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IL-6 is involved both in immune responses and in inflammation, hematopoiesis, bone metabolism and embryonic development. IL-6 plays roles in chronic inflammation (closely related to chronic inflammatory diseases, autoimmune diseases and cancer) and even in the cytokine storm of corona virus disease 2019 (COVID-19). Acute inflammation during the immune response and wound healing is a well-controlled response, whereas chronic inflammation and the cytokine storm are uncontrolled inflammatory responses. Non-immune and immune cells, cytokines such as IL-1β, IL-6 and tumor necrosis factor alpha (TNFα) and transcription factors nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3) play central roles in inflammation. Synergistic interactions between NF-κB and STAT3 induce the hyper-activation of NF-κB followed by the production of various inflammatory cytokines. Because IL-6 is an NF-κB target, simultaneous activation of NF-κB and STAT3 in non-immune cells triggers a positive feedback loop of NF-κB activation by the IL-6–STAT3 axis. This positive feedback loop is called the IL-6 amplifier (IL-6 Amp) and is a key player in the local initiation model, which states that local initiators, such as senescence, obesity, stressors, infection, injury and smoking, trigger diseases by promoting interactions between non-immune cells and immune cells. This model counters dogma that holds that autoimmunity and oncogenesis are triggered by the breakdown of tissue-specific immune tolerance and oncogenic mutations, respectively. The IL-6 Amp is activated by a variety of local initiators, demonstrating that the IL-6–STAT3 axis is a critical target for treating diseases. [ABSTRACT FROM AUTHOR]

Zhou et al. (Nature) and Hoffmann et al. (Cell) identify ACE2 as a SARS-CoV-2 receptor, and the latter show its entry mechanism depends on cellular serine protease TMPRSS2. These results may explain proinflammatory cytokine release via the associated angiotestin II pathway and a possible therapeutic target via the IL-6-STAT3 axis. Understanding the cell entry mechanism of pandemic coronavirus SARS-CoV-2 is crucial for treating the disease. Zhou et al. (Nature) and Hoffmann et al. (Cell) identify ACE2 as a SARS-CoV-2 receptor, and the latter show its entry mechanism depends on cellular serine protease TMPRSS2. These results suggest several possible therapeutic targets, including the IL-6-STAT3 axis previously associated with cytokine release syndromes. [ABSTRACT FROM AUTHOR]

Labyrinth seals are used in various kinds of turbo machines to reduce internal leakage flow. The working fluid, or the gas passing through the rotor shaft labyrinth seals, often generates driving force components that may increase the unstable vibration of the rotor. It is important to know the accurate rotordynamic force components for predicting the instability of the rotor-bearing-seal system. The major goals of this research were to calculate the rotordynamic force of a labyrinth seals utilizing a commercial CFD program and to further compare those results to an existing bulk flow computer program currently used by major US machinery manufacturers. The labyrinth seals of a steam turbine and a compressor eye seal are taken as objects of analysis. For each case, a 3D model with eccentric rotor was solved to obtain the rotordynamic force components. The leakage flow and rotor dynamics force predicted by CFX TASCFlow are compared with the results of the existing bulk flow analysis program DYNLAB. The results show that the bulk flow program gives a pessimistic prediction of the destabilizing forces for the conditions under investigation. Further research work will be required to fully understand the complex leakage flows in turbo machinery. [ABSTRACT FROM AUTHOR]

The traditional method for bearing and damper analysis usually involves a development of rather complicated numerical calculation programs that may just focus on a simplified and specific physical model. The application of the general CFD codes may make this analysis available and effective where complex flow geometries are involved or when more detailed solutions are needed. In this study, CFX-TASCflow is employed to simulate various fixed geometry fluid-film bearing and damper designs. Some of the capabilities in CFX-TASCflow are applied to simulate the pressure field and calculate the static and dynamic characteristics of hydrodynamic, hydrostatic, and hybrid bearings as well as squeeze film dampers. The comparison between the CFD analysis and current computer programs used in industry has been made. The results show reasonable agreement in general. Some of the possible reasons for the differences are discussed. It leaves room for further investigation and improvement on the methods of computation. [ABSTRACT FROM AUTHOR]

