Sorafenib triggers ferroptosis via inhibition of HBXIP/SCD axis in hepatocellular carcinoma

Sorafenib, which inhibits multiple kinases, is an effective frontline therapy for hepatocellular carcinoma (HCC). Ferroptosis is a form of iron-dependent programmed cell death regulated by lipid peroxidation, which can be induced by sorafenib treatment. Oncoprotein hepatitis B X-interacting protein (HBXIP) participates in multiple biological pro-tumor processes, including growth, metastasis, drug resistance, and metabolic reprogramming. However, the role of HBXIP in sorafenib-induced ferroptotic cell death remains unclear. In this study, we demonstrated that HBXIP prevents sorafenib-induced ferroptosis in HCC cells. Sorafenib decreased HBXIP expression, and overexpression of HBXIP blocked sorafenib-induced HCC cell death. Interestingly, suppression of HBXIP increased malondialdehyde (MDA) production and glutathione (GSH) depletion to promote sorafenib-mediated ferroptosis and cell death. Ferrostatin-1, a ferroptosis inhibitor, reversed the enhanced anticancer effect of sorafenib caused by HBXIP silencing in HCC cells. Regarding the molecular mechanism, HBXIP transcriptionally induced the expression of stearoyl-CoA desaturase (SCD) via coactivating the transcriptional factor ZNF263, resulting in the accumulation of free fatty acids and suppression of ferroptosis. Functionally, activation of the HBXIP/SCD axis reduced the anticancer activity of sorafenib and suppressed ferroptotic cell death in vivo and in vitro. HBXIP/SCD axis-mediated ferroptosis can serve as a novel downstream effector of sorafenib. Our results provide new evidence for clinical decisions in HCC therapy.

SMYD2-mediated TRAF2 methylation promotes the NF-κB signaling pathways in inflammatory diseases

BACKGROUND

The methylation of lysine residues has been involved in the multiple biological and diseases processes. Recently, some particular non-histone proteins have been elucidated to be methylated by SMYD2, a SET and MYND domain protein with lysine methyltransferase activity.

METHODS

SMYD2 was evaluated in synovial tissue and cells derived from rheumatoid arthritis patients. We confirmed TRAF2 could be methylated by SMYD2 using Mass spectrometry, pull-down, immunoprecipitation, methyltransferase assay, ubiquitination assay, luciferase reporter assays, and western blot analyses. Using loss- and gain-of function studies, we explored the biological functions of SMYD2 in vitro and in vivo. Using acute and chronic inflammation with different mice models to determine the impact of SMYD2.

RESULTS

Here, we first time confirmed that the cytoplasmic protein TRAF2 as the kernel node for NF-κB signaling pathway could be methylated by SMYD2. SMYD2-mediated TRAF2 methylation contributed to the durative sensitization of NF-κB signaling transduction through restraining its own proteolysis and enhancing the activity. In addition, we found knocking down of SMYD2 has different degrees of mitigation in acute and chronic inflammation mice models. Furthermore, as the lysine-specific demethylase, LSD1 could resist methylation on TRAF2 induced by SMYD2.

CONCLUSIONS

Our data uncovered an unprecedented cytoplasmic protein network that employed methylation of TRAF2 for the maintenance of NF-κB activation during inflammatory diseases.

Everolimus and plicamycin specifically target chemoresistant colorectal cancer cells of the CMS4 subtype

Colorectal cancers (CRC) can be classified into four consensus molecular subtypes (CMS), among which CMS1 has the best prognosis, contrasting with CMS4 that has the worst outcome. CMS4 CRC is notoriously resistant against therapeutic interventions, as demonstrated by preclinical studies and retrospective clinical observations. Here, we report the finding that two clinically employed agents, everolimus (EVE) and plicamycin (PLI), efficiently target the prototypic CMS4 cell line MDST8. As compared to the prototypic CMS1 cell line LoVo, MDST8 cells treated with EVE or PLI demonstrated stronger cytostatic and cytotoxic effects, increased signs of apoptosis and autophagy, as well as a more pronounced inhibition of DNA-to-RNA transcription and RNA-to-protein translation. Moreover, nontoxic doses of EVE and PLI induced the shrinkage of MDST8 tumors in mice, yet had only minor tumor growth-reducing effects on LoVo tumors. Altogether, these results suggest that EVE and PLI should be evaluated for their clinical activity against CMS4 CRC.

Interdiction of Protein Folding for Therapeutic Drug Development in SARS CoV-2

In this article, we predict the folding initiation events of the ribose phosphatase domain of protein Nsp3 and the receptor binding domain of the spike protein from the severe acute respiratory syndrome (SARS) coronavirus-2. The calculations employ the sequential collapse model and the crystal structures to identify the segments involved in the initial contact formation events of both viral proteins. The initial contact locations may provide good targets for therapeutic drug development. The proposed strategy is based on a drug binding to the contact location, thereby aiming to prevent protein folding. Peptides are suggested as a natural choice for such protein folding interdiction drugs.

Long non-coding RNA H19 promotes the proliferation, migration and invasion while inhibits apoptosis of hypertrophic scarring fibroblasts by targeting miR-3187-3p/GAB1 axis

BACKGROUND

It had been reported that long non-coding RNA (lncRNA) H19 was associated with the proliferation of fibroblasts. However, the regulatory mechanism of H19 remains unclear. Thus, the study was designed to explore the underlying mechanism of H19 in the process of Hypertrophic scarring (HS).

METHODS

The expression levels of H19, miR-3187-3p, and growth factor receptor binding 2-associated binding protein 1 (GAB1) in HS tissues and HS fibroblasts were measured by real-time quantitative polymerase chain reaction (RT-qPCR) assay. The biological behaviors of HS fibroblasts, such as cell proliferation, apoptosis, migration, and invasion were assessed by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazol-3-ium bromide (MTT), colony formation, flow cytometry, and transwell assays, respectively. The protein expression level was quantified by western blot assay. The interaction association between miR-3187-3p and H19 or GAB1 was predicted by Starbase database analysis and confirmed by dual-luciferase reporter assay, respectively.

RESULTS

H19 was significantly increased in HS tissues and HS fibroblasts. Loss-of-functional experiments revealed that knockdown of H19 inhibited the development of HS. Moreover, silencing of H19 impeded the proliferation, migration, and invasion, while enhanced apoptosis of HS fibroblasts by increasing miR-3187-3p expression. In addition, overexpression of GAB1 could abolish miR-3187-3p overexpression-induced effects on cell proliferation, apoptosis, migration, and invasion of HS fibroblasts. Mechanistically, H19 could act as a sponge of miR-3187-3p to upregulate the expression of GAB1 in HS fibroblasts.

CONCLUSION

Collectively, our results revealed that H19 promoted the proliferation, migration, and invasion, while impeded apoptosis of HS fibroblasts by targeting miR-3187-3p/GAB1 axis.

Methyl-CpG-binding domain 3 inhibits stemness of pancreatic cancer cells via Hippo signaling

Methyl-CpG-binding domain 3 (MBD3), as an induced stem cells reprogramming barrier, has an abnormal expression in various prevalent malignancies. However, in pancreatic cancer cell stemness, the roles of MBD3 remain unclear. In our study, the effects of MBD3 were investigated on the proliferation, stemness and the underlying mechanism in pancreatic cancer cells. Firstly, MBD3 knockdown was proved to promote proliferation and sphere formation of pancreatic cancer cells and tumorigenesis, while MBD3 upregulation inhibited the above results. Also, MBD3 downregulation notably increased stemness markers level of OCT4, NANOG and SOX2, and MBD3 upregulation resulted in the opposite effects. Mechanically, it was found that MBD3 involved in activation of Hippo pathway. There was a negative correlation between MBD3 and YAP expression in TCGA database. MBD3 knockdown improved YAP expression, and promoted YAP nuclear translocation increased TEAD luciferase activity, while MBD3 overexpression reversed the above results. Further evidence revealed that YAP could bind to MBD3, and decreased MBD3 expression. Collectively, MBD3 bound to YAP to significantly inhibit proliferation and weaken stemness maintenance in pancreatic cancer cells, as well as reduce tumorigenesis via Hippo signaling. Thus, MBD3 may serve as a potential molecular biomarker for exploring new therapeutic strategies to treat pancreatic cancer.

