Cytoplasmic Signaling Proteins Research Articles

Fn14 and TNFR2 as regulators of cytotoxic TNFR1 signaling.

Tumor necrosis factor (TNF) receptor 1 (TNFR1), TNFR2 and fibroblast growth factor-inducible 14 (Fn14) belong to the TNF receptor superfamily (TNFRSF). From a structural point of view, TNFR1 is a prototypic death domain (DD)-containing receptor. In contrast to other prominent death receptors, such as CD95/Fas and the two TRAIL death receptors DR4 and DR5, however, liganded TNFR1 does not instruct the formation of a plasma membrane-associated death inducing signaling complex converting procaspase-8 into highly active mature heterotetrameric caspase-8 molecules. Instead, liganded TNFR1 recruits the DD-containing cytoplasmic signaling proteins TRADD and RIPK1 and empowers these proteins to trigger cell death signaling by cytosolic complexes after their release from the TNFR1 signaling complex. The activity and quality (apoptosis versus necroptosis) of TNF-induced cell death signaling is controlled by caspase-8, the caspase-8 regulatory FLIP proteins, TRAF2, RIPK1 and the RIPK1-ubiquitinating E3 ligases cIAP1 and cIAP2. TNFR2 and Fn14 efficiently recruit TRAF2 along with the TRAF2 binding partners cIAP1 and cIAP2 and can thereby limit the availability of these molecules for other TRAF2/cIAP1/2-utilizing proteins including TNFR1. Accordingly, at the cellular level engagement of TNFR2 or Fn14 inhibits TNFR1-induced RIPK1-mediated effects reaching from activation of the classical NFκB pathway to induction of apoptosis and necroptosis. In this review, we summarize the effects of TNFR2- and Fn14-mediated depletion of TRAF2 and the cIAP1/2 on TNFR1 signaling at the molecular level and discuss the consequences this has in vivo.

Multiplexed Single-Cell Plasmonic Immunoassay of Intracellular Signaling Proteins Enables Non-Destructive Monitoring of Cell Fate.

It is of significant importance in cancer biology to identify signaling pathways that play key roles in cell fate determination. Dissecting cellular signaling pathways requires the measurement of a large number of signaling proteins. However, tools for simultaneously monitoring multiple signaling pathway components in single living cells remain limited at present. Herein, we describe an approach, termed multiplexed single-cell plasmonic immunosandwich assay (mxscPISA), for simultaneous detection of multiple signaling proteins in individual living cells. This approach enabled simultaneous non-destructive monitoring of multiple (up to five, currently the highest multiplexing capacity in living cells) cytoplasmic and nucleus signaling proteins in individual cells with ultrahigh detection sensitivity. As a proof of principle, the epidermal growth factor receptor (EGFR) pathway, which plays a central role in cell fate determination, was investigated using this approach in this study. We found that there were differential attenuation rate of pro-survival and accumulation rate of pro-death signaling protein of the EGFR pathway in response to EGFR inactivation. These findings implicate that, after EGFR inactivation, a transient imbalance between survival and apoptotic signaling outputs contributed to the final cell fate of death. The mxscPISA approach can be a promising tool to reveal a signaling dynamic pattern at the single-cell level and to identify key components of signaling pathways that contribute to the final cell fate using only a limited number of cells.

Cannabinoids as Key Regulators of Inflammasome Signaling: A Current Perspective.