The molecular cloning and biological analyses of cytokines have led us to a general understanding of their pleiotropism and redundancy. These features have been ascribed to the composition of cytokine receptor complexes, which include a signal-transducing receptor subunit that is used by all members of a cytokine family and a binding subunit that is specific for each cytokine. Even though a given cytokine uses the same receptor complex when binding to various cell types, the cytokine elicits quite specific and distinct biological responses in different types of cells. Even in the same type of cell, the responses to a given cytokine could vary depending on the location of the cell and the condition of its microenvironment. Important mediators for the main cytokine signal-transduction pathway are the Janus kinases (Jaks) and signal transducer and activator of transcription (STATs). Selective usage of members of the Jak and STAT families by a given cytokine receptor is partly responsible for the specificity of cytokine action. In addition to the Jak–STAT pathway, a cytokine receptor complex can simultaneously operate multiple signal-transduction pathways, which usually express contradictory properties. These contradictory signals from a single cytokine are orchestrated to evoke a unified biological response in the cell. Here we discuss the molecular mechanisms that regulate how the cell specificity of cytokine signals is regulated, especially focusing on the IL-6/gp130 system. [Copyright &y& Elsevier]

Interleukin 6 (IL-6), which was originally identified as a B-cell differentiation factor, is now known to be a multifunctional cytokine that regulates the immune response, hematopoiesis, the acute phase response, and inflammation. Deregulation of IL-6 production is implicated in the pathology of several disease processes. The expression of constitutively high levels of IL-6 in transgenic mice results in fatal plasmacytosis, which has been implicated in human multiple myeloma. Increased IL-6 levels are also observed in several diseases, including rheumatoid arthritis (RA), systemic-onset juvenile chronic arthritis (JCA), osteoporosis, and psoriasis. IL-6 is critically involved in experimentally induced autoimmune disease, such as antigen-induced arthritis (AIA), and experimental allergic encephalomyelitis. All these clinical data and animal models suggest that IL-6 plays critical roles in the pathogenesis of autoimmune diseases. Here we review the evidence for the involvement of IL-6 in the pathophysiology of autoimmune diseases and chronic inflammatory proliferative diseases (CIPD) and discuss the possible molecular mechanisms of its involvement. [Copyright &y& Elsevier]

Members of the IL-6 cytokine family are involved in a variety of biological responses, including the immune response, inflammation, hematopoiesis, and oncogenesis by regulating cell growth, survival, and differentiation. These cytokines use gp130 as a common receptor subunit. The binding of ligand to gp130 activates the JAK/STAT signal transduction pathway, where STAT3 plays a central role in transmitting the signals from the membrane to the nucleus. STAT3 is essential for gp130-mediated cell survival and G1 to S cell-cycle-transition signals. Both c-myc and pim have been identified as target genes of STAT3 and together can compensate for STAT3 in cell survival and cell-cycle transition. STAT3 is also required for gp130-mediated maintenance of the pluripotential state of proliferating embryonic stem cells and for the gp130-induced macrophage differentiation of M1 cells. Furthermore, STAT3 regulates cell movement, such as leukocyte, epidermal cell, and keratinocyte migration. STAT3 also appears to regulate B cell differentiation into antibody-forming plasma cells. Since the IL-6/gp130/STAT3 signaling pathway is involved in both B cell growth and differentiation into plasma cells it is likely to play a central role in the generation of plasma cell neoplasias. Oncogene (2000) 19, 2548–2556 [ABSTRACT FROM AUTHOR]

Discusses the role of Gab-family adapter molecules in signal transduction of cytokine and growth factor receptors and T and B cell antigen receptors. Interaction of Gab proteins with the protein tyrosine phosphatase SHP-2; Gab1 in growth factor receptor signaling; Gab1 and Gab2 in cytokine receptor signaling.

