression in skin cutaneous melanoma: Modulation of tumor cell invasion, migration, and EMT via PAK1 inhibition

OBJECTIVE

This study aimed to investigate the expression and functional role of NISCH in skin cutaneous melanoma (SKCM), exploring its association with clinical characteristics and its potential impact on human skin melanoma cell behavior.

METHODS

The research assessed differential NISCH expression in SKCM tissues using the GEPIA (Gene Expression Profiling Interactive Analysis) database and validated these findings through immunohistochemical staining of 45 clinical samples. To affirm NISCH expression at the cellular level, three human skin melanoma cell lines (RPMI-7951, A375, MEL-5), and the human normal skin cell line HEMa underwent quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting. Transwell experiments evaluated the migration and invasion capabilities of RPMI-7951 and A375 cells post-transduction with NISCH or PAK1 lentiviral activation particles. Additionally, qRT-PCR analysis of epithelial-mesenchymal transition (EMT)-related gene expression (Vimentin, E-cadherin, N-cadherin) was conducted in A375 and RPMI-7951 cells.

RESULTS

SKCM tissues exhibited significantly reduced NISCH expression compared to normal tissues. Immunohistochemical analysis revealed predominant nuclear localization of NISCH in melanoma cells, with reduced expression significantly correlating with sex, advanced stage, and lymph node metastasis. Melanoma cell lines displayed lower NISCH expression levels compared to normal skin cells. Functional experiments showcased that NISCH overexpression suppressed p-PAK1/PAK1, while PAK1 upregulation notably increased melanoma cell migration, invasion, and induced EMT. Remarkably, NISCH overexpression counteracted PAK1-induced effects on EMT, migration, and invasion in melanoma cells.

CONCLUSION

NISCH may significantly influence the aggressive behavior of SKCM cells via the PAK1 pathway, making it a potential therapeutic target for managing melanoma metastasis.

Analysis of the nischarin expression across human tumor types reveals its context-dependent role and a potential as a target for drug repurposing in oncology

Nischarin was reported to be a tumor suppressor that plays a critical role in breast cancer initiation and progression, and a positive prognostic marker in breast, ovarian and lung cancers. Our group has found that nischarin had positive prognostic value in female melanoma patients, but negative in males. This opened up a question whether nischarin has tumor type-specific and sex-dependent roles in cancer progression. In this study, we systematically examined in the public databases the prognostic value of nischarin in solid tumors, regulation of its expression and associated signaling pathways. We also tested the effects of a nischarin agonist rilmenidine on cancer cell viability in vitro. Nischarin expression was decreased in tumors compared to the respective healthy tissues, most commonly due to the deletions of the nischarin gene and promoter methylation. Unlike in healthy tissues where it was located in the cytoplasm and at the membrane, in tumor tissues nischarin could also be observed in the nuclei, implying that nuclear translocation may also account for its cancer-specific role. Surprisingly, in several cancer types high nischarin expression was a negative prognostic marker. Gene set enrichment analysis showed that in tumors in which high nischarin expression was a negative prognostic marker, signaling pathways that regulate stemness were enriched. In concordance with the findings that nischarin expression was negatively associated with pathways that control cancer growth and progression, nischarin agonist rilmenidine decreased the viability of cancer cells in vitro. Taken together, our study lays a ground for functional studies of nischarin in a context-dependent manner and, given that nischarin has several clinically approved agonists, provides rationale for their repurposing, at least in tumors in which nischarin is predicted to be a positive prognostic marker.

Contribution of Nischarin/IRAS in CNS development, injury and diseases

BACKGROUND

Murine Nischarin and its human homolog IRAS are scaffold proteins highly expressed in the central nervous system (CNS). Nischarin was initially discovered as a tumor suppressor protein, and recent studies have also explored its potential value in the CNS. Research on IRAS has largely focused on its effect on opioid dependence. Although the role of Nischarin/IRAS in the physiological function and pathological process of the CNS has gradually attracted attention and the related research results are expected to be applied in clinical practice, there is no systematic review of the role and mechanisms of Nischarin/IRAS in the CNS so far.

AIM OF REVIEW

This review will systematically analyze the role and mechanism of Nischarin/IRAS in the CNS, and provide necessary references and possible targets for the treatment of neurological diseases, thereby broadening the direction of Nischarin/IRAS research and facilitating clinical translation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The pathophysiological processes affected by dysregulation of Nischarin/IRAS expression in the CNS are mainly introduced, including spinal cord injury (SCI), opioid dependence, anxiety, depression, and autism. The molecular mechanisms such as factors regulating Nischarin/IRAS expression and signal transduction pathways regulated by Nischarin/IRAS are systematically summarized. Finally, the clinical application of Nischarin/IRAS has been prospected.

Nischarin expression may have differing roles in male and female melanoma patients

Due to the development of resistance to previously effective therapies, there is a constant need for novel treatment modalities for metastatic melanoma. Nischarin (NISCH) is a druggable scaffolding protein reported as a tumor suppressor and a positive prognostic marker in breast and ovarian cancers through regulation of cancer cell survival, motility and invasion. The aim of this study was to examine the expression and potential role of nischarin in melanoma. We found that nischarin expression was decreased in melanoma tissues compared to the uninvolved skin, and this was attributed to the presence of microdeletions and hyper-methylation of the NISCH promoter in the tumor tissue. In addition to the previously reported cytoplasmic and membranous localization, we observed nischarin in the nuclei in melanoma patients' tissues. NISCH expression in primary melanoma had favorable prognostic value for female patients, but, unexpectedly, high NISCH expression predicted worse prognosis for males. Gene set enrichment analysis suggested significant sex-related disparities in predicted association of NISCH with several signaling pathways, as well as with different tumor immune infiltrate composition in male and female patients. Taken together, our results imply that nischarin may have a role in melanoma progression, but that fine-tuning of the pathways it regulates is sex-dependent. KEY MESSAGES: Nischarin is a tumor suppressor whose role has not been investigated in melanoma. Nischarin expression was downregulated in melanoma tissue compared to the normal skin. Nischarin had the opposite prognostic value in male and female melanoma patients. Nischarin association with signaling pathways differed in females and males. Our findings challenge the current view of nischarin as a universal tumor suppressor.

Rilmenidine extends lifespan and healthspan in Caenorhabditis elegans via a nischarin I1-imidazoline receptor

Repurposing drugs capable of extending lifespan and health span has a huge untapped potential in translational geroscience. Here, we searched for known compounds that elicit a similar gene expression signature to caloric restriction and identified rilmenidine, an I1-imidazoline receptor agonist and prescription medication for the treatment of hypertension. We then show that treating Caenorhabditis elegans with rilmenidine at young and older ages increases lifespan. We also demonstrate that the stress-resilience, health span, and lifespan benefits of rilmenidine treatment in C. elegans are mediated by the I1-imidazoline receptor nish-1, implicating this receptor as a potential longevity target. Consistent with the shared caloric-restriction-mimicking gene signature, supplementing rilmenidine to calorically restricted C. elegans, genetic reduction of TORC1 function, or rapamycin treatment did not further increase lifespan. The rilmenidine-induced longevity required the transcription factors FOXO/DAF-16 and NRF1,2,3/SKN-1. Furthermore, we find that autophagy, but not AMPK signaling, was needed for rilmenidine-induced longevity. Moreover, transcriptional changes similar to caloric restriction were observed in liver and kidney tissues in mice treated with rilmenidine. Together, these results reveal a geroprotective and potential caloric restriction mimetic effect by rilmenidine that warrant fresh lines of inquiry into this compound.

Thymoquinone activates imidazoline receptor to enhance glucagon-like peptide-1 secretion in diabetic rats

INTRODUCTION

Thymoquinone (TQ) is one of the principal bioactive ingredients proven to exhibit anti-diabetic effects. Recently, glucagon-like peptide-1 (GLP-1) has been found to be involved in antidiabetic effects in rats. The aim of this study was to evaluate the mediation of GLP-1 in the antidiabetic effect of TQ and to understand the possible mechanisms.