NADPH oxidase subunit NOXO1 is a target for emphysema treatment in COPD

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and death worldwide. Peroxynitrite, formed from nitric oxide, which is derived from inducible nitric oxide synthase, and superoxide, has been implicated in the development of emphysema, but the source of the superoxide was hitherto not characterized. Here, we identify the non-phagocytic NADPH oxidase organizer 1 (NOXO1) as the superoxide source and an essential driver of smoke-induced emphysema and pulmonary hypertension development in mice. NOXO1 is consistently upregulated in two models of lung emphysema, Cybb (also known as NADPH oxidase 2, Nox2)-knockout mice and wild-type mice with tobacco-smoke-induced emphysema, and in human COPD. Noxo1-knockout mice are protected against tobacco-smoke-induced pulmonary hypertension and emphysema. Quantification of superoxide, nitrotyrosine and multiple NOXO1-dependent signalling pathways confirm that peroxynitrite formation from nitric oxide and superoxide is a driver of lung emphysema. Our results suggest that NOXO1 may have potential as a therapeutic target in emphysema.

Tubulin Resists Degradation by Cereblon-Recruiting PROTACs

Dysregulation of microtubules and tubulin homeostasis has been linked to developmental disorders, neurodegenerative diseases, and cancer. In general, both microtubule-stabilizing and destabilizing agents have been powerful tools for studies of microtubule cytoskeleton and as clinical agents in oncology. However, many cancers develop resistance to these agents, limiting their utility. We sought to address this by developing a different kind of agent: tubulin-targeted small molecule degraders. Degraders (also known as proteolysis-targeting chimeras (PROTACs)) are compounds that recruit endogenous E3 ligases to a target of interest, resulting in the target's degradation. We developed and examined several series of α- and β-tubulin degraders, based on microtubule-destabilizing agents. Our results indicate, that although previously reported covalent tubulin binders led to tubulin degradation, in our hands, cereblon-recruiting PROTACs were not efficient. In summary, while we consider tubulin degraders to be valuable tools for studying the biology of tubulin homeostasis, it remains to be seen whether the PROTAC strategy can be applied to this target of high clinical relevance.

Improvement of Psoriasis by Alteration of the Gut Environment by Oral Administration of Fucoidan from Cladosiphon Okamuranus

Psoriasis is a chronic autoimmune inflammatory disease for which there is no cure; it results in skin lesions and has a strong negative impact on patients' quality of life. Fucoidan from Cladosiphon okamuranus is a dietary seaweed fiber with immunostimulatory effects. The present study reports that the administration of fucoidan provided symptomatic relief of facial itching and altered the gut environment in the TNF receptor-associated factor 3-interacting protein 2 (Traf3ip2) mutant mice (m-Traf3ip2 mice); the Traf3ip2 mutation was responsible for psoriasis in the mouse model used in this study. A fucoidan diet ameliorated symptoms of psoriasis and decreased facial scratching. In fecal microbiota analysis, the fucoidan diet drastically altered the presence of major intestinal opportunistic microbiota. At the same time, the fucoidan diet increased mucin volume in ileum and feces, and IgA contents in cecum. These results suggest that dietary fucoidan may play a significant role in the prevention of dysfunctional immune diseases by improving the intestinal environment and increasing the production of substances that protect the immune system.

Cucurbitacin B Inhibits the Hippo-YAP Signaling Pathway and Exerts Anticancer Activity in Colorectal Cancer Cells

BACKGROUND Colorectal carcinoma (CRC) is one of the most frequently diagnosed malignancies. Cucurbitacin B (CuB) is a natural compound isolated from herbs and shows anticancer activity in several cancers. MATERIAL AND METHODS Here, we analyzed the effects of different CuB concentrations on the proliferative and invasive behaviors of CRC cells using MTT, clonogenic assay, Transwell invasion, and wound healing assays. Flow cytometry was performed to measure the apoptotic effects of CuB on CRC cells. Western blot and real-time PCR were used to investigate the expression of apoptosis and Hippo-YAP signaling pathway proteins. RESULTS CuB inhibited the proliferation and invasion of CRC cells while promoting apoptosis. In addition, the Western blot and real-time PCR results indicated that CuB suppressed YAP expression and its downstream target genes Cyr 61 and c-Myc in CRC cells. To assess the underlying mechanism, we investigated the upstream regulating factor LATS1, and the results revealed that CuB upregulated LATS1 expression in CRC cells. CONCLUSIONS In conclusion, our findings uncovered a novel therapeutic mechanism of CuB and suggest that there is therapeutic potential and feasibility in developing novel YAP inhibitors for cancer treatment.

The pro-apoptotic protein Bmf co-operates with Bim and Puma in neuron death induced by β-amyloid or NGF deprivation

The pro-apoptotic Bcl-2 homology 3 domain only (BH3-only) proteins are central regulators of cell death in various physiological and pathological conditions, including Alzheimer's disease (AD). Bcl-2 modifying factor (Bmf) is one such BH3-only protein that is implicated in various death paradigms such as anoikis, seizures, cancer and autoimmunity. It also co-operates with other BH3-only proteins such as Bim in various death paradigms. However, its role in neurodegeneration is under-investigated. Here, we report for the first time the essential role of Bmf and its co-operativity with direct activator BH3-only proteins Bim and Puma in neuron death induced by beta-amyloid (Aβ) toxicity or NGF deprivation. Oligomeric Aβ is main pathologic species in AD and NGF deprivation is relevant for both developmental as well as pathologic neuron death. We find that Bmf over-expression causes cell death and Bmf knockdown protects neurons against death evoked by Aβ or NGF deprivation. We also find that Bmf co-operates with other important BH3-only proteins such as Bim and Puma in neuron death induced by Aβ or NGF deprivation. Simultaneous knocking down of these molecules by their respective shRNAs provide enhanced protection against Aβ. Taken together, our results elucidate the essential role of Bmf and its co-operative effects with already known neuron death inducers, Bim and Puma, in neuron death evoked by Aβ treatment or NGF deprivation.

Dipeptidyl Peptidase-4 Inhibition With Saxagliptin Ameliorates Angiotensin II-Induced Cardiac Diastolic Dysfunction in Male Mice

Activation of the renin-angiotensin-aldosterone system is common in hypertension and obesity and contributes to cardiac diastolic dysfunction, a condition for which no treatment currently exists. In light of recent reports that antihyperglycemia incretin enhancing dipeptidyl peptidase (DPP)-4 inhibitors exert cardioprotective effects, we examined the hypothesis that DPP-4 inhibition with saxagliptin (Saxa) attenuates angiotensin II (Ang II)-induced cardiac diastolic dysfunction. Male C57BL/6J mice were infused with either Ang II (500 ng/kg/min) or vehicle for 3 weeks receiving either Saxa (10 mg/kg/d) or placebo during the final 2 weeks. Echocardiography revealed Ang II-induced diastolic dysfunction, evidenced by impaired septal wall motion and prolonged isovolumic relaxation, coincident with aortic stiffening. Ang II induced cardiac hypertrophy, coronary periarterial fibrosis, TRAF3-interacting protein 2 (TRAF3IP2)-dependent proinflammatory signaling [p-p65, p-c-Jun, interleukin (IL)-17, IL-18] associated with increased cardiac macrophage, but not T cell, gene expression. Flow cytometry revealed Ang II-induced increases of cardiac CD45+F4/80+CD11b+ and CD45+F4/80+CD11c+ macrophages and CD45+CD4+ lymphocytes. Treatment with Saxa reduced plasma DPP-4 activity and abrogated Ang II-induced cardiac diastolic dysfunction independent of aortic stiffening or blood pressure. Furthermore, Saxa attenuated Ang II-induced periarterial fibrosis and cardiac inflammation, but not hypertrophy or cardiac macrophage infiltration. Analysis of Saxa-induced changes in cardiac leukocytes revealed Saxa-dependent reduction of the Ang II-mediated increase of cardiac CD11c messenger RNA and increased cardiac CD8 gene expression and memory CD45+CD8+CD44+ lymphocytes. In summary, these results demonstrate that DPP-4 inhibition with Saxa prevents Ang II-induced cardiac diastolic dysfunction, fibrosis, and inflammation associated with unique shifts in CD11c-expressing leukocytes and CD8+ lymphocytes.