The O-linked sugar chains were liberated from porcine zona pellucida glycoproteins by alkaline-borohydride treatment and the structures of neutral oligosaccharides were determined. The major oligosaccharides had the following structures with type-1 cores, (Galβ1→4GlcNAcβ1→3)1 3-Galβ1→3N-acetylgalactosaminitol (54%) and GlcNAcβ1→3(Galβ1→4GlcNAcβ1→3)0 1Galβ1→3N-acetylgalactosaminitol (16%). Approximately 6% of the oligosaccharides had the structure with a type-3 core. Galβ1→4GlcNAcβ1→3N-acetylgalactosaminitol. Oligosaccharides having α-galactose (2%) and β-GalNAc (4%) at their non-reducing termini were also found as minor components. [ABSTRACT FROM AUTHOR]

Signaling via suppressors of cytokine signaling (SOCS) is an important negative feedback system for cytokine-mediated signal transduction. Recently in Molecular Cell, described the tertiary structure of SOCS3 in complex with a phosphotyrosine-containing peptide from the IL-6 receptor subunit gp130, and they identified the specific amino acids that are critical for binding. [Copyright &y& Elsevier]

New evidence revives the old idea that B cells are the principal effectors in rheumatoid arthritis: autoantibodies against a ubiquitous antigen cause joint-specific disease. The resolution of these conflicting hypotheses resides in the joint itself. (On-Ko-Chi-Shin) the new idea resides within the old." [ABSTRACT FROM AUTHOR]

Since the molecular cloning of interleukin-6 (IL-6) in 1986, many other cytokines have been found to share the same signal transducer, gp130, in their receptor complexes. Thus, the IL-6 family of cytokines now consists of ten members. Although some of the family members' functions are redundant as a result of the expression of gp130, there are also functional distinctions between members. The mechanisms that determine functional redundancies and distinctions are not completely understood. Yet, research has clarified the role of IL-6 family cytokines in autoimmune diseases and has led to effective therapies that target them. Here, we review the IL-6 family of cytokines in autoimmune diseases, with a particular focus on the prototypical member IL-6, from the viewpoints of their structure, signaling, and biological features and discuss possible mechanisms of their functional pleiotropy. Ten receptors for cytokines in the IL-6 family share the signal transducer gp130. Some functions of these cytokines are redundant, but others are distinct and specific. Murakami et al. review the IL-6 cytokine family from the viewpoints of structure, signaling, and biological features and discuss mechanisms of their functional pleiotropy. [ABSTRACT FROM AUTHOR]

Investigates the promotion of Ras/MAPK regulation of epidermal growth and differentiation using Gab1 and SHP-2. Reduction of active level of basal levels active Ras and downstream MAPK proteins; Demonstration of hypoplasia; Enhancement of differentiation.

V-Src induces tyrosine phosphorylation of various cellular proteins and activates a number of signaling molecules including the Jak family of proteins tyrosine kinases and Stat (signal transducers and activators of transcription) proteins. Many cellular effects elicited by v-Src are mediated through Ras, a molecular switch linking growth factor receptors and non-receptor tyrosine kinases to many downstream effectors. In this report, we demonstrated that v-H-Ras and v-Src both induced cellular transformation. However, the activation of Jak1 and Stat3 were only observed in v-Src transformed cells. Using reporter gene assays, we further showed that activation of Stat3 and possibly of Jak1 by v-Src were mediated through a Ras-independent pathway. As Stat3 activation has recently been shown to be required for cellular transformation by v-Src, our results suggest that activation of the Jak-Stat pathway may serve as a modulator in some but not all transformation processes. [ABSTRACT FROM AUTHOR]