MATERIAL AND METHODS

NCI-H716 cells and CHO-K1 cells were used to investigate the effects of TQ on GLP-1 secretion in vitro. In type 1 diabetic rats, the changes in plasma glucose and GLP-1 levels were evaluated with TQ treatment.

RESULTS

The direct effect of TQ on imidazoline receptors (I-Rs) was identified in CHO-K1 cells overexpressing I-Rs. Additionally, in the intestinal NCI-H716 cells that may secrete GLP-1, TQ treatment enhanced GLP-1 secretion in a dose-dependent manner. However, these effects of TQ were reduced by ablation of I-Rs with siRNA in NCI-H716 cells. Moreover, these effects were inhibited by BU224, the imidazoline I2 receptor (I-2R) antagonist. In diabetic rats, TQ increased plasma GLP-1 levels, which were inhibited by BU-224 treatment. Functionally, TQ-attenuated hyperglycemia is also evidenced through GLP-1 using pharmacological manipulations.

CONCLUSIONS

This report demonstrates that TQ may promote GLP-1 secretion through I-R activation to reduce hyperglycemia in type-1 diabetic rats.

The non-adrenergic imidazoline-1 receptor protein nischarin is a key regulator of astrocyte glutamate uptake

Astrocytic GLT-1 is the main glutamate transporter involved in glutamate buffering in the brain, pivotal for glutamate removal at excitatory synapses to terminate neurotransmission and for preventing excitotoxicity. We show here that the surface expression and function of GLT-1 can be rapidly modulated through the interaction of its N-terminus with the nonadrenergic imidazoline-1 receptor protein, Nischarin. The phox domain of Nischarin is critical for interaction and internalization of surface GLT-1. Using live super-resolution imaging, we found that glutamate accelerated Nischarin-GLT-1 internalization into endosomal structures. The surface GLT-1 level increased in Nischarin knockout astrocytes, and this correlated with a significant increase in transporter uptake current. In addition, Nischarin knockout in astrocytes is neuroprotective against glutamate excitotoxicity. These data provide new molecular insights into regulation of GLT-1 surface level and function and suggest new drug targets for the treatment of neurological disorders.

•

Nischarin phox domain interacts with the N-terminus of the glutamate transporter, GLT-1

•

Nischarin promotes internalization of GLT-1 to endosomes

•

Glutamate modulates GLT-1 surface levels by regulating the Nischarin-GLT-1 interaction

•

Nischarin loss enhances GLT-1 surface levels, transport currents, and neuroprotection

Role of Nischarin in the pathology of diseases: a special emphasis on breast cancer

Nischarin has been demonstrated to have tumor suppressor functions. In this review, we comprehensively discuss up to date information about Nischarin. In addition, this paper aims to report the prognostic value, clinical relevance, and biological significance of the Nischarin gene (NISCH) in breast cancer (BCa) patients using the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) and The Cancer Genome Atlas (TCGA) datasets. We evaluated NISCH gene expression and its correlation to patient survival, baseline expression, and expression variation based on age groups, tumor stage, tumor size, tumor grade, and lymph node status in different subtypes of BCa. Since NISCH has been extensively reported to inhibit EMT and cancer cell migration, we also checked for the correlation between NISCH and EMT genes in addition to the correlation between NISCH and cell migration genes. Our results indicate that NISCH is a tumor suppressor that plays a critical role in BCa initiation, progression, and tumor development. We find that there is a higher level of NISCH expression in normal breast tissues compared to breast cancer tissues. Also, aggressive subtypes of breast cancers, such as the triple negative/basal category, have decreased levels of NISCH as the disease progresses. Finally, we report that NISCH is inversely correlated with many EMT and cancer cell migration genes in BCa. Interestingly, we identified a significant negative correlation between NISCH expression and its methylation in breast cancer patients. Overall, the goal of this report is to establish a strong clinical basis for further investigation into the cellular, molecular, and physiological roles of NISCH in BCa. Ultimately, NISCH gene expression might be clinically harnessed as a biomarker or predictor of invasiveness and metastasis in BCa.

Nischarin Deletion Reduces Oxidative Metabolism and Overall ATP: A Study Using a Novel NISCHΔ5-6 Knockout Mouse Model

Nischarin (Nisch) is a cytosolic scaffolding protein that harbors tumor-suppressor-like characteristics. Previous studies have shown that Nisch functions as a scaffolding protein and regulates multiple biological activities. In the current study, we prepared a complete Nisch knockout model, for the first time, by deletion of exons 5 and 6. This knockout model was confirmed by Qrt–PCR and Western blotting with products from mouse embryonic fibroblast (MEF) cells. Embryos and adult mice of knockouts are significantly smaller than their wild-type counterparts. Deletion of Nisch enhanced cell migration, as demonstrated by wound type and transwell migration assays. Since the animals were small in size, we investigated Nisch’s effect on metabolism by conducting several assays using the Seahorse analyzer system. These data indicate that Nisch null cells have lower oxygen consumption rates, lower ATP production, and lower levels of proton leak. We examined the expression of 15 genes involved in lipid and fat metabolism, as well as cell growth, and noted a significant increase in expression for many genes in Nischarin null animals. In summary, our results show that Nischarin plays an important physiological role in metabolic homeostasis.

Understanding the role of integrins in breast cancer invasion, metastasis, angiogenesis, and drug resistance

Integrins are cell adhesion receptors, which are typically transmembrane glycoproteins that connect to the extracellular matrix (ECM). The function of integrins regulated by biochemical events within the cells. Understanding the mechanisms of cell growth by integrins is important in elucidating their effects on tumor progression. One of the major events in integrin signaling is integrin binding to extracellular ligands. Another event is distant signaling that gathers chemical signals from outside of the cell and transmit the signals upon cell adhesion to the inside of the cell. In normal breast tissue, integrins function as checkpoints to monitor effects on cell proliferation, while in cancer tissue these functions altered. The combination of tumor microenvironment and its associated components determines the cell fate. Hypoxia can increase the expression of several integrins. The exosomal integrins promote the growth of metastatic cells. Expression of certain integrins is associated with increased metastasis and decreased prognosis in cancers. In addition, integrin-binding proteins promote invasion and metastasis in breast cancer. Targeting specific integrins and integrin-binding proteins may provide new therapeutic approaches for breast cancer therapies. This review will examine the current knowledge of integrins' role in breast cancer.

siRNA Therapeutics: Future Promise for Neurodegenerative Diseases

Neurodegenerative diseases (ND), as a group of central nervous system (CNS) disorders, are among the most prominent medical problems of the 21st century. They are often associated with considerable disability, motor dysfunction and dementia and are more common in the aged population. ND imposes a psychologic, economic and social burden on the patients and their families. Currently, there is no effective treatment for ND. Since many ND result from the gain of function of a mutant allele, small interference RNA (siRNA) can be a potential therapeutic agent for ND management. Based on the RNA interference (RNAi) approach, siRNA is a powerful tool for modulating gene expression through gene silencing. However, there are some obstacles in the clinical application of siRNA, including unfavorable immune response, off-target effects, instability of naked siRNA, nuclease susceptibility and a need to develop a suitable delivery system. Since there are some issues related to siRNA delivery routes, in this review, we focus on the application of siRNA in the management of ND treatment from 2000 to 2020.

Impact of Nischarin on EMT regulators in breast cancer cell lines

Nischarin is an integrin-binding protein, which is well known as a novel tumor suppressor. In breast cancer, Nischarin serves a critical role in breast cancer cell migration and invasion. However, the molecular mechanism underlying the role of Nischarin remains unclear. Recent findings have demonstrated that epithelial-mesenchymal transition (EMT) increases the capacity of cell migration and invasion. As a member of the integrin family, it was hypothesized that Nischarin may regulate cellular processes via various signaling pathways associated with the EMT process. The present study detected the mRNA levels of EMT regulators via reverse transcription-quantitative PCR and related protein levels via western blotting in breast cancer cells, following NISCH-overexpression and -knockdown. The results demonstrated that Nischarin inhibits cell proliferation, migration and invasion in breast cancer cells. Furthermore, when the NISCH gene was overexpressed, the relative mRNA level of E-cadherin was increased, while the relative mRNA levels of several transcription factors, such as Snail, ZEB1, N-cadherin, Slug, Twist1 and vimentin, decreased. When NISCH was silenced, these results were reversed. The present results demonstrated that Nischarin suppresses cell migration and invasion via inhibiting the EMT process.