Inflammasomes are cytoplasmic inflammatory signaling protein complexes that detect microbial materials, sterile inflammatory insults, and certain host-derived elements. Inflammasomes, once activated, promote caspase-1–mediated maturation and secretion of pro-inflammatory cytokines, interleukin (IL)-1β and IL-18, leading to pyroptosis. Current advances in inflammasome research support their involvement in the development of chronic inflammatory disorders in contrast to their role in regulating innate immunity. Cannabis (marijuana) is a natural product obtained from the Cannabis sativa plant, and pharmacologically active ingredients of the plant are referred to as cannabinoids. Cannabinoids and cannabis extracts have recently emerged as promising novel drugs for chronic medical conditions. Growing evidence indicates the potent anti-inflammatory potential of cannabinoids, especially Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiol (CBD), and synthetic cannabinoids; however, the mechanisms remain unclear. Several attempts have been made to decipher the role of cannabinoids in modulating inflammasome signaling in the etiology of chronic inflammatory diseases. In this review, we discuss recently published evidence on the effect of cannabinoids on inflammasome signaling. We also discuss the contribution of various cannabinoids in human diseases concerning inflammasome regulation. Lastly, in the milieu of coronavirus disease-2019 (COVID-19) pandemic, we confer available evidence linking inflammasome activation to the pathophysiology of COVID-19 suggesting overall, the importance of cannabinoids as possible drugs to target inflammasome activation in or to support the treatment of a variety of human disorders including COVID-19.

Phactr1 regulates Slack (KCNT1) channels via protein phosphatase 1 (PP1).

The Slack (KCNT1) gene encodes sodium-activated potassium channels that are abundantly expressed in the central nervous system. Human mutations alter the function of Slack channels, resulting in epilepsy and intellectual disability. Most of the disease-causing mutations are located in the extended cytoplasmic C-terminus of Slack channels and result in increased Slack current. Previous experiments have shown that the C-terminus of Slack channels binds a number of cytoplasmic signaling proteins. One of these is Phactr1, an actin-binding protein that recruits protein phosphatase 1 (PP1) to certain phosphoprotein substrates. Using co-immunoprecipitation, we found that Phactr1 is required to link the channels to actin. Using patch clamp recordings, we found that co-expression of Phactr1 with wild-type Slack channels reduces the current amplitude but has no effect on Slack channels in which a conserved PKC phosphorylation site (S407) that regulates the current amplitude has been mutated. Furthermore, a Phactr1 mutant that disrupts the binding of PP1 but not that of actin fails to alter Slack currents. Our data suggest that Phactr1 regulates the Slack by linking PP1 to the channel. Targeting Slack-Phactr1 interactions may therefore be helpful in developing the novel therapies for brain disorders associated with the malfunction of Slack channels.

Separating Pathways in the Extracellular ESCRT Service

We have known for a long time that cells communicate with their neighbors by secreting a wide array of small molecules and macromolecules. However, in the past three decades, it has become increasingly apparent that cells also release membrane-bounded vesicles not merely to discard selected cellular contents but as an extension of the intercellular communication network. Indeed, there is now vigorous and widespread interest in the roles of these extracellular vesicles (ECVs) as purveyors between cells of growth factors, selected receptors, cytoplasmic signaling proteins, transcription factors, a range of nucleic acid transcripts, DNA, and selected lipids (1).

Identification of STS-1 as a novel ShcA-binding protein

ShcA is a cytoplasmic signaling protein that supports signal transduction by receptor protein-tyrosine kinases by providing auxiliary tyrosine phosphorylation sites that engage additional signaling proteins. The principal binding partner for tyrosine phosphorylation sites on ShcA is Grb2. In the current study, we have used phosphotyrosine-containing peptides to isolate and identify STS-1 as a novel ShcA-binding protein. Our results further show that the interaction between STS-1 and ShcA is regulated in response to EGF receptor activation.

Abstract 3441: A novel lncRNA-mediated YAP1 signaling pathway activation in epithelial ovarian cancer