Proliferation in culture of primordial germ cells derived from embryonic stem cell: induction by retinoic acid

An in vitro system that supports primordial germ cells (PGCs) survival and proliferation is useful for enhancement of these cells and efficient transplantation in infertility disorders. One approach is cultivation of PGCs under proper conditions that allow self-renewal and proliferation of PGCs. For this purpose, we compared the effects of different concentrations of retinoic acid (RA), and the effect of PGCs co-culture (Co-C) with SIM mouse embryo-derived thioguanine- and ouabain-resistant (STO) cells on the proliferation of embryonic stem cells (ESCs)-derived PGCs. One-day-old embryoid body (EB) was cultured for 4 days in simple culture system in the presence of 5 ng/ml bone morphogenetic protein-4 (BMP4) (SCB group) for PGC induction. For PGC enrichment, ESCs-derived germ cells were cultured for 7 days in the presence of different doses (0-5  μM) of RA, both in the simple and STO Co-C systems. At the end of the culture period, viability and proliferation rates were assessed and expression of mouse vasa homologue (Mvh),  α6 integrin,  β1 integrin, stimulated by retinoic acid 8 (Stra8) and piwi (Drosophila)-like 2 (Piwil2) was evaluated using quantitative PCR. Also, the inductive effects were investigated immunocytochemically with Mvh and cadherin1 (CDH1) on the selected groups. Immunocytochemistry/PCR results showed higher expression of Mvh, the PGC-specific marker, in 3  μM RA concentrations on the top of the STO feeder layer. Meanwhile, assessment of the Stra8 mRNA and CDH1 protein, the specific makers for spermatogonia, showed no significant differences between groups. Based on the results, it seems that in the presence of 3 μM RA on top of the STO feeder layer cells, the majority of the cells transdifferentiated into germ cells were PGCs.

Toll-like receptor ligands induce cytokine and chemokine production in human inner ear endolymphatic sac fibroblasts

OBJECTIVE

Against recent reports concerning cytokine or chemokine in mouse or rat inner ear cells, it is almost unknown whether human inner ear cells would produce cytokine or chemokine. We have for the first time established the human inner-ear-derived fibroblasts from endolymphatic sac.

METHODS

The expression levels of Toll-like receptors (TLRs) in human endolymphatic sac fibroblasts, and the effect on cytokine or chemokine production of the TLR ligands have been examined. To demonstrate the intracellular pathways involved in the regulation of cytokine-production, we used specific inhibitors of c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK), p38 mitogen-activated protein kinase (p38 MAPK)-signaling and N-acetyl-l-cysteine (NAC).

RESULTS

TLR 2, 3, 4 and 9 were highly expressed in human endolymphatic sac fibroblasts. The TLR 3 ligand, polyinosinic-polycytidylic acid (poly(I:C)) significantly enhanced the secretion of thymic stromal lymphopoietin (TSLP), B lymphocyte stimulator (BLyS), IFNγ-inducible protein 10 (IP-10), and macrophage inflammatory protein 1 alpha (MIP-1α) from the cells. The inhibitor of JNK strongly reduced the poly(I:C)-induced TSLP-production. The antioxidant drug, NAC also reduced the TSLP-production in fibroblasts stimulated with poly(I:C).

CONCLUSION

Our findings suggest human inner-ear-endolymphatic sac derived fibroblasts can produce the cytokine and chemokine in response to TLR ligands and play a certain role during the initiation of an immune response.

Design and Synthesis of Irreversible Analogues of Bardoxolone Methyl for the Identification of Pharmacologically Relevant Targets and Interaction Sites

Semisynthetic triterpenoids such as bardoxolone methyl (methyl-2-cyano 3,12-dioxooleano-1,9-dien-28-oate; CDDO-Me) (4) are potent inducers of antioxidant and anti-inflammatory signaling pathways, including those regulated by the transcription factor Nrf2. However, the reversible nature of the interaction between triterpenoids and thiols has hindered attempts to identify pharmacologically relevant targets and characterize the sites of interaction. Here, we report a shortened synthesis and SAR profiling of 4, enabling the design of analogues that react irreversibly with model thiols, as well as the model protein glutathione S-transferase P1, in vitro. We show that one of these analogues, CDDO-epoxide (13), is comparable to 4 in terms of cytotoxicity and potency toward Nrf2 in rat hepatoma cells and stably modifies specific cysteine residues (namely, Cys-257, -273, -288, -434, -489, and -613) within Keap1, the major repressor of Nrf2, both in vitro and in living cells. Supported by molecular modeling, these data demonstrate the value of 13 for identifying site(s) of interaction with pharmacologically relevant targets and informing the continuing development of triterpenoids as novel drug candidates.

Current understanding of the molecular biology of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PanNETs) are complicated and often deadly neoplasms. A recent increased understanding of their molecular biology has contributed to expanded treatment options. DNA sequencing of samples derived from patients with PanNETs and rare genetic syndromes such as multiple endocrine neoplasia type 1 (MEN1) and Von Hippel-Lindau (VHL) syndrome reveals the involvement of MEN1, DAXX/ATRX, and the mammalian target of rapamycin (mTOR) pathways in PanNET tumorigenesis. Gene knock-out/knock-in studies indicate that inactivation of factors including MEN1 and abnormal PI3K/mTOR signaling uncouples endocrine cell cycle progression from the control of environmental cues such as glucose, leading to islet cell overgrowth. In addition, accumulating evidence suggests that further impairment of endothelial-endocrine cell interactions contributes to tumor invasion and metastasis. Recent phase III clinical trials have shown that therapeutic interventions, such as sunitinib and everolimus, targeting those signal transduction pathways improve disease-free survival rates. Yet, cure in the setting of advanced disease remains elusive. Further advances in our understanding of the molecular mechanisms of PanNETs and improved preclinical models will assist in developing personalized therapy utilizing novel drugs to provide prolonged control or even cure the disease.

New player on an old field; the keap1/Nrf2 pathway as a target for treatment of type 2 diabetes and metabolic syndrome

Nuclear erythroid factor 2 like 2 (Nrf2) has been described as a transcription factor that serves as a master regulator of the adaptive response to exogenous and endogenous oxidative and electrophilic stresses. Evidence of Nrf2 crosstalk with other molecular pathways is increasing; recent publications have proposed a role of Nrf2 in the development of obesity and in the highly regulated process of adipocyte differentiation through its interaction with other transcription factors and receptors implicated in metabolic regulation. In the present review, we discuss the available data on the possible role of Nrf2 in obesity and metabolic syndrome and the feasibility of using Nrf2 as a therapeutic target in the clinical setting.

Optimizing Helicoverpa zea (Lepidoptera: Noctuidae) insecticidal efficacy in Minnesota sweet corn: a logistic regression to assess timing parameters

Late-season plantings of sweet corn in Minnesota result in an abundant supply of silking corn, Zea mays L., throughout August to early September that is highly attractive to the corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). During a 10-yr period, 1997-2006, insecticide efficacy trials were conducted in late-planted sweet corn in Minnesota for management of H. zea. These data were used to develop a logistic regression model to identify the variables and interactions that most influenced efficacy (proportion control) of late-instar H. zea. The pyrethroid lambdacyhalothrin (0.028 kg [AI]/ha) is a commonly used insecticide in sweet corn and was therefore chosen for use in parameter evaluation. Three variables were found to be significant (alpha = 0.05), the percentage of plants silking at the time of the first insecticide application, the interval between the first and second insecticide applications, and the interval between the last insecticide application and harvest. Odds ratio estimates indicated that as the percentage of plants silking at the time of first application increased, control of H. zea increased. As the interval between the first and second insecticide application increased, control of H. zea decreased. Finally, as the interval between the last insecticide application and harvest increased, control of H. zea increased. An additional timing trial was conducted in 2007 by using lambda-cyhalothrin, to evaluate the impact of the percentage of plants silking at the first application. The results indicated no significant differences in efficacy against late-instar H. zea at 0, 50, 90, and 100% of plants silking at the first application (regimes of five or more sprays). The implications of these effects are discussed within the context of current integrated pest management programs for late-planted sweet corn in the upper midwestern United States.

Antiviral suppression vs restoration of RIG-I signaling by hepatitis C protease and polymerase inhibitors

BACKGROUND & AIMS

Expression of the nonstructural protein (NS)3/4A protease in cells infected with hepatitis C virus (HCV) results in cleavage of the mitochondrial antiviral-signaling protein (MAVS) and disruption of signaling pathways that lead to viral activation of interferon regulatory factor 3 (IRF-3) and synthesis of type 1 interferons (IFN-alpha/beta). High concentrations of inhibitors of NS3/4A reverse this signaling defect, but quantitative analyses of this potential therapeutic effect are lacking. This study quantitatively assessed the rescue of IRF-3 signaling by NS3/4A inhibitors, compared with in vitro antiviral activity.

METHODS

Antiviral activities of 2 NS3/4A protease inhibitors (TMC435350 and an analog, TMC380765) and a nonnucleoside polymerase inhibitor (Tib-3) were determined in HCV replicon cells and in cells infected with genotype 1a and 2a viruses. The capacity to rescue IRF-3 activation in these cells was assessed by monitoring IFN-beta promoter activity following challenge with Sendai virus. Inhibitor-induced changes in NS3 and MAVS expression were assessed in immunoblots.