Imidazoline Receptor System: The Past, the Present, and the Future

Imidazoline receptors historically referred to a family of nonadrenergic binding sites that recognize compounds with an imidazoline moiety, although this has proven to be an oversimplification. For example, none of the proposed endogenous ligands for imidazoline receptors contain an imidazoline moiety but they are diverse in their chemical structure. Three receptor subtypes (I₁, I₂, and I₃) have been proposed and the understanding of each has seen differing progress over the decades. I₁ receptors partially mediate the central hypotensive effects of clonidine-like drugs. Moxonidine and rilmenidine have better therapeutic profiles (fewer side effects) than clonidine as antihypertensive drugs, thought to be due to their higher I₁/α ₂-adrenoceptor selectivity. Newer I₁ receptor agonists such as LNP599 [3-chloro-2-methyl-phenyl)-(4-methyl-4,5-dihydro-3H-pyrrol-2-yl)-amine hydrochloride] have little to no activity on α ₂-adrenoceptors and demonstrate promising therapeutic potential for hypertension and metabolic syndrome. I₂ receptors associate with several distinct proteins, but the identities of these proteins remain elusive. I₂ receptor agonists have demonstrated various centrally mediated effects including antinociception and neuroprotection. A new I₂ receptor agonist, CR4056 [2-phenyl-6-(1H-imidazol-1yl) quinazoline], demonstrated clear analgesic activity in a recently completed phase II clinical trial and holds great promise as a novel I₂ receptor-based first-in-class nonopioid analgesic. The understanding of I₃ receptors is relatively limited. Existing data suggest that I₃ receptors may represent a binding site at the Kir6.2-subtype ATP-sensitive potassium channels in pancreatic β-cells and may be involved in insulin secretion. Despite the elusive nature of their molecular identities, recent progress on drug discovery targeting imidazoline receptors (I₁ and I₂) demonstrates the exciting potential of these compounds to elicit neuroprotection and to treat various disorders such as hypertension, metabolic syndrome, and chronic pain.

Coupling of Integrin α5 to Annexin A2 by Flow Drives Endothelial Activation

RATIONALE

Atherosclerosis preferentially occurs at specific sites of the vasculature where endothelial cells (ECs) are exposed to disturbed blood flow. Translocation of integrin α5 to lipid rafts promotes integrin activation and ligation, which is critical for oscillatory shear stress (OSS)-induced EC activation. However, the underlying mechanism of OSS promoted integrin α5 lipid raft translocation has remained largely unknown.

OBJECTIVE

The objective of this study was to specify the mechanotransduction mechanism of OSS-induced integrin α5 translocation and subsequent EC activation.

METHODS AND RESULTS

Mass spectrometry studies identified endothelial ANXA2 (annexin A2) as a potential carrier allowing integrin α5β1 to traffic in response to OSS. Interference by siRNA of AnxA2 in ECs greatly decreased OSS-induced integrin α5β1 translocation to lipid rafts, EC activation, and monocyte adhesion. Pharmacological and genetic inhibition of PTP1B (protein tyrosine phosphatase 1B) blunted OSS-induced integrin α5β1 activation, which is dependent on Piezo1-mediated calcium influx in ECs. Furthermore, ANXA2 was identified as a direct substrate of activated PTP1B by mass spectrometry. Using bioluminescence resonance energy transfer assay, PTP1B-dephosphorylated ANXA2 at Y24 was found to lead to conformational freedom of the C-terminal core domain from the N-terminal domain of ANXA2. Immunoprecipitation assays showed that this unmasked ANXA2-C-terminal core domain specifically binds to an integrin α5 nonconserved cytoplasmic domain but not β1. Importantly, ectopic lentiviral overexpression of an ANXA2^Y24F mutant increased and shRNA against Ptp1B decreased integrin α5β1 ligation, inflammatory signaling, and progression of plaques at atheroprone sites in apolipoprotein E (ApoE)^-/- mice. However, the antiatherosclerotic effect of Ptp1B shRNA was abolished in AnxA2^-/-ApoE^-/- mice.

CONCLUSIONS

Our data elucidate a novel endothelial mechanotransduction molecular mechanism linking atheroprone flow and activation of integrin α5β1, thereby identifying a class of potential therapeutic targets for atherosclerosis. Graphic Abstract: An graphic abstract is available for this article.

Knockout model reveals the role of Nischarin in mammary gland development, breast tumorigenesis and response to metformin treatment

Previously, our lab discovered the protein Nischarin and uncovered its role in regulating cell migration and invasion via its interactions with several proteins. We subsequently described a role for Nischarin in breast cancer, in which it is frequently underexpressed. To characterize Nischarin's role in breast tumorigenesis and mammary gland development more completely, we deleted a critical region of the Nisch gene (exons 7-10) from the mouse genome and observed the effects. Mammary glands in mutant animals showed delayed terminal end bud formation but did not develop breast tumors spontaneously. Therefore, we interbred the animals with transgenic mice expressing the mouse mammary tumor virus-polyoma middle T-antigen (MMTV-PyMT) oncogene. The MMTV-PyMT mammary glands lacking Nischarin showed increased hyperplasia compared to wild-type animal tissues. Furthermore, we observed significantly increased tumor growth and metastasis in Nischarin mutant animals. Surprisingly, Nischarin deletion decreased activity of AMPK and subsequently its downstream effectors. Given this finding, we treated these animals with metformin, which enhances AMPK activity. Here, we show for the first time, metformin activates AMPK signaling and inhibits tumor growth of Nischarin lacking PyMT tumors suggesting a potential use for metformin as a cancer therapeutic, particularly in the case of Nischarin-deficient breast cancers.

The role of IRAS/Nischarin involved in the development of morphine tolerance and physical dependence

Morphine is a potent opioid analgesic used to alleviate moderate or severe pain, but the development of drug tolerance and dependence limits its use in pain management. Our previous studies showed that the candidate protein for I1 imidazoline receptor, imidazoline receptor antisera-selected (IRAS)/Nischarin, interacts with μ opioid receptor (MOR) and modulates its trafficking. However, there is no report of the effect of IRAS on morphine tolerance and physical dependence. In the present study, we found that IRAS knockout (KO) mice showed exacerbated analgesic tolerance and physical dependence compared to wild-type (WT) mice by chronic morphine treatment. Chronic morphine treatment down-regulated the expression of MOR in spinal cord of IRAS KO mice, while had no significant effect on MOR expression in WT mice. We observed the compensatory increase of cAMP accumulation in spinal cord after morphine tolerance, and this change was more significant in KO mice than WT mice. Furthermore, KO mice showed more elevation in the phosphorylation of AMPA receptor GluR1-S845 than WT mice, while the total expression of GluR1 remained unchanged after morphine dependence. Altogether, these data suggest that IRAS may play an important role in the development of morphine tolerance and physical dependence in vivo through modulating MOR expression, as well as AMPA GluR1-S845 phosphorylation, which might be one of the mechanisms underlying the development of opiate addiction.