Abstract Background: The long noncoding RNA (lncRNA) urothelial cancer associated 1 (UCA1) is upregulated in many cancer types, including ovarian cancer. In high grade serous ovarian cancers (HGSOCs), we had previously found that UCA1 expression negatively correlates with patients’ total survival and disease-free survival and that UCA1 knockout significantly impairs tumor growth in vivo. In addition, UCA1 promotes ovarian cancer cell growth via activating the YAP1 signaling pathway. Purpose: Our present study aims to dissect the molecular mechanisms underlying YAP1 signaling activation by UCA1. Methods: To characterize the UCA1 interactome, we utilized a modified in vivo RNA antisense purification method (UCA1-iRAP). This UCA1-iRAP method uses streptavidin-coupled magnetic beads to pull down biotin-labeled antisense probes which are complementary to the target RNA. In such a way, UCA1 RNA will be specifically enriched together with its in vivo-associated proteins, RNAs and/or genomic DNA, which can be profiled using mass spectrometry (MS) and next generation sequencing (NGS), respectively. Results: Using UCA1-iRAP RNA-Seq and UCA1-iRAP protein MS, we comprehensively annotated the UCA1-interacting RNAs as well as UCA1-associated proteins. Interestingly many of the proteins identified were not known to have RNA-binding potential. Integration of NGS and MS data with multilayered functional and molecular characterization of UCA1 knockout, knockdown and overexpression models identified a YAP1 modulator involved in UCA1-mediated regulation of YAP1 signaling. Through repressing this YAP1 modulator via direct RNA-protein interaction, UCA1 promotes nuclear translocation of YAP1, resulting in activation of YAP1 target genes expression. Conclusions: Our analyses indicate, for the first time, that UCA1 promotes ovarian cancer cell growth by activating YAP1 signaling via direct interaction with a YAP1 modulator. The interaction between UCA1 and this YAP1 modulator leads to activation of YAP1 signaling by nuclear translocation of YAP1. In summary, we characterize a novel UCA1-YAP1 signaling axis active in HGSOCs and also reveal that oncogenic lncRNA’s binding potential of cytoplasmic signaling proteins could be a common mechanism of post-translational control of signaling pathways deregulated in cancer. Note: This abstract was not presented at the meeting. Citation Format: Xianzhi Lin, Rosario I. Corona, Simon A. Gayther, Dennis L. Hazelett, Kate Lawrenson. A novel lncRNA-mediated YAP1 signaling pathway activation in epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3441. doi:10.1158/1538-7445.AM2017-3441

MALT1 proteolytic activity is necessary for FcɛRI-mediated cytokine production in mast cells

Abstract IgE mediated mast cell activation triggered by multivalent antigen crosslinking of FcɛRI receptors leads to the release of a wide range of inflammatory mediators. Recent studies revealed that B cell lymphoma 10 (Bcl10) and mucosa-associated lymphoid tissue 1 (MALT1) are required for IgE-induced nuclear factor κB (NF-κB)-induced proinflammatory cytokine production, while dispensible for mast cell degranulation and leukotriene synthesis. MALT1, a cytoplasmic signaling protein, possesses at least two functions: scaffolding activity and proteolytic activity. The contribution of MALT1 proteolytic activity to mast cell function has not yet been evaluated. We hypothesize that MALT1 proteolytic activity is necessary for FcɛRI-dependent proinflammatory cytokine production. In order to test our hypothesis, we compared the activation of bone marrow derived mast cells (BMMC) from wild type mice, MALT1 knockout mice (MALT1−/−), and mice harboring a mutant, proteolytically inactive MALT1 (MALT1PD/PD). We find MALT1 protease is active in wild-type BMMCs as evidenced by RelB cleavage, and is absent, as expected, in MALT1−/− and MALT1PD/PD BMMCs. Cytokine gene expression and production in response to IgE mediated FcɛRI crosslinking is equivalently abrogated in both MALT1−/− and MALT1PD/PD BMMCs as compared to wild type. These findings suggest that the contribution of MALT1 to IgE mediated responses can be largely attributed to its protease activity. The MALT1 protease has been shown to be drugable, and pharmaceutically targeting the MALT1 protease activity may represent a promising approach to abrogating late phase pathologic mast cell activation.