RESULTS

Both protease inhibitors were capable of rescuing IFN-beta promoter activation but only at concentrations approximately 100-fold the antiviral 50% effective concentration (EC(50)) for genotype 1 virus. No rescue was observed with the polymerase inhibitor, even at a concentration 600-fold greater than the EC(50). IRF-3 activation did not correlate with reductions in NS3/4A levels or detection of full-length MAVS. Overexpression of the product of NS3/4A cleavage of MAVS did not result in a dominant-negative effect on signaling.

CONCLUSIONS

NS3/4A protease inhibitors can restore IRF-3 signaling in HCV-infected cells but only at concentrations far in excess of the antiviral EC(50).

Antineoplastic effect of rapamycin is potentiated by inhibition of IRS-1 signaling in prostate cancer cells xenografts

Proper activation of phosphoinositide 3-kinase-Akt pathway is critical for the prevention of tumorigenesis. Recent data have characterized a negative feedback loop, wherein mammalian target of rapamycin (mTOR) blocks additional activation of the Akt/mTOR pathway through inhibition insulin receptor substrate 1 (IRS-1) function. However, the potential of IRS-1 inhibition during rapamycin treatment has not been examined. Herein, we show that IRS-1 antisense oligonucleotide and rapamycin synergistically antagonize the activation of mTOR in vivo and induced tumor suppression, through inhibition of proliferation and induction of apoptosis, in prostate cancer cell xenografts. These data demonstrate that the addition of agents that blocks IRS-1 potentiate the effect of mTOR inhibition in the growth of prostate cancer cell xenografts.

Effects of amide constituents from pepper on adipogenesis in 3T3-L1 cells

Several amide constituents (piperlonguminine and retrofractamides A, B, and C) from the fruit of Piper chaba promoted adipogenesis of 3T3-L1 cells. Among them, retrofractamide A was the most active and significantly increased the amount of adiponectin released into the medium and the uptake of 2-deoxyglucose into the cells. Retrofractamide A also increased mRNA levels of adiponectin, peroxisome proliferator-activated receptor gamma2 (PPARgamma2), glucose transporter 4 (GLUT4), and insulin receptor substrate 1 (IRS-1), but did not act as a PPARgamma agonist different from troglitazone.

Biphasic modulation of insulin receptor substrate-1 during goitrogenesis

Insulin receptor substrate-1 (IRS-1) is the main intracellular substrate for both insulin and insulin-like growth factor I (IGF-I) receptors and is critical for cell mitogenesis. Thyrotropin is able to induce thyroid cell proliferation through the cyclic AMP intracellular cascade; however, the presence of either insulin or IGF-I is required for the mitogenic effect of thyroid-stimulating hormone (TSH) to occur. The aim of the present study was to determine whether thyroid IRS-1 content is modulated by TSH in vivo. Strikingly, hypothyroid goitrous rats, which have chronically high serum TSH levels (control, C = 2.31 +/- 0.28; methimazole (MMI) 21d = 51.02 +/- 6.02 ng/mL, N = 12 rats), when treated with 0.03% MMI in drinking water for 21 days, showed significantly reduced thyroid IRS-1 mRNA content. Since goiter was already established in these animals by MMI for 21 days, we also evaluated IRS-1 expression during goitrogenesis. Animals treated with MMI for different periods of time showed a progressive increase in thyroid weight (C = 22.18 +/- 1.21; MMI 5d = 32.83 +/- 1.48; MMI 7d = 31.1 +/- 3.25; MMI 10d = 33.8 +/- 1.25; MMI 14d = 45.5 +/- 2.56; MMI 18d = 53.0 +/- 3.01; MMI 21d = 61.9 +/- 3.92 mg, N = 9-15 animals per group) and serum TSH levels (C = 1.57 +/- 0.2; MMI 5d = 9.95 +/- 0.74; MMI 7d = 10.38 +/- 0.84; MMI 10d = 17.72 +/- 1.47; MMI 14d = 25.65 +/- 1.23; MMI 18d = 35.38 +/- 3.69; MMI 21d = 31.3 +/- 2.7 ng/mL, N = 9-15 animals per group). Thyroid IRS-1 mRNA expression increased progressively during goitrogenesis, being significantly higher by the 14th day of MMI treatment, and then started to decline, reaching the lowest values by the 21st day, when a significant reduction was detected. In the liver of these animals, however, a significant decrease of IRS-1 mRNA was detected after 14 days of MMI treatment, a mechanism probably involved in the insulin resistance that occurs in hypothyroidism. The increase in IRS-1 expression during goitrogenesis may represent an important event associated with the increased rate of cell mitosis promoted by TSH and indicates that insulin and IGF-I are important co-mitogenic factors in vivo, possibly acting through the activation of IRS-1.

Acute physical exercise reverses S-nitrosation of the insulin receptor, insulin receptor substrate 1 and protein kinase B/Akt in diet-induced obese Wistar rats

Early evidence demonstrates that exogenous nitric oxide (NO) and the NO produced by inducible nitric oxide synthase (iNOS) can induce insulin resistance. Here, we investigated whether this insulin resistance, mediated by S-nitrosation of proteins involved in early steps of the insulin signal transduction pathway, could be reversed by acute physical exercise. Rats on a high-fat diet were subjected to swimming for two 3 h-long bouts, separated by a 45 min rest period. Two or 16 h after the exercise protocol the rats were killed and proteins from the insulin signalling pathway were analysed by immunoprecipitation and immunoblotting. We demonstrated that a high-fat diet led to an increase in the iNOS protein level and S-nitrosation of insulin receptor beta (IR beta), insulin receptor substrate 1 (IRS1) and Akt. Interestingly, an acute bout of exercise reduced iNOS expression and S-nitrosation of proteins involved in the early steps of insulin action, and improved insulin sensitivity in diet-induced obesity rats. Furthermore, administration of GSNO (NO donor) prevents this improvement in insulin action and the use of an inhibitor of iNOS (L-N6-(1-iminoethyl)lysine; L-NIL) simulates the effects of exercise on insulin action, insulin signalling and S-nitrosation of IR beta, IRS1 and Akt. In summary, a single bout of exercise reverses insulin sensitivity in diet-induced obese rats by improving the insulin signalling pathway, in parallel with a decrease in iNOS expression and in the S-nitrosation of IR/IRS1/Akt. The decrease in iNOS protein expression in the muscle of diet-induced obese rats after an acute bout of exercise was accompanied by an increase in AMP-activated protein kinase (AMPK) activity. These results provide new insights into the mechanism by which exercise restores insulin sensitivity.

Cell adhesion proteins altered by 17beta estradiol and parathion in breast epithelial cells

The association between breast cancer initiation and prolonged exposure to estrogen suggests that this hormone may also have an etiologic role in such a process. On the other hand, many studies have found an association between human cancer and exposure to agricultural pesticides such as parathion, an organophosphorous pesticide used in agriculture to control mosquito plagues. However, the key factors behind the initiation of breast cancer remain to be elucidated. The aim of this study was to determine the effect of 17beta estradiol (estrogen) and parathion on protein expression in cell transformation of human breast epithelial cells in vitro. Estrogen and parathion alone and in combination induced malignant transformation of an immortalized human breast epithelial cell line, MCF-I0F, as indicated by anchorage independency and invasive capabilities. The results indicate that a combination of estrogen and parathion increased the expression of related cell adhesion proteins such as Dvl, Notch, CD146 and beta catenin. In conclusion, it can be suggested that pesticides affect human breast cell adhesion changes indicative of transformation.

Chemical inhibition through conformational stabilization of Rho GTPase effectors

The Rho family of small GTP-binding proteins can activate a large number of downstream effectors and participate in a wide variety of biological processes, including cell motility, membrane trafficking, cell polarity, gene transcription, and mitosis. Specific small-molecule inhibitors of individual effector proteins downstream of Rho GTPases would be powerful tools to elucidate the contributions of particular effectors to these processes. In this chapter we describe the identification of a chemical inhibitor of a Rho effector and scaffolding protein neural-Wiskott-Aldrich syndrome protein (N-WASP), and the discovery of its novel mechanism of action, stabilization of N-WASP's native autoinhibited conformation. Inasmuch as several other Rho GTPase effectors are regulated by autoinhibition, we discuss how this regulatory mechanism could be exploited by small molecules to develop highly specific inhibitors of other Rho GTPase effectors. We illustrate this concept with the Rac/Cdc42 effector p21-activated kinase (Pak1) and the Rho effector mammalian diaphanous-related formin (mDia1).