Exosomes from Nischarin-Expressing Cells Reduce Breast Cancer Cell Motility and Tumor Growth

Exosomes are small extracellular microvesicles that are secreted by cells when intracellular multivesicular bodies fuse with the plasma membrane. We have previously demonstrated that Nischarin inhibits focal adhesion formation, cell migration, and invasion, leading to reduced activation of focal adhesion kinase. In this study, we propose that the tumor suppressor Nischarin regulates the release of exosomes. When cocultured on exosomes from Nischarin-positive cells, breast cancer cells exhibited reduced survival, migration, adhesion, and spreading. The same cocultures formed xenograft tumors of significantly reduced volume following injection into mice. Exosomes secreted by Nischarin-expressing tumors inhibited tumor growth. Expression of only one allele of Nischarin increased secretion of exosomes, and Rab14 activity modulated exosome secretions and cell growth. Taken together, this study reveals a novel role for Nischarin in preventing cancer cell motility, which contributes to our understanding of exosome biology. SIGNIFICANCE: Regulation of Nischarin-mediated exosome secretion by Rab14 seems to play an important role in controlling tumor growth and migration.See related commentary by McAndrews and Kalluri, p. 2099.

Development of insulin resistance in Nischarin mutant female mice

BACKGROUND/OBJECTIVES

NISCH-STAB1 is a newly identified locus correlated to human waist-hip ratio (WHR), which is a risk indicator of developing obesity-associated diabetes. Our previous studies have shown that Nisch mutant male mice increased glucose tolerance in chow-fed conditions. Thus we hypothesized that Nisch mutant mice will have changes in insulin resistance, adipocytes, hepatic steatosis when mice are fed with high-fat diet (HFD).

METHODS

Insulin resistance was assessed in Nisch mutant mice and WT mice fed with high-fat diet (60% by kCal) or chow diet. Whole-body energy metabolism was examined using an indirect calorimeter. Adipose depots including inguinal white adipose tissue (WAT), perigonadal WAT, retroperitoneal WAT, and mesenteric WAT were extracted. Area and eqdiameter of each adipocyte were determined, and insulin signaling was examined as well. Paired samples of subcutaneous and omental visceral adipose tissue were obtained from 400 individuals (267 women, 133 men), and examined the expression of Nischarin.

RESULTS

We found that insulin signaling was impaired in major insulin-sensitive tissues of Nisch mutant female mice. When mice were fed with HFD for 15 weeks, the Nisch mutant female mice not only developed severe insulin resistance and decreased glucose tolerance compared with wild-type control mice, but also accumulated more white fat, had larger adipocytes and developed severe hepatic steatosis than wild-type control mice. To link our animal studies to human diseases, we further analyzed Nischarin expression in the paired human samples of visceral and subcutaneous adipose tissue from Caucasians. In humans, we found that Nischarin expression is attenuated in adipose tissue with obesity. More importantly, we found that Nischarin mRNA inversely correlated with parameters of obesity, fat distribution, lipid and glucose metabolism.

CONCLUSIONS

Taken together, our data revealed sexual dimorphism of Nischarin in body fat distribution, insulin resistance, and glucose tolerance in mice.

Imidazoline receptors agonists: possible mechanisms of endothelioprotection

Imidazoline receptor agonists are one of the groups of contemporary antihypertensive drugs with the pleiotropic cardiovascular effects. In this review, the historical, physiological, pathophysiological aspects concerning imidazoline receptor agonists and possible mechanisms for their participation in endothelioprotection were considered. Illuminated the molecular biology of each subtype of imidazoline receptors and their significance in the pharmacological correction of cardiovascular disease.

IR type 1 are localized in the brain nucleus, carrying out the descending tonic control of sympathetic activation, as well as in the endothelial cells of the vessels and kidneys. Their activation leads to a decrease in blood pressure, slowing the remodeling of the vascular wall and increasing sodium nares. IR type 2 is expressed predominantly in the adrenal gland, fat and muscle tissues. The physiological effects of their stimulation are associated with an increase in glucose utilization by peripheral tissues. IR type 3 are mainly present in pancreatic cells and are associated with the regulation of insulin secretion. Their stimulation leads to an increase in insulin liberation. Thus, IR agonists are able to improve endothelial function through various mechanisms, including blood pressure reduction, improvement in metabolic profile, and direct positive effects on the vascular wall.

Current information on the pharmacological effects of this group compounds allows us to conclude that they are a promising group for correcting endothelial dysfunction and complications associated with it.

Expression of long noncoding RNA MALAT1 correlates with increased levels of Nischarin and inhibits oncogenic cell functions in breast cancer

Malat1 is a long noncoding RNA with a wide array of functions, including roles in regulating cancer cell migration and metastasis. However, the nature of its involvement in control of these oncogenic processes is incompletely understood. In the present study, we investigate the role of Malat1 and the effects of Malat1 KO in a breast cancer cell model. Our selection of Malat1 as the subject of inquiry followed initial screening experiments seeking to identify lncRNAs which are altered in the presence or absence of Nischarin, a gene of interest previously discovered by our lab. Nischarin is a well characterized tumor suppressor protein and actively represses cell proliferation, migration, and invasion in breast cancer. Our microarray screen for lncRNAs revealed multiple lncRNAs to be significantly elevated in cells ectopically expressing Nischarin compared to control cancer cells, which have only marginal Nisch expression. Using these cells, we assess how the link between Nischarin and Malat1 affects cancer cell function, finding that Malat1 confers an inhibitory effect on cell growth and migration which is lost following Malat1 KO, but in a Nisch-dependent context. Specifically, Malat1 KO in the background of low Nischarin expression had a limited effect on cell functions, while Malat1 KO in cells with high levels of Nischarin led to significant increases in cell proliferation and migration. In summary, this project provides further clarity concerning the function of Malat1, specifically in breast cancer, while also indicating that the Nischarin expression context is an important factor in the determining how Malat1 activity is governed in breast cancer.

The membrane-distal regions of integrin α cytoplasmic domains contribute differently to integrin inside-out activation

Functioning as signal receivers and transmitters, the integrin α/β cytoplasmic tails (CT) are pivotal in integrin activation and signaling. 18 α integrin subunits share a conserved membrane-proximal region but have a highly diverse membrane-distal (MD) region at their CTs. Recent studies demonstrated that the presence of α CTMD region is essential for talin-induced integrin inside-out activation. However, it remains unknown whether the non-conserved α CTMD regions differently regulate the inside-out activation of integrin. Using αIIbβ3, αLβ2, and α5β1 as model integrins and by replacing their α CTMD regions with those of α subunits that pair with β3, β2, and β1 subunits, we analyzed the function of CTMD regions of 17 α subunits in talin-mediated integrin activation. We found that the α CTMD regions play two roles on integrin, which are activation-supportive and activation-regulatory. The regulatory but not the supportive function depends on the sequence identity of α CTMD region. A membrane-proximal tyrosine residue present in the CTMD regions of a subset of α integrins was identified to negatively regulate integrin inside-out activation. Our study provides a useful resource for investigating the function of α integrin CTMD regions.

Nischarin regulates focal adhesion and Invadopodia formation in breast cancer cells

Background

During metastasis, tumor cells move through the tracks of extracellular matrix (ECM). Focal adhesions (FAs) are the protein complexes that link the cell cytoskeleton to the ECM and their presence is necessary for cell attachment. The tumor suppressor Nischarin interacts with a number of signaling proteins such as Integrin α5, PAK1, LIMK1, LKB1, and Rac1 to prevent cancer cell migration. Although previous findings have shown that Nischarin exerts this migratory inhibition by interacting with other proteins, the effects of these interactions on the entire FA machinery are unknown.

Methods

RT-PCR, Western Blotting, invadopodia assays, and immunofluorescence were used to examine FA gene expression and determine whether Nischarin affects cell attachment, as well as the proteins that regulate it.

Results

Our data show that Nischarin prevents cell migration and invasion by altering the expression of key focal adhesion proteins. Furthermore, we have found that Nischarin-expressing cells have reduced ability to attach the ECM, which in turn leads to a decrease in invadopodia-mediated matrix degradation.

Conclusions

These experiments demonstrate an important role of Nischarin in regulating cell attachment, which adds to our understanding of the early events of the metastatic process in breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0764-6) contains supplementary material, which is available to authorized users.