A Novel CD34/ETO2/Ifngr gene Regulatory Axis Is Implicated in Poor-Prognosis Cases of t(8;21) AML

Abstract Background:Roughly 15% of AML cases are derived from the t(8;21) translocation, a molecular event that results in the production of the AML1-ETO (AE) fusion transcription factor. This aberrant protein induces a broad dysregulation of the transcriptome and causes expansion of leukemia stem cells (LSCs), which predisposes clones to an increased risk of second-hit mutations. In isolation, without the presence of type I mutations, the t(8;21) mark is considered to be one of favorable prognosis. However, a number of LSC characteristics have been shown to influence patient survival, including expression levels of the cell surface glycoprotein, CD34, and of the truncated isoform of AE, AML1-ETO9a (AE9a). Despite these findings, a unified model of how these factors interact to further the progression of t(8;21) AML has not been determined. Here, we use a combination of in vitro assays and bioinformatic analyses of patient datasets with the hopes of identifying an underlying connection between independent, prognostic factors. Results: We first performed gene knockdown studies with shRNA constructs (against AE) in a pKLO.1 backbone, which was transduced into the AML-model cell line Kasumi-1. Subsequent RT-PCR showed a large decrease in CD34 expression and, serving as a control, an increase in RASSF2, a cytoplasmic signaling protein normally repressed by AE. This led us to perform gene overexpression of cDNA encoding AE or AE9a into CD34-enriched cord blood HSCs. Interestingly, we were able to show that both AE and AE9a increased the expression of CD34, and AE9a was able to do so to a greater extent. This prompted us to analyze previous ChIP-seq data from Kasumi-1 cells, and we discovered high levels of AE binding to an upstream enhancer of CD34. While this site was free of any E-box binding motifs, we nonetheless observed binding peaks of the E-protein HEB, and further gene knock-down studies showed that HEB recruitment to this site depended on AE and, in turn, CD34 expression depended on HEB recruitment. Next, we used differential gene expression analyses to determine the CD34-coexpressed genes from a publically available patient microarray dataset (GSE14468, n=516). CD34-high patient samples showed an accompanying enrichment of JUP, KIT, CD133, HEB, E2A and ETO2, and a decrease in immune signaling molecules such as IFNGR1 and IFNGR2. ETO2 is the only ETO family member significantly expressed in HSCs and is an important corepressor of E-proteins HEB and E2A; it is thought to help repress the pro-differentiation and anti-proliferation effects of E-proteins. ETO2, being an ETO family member, is also able to oligomerize with other ETO family members, such as ETO, and thus may play a role in modifying the functions of the AE-transcriptional complex. Intriguingly, we have evidence that AE and AE9a repress ETO2, although AE9a does so to a lessened extent. We then performed Kaplan-Meier analyses on subgroups of non-CBF AML and t(8;21) AML cases. Unsurprisingly, we found that both groups experienced lower event-free survival when CD34 and ETO2 were high (p=.028 and p=.040), and the t(8;21) group when IFNGR was low (p=.014). Additionally, although CD34 expression was higher in t(8;21) patients compared to non-CBF AML (p=.0027), ETO2 expression was lower (p=.025). If both subgroups were further divided into CD34-high and CD34-low groups, ETO2 expression was, in both cases, higher in the CD34-high patients and lower in the CD34-low patients, suggesting a possible regulatory link between these two genes. Finally, we performed ETO2 gene knockdown experiments in CD34+ HSCs and observed an increase in IFNGR1 and IFNGR2 expression. Conclusions: Our findings suggest a clinically relevant association between CD34, ETO2, and IFNGR in both t(8;21) and non-CBF AML. We believe this regulatory axis is especially relevant in relapse likelihood and may be hijacked by LSCs to preserve their "stemness" and resistance to therapy. Our findings may suggest that AE simultaneously activates CD34 and represses ETO2, providing explanation for why full-length AE is slow to induce leukemia in mouse models and a relatively good prognostic mark in humans. Additionally, our findings suggest a loss of ETO2repression as a potential mechanism by which the AE9a isoform, and perhaps other second-hit mutations, converts LSCs to a more dangerous phenotype. Supported by NIH grants R01HL093195-01A1 to JZ and T32 training grant T32GM008306-26A1 Disclosures No relevant conflicts of interest to declare.

Engineering a minimal G protein to facilitate crystallisation of G protein-coupled receptors in their active conformation.