The regulation of the three major acute-phase proteins α2-macroglobulin, cysteine proteinase inhibitor and α1-antitrypsin by recombinant human interleukin-1β, recombinant human interleukin-6 and recombinant human tumor necrosis factor α was studied in rat hepatocyte primary cultures. Synthesis and secretion of the acute-phase proteins was measured after labeling with [35S]methionine and immunoprecipitation. Incubation of hepatocytes with interleukin-6 led to dose-dependent and time-dependent changes in the synthesis of the three major acute-phase proteus and albumin, similar to those occurring m vivo during experimental inflammation. α2-Macroglobulin and cysteine proteinase inhibitor synthesis was induced 54-fold and 8-fold, respectively, 24 h after the addition of 100 units/ml interleukin-6. At the same time synthesis of the negative acute-phase protein albumin was reduced to 30% of controls. Half-maximal effects were achieved with 4 units interleukin-6/ml. Interleukin-lβ bad only a partial effect on the regulation of the fore proteins studied: only a twofold stimulation of α2-macroglobulin and a 60% reduction of albumin synthesis were observed. Tumor necrosis factor α did not alter the synthesis of acute-phase proteins. The stimulation of α2-macroglobulin and cysteine proteinase inhibitor synthesis by interleukin-6 was inhibited by interleukin-lβ in a dose-dependent manner. In pulse-chase experiments the effect of interleukin-lβ, interleukin-6 and tumor necrosis factor a on the secretion of acute-phase proteins was examined. Interleukin-6 markedly accelerated the secretion of total proteins and α2-macroglobulin, whereas the secretion of cysteine proteinase inhibitor, α1-antitrypsin and albumin was not affected. The inhibition of N-glycosylation by tunicamycin abolished the effect of interleukin-6 on the secretion of α2-macroglobulin, indicating a possible role of interleukin-6 on N-glycosylation. [ABSTRACT FROM AUTHOR]

Focuses on interleukin-6 family cytokine members, CLC/NNT1/BSF3 and interleukin-27. Receptor complexes; Alpha-chain like molecules; Ligand-specific receptor of CT-1; Gene expression of WSX1; Role on T cell helper or suppresor function.

Zinc (Zn) is an essential nutrient, and Zn deficiency causes immunodeficiency and skin disorders. Basophils express FcɛRI on their surface and release multiple mediators after receptor cross-linking, including large amounts of IL-4. However, the mechanisms involved in the FcɛRI-mediated regulation of basophil IL-4 production are currently unclear. Here, we show that the Zn-binding metallothionein (MT) proteins are essential for the FcɛRI-induced basophil production of IL-4. Basophils from MT-I/II(−/−) mice produced significantly less FcɛRI-induced IL-4 than did wild-type basophils. The MTs were involved in maintaining intracellular Zn levels, thereby regulated the calcineurin activity and nuclear factor of activated T-cell (NFAT)-mediated IL-4 production. These results suggest that the MT-dependent control of Zn homeostasis is a novel mechanism for regulating basophil IL-4 production. [ABSTRACT FROM AUTHOR]

An IL-6-triggered NF-κB loop: the ‘IL-6 amplifier’ occurs in epithelia of a transplanted human lung.The IL-6 amplifier, a positive feedback loop for NFκB signaling, which was originally found to be activated by IL-17A and IL-6 stimulation in non-immune cells, is molecularly a simultaneous activator of NFκB and signal transducer and activator of transcription 3 (STAT3), functionally a local chemokine inducer and pathologically a machinery for inflammation development. It has been shown that IL-6 amplifier activation in epithelial cells contributes to rejection responses in a mouse chronic rejection model that develops a bronchiolitis obliterans (BO)-like disease. We investigated whether the IL-6 amplifier is activated in BO regions of a human lung graft after allogeneic transplantation. NFκB and STAT3 molecules were phosphorylated in the epithelial regions of bronchi that localized in the BO regions. Additionally, chemokine ligand 2 (CCL2), and CD4+ T cells and macrophages increased in these regions. Furthermore, human lung epithelial cells expressed CCL2 after stimulation by IFNγ in the presence of IL-6 and epidermal growth factor via enhanced STAT3 signaling, which parallels behavior seen in the mouse model. Thus, our results suggest that the IL-6 amplifier in the epithelial cells of grafts is involved in chronic rejection after lung transplantation, suggesting that the amplifier may be a valuable therapeutic target to prevent chronic rejection after lung transplantation. [ABSTRACT FROM PUBLISHER]