Proteomic Dissection of Nanotopography-Sensitive Mechanotransductive Signaling Hubs that Foster Neuronal Differentiation in PC12 Cells

Neuronal cells are competent in precisely sensing nanotopographical features of their microenvironment. The perceived microenvironmental information will be “interpreted” by mechanotransductive processes and impacts on neuronal functioning and differentiation. Attempts to influence neuronal differentiation by engineering substrates that mimic appropriate extracellular matrix (ECM) topographies are hampered by the fact that profound details of mechanosensing/-transduction complexity remain elusive. Introducing omics methods into these biomaterial approaches has the potential to provide a deeper insight into the molecular processes and signaling cascades underlying mechanosensing/-transduction but their exigence in cellular material is often opposed by technical limitations of major substrate top-down fabrication methods. Supersonic cluster beam deposition (SCBD) allows instead the bottom-up fabrication of nanostructured substrates over large areas characterized by a quantitatively controllable ECM-like nanoroughness that has been recently shown to foster neuron differentiation and maturation. Exploiting this capacity of SCBD, we challenged mechanosensing/-transduction and differentiative behavior of neuron-like PC12 cells with diverse nanotopographies and/or changes of their biomechanical status, and analyzed their phosphoproteomic profiles in these settings. Versatile proteins that can be associated to significant processes along the mechanotransductive signal sequence, i.e., cell/cell interaction, glycocalyx and ECM, membrane/f-actin linkage and integrin activation, cell/substrate interaction, integrin adhesion complex, actomyosin organization/cellular mechanics, nuclear organization, and transcriptional regulation, were affected. The phosphoproteomic data suggested furthermore an involvement of ILK, mTOR, Wnt, and calcium signaling in these nanotopography- and/or cell mechanics-related processes. Altogether, potential nanotopography-sensitive mechanotransductive signaling hubs participating in neuronal differentiation were dissected.

A Biomarker to Differentiate between Primary and Cocaine-Induced Major Depression in Cocaine Use Disorder: The Role of Platelet IRAS/Nischarin (I1-Imidazoline Receptor)

The association of cocaine use disorder (CUD) and comorbid major depressive disorder (MDD; CUD/MDD) is characterized by high prevalence and poor treatment outcomes. CUD/MDD may be primary (primary MDD) or cocaine-induced (CUD-induced MDD). Specific biomarkers are needed to improve diagnoses and therapeutic approaches in this dual pathology. Platelet biomarkers [5-HT2A receptor and imidazoline receptor antisera selected (IRAS)/nischarin] were assessed by Western blot in subjects with CUD and primary MDD (n = 16) or CUD-induced MDD (n = 9; antidepressant free, AD-; antidepressant treated, AD+) and controls (n = 10) at basal level and/or after acute tryptophan depletion (ATD). Basal platelet 5-HT2A receptor (monomer) was reduced in comorbid CUD/MDD subjects (all patients: 43%) compared to healthy controls, and this down-regulation was independent of AD medication (decreases in AD-: 47%, and in AD+: 40%). No basal differences were found for IRAS/nischarin contents in AD+ and AD- comorbid CUD/MDD subjects. The comparison of IRAS/nischarin in the different subject groups during/after ATD showed opposite modulations (i.e., increases and decreases) in response to low plasma tryptophan levels with significant differences discriminating between the subgroups of CUD with primary MDD and CUD-induced MDD. These specific alterations suggested that platelet IRAS/nischarin might be useful as a biomarker to discriminate between primary and CUD-induced MDD in this dual pathology.

Investigation of morin-induced insulin secretion in cultured pancreatic cells

Morin is a flavonoid contained in guava that is known to reduce hyperglycemia in diabetes. Insulin secretion has been demonstrated to increase following the administration of morin. The present study is designed to investigate the potential mechanism(s) of morin-induced insulin secretion in the MIN6 cell line. First, we identified that morin induced a dose-dependent increase in insulin secretion and intracellular calcium content in MIN6 cells. Morin potentiated glucose-stimulated insulin secretion (GSIS). Additionally, we used siRNA for the ablation of imidazoline receptor protein (NISCH) expression in MIN6 cells. Interestingly, the effects of increased insulin secretion by morin and canavanine were markedly reduced in Si-NISCH cells. Moreover, we used KU14R to block imidazoline I₃ receptor (I-3R) that is known to enhance insulin release from the pancreatic β-cells. Without influence on the basal insulin secretion, KU14R dose-dependently inhibited the increased insulin secretion induced by morin or efaroxan in MIN6 cells. Additionally, effects of increased insulin secretion by morin or efaroxan were reduced by diazoxide at the dose sufficient to open K_ATP channels and attenuated by nifedipine at the dose used to inhibit L-type calcium channels. Otherwise, phospholipase C (PLC) is introduced to couple with imidazoline receptor (I-R). The PLC inhibitor dose-dependently inhibited the effects of morin in MIN6 cells. Similar blockade was also observed in protein kinase C (PKC) inhibitor-treated cells. Taken together, we found that morin increases insulin secretion via the activation of I-R in pancreatic cells. Therefore, morin would be useful to develop in the research and treatment of diabetic disorders.

Nischarin inhibition alters energy metabolism by activating AMP-activated protein kinase

Nischarin (Nisch) is a key protein functioning as a molecular scaffold and thereby hosting interactions with several protein partners. To explore the physiological importance of Nisch, here we generated Nisch loss-of-function mutant mice and analyzed their metabolic phenotype. Nisch-mutant embryos exhibited delayed development, characterized by small size and attenuated weight gain. We uncovered the reason for this phenotype by showing that Nisch binds to and inhibits the activity of AMP-activated protein kinase (AMPK), which regulates energy homeostasis by suppressing anabolic and activating catabolic processes. The Nisch mutations enhanced AMPK activation and inhibited mechanistic target of rapamycin signaling in mouse embryonic fibroblasts as well as in muscle and liver tissues of mutant mice. Nisch-mutant mice also exhibited increased rates of glucose oxidation with increased energy expenditure, despite reduced overall food intake. Moreover, the Nisch-mutant mice had reduced expression of liver markers of gluconeogenesis associated with increased glucose tolerance. As a result, these mice displayed decreased growth and body weight. Taken together, our results indicate that Nisch is an important AMPK inhibitor and a critical regulator of energy homeostasis, including lipid and glucose metabolism.

A mutation in Nischarin causes otitis media via LIMK1 and NF-κB pathways

Otitis media (OM), inflammation of the middle ear (ME), is a common cause of conductive hearing impairment. Despite the importance of the disease, the aetiology of chronic and recurrent forms of middle ear inflammatory disease remains poorly understood. Studies of the human population suggest that there is a significant genetic component predisposing to the development of chronic OM, although the underlying genes are largely unknown. Using N-ethyl-N-nitrosourea mutagenesis we identified a recessive mouse mutant, edison, that spontaneously develops a conductive hearing loss due to chronic OM. The causal mutation was identified as a missense change, L972P, in the Nischarin (NISCH) gene. edison mice develop a serous or granulocytic effusion, increasingly macrophage and neutrophil rich with age, along with a thickened, inflamed mucoperiosteum. We also identified a second hypomorphic allele, V33A, with only modest increases in auditory thresholds and reduced incidence of OM. NISCH interacts with several proteins, including ITGA5 that is thought to have a role in modulating VEGF-induced angiogenesis and vascularization. We identified a significant genetic interaction between Nisch and Itga5; mice heterozygous for Itga5-null and homozygous for edison mutations display a significantly increased penetrance and severity of chronic OM. In order to understand the pathological mechanisms underlying the OM phenotype, we studied interacting partners to NISCH along with downstream signalling molecules in the middle ear epithelia of edison mouse. Our analysis implicates PAK1 and RAC1, and downstream signalling in LIMK1 and NF-κB pathways in the development of chronic OM.