G protein-coupled receptors (GPCRs) modulate cytoplasmic signalling in response to extracellular stimuli, and are important therapeutic targets in a wide range of diseases. Structure determination of GPCRs in all activation states is important to elucidate the precise mechanism of signal transduction and to facilitate optimal drug design. However, due to their inherent instability, crystallisation of GPCRs in complex with cytoplasmic signalling proteins, such as heterotrimeric G proteins and β-arrestins, has proved challenging. Here, we describe the design of a minimal G protein, mini-Gs, which is composed solely of the GTPase domain from the adenylate cyclase stimulating G protein Gs. Mini-Gs is a small, soluble protein, which efficiently couples GPCRs in the absence of Gβγ subunits. We engineered mini-Gs, using rational design mutagenesis, to form a stable complex with detergent-solubilised β1-adrenergic receptor (β1AR). Mini G proteins induce similar pharmacological and structural changes in GPCRs as heterotrimeric G proteins, but eliminate many of the problems associated with crystallisation of these complexes, specifically their large size, conformational dynamics and instability in detergent. They are therefore novel tools, which will facilitate the biochemical and structural characterisation of GPCRs in their active conformation.

Costimulation of IL-2 Production through CD28 Is Dependent on the Size of Its Ligand

Optimal T cell activation typically requires engagement of both the TCR and costimulatory receptors, such as CD28. Engagement of CD28 leads to tyrosine phosphorylation of its cytoplasmic region and recruitment of cytoplasmic signaling proteins. Although the exact mechanism of CD28 signal transduction is unknown, CD28 triggering has similarities to the TCR, which was proposed to use the kinetic-segregation (KS) mechanism. The KS model postulates that, when small receptors engage their ligands within areas of close (∼15 nm) contact in the T cell/APC interface, this facilitates phosphorylation by segregating the engaged receptor/ligand complex from receptor protein tyrosine phosphatases with large ectodomains, such as CD45. To test this hypothesis, we examined the effect of elongating the extracellular region of the CD28 ligand, CD80, on its ability to costimulate IL-2 production by primary T cells. CD80 elongation reduced its costimulatory effect without abrogating CD28 binding. Confocal microscopy revealed that elongated CD80 molecules were less well segregated from CD45 at the T cell/APC interface. T cells expressing CD28 harboring a key tyrosine-170 mutation were less sensitive to CD80 elongation. In summary, the effectiveness of CD28 costimulation is inversely proportional to the dimensions of the CD28-CD80 complex. Small CD28-CD80 complex dimensions are required for optimal costimulation by segregation from large inhibitory tyrosine phosphatases. These results demonstrate the importance of ligand dimensions for optimal costimulation of IL-2 production by T cells and suggest that the KS mechanism contributes to CD28 signaling.

Hepatocyte TRAF3 promotes insulin resistance and type 2 diabetes in mice with obesity.

ObjectiveMetabolic inflammation is believed to promote insulin resistance and type 2 diabetes progression in obesity. TRAF3, a cytoplasmic signaling protein, has been known to mediate/modulate cytokine signaling in immune cells. The goal is to define the metabolic function of hepatic TRAF3 in the setting of obesity.MethodsHepatocyte-specific TRAF3 knockout mice were generated using the loxp/albumin-cre system. Liver TRAF3 was deleted in adult obese mice via Cre adenoviral infection. Both high fat diet-induced and genetic obesity were examined. TRAF3 levels and insulin signaling were measured by immunoblotting. Insulin sensitivity, hepatic glucose production, and glucose metabolism were examined by glucose, insulin, and pyruvate tolerance tests. Hepatic steatosis was examined by Oil red O staining of liver sections and measuring liver triacylglycerol levels.ResultsLiver TRAF3 levels were lower in the fasted states in normal mice, and were aberrantly higher in obese mice and in mice with streptozotocin-induced hyperglycemia. Glucose directly increased TRAF3 levels in primary hepatocytes. Hepatocyte-specific deletion of TRAF3 decreased hyperinsulinemia, insulin resistance, glucose intolerance, and hepatic steatosis in mice with either high fat diet-induced obesity or genetic obesity (ob/ob); conversely, in lean mice, adenovirus-mediated overexpression of TRAF3 in the liver induced hyperinsulinemia, insulin resistance, and glucose intolerance. Deletion of TRAF3 enhanced the ability of insulin to stimulate phosphorylation of Akt in hepatocytes, whereas overexpression of TRAF3 suppressed insulin signaling.ConclusionsGlucose increases the levels of hepatic TRAF3. TRAF3 in turn promotes hyperglycemia through increasing hepatic glucose production, thus forming a glucose-TRAF3 reinforcement loop in the liver. This positive feedback loop may drive the progression of type 2 diabetes and nonalcoholic fatty liver disease in obesity.