The tumor suppressor Wnt inhibitory factor 1 is frequently methylated in nasopharyngeal and esophageal carcinomas

Aberrant activation of the wingless-type- (Wnt)-signaling pathway is common in many cancers including nasopharyngeal (NPC) and esophageal squamous cell (ESCC) carcinomas, both prevalent in Southern China and Southeast Asia. However, the molecular mechanism leading to this abnormality is still obscure. Wnt inhibitory factor-1 (WIF1) is a secreted antagonist of the Wnt pathway, and is recently shown to be inactivated by epigenetic mechanism in some tumors. Here, we examined whether WIF1 is also inactivated epigenetically in NPC and ESCC. With semiquantitative reverse transcription-PCR and methylation-specific PCR, we detected WIF1 downregulation or silencing in 6/6 of NPC and 12/19 of ESCC cell lines, which is well correlated with its methylation status. Methylation was further confirmed by high-resolution bisulfite genomic sequencing. Methylation was also frequently observed in a large collection of primary tumors of NPC (85%, 55/65) and ESCC (27%, 25/92), with WIF1 expressed and unmethylated in normal NPC and esophageal cell lines and normal tissues. Treatment of 5-aza-2'-deoxycytidine demethylated WIF1 and induced its expression in NPC and ESCC cell lines, highlighting a direct role of epigenetic inactivation. Ectopic expression of WIF1 in NPC and ESCC tumor cells resulted in significant inhibition of tumor cell colony formation, similar to TP53, and also significant downregulation of beta-catenin protein level in NPC cells. Thus, WIF1 functions as a tumor suppressor for both NPC and ESCC through suppressing the Wnt-signaling pathway, but is frequently silenced by epigenetic mechanism in a tumor-specific way. Our study indicates that epigenetic inactivation of WIF1 contributes to the aberrant activation of Wnt pathway and is involved in the pathogenesis of both tumors. WIF1 methylation could also serve as a specific biomarker for these tumors.

Activation of the canonical Wnt pathway by the antipsychotics haloperidol and clozapine involves dishevelled-3

Protein kinase B (Akt), glycogen synthase kinase-3 (GSK-3) and members of the Wnt signal transduction pathway were recently found to be altered in schizophrenia and targeted by antipsychotic drugs. In the current study, selected Wnt signalling proteins were investigated to determine if they are altered by the antipsychotics clozapine or haloperidol in the rat prefrontal cortex. Pheochromocytoma (PC12) and neuroblastoma (SH-SY5Y) cells were also used to elucidate how antipsychotics generated the pattern of changes observed in vivo. Western blotting (WB) revealed that treatment with haloperidol or clozapine caused an up-regulation of Wnt-5a, dishevelled-3, Axin, total and phosphorylated GSK-3 and beta-catenin protein levels. Treatment of PC12 and SH-SY5Y cells with a variety of pharmacological agents as well as the over-expression of several Wnt related proteins failed to mimic the pattern observed in vivo following antipsychotic treatment. However, the over-expression of dishevelled-3 nearly perfectly duplicated the changes observed in vivo. Immunoprecipitations (IP) conducted using protein isolated from the rat prefrontal cortex indicated that dishevelled-3 is associated with the D2 dopamine receptor thereby suggesting that antipsychotics may act on dishevelled-3 via D2 dopamine receptors to initiate a cascade of downstream changes involving Axin, GSK-3 and beta-catenin that may help to alleviate psychosis in schizophrenic patients.

Antibody response in mice infected with Mesocestoides vogae (syn. Mesocestoides corti) tetrathyridia after treatment with praziquantel and liposomised glucan

The therapeutic effect of praziquantel (PZQ) involves synergy with the humoral immune response during helminth infections, which is modulated by parasitic antigens. During experimental murine infections with the larval stage of cestoda Mesocestoides vogae (syn. M. corti), dynamic changes in the IgG and IgM antibody serum levels to both soluble somatic and secretory larval antigens were investigated after administration of PZQ alone and after its co-administration with the immunomodulator (l-->3)-beta-D-glucan entrapped in liposomes (lip.glucan). During the 2 weeks of follow-up after termination of therapy, specific IgG and IgM serum levels to the somatic antigens (enzyme-linked immunosorbent assay test) significantly decreased, whereas concentrations of the antibodies to the secretory antigens moderately increased, both in comparison with the control. Moreover, the number of immunogenic larval antigens (analysed by Western blot) was higher after combined therapy in comparison with single drug administration, which correlated with the intensity of reduction of the larval counts in the liver and peritoneal cavity of mice. Our data showed that administration of PZQ alone and in combination with lip.glucan resulted in marked changes in the dynamics of IgG and IgM antibodies to the somatic larval antigens, which were probably induced by the newly exposed antigens. In this respect, glucan can enhance chemotherapeutic activity of PZQ against larval cestodes by means of stimulation of the macrophage/monocyte effector functions, which seemed to contribute to the more intense larval damage.

Livin/ML-IAP as a new target for cancer treatment

Livin is a member of the inhibitors of apoptosis protein (IAP) gene family, which encodes negative regulatory proteins that prevent cell apoptosis. Livin is selectively expressed in the most common human neoplasms and appears to be involved in tumor cell resistance to chemotherapeutic agents. Several studies in vitro and in vivo have demonstrated that down-regulation of Livin expression increases the apoptotic rate, reduces tumor growth potential and sensitized tumor cells to chemotherapeutic drugs. This review will focus on the role of this protein during cancer development and progression and will demonstrate possible targets for cancer therapy.

Chemotherapy disrupts activity of translational regulatory proteins in bone marrow stromal cells

OBJECTIVE

Bone marrow stromal cell function is a critical influence on hematopoietic reconstitution following progenitor or stem cell transplantation. Stromal cells support hematopoietic cell migration, survival, and proliferation. We have previously reported that stromal cell matrix metalloproteinase-2 (MMP-2) is necessary for optimal support of pro-B-cell chemotaxis through its regulation of stromal cell-derived factor-1 (CXCL12) release. Following exposure to the topoisomerase II inhibitor, etoposide (VP-16), stromal cell MMP-2 protein expression is reduced. The current study investigated the mechanism by which VP-16 may alter translation of MMP-2 in bone marrow stromal cells.

MATERIALS AND METHODS

Bone marrow stromal cells were exposed to chemotherapeutic agents etoposide, melphalan, and 4-hydroperoxycyclophosphamide (4HC) and evaluated for MMP-2 expression by enzyme-linked immunosorbent assay and support of pro-B-cell chemotaxis by chemotaxis assay. Western blot analyses were completed to evaluate phosphorylation of stromal cell translational regulatory proteins 4E binding protein-1 (4EBP-1), P70(S6K), and S6 or MMP-2 in the presence of chemotherapy, or the chemical inhibitors rapamycin or LY294002.

RESULTS

Rapid dephosphorylation of 4EBP-1, P70(S6K), and S6 following VP-16 exposure was observed, consistent with blunted translational efficiency. We also observed that inhibition of stromal cell mammalian target of rapamycin with rapamycin, or phosphatidylinositol 3 kinase with LY294002, resulted in inhibition of stromal cell MMP-2 protein. In addition we found that the chemotherapeutic agents melphalan and 4HC disrupt bone marrow stromal cell MMP-2 protein expression and support of chemotaxis.

CONCLUSIONS

These data suggest that one mechanism by which chemotherapy may alter stromal cells of the bone marrow microenvironment is through disrupted translation of proteins.

MK-0457, a novel kinase inhibitor, is active in patients with chronic myeloid leukemia or acute lymphocytic leukemia with the T315I BCR-ABL mutation

MK-0457 (VX-680) is a small-molecule aurora kinase (AK) inhibitor with preclinical antileukemia activity. The T315I BCR-ABL mutation mediates resistance to imatinib, nilotinib, and dasatinib. MK-0457 has in vitro activity against cells expressing wild-type or mutated BCR-ABL, including the T315I BCR-ABL mutation. Three patients with T315I abl-mutated chronic myeloid leukemia (CML) or Philadelphia chromosome (Ph)-positive acute lymphocytic leukemia (ALL) have achieved clinical responses to doses of MK-04547 that are not associated with adverse events. Higher MK-0457 dose levels were associated with clinical responses and down-regulation of CrkL phosphorylation in leukemia cells. The possible role of AK inhibition in these clinical responses requires further investigation. The currently reported cases are the first observed clinical activity of a kinase inhibitor against the T315I phenotype. The observation of responses in 3 patients with T315I phenotype-refractory CML or Ph-positive ALL, at doses of MK-0457 associated with no significant extramedullary toxicity, is very encouraging.