The IL-6-amplifier first was discovered as a synergistic activation mechanism for NF-KB/STAT3 in type 1 collagen+ cells. This process is marked by the hyperinduction of chemokines and subsequent local inflammation that leads to autoimmune diseases. In this study, we show that IL-6 amplifier activation in grafts plays important roles in allogeneic graft rejection by using a tracheal heterotopic transplantation model that includes bronchiolitis obliterans, a pathological marker for chronic rejection. IL-6, epidermal growth factor, and IFN-&ggr; all stimulate IL-6 amplifier activation, whereas CCL2, a chemotactic factor for Thl cells, was one of the amplifier's main targets. Interestingly, IFN-&ggr; hyperinduced CCL2 in type 1 collagen+ cells via the IL-6 amplifier at least in vitro. In addition, we detected IL-6, CCL2, phospho-STAT3, and phospho-NF-KB in epithelial type 1 collagen+ cells of allogeneic tracheal grafts. These results show that IL-6 amplifler activation in grafts plays a critical role for graft rejection responses after allogeneic transplantation, including chronic rejection. From these results, we consider whether the IL-6 amplifler in grafts might be a valuable therapeutic target for the prevention of transplant rejection, including chronic rejection. [ABSTRACT FROM AUTHOR]

Recent studies have shown that zinc ion (Zn) can behave as an intracellular signaling molecule. We previously demonstrated that mast cells stimulated through the high-affinity IgE receptor (FceRI) rapidly release intracellular Zn from the endoplasmic reticulum (ER), and we named this phenomenon the "Zn wave". However, the molecules responsible for releasing Zn and the roles of the Zn wave were elusive. Here we identified the pore-forming α1 subunit of the Cav1.3 (α1D) L-type calcium channel (LTCC) as the gatekeeper for the Zn wave. LTCC antagonists inhibited the Zn wave, and an agonist was sufficient to induce it. Notably, α1D was mainly localized to the ER rather than the plasma membrane in mast cells, and the Zn wave was impaired by α1D knockdown. We further found that the LTCC-mediated Zn wave positively controlled cytokine gene induction by enhancing the DNA-binding activity of NF-κB. Consistent with this finding, LTCC antagonists inhibited the cytokine-mediated delayed-type allergic reaction in mice without affecting the immediate-type allergic reaction. These findings indicated that the LTCC α1D subunit located on the ER membrane has a novel function as a gatekeeper for the Zn wave, which is involved in regulating NF-κB signaling and the delayed-type allergic reaction. [ABSTRACT FROM AUTHOR]

Summary: Although it is believed that neural activation can affect immune responses, very little is known about the neuroimmune interactions involved, especially the regulators of immune traffic across the blood-brain barrier which occurs in neuroimmune diseases such as multiple sclerosis (MS). Using a mouse model of MS, experimental autoimmune encephalomyelitis, we show that autoreactive T cells access the central nervous system via the fifth lumbar spinal cord. This location is defined by IL-6 amplifier-dependent upregulation of the chemokine CCL20 in associated dorsal blood vessels, which in turn depends on gravity-induced activation of sensory neurons by the soleus muscle in the leg. Impairing soleus muscle contraction by tail suspension is sufficient to reduce localized chemokine expression and block entry of pathogenic T cells at the fifth lumbar cord, suggesting that regional neuroimmune interactions may offer therapeutic targets for a variety of neurological diseases. [ABSTRACT FROM AUTHOR]