Metformin effects on biochemical recurrence and metabolic signaling in the prostate.

Metformin has received considerable attention as a potential anti-cancer agent. Animal and in-vitro prostate cancer (PCa) models have demonstrated decreased tumor growth with metformin, however the precise mechanisms are unknown. We examine the effects of metformin on PCa biochemical recurrence (BCR) in a large clinical database followed by evaluating metabolic signaling changes in a cohort of men undergoing prostate needle biopsy (PNB). Men treated for localized PCa were identified in a comprehensive clinical database between 2001 and 2010. Cox regression was performed to determine association with BCR relative to metformin use. We next identified a separate case-control cohort of men undergoing prostate needle biopsy (PNB) stratified by metformin use. Differences in mean IHC scores were compared with linear regression for phosphorylated IR, IGF-IR, AKT, and AMPK. One thousand seven hundred and thirty four men were evaluated for BCR with mean follow up of 41 months (range 1-121 months). "Ever" metformin use was not associated with BCR (HR 1.12, 0.77-1.65), however men reporting both pre/post-treatment metformin use had a 45% reduction in BCR (HR = 0.55 (0.31-0.96)). For the tissue-based study, 48 metformin users and 42 controls underwent PNB. Significantly greater staining in phosphorylated nuclear (p-IR, p-AKT) and cytoplasmic (p-IR, p-IGF-1R) insulin signaling proteins were seen in patients with PCa detected compared to those with negative PNB (P-values all <0.006). When stratified by metformin use, IGF-1R remained significantly elevated (P = 0.01) in men with PCa detected whereas p-AMPK (P = 0.05) was elevated only in those without PCa. Metformin use is associated with reduced BCR after treatment of localized PCa when considering pre-diagnostic and cumulative dosing. In men with cancer detected on PNB, insulin signaling markers were significantly elevated compared to negative PNB patients. The finding of IGF-1R elevation in positive PNBs versus p-AMPK elevation in negative PNBs suggests altered metabolic pathway activation precipitated by metformin use.

Intracellular Ca2+ signaling and preimplantation development.

The key, versatile role of intracellular Ca2+ signaling during egg activation after fertilization has been appreciated for several decades. More recently, evidence has accumulated supporting the concept that cytoplasmic Ca2+ is also a major signaling nexus during subsequent development of the fertilized ovum. This chapter will review the molecular reactions that regulate intracellular Ca2+ levels and cell function, the role of Ca2+ signaling during egg activation and specific examples of repetitive Ca2+ signaling found throughout pre- and peri-implantation development. Many of the upstream and downstream pathways utilized during egg activation are also critical for specific processes that take place during embryonic development. Much remains to be done to elucidate the full complexity of Ca2+ signaling mechanisms in preimplantation embryos to the level of detail accomplished for egg activation. However, an emerging concept is that because this second messenger can be modulated downstream of numerous receptors and is able to bind and activate multiple cytoplasmic signaling proteins, it can help the coordination of development through up- and downstream pathways that change with each embryonic stage.