Otitis media (OM) is the most common cause of deafness in children and is primarily characterised by inflammation of the middle ear. It is the most common cause of surgery in children in the developed world, with many children developing recurrent and chronic forms of OM undergoing tympanostomy tube insertion. There is evidence that a significant genetic component contributes towards the development of recurrent and chronic forms of OM. The mouse has been a powerful tool for identifying the genes involved in chronic OM. In this study we identified and characterised edison, a novel mouse model of chronic OM that shares important features with the chronic disease in humans. A mutation in the Nisch gene causes edison mice to spontaneously develop OM following birth and subsequently develop chronic OM, with an associated hearing loss. Our molecular analysis of the mutation reveals the underlying pathological mechanisms and pathways involved in OM in the edison mouse, involving PAK1, RAC1 and downstream signalling in LIMK1 and NF-κB pathways. Identification of the edison mutant provides an important genetic disease model of chronic OM and implicates a new gene and genetic pathways involved in predisposition to OM.

Identification of morin as an agonist of imidazoline I-3 receptor for insulin secretion in diabetic rats

Morin is a flavonoid contained in guava that is known to reduce hyperglycemia in diabetics. Morin has been demonstrated to increase plasma insulin. However, the mechanism(s) remains unknown. The present study is designed to investigate the effect of morin on the imidazoline receptor (I-R) that regulates insulin secretion. We used Chinese hamster ovary (CHO) cells transfected with an I-R expression construct (NISCH-CHO-K1 cells) to identify the direct effect of morin on the I-R. Moreover, the imidazoline I₃ receptor (I-3R) is known to be present in pancreatic β cells and involved in insulin secretion. Therefore, we applied a specific antagonist (KU14R) to block I-3R in diabetic rats. Additionally, the effect of morin on insulin secretion was characterized in isolated pancreatic islets. Morin decreased blood glucose levels by increasing plasma insulin levels in diabetic rats. In CHO cells expressing an I-R, morin increased calcium influx in a dose-dependent manner. Additionally, KU14R dose-dependently inhibited the morin-induced effects, including hypoglycemia and the increase in insulin secretion and plasma C-peptide levels, in diabetic rats. Furthermore, morin enhanced insulin secretion from isolated pancreatic islets, and this effect was also dose-dependently inhibited by KU14R. Phospholipase C (PLC) is known to couple with the I-R, and a PLC inhibitor dose-dependently attenuated the insulin secretion induced by morin in isolated pancreatic islets. Taken together, these data suggest that morin can activate I-3R to enhance insulin secretion. Therefore, it would be useful to develop morin into a treatment for diabetic disorders.

Diosmin, a Citrus Nutrient, Activates Imidazoline Receptors to Alleviate Blood Glucose and Lipids in Type 1-Like Diabetic Rats

Diosmin is a nutrient that is widely contained in citrus and that has been indicated to improve glucose metabolism in diabetic disorders. Recently, we demonstrated that diosmin induces β-endorphin to lower hyperglycemia in diabetic rats. However, the mechanisms of diosmin in opioid secretion were unclear. Therefore, we focused on the secretion of opioids from isolated adrenal glands induced by diosmin. The changes in the released β-endorphin-like immunoreactivity (BER) were determined using ELISA. Diosmin increased the BER level in a dose-dependent manner, and this effect was markedly reduced in the absence of calcium ions. Activation of the imidazoline I-2 receptor (I-2R) has been introduced to induce opioid secretion. Interestingly, we observed that diosmin activates CHO cells expressing I-R. Additionally, diosmin-increased BER was inhibited by the blockade of I-2R in isolated adrenal glands. Additionally, an antagonist of I-2R blocked diosmin-induced effects, including the reduction in hyperglycemia and the increase in plasma BER in streptozotocin-induced diabetic rats (STZ-diabetic rats). Repeated treatment of STZ-diabetic rats with diosmin for one week induced changes in hepatic glycogen, lipid levels, and the expression of phosphoenolpyruvate carboxykinase (PEPCK). Furthermore, an antagonist of I-2R blocked the diosmin-induced changes. Additionally, plasma lipids modified by diosmin were also reversed by the blockade of I-2R in STZ-diabetic rats. Taken together, we suggest that diosmin may activate I-2R to enhance the secretion of β-endorphin from adrenal glands and to influence metabolic homeostasis, resulting in alleviation of blood glucose and lipids in STZ-diabetic rats.

Expression of Nischarin negatively correlates with estrogen receptor and alters apoptosis, migration and invasion in human breast cancer

Nischarin, a novel integrin binding protein, has been demonstrated its negative effects on cell migration and invasion. However, the biological role of Nischarin in breast cancer has not been fully elucidated yet. Our study aimed to analyze the association between Nischarin expression and clinical features of breast cancer patients, and further investigate the role of Nischarin in breast cancer cells apoptosis, migration and invasion. Results showed that Nischarin expression was significantly lower in breast cancer tissues (37.8%, 23/67) than in normal tissues (61.8%, 21/34; P < 0.05), and the expression of Nischarin significantly negatively correlated with estrogen receptor status. Similarly, Nischarin expression was highest in normal breast cell line HBL-100 while triple-negative breast cancer cell line MDA-MB-231 had the lowest expression of Nischarin. Further experiments demonstrated that overexpression of Nischarin may induce apoptosis, and inhibit cell migration and invasion. The present data confirmed that Nishcharin might be a novel tumor suppressor and plays an important role in breast cancer cell apoptosis and metastasis, which can be used as a potential therapeutic target for breast cancer treatment.

Dysregulation of IRAS/nischarin and other potential I1-imidazoline receptors in major depression postmortem brain: Downregulation of basal contents by antidepressant drug treatments

BACKGROUND

Major depressive disorder (MDD) has been associated with altered brain densities of imidazoline receptors (I₁-IR and I₂-IR types).

METHODS

The contents of potential I₁-IR IRAS/nischarin (167kDa) and, for comparison, those of I₁- (85kDa) and I₂- (45kDa and 30kDa) IR proteins were quantified by western blotting in postmortem prefrontal cortex (PFC/BA9) of antidepressant-free ([MDD(-)], n=9) and antidepressant-treated ([MDD(+)], n=12) subjects and matched controls (n=19).

RESULTS

In MDD, regardless of antidepressant treatment (n=21), IRAS/nischarin was not altered in PFC/BA9. However, the content of IRAS/nischarin was found modestly and not significantly increased (+19%, p=0.075) in MDD(-) and significantly decreased (-24%, p=0.001) in MDD(+), revealing that basal I₁-IR content was downregulated by antidepressants. Putative 85kDa I₁-IR was upregulated (+35%, p=0.035) in MDD(-) but it was not reduced (-14%, p=0.37) in MDD(+). There was a positive correlation (r=0.33, p=0.037, n=40) between the contents of IRAS/nischarin and 85kDa IR proteins in PFC/BA9 (control and MDD subjects). In MDD and regardless of antidepressants, the content of cortical 45kDa I₂-IR was increased (+31%, p=0.006) and that of 30kDa I₂-IR decreased (-14%, p=0.002), indicating basal dysregulations of these potential IRs.

LIMITATIONS

MDD(+) subjects had been treated with a variety of antidepressant drugs. The results must be understood in the context of suicide victims with MDD.

CONCLUSIONS

The dysregulation of IRAS/nischarin in depressed brains is a major novel finding that supports a role of this potential I₁-IR in the neurobiology of MDD and in the molecular mechanisms of antidepressant drugs.

Nischarin-siRNA delivered by polyethylenimine-alginate nanoparticles accelerates motor function recovery after spinal cord injury

A previous study by our group found that inhibition of nischarin promotes neurite outgrowth and neuronal regeneration in Neuro-2a cells and primary cortical neurons. In recent years, more and more studies have shown that nanomaterials have good prospects in treatment of spinal cord injury. We proposed that small interfering RNA targeting nischarin (Nis-siRNA) delivered by polyethyleneimine-alginate (PEI-ALG) nanoparticles promoted motor function recovery in rats with spinal cord injury. Direct microinjection of 5 μL PEI-ALG/Nis-siRNA into the spinal cord lesion area of spinal cord injury rats was performed. From day 7 after surgery, Basso, Beattie and Bresnahan score was significantly higher in rats from the PEI-ALG/Nis-siRNA group compared with the spinal cord injury group and PEI-ALG/Control-siRNA group. On day 21 after injection, hematoxylin-eosin staining showed that the necrotic area was reduced in the PEI-ALG/Nis-siRNA group. Immunohistochemistry and western blot assay results confirmed successful inhibition of nischarin expression and increased protein expression of growth-associated protein-43 in the PEI-ALG/Nis-siRNA group. These findings suggest that a complex of PEI-ALG nanoparticles and Nis-siRNA effectively suppresses nischarin expression, induces expression of growth-associated protein-43, and accelerates motor function recovery after spinal cord injury.