The human SLC39A13 gene encodes ZIP13, a member of the LZT (LIV-1 subfamily of ZIP zinc transporters) family. The ZIP13 protein is important for connective tissue development, and its loss of function is causative for the spondylocheiro dysplastic form of Ehlers-Danlos syndrome. However, this protein has not been characterized in detail. Here we report the first detailed biochemical characterization of the human ZIP13 protein using its ectopic expressed and the purified recombinant protein. Protease accessibility, microscopic, and computational analyses demonstrated that ZIP13 contains eight putative transmembrane domains and a unique hydrophilic region and that it resides with both its N and C termini facing the luminal side on the Golgi. Analyses including cross-linking, immunoprecipitation, Blue Native-PAGE, and size-exclusion chromatography experiments indicated that the ZIP13 protein may form a homo-dimer. We also demonstrated that ZIP13 mediates zinc influx, as assessed by monitoring the expression of the metallothionein gene and by detecting the intracellular zinc level with a zinc indicator, FluoZin-3. Our data indicate that ZIP13 is a homo-dimerized zinc transporter that possesses some domains that are not found in other LZT family members. This is the first biochemical characterization of the physiologically important protein ZIP13 and the demonstration of homo-dimerization for a mammalian ZIP zinc transporter family member. This biochemical characterization of the human ZIP13 protein provides important information for further investigations of its structural characteristics and function. [ABSTRACT FROM AUTHOR]

The essential trace element zinc (Zn) is widely required in cellular functions, and abnormal Zn homeostasis causes a variety of health problems that include growth retardation, immunodeficiency, hypogonadism, and neuronal and sensory dysfunctions. Zn homeostasis is regulated through Zn transporters, permeable channels, and metallothioneins. Recent studies highlight Zn's dynamic activity and its role as a signaling mediator. Zn acts as an intracellular signaling molecule, capable of communicating between cells, converting extracellular stimuli to intracellular signals, and controlling intracellular events. We have proposed that intracellular Zn signaling falls into two classes, early and late Zn signaling. This review addresses recent findings regarding Zn signaling and its role in physiological processes and pathogenesis. [ABSTRACT FROM AUTHOR]

Mast cells are major players in allergic responses. IgE-dependent activation through FceR leads to degranulation and cytokine production, both of which require Gab2. To clarify how the signals diverge at Gab2, we established Gab2 knock-in mice that express Gab2 mutated at either the PI3K or SH2 domain-containing protein tyrosine phosphatase-2 (SHP2) binding sites. Examination of these mutants showed that both binding sites were required for the degranulation and anaphylaxis response but not for cytokine production or contact hypersensitivity. Furthermore, the PI3K, but not the SHP2, binding site was important for granule translocation during degranulation. We also identified a small GTPase, ADP-ribosylation factor (ARF)1, as the downstream target of PI3K that regulates granule translocation. FcϵRI stimulation induced ARF1 activation, and this response was dependent on Fyn and the PI3K binding site of Gab2. ARF1 activity was required for FcϵRI-mediated granule translocation. These data indicated that Fyn/Gab2/PI3K/ARF1-mediated signaling is specifically involved in granule translocation and the anaphylaxis response. [ABSTRACT FROM AUTHOR]

Aberrant zinc (Zn) homeostasis is associated with abnormal control of mammalian growth, although the molecular mechanisms of Zn's roles in regulating systemic growth remain to be clarified. Here we report that the cell membrane-localized Zn transporter SLC39A14 controls G-protein coupled receptor (GPCR)-mediated signaling. Mice lacking Slc39α14 (Slc39α14-KO mice) exhibit growth retardation and impaired gluconeogenesis, which are attributable to disrupted GPCR signaling in the growth plate, pituitary gland, and liver. The decreased signaling is a consequence of the reduced basal level of cyclic adenosine monophosphate (cAMP) caused by increased phosphodiesterase (PDE) activity in Slc39α14-KO cells. We conclude that SLC39A14 facilitates GPCR-mediated cAMP-CREB signaling by suppressing the basal PDE activity, and that this is one mechanism for Zn's involvement in systemic growth processes. Our data highlight SLC39A14 as an important novel player in GPCR-mediated signaling. In addition, the Slc39α14-KO mice may be useful for studying the GPCR-associated regulation of mammalian systemic growth. [ABSTRACT FROM AUTHOR]