Acetaldehyde promotes rapamycin-dependent activation of p70(S6K) and glucose uptake despite inhibition of Akt and mTOR in dopaminergic SH-SY5Y human neuroblastoma cells

Alcohol intake is one of the important lifestyle factors for the risk of insulin resistance and type 2 diabetes. Acetaldehyde, the major ethanol metabolite which is far more reactive than ethanol, has been postulated to participate in alcohol-induced tissue injury although its direct impact on insulin signaling is unclear. This study was designed to examine the effect of acetaldehyde on glucose uptake and insulin signaling in human dopaminergic SH-SY5Y cells. Akt, mammalian target of rapamycin (mTOR), ribosomal-S6 kinase (p70(S6K)), the eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) and insulin receptor substrate (IRS)-2 were evaluated by Western blot analysis. Glucose uptake and apoptosis were measured using [(3)H]-2-deoxyglucose uptake and caspase-3 assay, respectively. Short-term exposure (12 h) of acetaldehyde (150 muM) facilitated glucose uptake in a rapamycin-dependent manner without affecting apoptosis, IRS-2 expression and insulin-stimulated glucose uptake in SH-SY5Y cells. Acetaldehyde suppressed basal and insulin-stimulated Akt phosphorylation without affecting total Akt expression. Acetaldehyde inhibited mTOR phosphorylation without affecting total mTOR and insulin-elicited response on mTOR phosphorylation. Rapamycin, which inhibits mTOR leading to inactivation of p70(S6K), did not affect acetaldehyde-induced inhibition on phosphorylation of Akt and mTOR. Interestingly, acetaldehyde enhanced p70(S6K) activation and depressed 4E-BP1 phosphorylation, the effect of which was blunted and exaggerated, respectively, by rapamycin. Collectively, these data suggested that acetaldehyde did not adversely affect glucose uptake despite inhibition of insulin signaling cascade at the levels of Akt and mTOR, possibly due to presence of certain mechanism(s) responsible for enhanced p70(S6K) phosphorylation.

Signal transduction induced by apoptotic cells inhibits HIV transcription in monocytes/macrophages

The primary targets of HIV are CD4(+) T cells and macrophages. HIV infection is associated with an increase in apoptosis of infected and uninfected CD4(+) T cells, and these infected cells undergo apoptosis and produce HIV virions with phosphatidylserine (PS) on their surface. During phagocytosis of apoptotic cells, macrophages, using an array of receptors, are able to perceive various surface changes on apoptotic cells. The engagement of phagocytic receptors by ligands on the apoptotic cell surface results in the activation of signaling cascades, which facilitate engulfment. In this study, we examined how PS associated with virions and apoptotic cells influences HIV replication. We demonstrate that virus-associated PS is required for HIV infection of macrophages at a step prior to integration but following strong-stop, indicating that PS-initiated signals alter the establishment of HIV provirus. Conversely, apoptotic cells inhibited HIV transcription in infected macrophages, although this ability to suppress transcription was independent of PS. Furthermore, we show that ELMO, a key signaling molecule that participates in the phagocytosis of apoptotic cells, inhibited HIV transcription; however, knocking down endogenous ELMO expression in infected U937 cells rescued HIV transcription when these cells were coincubated with apoptotic targets. Taken together, these data show that apoptotic cells and the signals, which they initiate upon recognition by macrophages, influence the successful establishment of HIV infection and provirus transcription.

All-trans retinoic acid induces p62DOK1 and p56DOK2 expression which enhances induced differentiation and G0 arrest of HL-60 leukemia cells

p62(DOK1) (DOK1) and p56(DOK2) (DOK2) are sequence homologs that act as docking proteins downstream of receptor or nonreceptor tyrosine kinases. Originally identified in chronic myelogenous leukemia cells as a highly phosphorylated substrate for the chimeric p210(bcr-abl) protein, DOK1 was suspected to play a role in leukemogenesis. However, p62(DOK1-/-) fibroblast knockout cells were found to have enhanced MAPK signaling and proliferation due to growth factors, suggesting negative regulatory capabilities for DOK1. The role of DOK1 and DOK2 in leukemogeneis thus is enigmatic. The data in this report show that both the DOK1 and the DOK2 adaptor proteins are constitutively expressed in the myelomonoblastic leukemia cell line, HL-60, and that expression of both proteins is induced by the chemotherapeutic differentiation causing agents, all-trans retinoic acid (atRA) and 1,25-dihydroxyvitamin D3 (VD3). Ectopic expression of either protein enhances atRA- or VD3-induced growth arrest, differentiation, and G(0)/G(1) cell cycle arrest and results in increased ERK1/2 phosphorylation. DOK1 and DOK2 are similarly effective in these capabilities. The data provide evidence that DOK1 and DOK2 proteins have a similar role in regulating cell proliferation and differentiation and are positive regulators of the MAPK signaling pathway in this context.

Irbesartan restores the in-vivo insulin signaling pathway leading to Akt activation in obese Zucker rats

BACKGROUND

Angiotensin II (AII) has been shown to contribute to the pathogenesis of hypertension and insulin resistance. In addition, the administration of selective AII type 1 receptor blockers has been shown to improve insulin sensitivity. However, only a few studies have addressed the molecular mechanisms involved in this association. Furthermore, in a previous study we illustrated that obese Zucker rats (OZR) present increased serine 994 (Ser994) phosphorylation of hepatic insulin receptor, and this event seems to be implicated in the regulation of the intrinsic IRK in this model of insulin resistance.

OBJECTIVE AND DESIGN

We examined the effects of chronic treatment with irbesartan (50 mg/kg a day for 6 months) on the hepatic insulin signaling system of OZR.

METHODS

The extent of phosphorylation of several components of the insulin signaling system was assessed by immunoprecipitation, followed by immunoblotting with phosphospecific antibodies. In addition, liver AII levels and fat deposits were determined by immunohistochemistry and Oil red O, respectively.

RESULTS

OZR displayed a marked attenuation in the in-vivo phosphorylation of several components of the insulin signaling pathways in the liver, together with significantly higher hepatic AII levels and hepatic steatosis when compared with lean Zucker rats. We found that in the livers of OZR long-term administration of irbesartan is associated with: (i) increased insulin-stimulated insulin receptor tyrosine phosphorylation; (ii) decreased insulin receptor Ser994 phosphorylation; (iii) augmented insulin receptor substrate (IRS) 1 and 2 abundance and tyrosine phosphorylation; (iv) augmented association between IRS and the p85 regulatory subunit of phosphatidylinositol 3-kinase; (v) increased insulin-induced Akt phosphorylation; and (vi) decreased hepatic steatosis.

CONCLUSION

The present study provides substantial information that demonstrates that long-term selective AII blockade by irbesartan improves insulin signaling and is associated with decreased insulin receptor Ser994 phosphorylation in the liver of a representative animal model of the human metabolic syndrome.

The mAKAP complex participates in the induction of cardiac myocyte hypertrophy by adrenergic receptor signaling

Maladaptive cardiac hypertrophy can progress to congestive heart failure, a leading cause of morbidity and mortality in the United States. A better understanding of the intracellular signal transduction network that controls myocyte cell growth may suggest new therapeutic directions. mAKAP is a scaffold protein that has recently been shown to coordinate signal transduction enzymes important for cytokine-induced cardiac hypertrophy. We now extend this observation and show mAKAP is important for adrenergic-mediated hypertrophy. One function of the mAKAP complex is to facilitate cAMP-dependent protein kinase A-catalyzed phosphorylation of the ryanodine receptor Ca2+-release channel. Experiments utilizing inhibition of the ryanodine receptor, RNA interference of mAKAP expression and replacement of endogenous mAKAP with a mutant form that does not bind to protein kinase A demonstrate that the mAKAP complex contributes to pro-hypertrophic signaling. Further, we show that calcineurin Abeta associates with mAKAP and that the formation of the mAKAP complex is required for the full activation of the pro-hypertrophic transcription factor NFATc. These data reveal a novel function of the mAKAP complex involving the integration of cAMP and Ca2+ signals that promote myocyte hypertrophy.