Specific Phosphorylations Transmit Signals from Leukocyte β2 to β1 Integrins and Regulate Adhesion

The regulation of integrins expressed on leukocytes must be controlled precisely, and members of different integrin subfamilies have to act in concert to ensure the proper traffic of immune cells to sites of inflammation. The activation of β2 family integrins through the T cell receptor or by chemokines leads to the inactivation of very late antigen 4. The mechanism(s) of this cross-talk has not been known. We have now elucidated in detail how the signals are transmitted from leukocyte function-associated antigen 1 and show that, after its activation, the signaling involves specific phosphorylations of β2 integrin followed by interactions with cytoplasmic signaling proteins. This results in loss of β1 phosphorylation and a decrease in very late antigen 4 binding to its ligand vascular cell adhesion molecule 1. Our results show how a member of one integrin family regulates the activity of another integrin. This is important for the understanding of integrin-mediated processes.

150: Haematopoietic cell kinase activation promotes IL-11 dependent gastric cancer progression and invasion in mice

Gastric cancer has a high mortality rate associated with its late stage diagnosis. Although Gp130 knock-in mutant mice (gp130 F / F ) develop benign gastric tumours dependent upon IL-11-induced Stat3/mTORC activation with hallmarks of early stage intestinal-type gastric cancer in humans [1] , [2] , there is an urgent need to develop mouse models that mimic the progression from adenoma to carcinoma and metastasis. Macrophages are a major component of the tumour micro-environment, and their increased numbers and alternative activation is commonly associated with tumour progression and metastasis. Haematopoietic Cell Kinase (Hck) is a myeloid-specific Src family kinase that is involved in polarization of alternatively activated macrophages, which correlate with a poor prognosis for human gastric cancer. To establish whether aberrant Hck activation would induce tumourigenesis, Hck mutant mice that exhibit constitutive kinase activation (Hck Up / Up ) were crossed with gp130 F /+ mice that are predisposed to gastric tumour development. Surprisingly, the resulting gp130 F /+ ;Hck Up / Up compound mutants developed tumours similar to gp130[F/F] animals, while gp130 F /+ mice remained tumour-free. Furthermore, tumours in 9 month old gp130 F /+ ;Hck Up / Up mutants showed sub-mucosal invasion, which was not observed in gp130 F / F mice. Western blotting and immunohistochemical analysis revealed a significant increase in tumour cell proliferation in gp130 F /+ ;Hck Up / Up mutants compared to gp130 F / F animals, consistent with an increased abundance of the activated forms of Stat3, Erk, Akt and S6 cytoplasmic signalling proteins. While the total number of macrophages remained unaffected, qPCR analysis of purified tumour-associated macrophages from gp130 F /+ ; Hck Up / Up mice showed a significant increase in markers of alternative macrophage activation, including Il4 , Il13 , Arg1 and Ym1 when compared to cells from gp130 F / F animals. Furthermore, reciprocal adoptive transfer of Hck Up / Up bone-marrow into gp130 mutant recipients was sufficient to increase tumour burden and promote alternative macrophage polarisation. Collectively, our results demonstrate that aberrant Hck activation promotes polarisation towards alternative macrophage activation and confers an invasive gastric cancer phenotype.

Multiplex Proteomic Analysis of Cells in Fine Needle Aspiration Samples: How Soon Can We Expect to Individualize Therapy by Comparing Pre- and Posttreatment Biopsies?

Individualized therapy of the future will be guided by panels of biomarkers that include proteins, nucleic acids, and metabolites. Among these analyte classes, proteins can provide direct functional information central to the disease. The added bonus is that the protein, or phosphoprotein, biomarker is the drug target itself and/or the direct readout of the signaling activity being inhibited. An example is the selection of kinase inhibitor therapy based on phosphorylated receptor tyrosine kinases, such as human epidermal growth factor receptor 2, protein kinase B, epidermal growth factor receptor, MET receptor tyrosine kinase, or cytoplasmic signaling proteins, such as mammalian target of rapamycin. Yet it has not been easy to quantitatively measure a panel of protein/phosphoprotein biomarkers in tissue biopsy samples with high precision, sensitivity, and accuracy, which are essential attributes if the data are used to select patient therapies. Addressing this challenge, Ullal et al. (1) described a new technology that uses DNA barcode labeling of antibodies for multiplex proteomic/phosphoprotein analysis of cells in a tumor fine needle aspiration (FNA).2 FNAs are challenging clinical specimens that contain relatively few cells compared to a tissue biopsy. Why is this method important, how does it compare to existing multiplexed clinical proteomic technologies, and when can we hope to see this platform routinely used in the clinical laboratory? The author's platform (1) is divided into serial stages. In the first stage, the cells are passed through a microfluidic chamber where tumor cells are separated from host cells. Here, the cell mixture is exposed to antibodies tagged with magnetic particles. This permits the removal of contaminating immune cells or positive selection of tumor cells. In the second stage, the cancer cells are incubated with a cocktail of antibodies that are labeled with DNA “barcodes.” Each barcode is a different 70-nucleotide sequence. The DNA …