Abstract: Morphological and biochemical phenotypes of cardiomyocyte hypertrophy are determined by neurohumoral factors. Stimulation of G protein-coupled receptor (GPCR) results in uniform cell enlargement in all directions with an increase in skeletal α-actin (α-SKA) gene expression, while stimulation of gp130 receptor by interleukin-6 (IL-6)-related cytokines induces longitudinal elongation with no increase in α-SKA gene expression. Thus, α-SKA is a discriminating marker for hypertrophic phenotypes; however, regulatory mechanisms of α-SKA gene expression remain unknown. Here, we clarified the role of SH2-containing protein tyrosine phosphatase 2 (SHP2) in α-SKA gene expression. In neonatal rat cardiomyocytes, endothelin-1 (ET-1), a GPCR agonist, but not leukemia inhibitory factor (LIF), an IL-6-related cytokine, induced RhoA activation and promotes α-SKA gene expression via RhoA. In contrast, LIF, but not ET-1, induced activation of SHP2 in cardiomyocytes, suggesting that SHP2 might negatively regulate α-SKA gene expression downstream of gp130. Therefore, we examined the effect of adenovirus-mediated overexpression of wild-type SHP2 (SHP2WT), dominant-negative SHP2 (SHP2C/S), or β-galactosidase (β-gal), on α-SKA gene expression. LIF did not upregulate α-SKA mRNA in cardiomyocytes overexpressing either β-gal or SHP2WT. In cardiomyocytes overexpressing SHP2C/S, LIF induced upregulation of α-SKA mRNA, which was abrogated by concomitant overexpression of either C3-toxin or dominant-negative RhoA. RhoA was activated after LIF stimulation in the cardiomyocytes overexpressing SHP2C/S, but not in myocytes overexpressing β-gal. Furthermore, SHP2 mediates LIF-induced longitudinal elongation of cardiomyocytes via ERK5 activation. Collectively, these findings indicate that SHP2 negatively regulates α-SKA expression via RhoA inactivation and suggest that SHP2 implicates ERK5 in cardiomyocyte elongation downstream of gp130. [Copyright &y& Elsevier]

Zinc (Zn) is an essential trace metal required by many enzymes and transcription factors for their activity or the maintenance of their structure. Zn has a variety of effects in the immune responses and inflammation, although it has not been well known how Zn affects these reactions on the molecular basis. We here showed that Zn suppresses Th17-mediated autoimmune diseases at lest in part by inhibiting the development of Th17 cells via attenuating STAT3 activation. In mice injected with type II collagen to induce arthritis, Zn treatment inhibited Th17 cell development. IL-6-mediated activation of STAT3 and in vitro Th17 cell development were all suppressed by Zn. Importantly, Zn binding changed the α-helical secondary structure of STAT3, disrupting the association of STAT3 with JAK2 kinase and with a phospho-peptide that included a STAT3-binding motif from the IL-6 signal transducer gp130. Thus, we conclude that Zn suppresses STAT3 activation, which is a critical step for Th17 development. [ABSTRACT FROM PUBLISHER]

Although recent studies have identified regulatory roles for Foxp3+CD8+ T cells, the mechanisms that induce their development and underlie their functions in vivo have not been elucidated. Here, we show that IL-6 positively regulates the Foxp3+CD8+ T-cell development and function. The Foxp3+CD8+ T cells that differentiated in vitro in the presence of IL-6 suppressed autoimmune colitis and arthritis in vivo. Moreover, Foxp3+CD8+ T cells that developed in vivo in the presence of enhanced IL-6 signaling suppressed the development of a spontaneous Th17 cell-mediated autoimmune arthritis. Thus, we concluded that Foxp3+CD8+ T cells develop in response to IL-6 and regulate chronic inflammation in Th17 cell-mediated F759 autoimmune arthritis. These results suggested that Foxp3+CD8+ T cells may develop in response to IL-6 under certain inflammatory conditions in vivo and may regulate some other chronic inflammation diseases. [ABSTRACT FROM PUBLISHER]