Inhibition of TRIP1/S8/hSug1, a component of the human 19S proteasome, enhances mitotic apoptosis induced by spindle poisons

Mitotic spindle poisons (e.g., Taxol and vinblastine), used as chemotherapy drugs, inhibit mitotic spindle function, activate the mitotic spindle checkpoint, arrest cells in mitosis, and then cause cell death by mechanisms that are poorly understood. By expression cloning, we identified a truncated version of human TRIP1 (also known as S8, hSug1), an AAA (ATPases associated with diverse cellular activities) family ATPase subunit of the 19S proteasome regulatory complex, as an enhancer of spindle poison-mediated apoptosis. Stable expression of the truncated TRIP1/S8/hSug1 in HeLa cells [OP-TRIP1(88-406)] resulted in a decrease of measurable cellular proteasome activity, indicating that OP-TRIP1(88-406) had a dominant-negative effect on proteasome function. OP-TRIP1(88-406) revealed an increased apoptotic response after treatment with spindle poisons or with proteasome inhibitors. The increased apoptosis coincided with a significant decrease in expression of BubR1, a kinase required for activation and maintenance of the mitotic spindle checkpoint in response to treatment with spindle poisons. Small interfering RNA (siRNA)-mediated knockdown of TRIP1/S8/hSug1 resulted in a reduction of general proteasome activity and an increase in mitotic index. The siRNA treatment also caused increased cell death after spindle poison treatment. These results indicate that inhibition of TRIP1/S8/hSug1 function by expression of a truncated version of the protein or by siRNA-mediated suppression enhances cell death in response to spindle poison treatment. Current proteasome inhibitor drugs in trial as anticancer agents target elements of the 20S catalytic subcomplex. Our results suggest that targeting the ATPase subunits in 19S regulatory complex in the proteasome may enhance the antitumor effects of spindle poisons.

Estrogen Dendrimer Conjugates that Preferentially Activate Extranuclear, Nongenomic Versus Genomic Pathways of Estrogen Action

Estrogenic hormones are classically thought to exert their effects by binding to nuclear estrogen receptors and altering target gene transcription, but estrogens can also have nongenomic effects through rapid activation of membrane-initiated kinase cascades. The development of ligands that selectively activate only the nongenomic pathways would provide useful tools to investigate the significance of these pathways. We have prepared large, abiotic, nondegradable poly(amido)amine dendrimer macromolecules that are conjugated to multiple estrogen molecules through chemically robust linkages. Because of their charge and size, these estrogen-dendrimer conjugates (EDCs) remain outside the nucleus. They stimulate ERK, Shc, and Src phosphorylation in MCF-7 breast cancer cells at low concentrations, yet they are very ineffective in stimulating transcription of endogenous estrogen target genes, being approximately 10,000-fold less potent than estradiol in genomic actions. In contrast to estradiol, EDC was not effective in stimulating breast cancer cell proliferation. Because these EDC ligands activate nongenomic activity at concentrations at which they do not alter the transcription of estrogen target genes, they should be useful in studying extranuclear initiated pathways of estrogen action in a variety of target cells.

Bacterial lipoprotein-induced self-tolerance and cross-tolerance to LPS are associated with reduced IRAK-1 expression and MyD88-IRAK complex formation

Tolerance to bacterial cell-wall components may represent an essential regulatory mechanism during bacterial infection. We have demonstrated previously that the inhibition of nuclear factor (NF)-kappaB and mitogen-activated protein kinase activation was present in bacterial lipoprotein (BLP) self-tolerance and its cross-tolerance to lipopolysaccharide (LPS). In this study, the effect of BLP-induced tolerance on the myeloid differentiation factor 88 (MyD88)-dependent upstream signaling pathway for NF-kappaB activation in vitro was examined further. When compared with nontolerant human monocytic THP-1 cells, BLP-tolerant cells had a significant reduction in tumor necrosis factor alpha (TNF-alpha) production in response to a high-dose BLP (86+/-12 vs. 6042+/-245 ng/ml, P < 0.01) or LPS (341+/-36 vs. 7882+/-318 ng/ml, P < 0.01) stimulation. The expression of Toll-like receptor 2 (TLR2) protein was down-regulated in BLP-tolerant cells, whereas no significant differences in TLR4, MyD88, interleukin-1 receptor-associated kinase 4 (IRAK-4), and TNF receptor-associated factor 6 expression were observed between nontolerant and BLP-tolerant cells, as confirmed by Western blot analysis. The IRAK-1 protein was reduced markedly in BLP-tolerant cells, although IRAK-1 mRNA expression remained unchanged as revealed by real-time reverse transcriptase-polymerase chain reaction analysis. Furthermore, decreased MyD88-IRAK immunocomplex formation, as demonstrated by immunoprecipitation, was observed in BLP-tolerant cells following a second BLP or LPS stimulation. BLP pretreatment also resulted in a marked inhibition in total and phosphorylated inhibitor of kappaB-alpha (IkappaB-alpha) expression, which was not up-regulated by subsequent BLP or LPS stimulation. These results demonstrate that in addition to the down-regulation of TLR2 expression, BLP tolerance is associated with a reduction in IRAK-1 expression, MyD88-IRAK association, and IkappaB-alpha phosphorylation. These findings further elucidate the molecular mechanisms underlying bacterial peptide tolerance.

Identification of tyrosine residues crucial for CD200R-mediated inhibition of mast cell activation

CD200 and its receptor CD200R are type-1 membrane glycoproteins, which contain two immunoglobulin-like domains. Engagement of CD200R by CD200 inhibits activation of myeloid cells. Unlike the majority of immune inhibitory receptors, CD200R does not contain an immunoreceptor tyrosine-based inhibitory motif but contains three tyrosine residues (Y286, Y289, and Y297) in the cytoplasmic domain. Y297 is located in an NPxY motif. Previously, we have shown that engagement of CD200R in mouse mast cells induces its tyrosine phosphorylation and recruitment of inhibitory adaptor proteins Dok1 and Dok2, leading to the inhibition of Ras/mitogen-activated protein kinase activation. In the present study, we examined the roles of these three tyrosines in CD200R-mediated inhibition by site-directed mutagenesis in mouse mast cells. Our data show that Y286 and Y297 are the major phosphorylation sites and are critical for CD200R-mediated inhibition of mast cell activation, and Y289 is dispensable. Our data also suggest that the Src family kinase may mediate the phosphorylation of CD200R and Dok.

AlFx affects the formation of focal complexes by stabilizing the Arf-GAP ASAP1 in a complex with Arf1

Aluminum fluoride (AlFx) is known to activate directly the alpha subunit of G-proteins but not the homologous small GTP-binding proteins. However, AlFx can stabilize complexes formed between Ras, RhoA or Cdc42 and their corresponding GTPase-activating proteins (GAPs). Here, we demonstrate that Arf1GDP can be converted into an active conformation by AlFx to form a complex with the Arf-GAP ASAP1 in vitro and in vivo. Within this complex ASAP1, which GAP activity is inoperative, can still alter the recruitment of paxillin to the focal complexes, thus indicating that ASAP1 interferes with focal complexes independently of its GAP activity.

Loss of RALT/MIG-6 expression in ERBB2-amplified breast carcinomas enhances ErbB-2 oncogenic potency and favors resistance to Herceptin

An emerging paradigm holds that loss of negative signalling to receptor tyrosine kinases (RTKs) is permissive for their oncogenic activity. Herein, we have addressed tumor suppression by RALT/MIG-6, a transcriptionally controlled feedback inhibitor of ErbB RTKs, in breast cancer cells. Knockdown of RALT expression by RNAi enhanced the EGF-dependent proliferation of normal breast epithelial cells, indicating that loss of RALT signalling in breast epithelium may represent an advantageous condition during ErbB-driven tumorigenesis. Although mutational inactivation of the RALT gene was not detected in human breast carcinomas, RALT mRNA and protein expression was strongly and selectively reduced in ERBB2-amplified breast cancer cell lines. Reconstitution of RALT expression in ERBB2-amplified SKBr-3 and BT474 cells inhibited ErbB-2-dependent mitogenic signalling and counteracted the ability of ErbB ligands to promote resistance to the ErbB-2-targeting drug Herceptin. Thus, loss of RALT expression cooperates with ERBB2 gene amplification to drive full oncogenic signalling by the ErbB-2 receptor. Moreover, loss of RALT signalling may adversely affect tumor responses to ErbB-2-targeting agents.

Transient activation of Ras-dependent signalling at the early stages of Herbimycin A induced erythroid differentiation of human K562 cells

AIM

To study the dynamics of Ras-dependent signalling in the course of Herbimycin A induced erythroid differentiation of human erythroleukemia K562 cells.

METHODS

p21Ras functional activity was analyzed by direct measurement of GTP/GDP ratio in anti-p21Ras immunoprecipitates of K562 cells previously incubated with H3(32)PO4. Dynamics of protein tyrosine phosphorylation was studied using Western blotting. Electrophoretic mobility shift assay was used to monitor Erk2 activation. Phosphotyrosine (pY)-containing proteins bound to recombinant glutathione-S-tranferase (GST)-fused form of adaptor protein Grb2 were identified using GST in vitro binding assay.