Leukocyte arrest: Biomechanics and molecular mechanisms of β2 integrin activation

Integrins are a group of heterodimeric transmembrane receptors that play essential roles in cell-cell and cell-matrix interaction. Integrins are important in many physiological processes and diseases. Integrins acquire affinity to their ligand by undergoing molecular conformational changes called activation. Here we review the molecular biomechanics during conformational changes of integrins, integrin functions in leukocyte biorheology (adhesive functions during rolling and arrest) and molecules involved in integrin activation.

Inhibitory effects of imidazoline receptor ligands on basal and kainic acid-induced neurotoxic signalling in mice

This in vivo study assessed the potential of the imidazoline receptor (IR) ligands moxonidine (selective I1-IR), BU224 (selective I2-IR) and LSL61122 (mixed I1/I2-IR) to dampen excitotoxic signalling induced by kainic acid (KA; 45 mg/kg) in the mouse brain (hippocampus and cerebral cortex). KA triggered a strong behavioural syndrome (seizures; maximal at 60-90 minutes) and sustained stimulation (at 72 hours with otherwise normal mouse behaviour) of pro-apoptotic c-Jun-N-terminal kinases (JNK) and calpain with increased cleavage of p35 into neurotoxic p25 (cyclin-dependent kinase 5 [Cdk5] activators) in mouse hippocampus. Pretreatment (five days) with LSL61122 (10 mg/kg), but not moxonidine (1 mg/kg) or BU224 (20 mg/kg), attenuated the KA-induced behavioural syndrome, and all three IR ligands inhibited JNK and calpain activation, as well as p35/p25 cleavage after KA in the hippocampus (effects also observed after acute IR drug treatments). Efaroxan (I1-IR, 10 mg/kg) and idazoxan (I2-IR, 10 mg/kg), postulated IR antagonists, did not antagonise the effects of moxonidine and LSL61122 on KA targets (these IR ligands showed agonistic properties inhibiting pro-apoptotic JNK). Brain subcellular preparations revealed reduced synaptosomal postsynaptic density-95 protein contents (a mediator of JNK activation) and indicated increased p35/Cdk5 complexes (with pro-survival functions) after treatment with moxonidine, BU224 and LSL61122. These results showed that I1- and I2-IR ligands (moxonidine and BU224), and especially the mixed I1/I2-IR ligand LSL61122, are partly neuroprotective against KA-induced excitotoxic signalling. These findings suggest a therapeutic potential of IR drugs in disorders associated with glutamate-mediated neurodegeneration.

Inhibition of Nischarin Expression Promotes Neurite Outgrowth through Regulation of PAK Activity

Nischarin is a cytoplasmic protein expressed in various organs that plays an inhibitory role in cell migration and invasion and the carcinogenesis of breast cancer cells. We previously reported that Nischarin is highly expressed in neuronal cell lines and is differentially expressed in the brain tissue of adult rats. However, the physiological function of Nischarin in neural cells remains unknown. Here, we show that Nischarin is expressed in rat primary cortical neurons but not in astrocytes. Nischarin is localized around the nucleus and dendrites. Using shRNA to knockdown the expression of endogenous Nischarin significantly increases the percentage of neurite-bearing cells, remarkably increases neurite length, and accelerates neurite extension in neuronal cells. Silencing Nischarin expression also promotes dendrite elongation in rat cortical neurons where Nischarin interacts with p21-activated kinase 1/2 (PAK1/2) and negatively regulates phosphorylation of both PAK1 and PAK2. The stimulation of neurite growth observed in cells with decreased levels of Nischarin is partially abolished by IPA3-mediated inhibition of PAK1 activity. Our findings indicate that endogenous Nischarin inhibits neurite outgrowth by blocking PAK1 activation in neurons.

Breast Cancer Tumor Suppressors: A Special Emphasis on Novel Protein Nischarin

Tumor suppressor genes regulate cell growth and prevent spontaneous proliferation that could lead to aberrant tissue function. Deletions and mutations of these genes typically lead to progression through the cell-cycle checkpoints, as well as increased cell migration. Studies of these proteins are important as they may provide potential treatments for breast cancers. In this review, we discuss a comprehensive overview on Nischarin, a novel protein discovered by our laboratory. Nischarin, or imidazoline receptor antisera-selected protein, is a protein involved in a vast number of cellular processes, including neuronal protection and hypotension. The NISCH promoter experiences hypermethylation in several cancers, whereas some highly aggressive breast cancer cells exhibit genomic loss of the NISCH locus. Furthermore, we discuss data illustrating a novel role of Nischarin as a tumor suppressor in breast cancer. Analysis of this new paradigm may shed light on various clinical questions. Finally, the therapeutic potential of Nischarin is discussed.

Immunodetection and subcellular distribution of imidazoline receptor proteins with three antibodies in mouse and human brains: Effects of treatments with I1- and I2-imidazoline drugs

Various imidazoline receptor (IR) proteins have been proposed to mediate the effects of selective I1- and I2-IR drugs. However, the association of these IR-binding proteins with classic I1- and I2-radioligand binding sites remains somewhat controversial. In this study, three IR antibodies (anti-NISCH and anti-nischarin for I1-IRs; and anti-IRBP for I1/I2-IRs) were used to immunodetect, characterize and compare IR protein patterns in brain (mouse and human; total homogenate, subcellular fractionation, grey and white matter) and some cell systems (neurones, astrocytes, human platelets). Various immunoreactive IRs (specific molecular weight bands coincidently detected with the different antibodies) were related to I1-IR (167 kDa, 105/115 kDa and 85 kDa proteins) or I2-IR (66 kDa, 45 kDa and 30 kDa proteins) types. The biochemical characterization of cortical 167 kDa protein, localized in the membrane/cytosol but not in the nucleus, indicated that this I1-IR also forms part of higher order nischarin-related complexes. The contents of I1-IR (167 kDa, 105/115 kDa, and 85 kDa) proteins in mouse brain cortex were upregulated by treatment with I1-drugs (moxonidine, efaroxan) but not with I2-drugs (BU-224, LSL 61122). Conversely, the contents of I2-IR (66 kDa, 45 kDa and 30 kDa) proteins in mouse brain cortex were modulated by treatment with I2-drugs (decreases after BU-224 and LSL 61122, and increases after idazoxan) but not with I1-drugs (with the exception of moxonidine). These findings further indicate that brain immunoreactive IR proteins exist in multiple forms that can be grouped in the already known I1- and I2-IR types, which are expressed both in neurones and astrocytes.