Regulation of LRP-1 expression: Make the point

The low-density lipoprotein receptor-related protein-1 (LRP-1) is a membrane receptor displaying both scavenging and signaling functions. The wide variety of extracellular ligands and of cytoplasmic scaffolding and signaling proteins interacting with LRP-1 gives it a major role not only in physiological processes, such as embryogenesis and development, but also in critical pathological situations, including cancer and neurological disorders. In this review, we describe the molecular mechanisms involved at distinct levels in the regulation of LRP-1, from its expression to the proper location and stability at the cell surface.

Disruption of Tumor Necrosis Factor Receptor Associated Factor 5 Exacerbates Pressure Overload Cardiac Hypertrophy and Fibrosis

The cytoplasmic signaling protein tumor necrosis factor (TNF) receptor-associated factor 5 (TRAF5), which was identified as a signal transducer for members of the TNF receptor super-family, has been implicated in several biological functions in T/B lymphocytes and the innate immune response against viral infection. However, the role of TRAF5 in cardiac hypertrophy has not been reported. In the present study, we investigated the effect of TRAF5 on the development of pathological cardiac hypertrophy induced by transthoracic aorta constriction (TAC) and further explored the underlying molecular mechanisms. Cardiac hypertrophy and function were evaluated with echocardiography, hemodynamic measurements, pathological and molecular analyses. For the first time, we found that TRAF5 deficiency substantially aggravated cardiac hypertrophy, cardiac dysfunction and fibrosis in response to pressure overload after 4 weeks of TAC compared to wild-type (WT) mice. Moreover, the mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK)-extracellular signal-regulated kinases 1/2 (ERK1/2) signaling pathway was more activated in TRAF5-deficient mice than WT mice. In conclusion, our results suggest that as an intrinsic cardioprotective factor, TRAF5 plays a crucial role in the development of cardiac hypertrophy through the negative regulation of the MEK-ERK1/2 pathway. J. Cell. Biochem. 115: 349-358, 2014. © 2013 Wiley Periodicals, Inc.

Valvular dystrophy associated filamin A mutations reveal a new role of its first repeats in small-GTPase regulation

Filamin A (FlnA) is a ubiquitous actin binding protein which anchors various transmembrane proteins to the cell cytoskeleton and provides a scaffold to many cytoplasmic signaling proteins involved in actin cytoskeleton remodeling in response to mechanical stress and cytokines stimulation. Although the vast majority of FlnA binding partners interact with the carboxy-terminal immunoglobulin like (Igl) repeats of FlnA, little is known on the role of the amino-N-terminal repeats. Here, using cardiac mitral valvular dystrophy associated FlnA–G288R and P637Q mutations located in the N-terminal Igl repeat 1 and 4 respectively as a model, we identified a new role of FlnA N-terminal repeats in small Rho-GTPases regulation. Using FlnA-deficient melanoma and HT1080 cell lines as expression systems we showed that FlnA mutations reduce cell spreading and migration capacities. Furthermore, we defined a signaling network in which FlnA mutations alter the balance between RhoA and Rac1 GTPases activities in favor of RhoA and provided evidences for a role of the Rac1 specific GTPase activating protein FilGAP in this process. Together our work ascribed a new role to the N-terminal repeats of FlnA in Small GTPases regulation and supports a conceptual framework for the role of FlnA mutations in cardiac valve diseases centered around signaling molecules regulating cellular actin cytoskeleton in response to mechanical stress.