RESULTS

It was shown that the relative quantity of GTP associated with Ras protein in non-induced cells varied from 27% to 37% upon 72 h of cell culturing. Herbimycin A caused 15% increase of GTP/GDP ratio at 3rd h. This index decreased during further investigated periods, although it did not reach control values even at 72nd h. Transient rise of Ras-GTP level at 3rd h of incubation in the presence of Herbimycin A correlated with the increase in tyrosine phosphorylation of proteins with apparent molecular weight of 210, 160, 140, 116 and 42 kDa, as well as with the activation of Erk2 and increase of binding of a set of pY-containing proteins with recombinant GST-fusion form of Ras activator, adaptor protein Grb2. Dramatic inhibition of interaction between docking protein Shc and GST-Grb2 was observed at late stages of cell induction (48-72 h) while binding of pY-containing proteins during this period did not differ significantly in control and differentiated cells.

CONCLUSION

The obtained results suggest that time-dependent changes in Grb2-mediated network of protein-protein interaction events might define implication of Ras-dependent signalling in Herbimycin A-induced erythroid differentiation of K562 cells.

MyD88-deficient mice develop severe intestinal inflammation in dextran sodium sulfate colitis

BACKGROUND

Gut commensal microbes affect the development and activation of the mucosal and systemic immune systems. However, the exact molecular mechanism of these microbes that is involved in the development of colitis remains unclear.

METHODS

The present study was conducted to determine the distinct role of the innate immune system in the development of a dextran sulfate sodium (DSS) colitis model in MyD88(-/-) mice, because myeloid differentiation protein (MyD88) is a major adaptor molecule essential for signaling via Toll-like receptors (TLRs). To this end, MyD88(-/-) and wild-type (WT) mice received sterile distilled water containing 1.2% DSS for 8 days. The survival rate, total clinical score (body weight loss, stool consistency, and rectal bleeding), colon length, and histological score were assessed. The expression of surface markers (F4/80 and CD4) on infiltrating lamina propria mononuclear cells was analyzed immunohistochemistrically.

RESULTS

MyD88(-/-) mice exhibited increased susceptibility to DSS-induced colitis, as reflected by significantly higher lethality and higher clinical and histological scores, and more severe colonic shortening compared to WT mice. Immunohistochemical analysis revealed a significant increase of both F4/80+ macrophages and CD4+ T cells in the inflamed mucosa in DSS-fed MyD88(-/-) mice compared to DSS-fed WT mice.

CONCLUSIONS

These findings suggest that, via MyD88 signaling, the innate immune system in the gut plays an important protective role in colitis.

ShcA regulates neurite outgrowth stimulated by neural cell adhesion molecule but not by fibroblast growth factor 2: evidence for a distinct fibroblast growth factor receptor response to neural cell adhesion molecule activation

Homophilic binding in trans of the neural cell adhesion molecule (NCAM) mediates adhesion between cells and leads, via activation of intracellular signaling cascades, to neurite outgrowth in primary neurons as well as in the neuronal cell line PC12. NCAM mediates neurite extension in PC12 cells by two principal routes of signaling: NCAM/Fyn and NCAM/fibroblast growth factor receptor (FGFR), respectively. Previous studies have shown that activation of mitogen-activated protein kinases is a pivotal point of convergence in NCAM signaling, but the mechanisms behind this activation are not clear. Here, we investigated the involvement of adaptor proteins in NCAM and fibroblast growth factor 2 (FGF2)-mediated neurite outgrowth in the PC12-E2 cell line. We found that both FGFR substrate-2 and Grb2 play important roles in NCAM as well as in FGF2-stimulated events. In contrast, the docking protein ShcA was pivotal to neurite outgrowth induced by NCAM, but not by FGF2, in PC12 cells. Moreover, in rat cerebellar granule neurons, phosphorylation of ShcA was stimulated by an NCAM mimicking peptide, but not by FGF2. This activation was blocked by inhibitors of both FGFR and Fyn, indicating that NCAM activates FGFR signaling in a manner distinct from FGF2 stimulation, and regulates ShcA phosphorylation by the concerted efforts of the NCAM/FGFR as well as the NCAM/Fyn signaling pathway.

Tyrosine phosphorylation of the a kinase anchoring protein 3 (AKAP3) and soluble adenylate cyclase are involved in the increase of human sperm motility by bicarbonate

Mammalian testicular spermatozoa are immotile, thus, to reach the oocyte, they need to acquire swimming ability under the control of different factors acting during the sperm transit through the epididymis and the female genital tract. Although bicarbonate is known to physiologically increase motility by stimulating soluble adenylate cyclase (sAC) activity of mammalian spermatozoa, no extensive studies in human sperm have been performed yet to elucidate the additional molecular mechanisms involved. In this light, we investigated the effect of in vitro addition of bicarbonate to human spermatozoa on the main intracellular signaling pathways involved in regulation of motility, namely, intracellular cAMP production and protein tyrosine phosphorylation. Bicarbonate effects were compared with those of the phosphatidyl-inositol-3 kinase inhibitor, LY294002, previously demonstrated to be a pharmacological stimulus for sperm motility. Bicarbonate addition to spermatozoa results in a significant increase in sperm motility as well as in several hyperactivation parameters. This stimulatory effect of bicarbonate and LY294002 is mediated by an increase in cAMP production and tyrosine phosphorylation of the A kinase anchoring protein, AKAP3. The specificity of bicarbonate effects was confirmed by inhibition with 4,4'-di-isothiocyanostilbene-2,2'-disulfonic acid. We remark that, in human spermatozoa, bicarbonate acts primarily through activation of sAC to stimulate tyrosine phosphorylation of AKAP3 and sperm motility because both effects are blunted by the sAC inhibitor 2OH-estradiol. In conclusion, our data provide the first evidence that bicarbonate stimulates human sperm motility and hyperactivation through activation of sAC and tyrosine phosphorylation of AKAP3, finally leading to an increased recruitment of PKA to AKAP3.

Short-term delay of Fas-stimulated apoptosis by GM-CSF as a result of temporary suppression of FADD recruitment in neutrophils: evidence implicating phosphatidylinositol 3-kinase and MEK1-ERK1/2 pathways downstream of classical protein kinase C

Granulocyte/macrophage colony-stimulating factor (GM-CSF) inhibits Fas-induced apoptosis of neutrophils. However, the exact step in the apoptotic pathway blocked by GM-CSF remained unclear. Here, we found that pretreatment of neutrophils with GM-CSF inhibits the recruitment of Fas-associated protein with death domain (FADD) to Fas, abolishing the formation of the death-inducing signaling complex required for Fas-induced apoptosis. Two-dimensional electrophoresis revealed that GM-CSF modifies the ratio of FADD subspecies. These GM-CSF-triggered changes were abrogated, and Fas-induced apoptosis was restored by an inhibitor of classical protein kinase C (PKC), Go6976, and by the combination of a phosphatidylinositol 3-kinase (PI-3K) inhibitor, LY294002, and an inhibitor of mitogen-activated protein kinase kinase (MEK)1, PD98059. Go6976 blocked GM-CSF-elicited phosphorylation of Akt/PKB and extracellular signal-regulated kinase (ERK)1/2. These results indicated that GM-CSF suppresses Fas-induced neutrophil apoptosis by inhibiting FADD binding to Fas, through redundant actions of PI-3K and MEK1-ERK1/2 pathways downstream of classical PKC.

Differential input by Ste5 scaffold and Msg5 phosphatase route a MAPK cascade to multiple outcomes

Pathway specificity is poorly understood for mitogen-activated protein kinase (MAPK) cascades that control different outputs in response to different stimuli. In yeast, it is not known how the same MAPK cascade activates Kss1 MAPK to promote invasive growth (IG) and proliferation, and both Fus3 and Kss1 MAPKs to promote mating. Previous work has suggested that the Kss1 MAPK cascade is activated independently of the mating G protein (Ste4)-scaffold (Ste5) system during IG. Here we demonstrate that Ste4 and Ste5 activate Kss1 during IG and in response to multiple stimuli including butanol. Ste5 activates Kss1 by generating a pool of active MAPKKK (Ste11), whereas additional scaffolding is needed to activate Fus3. Scaffold-independent activation of Kss1 can occur at multiple steps in the pathway, whereas Fus3 is strictly dependent on the scaffold. Pathway specificity is linked to Kss1 immunity to a MAPK phosphatase that constitutively inhibits basal activation of Fus3 and blocks activation of the mating pathway. These findings reveal the versatility of scaffolds and how a single MAPK cascade mediates different outputs.