Frequent Loss of NISCH Promotes Tumor Proliferation and Invasion in Ovarian Cancer via Inhibiting the FAK Signal Pathway

NISCH encodes the imidazoline receptor Nischarin and is a known tumor suppressor in many human malignancies; however, its roles in ovarian cancer are still largely unknown. Here, we aim to investigate the biologic functions of NISCH in ovarian cancer. We found that NISCH was significantly downregulated, which correlated considerably with advanced tumor stage, poor differentiation, lymph node metastasis, and the serous/mucinous subtypes in a panel of ovarian cancer tissues. Moreover, NISCH gene silencing was mainly the product of promoter hypermethylation, which could be reversed by treatment with 5-aza-dC. In vitro, NISCH overexpression suppressed cell proliferation and colony formation by hindering cell-cycle progression, whereas the opposite was observed in NISCH knockdown counterparts. In vivo, abundant NISCH expression hindered the growth of HO8910 xenografts, whereas NISCH knockdown accelerated the growth of SKOV3 xenografts. In addition, NISCH significantly attenuated cell invasion by inhibiting the phosphorylation of FAK and ERK, which could be neutralized by PF-562271 (a FAK/Pyk2 inhibitor). Accordingly, NISCH knockdown xenografts exhibited increased peritoneal/pelvic metastases that were not present in counterparts treated with PF-562271. Furthermore, NISCH expression in primary ovarian cancer cells predicted a cellular resistance to PF-562271. In conclusion, we showed that NISCH was frequently silenced by promoter hypermethylation in human ovarian cancer. NISCH manipulated cellular proliferation and invasion by arresting cell cycle and inhibiting the FAK signal. Our findings revealed the biologic functions of NISCH in ovarian cancer, and might be useful for treating patients with aberrant expression of NISCH.

Expression of integrin-binding protein Nischarin in metastatic breast cancer

The present study aimed to investigate the expression of Nischarin protein in primary breast cancer (PBC), and to evaluate its role in tumor metastasis. Paired specimens of breast cancer tissues and adjacent normal tissues were surgically obtained from 60 patients with PBC at the Zhejiang Cancer Hospital (Hangzhou, China). Nischarin protein concentrations were determined by an ELISA assay. Breast cancer tissues exhibited a significantly lower concentration of Nischarin (5.86±3.19 ng/ml) compared with that of the adjacent noncancerous tissues (9.25±3.65 ng/ml; P<0.001). Furthermore, cancer tissue from patients with lymph node metastasis had significantly lower levels of Nischarin protein (4.69±2.40 ng/ml) than those of patients without lymph node metastasis (7.04±3.47 ng/ml; P=0.004). There was no significant difference in Nischarin protein expression levels between patients with grade I, II or III PBC (grade I, 5.44±3.57 ng/ml; grade II, 6.42±3.85 ng/ml and grade III, 5.10±1.18 ng/ml; P=0.765). The significant differences in the expression of Nischarin between: i) Cancer tissue and noncancerous tissue and ii) patients with and without lymph node metastasis, suggested that Nischarin may have a significant role in tumor occurrence and metastasis of breast cancer. Nischarin expression may therefore be used as a marker to predict the invasiveness and metastasis of PBC.

Identification of specific mRNA signatures as fingerprints for carcinogenesis in mice induced by genotoxic and nongenotoxic hepatocarcinogens

Long-term rodent carcinogenicity studies for evaluation of chemicals and pharmaceuticals concerning their carcinogenic potential to humans are currently receiving critical revision. Additional data from mechanistic studies can support cancer risk assessment by clarifying the underlying mode of action. In the course of the IMI MARCAR project, a European consortium of EFPIA partners and academics, which aims to identify biomarkers for nongenotoxic carcinogenesis, a toxicogenomic mouse liver database was generated. CD-1 mice were orally treated for 3 and 14 days with 3 known genotoxic hepatocarcinogens: C.I. Direct Black 38, Dimethylnitrosamine and 4,4'-Methylenedianiline; 3 nongenotoxic hepatocarcinogens: 1,4-Dichlorobenzene, Phenobarbital sodium and Piperonyl butoxide; 4 nonhepatocarcinogens: Cefuroxime sodium, Nifedipine, Prazosin hydrochloride and Propranolol hydrochloride; and 3 compounds that show ambiguous results in genotoxicity testing: Cyproterone acetate, Thioacetamide and Wy-14643. By liver mRNA expression analysis using individual animal data, we identified 64 specific biomarker candidates for genotoxic carcinogens and 69 for nongenotoxic carcinogens for male mice at day 15. The majority of genotoxic carcinogen biomarker candidates possess functions in DNA damage response (eg, apoptosis, cell cycle progression, DNA repair). Most of the identified nongenotoxic carcinogen biomarker candidates are involved in regulation of cell cycle progression and apoptosis. The derived biomarker lists were characterized with respect to their dependency on study duration and gender and were successfully used to characterize carcinogens with ambiguous genotoxicity test results, such as Wy-14643. The identified biomarker candidates improve the mechanistic understanding of drug-induced effects on the mouse liver that result in hepatocellular adenomas and/or carcinomas in 2-year mouse carcinogenicity studies.

Role of the focal adhesion protein TRIM15 in colon cancer development

The tripartite motif containing (TRIM) proteins are a large family of proteins that have been implicated in many biological processes including cell differentiation, apoptosis, transcriptional regulation, and signaling pathways. Here, we show that TRIM15 co-localized to focal adhesions through homo-dimerization and significantly suppressed cell migration. Domain mapping analysis indicated that B-box2 and PRY domains were essential for TRIM15 localization to focal adhesions and inhibition of cell migration. Our protein-protein interaction screen of TRIM15 with the integrin adhesome identified several TRIM15 interacting proteins including coronin 1B, cortactin, filamin binding LIM protein1, and vasodilator-stimulated phosphoprotein, which are involved in actin cytoskeleton dynamics. TRIM15 expression was tissue-restricted and downregulated in colon cancer. Level of TRIM15 expression was associated with colon cancer cell migration, as well as both in vitro and in vivo tumor growth. These data provide novel insights into the role of TRIM15 as an additional component of the integrin adhesome, regulating cell migration, and suggest that TRIM15 may function as a tumor suppressor of colon cancer.

Moxonidine modulates cytokine signalling and effects on cardiac cell viability

Regression of left ventricular hypertrophy and improved cardiac function in SHR by the centrally acting imidazoline I1-receptor agonist, moxonidine, are associated with differential actions on circulating and cardiac cytokines. Herein, we investigated cell-type specific I1-receptor (also known as nischarin) signalling and the mechanisms through which moxonidine may interfere with cytokines to affect cardiac cell viability. Studies were performed on neonatal rat cardiomyocytes and fibroblasts incubated with interleukin (IL)-1β (5 ng/ml), tumor necrosis factor (TNF)-α (10 ng/ml), and moxonidine (10(-7) and 10(-5) M), separately and in combination, for 15 min, and 24 and 48 h for the measurement of MAPKs (ERK1/2, JNK, and p38) and Akt activation and inducible NOS (iNOS) expression, by Western blotting, and cardiac cell viability/proliferation and apoptosis by flow cytometry, MTT assay, and Live/Dead assay. Participation of imidazoline I1-receptors and the signalling proteins in the detected effects was identified using imidazoline I1-receptor antagonist and signalling protein inhibitors. The results show that IL-1β, and to a lower extent, TNF-α, causes cell death and that moxonidine protects against starvation- as well as IL-1β -induced mortality, mainly by maintaining membrane integrity, and in part, by improving mitochondrial activity. The protection involves activation of Akt, ERK1/2, p38, JNK, and iNOS. In contrast, moxonidine stimulates basal and IL-1β-induced fibroblast mortality by mechanisms that include inhibition of JNK and iNOS. Thus, apart from their actions on the central nervous system, imidazoline I1-receptors are directly involved in cardiac cell growth and death, and may play an important role in cardiovascular diseases associated with inflammation.

Meta-analysis of the differentially expressed breast cancer-related microRNA expression profiles

MicroRNAs (miRNAs), as non-coding RNA molecules, play an important role in regulating gene expression in cancer development. Meta-analysis was used to screen overlapping differentially expressed miRNAs (DEmiRNAs) in three studies. The miRanda was used to identify target genes related to overlapping DEmiRNAs. These Gene Ontology (GO) and Encyclopaedia of Genes and Genomes (KEGG) database were applied to further predict the function of these target genes. As a result, we obtained seven overlapping miRNAs and six significantly over-represented GO terms closely related to breast cancer. After KEGG pathways analysis, a total of seven key target genes were involved in the Wnt signalling pathway (p = 0.0002). Our findings from this study suggest that the altered levels of miRNAs might have great potential to serve as novel, non-invasive biomarkers for early detection of breast cancer.