Summary: Systemic cytokine activity in response to Toll-like receptor (TLR) signaling induces the expression of various proteins in the liver after infections. Here we show that Interleukin-7 (IL-7), the production of which was thought to occur at a constant rate in vivo, was a hepatically expressed protein that directly controled T cell responses. Depletion of IL-7 expression in the liver abrogated several TLR-mediated T cell events, including enhanced CD4+ T cell and CD8+ T cell survival, augmented CD8+ T cell cytotoxic activity, and the development of experimental autoimmune encephalitis, a Th17 cell-mediated autoimmune disease. Thus, T cell responses are regulated by hepatocyte-derived IL-7, which is expressed in response to TLR signaling in vivo. We suggested that TLR-induced IL-7 expression in the liver, which is an acute-phase response, may be a good diagnostic and therapeutic target for efficient vaccine developments and for conditions characterized by TLR-mediated T cell dysregulation, including autoimmune diseases. [Copyright &y& Elsevier]

Summary: Dysregulated cytokine expression and signaling are major contributors to a number of autoimmune diseases. Interleukin-17A (IL-17A) and IL-6 are important in many disorders characterized by immune self-recognition, and IL-6 is known to induce the differentiation of T helper 17 (Th17) cells. Here we described an IL-17A-triggered positive-feedback loop of IL-6 signaling, which involved the activation of the transcription factors nuclear factor (NF)-κB and signal transducer and activator of transcription 3 (STAT3) in fibroblasts. Importantly, enhancement of this loop caused by disruption of suppressor of cytokine signaling 3 (SOCS3)-dependent negative regulation of the IL-6 signal transducer gp130 contributed to the development of arthritis. Because this mechanism also enhanced experimental autoimmune encephalomyelitis (EAE) in wild-type mice, it may be a general etiologic process underlying other Th17 cell-mediated autoimmune diseases. [Copyright &y& Elsevier]

Grb2-associated binder 1 (Gab1) coordinates various receptor tyrosine kinase signaling pathways. Although skeletal muscle differentiation is regulated by some growth factors, it remains elusive whether Gab1 coordinates myogenic signals. Here, we examined the molecular mechanism of insulin-like growth factor-I (IGF-I)-mediated myogenic differentiation, focusing on Gab1 and its downstream signaling. Gab1 underwent tyrosine phosphorylation and subsequent complex formation with protein-tyrosine phosphatase SHP2 upon IGF-I stimulation in C2C12 myoblasts. On the other hand, Gab1 constitutively associated with phosphatidylinositol 3-kinase regulatory subunit p85. To delineate the role of Gab! in IGF-I-dependent signaling, we examined the effect of adenovirus-mediated forced expression of wild-type Gab1 (Gab1WT), mutated Gab1 that is unable to bind SHP2 (Gab1ΔSHP2), or mutated Gab1 that is unable to bind p85 (Gab1Δp85), on the differentiation of C2C12 myoblasts. IGF-I-induced myogenic differentiation was enhanced in myoblasts overexpressing Gab1ΔSHP2, but inhibited in those overexpressing either Gab1WT or Gab1Δp85. Conversely, IGF-I-induced extracellular signal-regulated kinase 1/2 (ERK1/2) activation was significantly repressed in myoblasts overexpressing Gab1ΔSHP2 but enhanced in those overexpressing either Gab1WT or Gab1Δp85. Furthermore, small interference RNA-mediated Gab! knockdown enhanced myogenic differentiation. Overexpression of catalytic-inactive SHP2 modulated IGF-I-induced myogenic differentiation and ERK1/2 activation similarly to that of Gab1ΔSHP2, suggesting that Gab1- SHP2 complex inhibits IGF-I-dependent myogenesis through ERK1/2. Consistently, the blockade of ERK1/2 pathway reversed the inhibitory effect of Gab1WT overexpression on myogenic differentiation, and constitutive activation of the ERK1/2 pathway suppressed the enhanced myogenic differentiation by overexpression of Gab1ΔSHP2. Collectively, these data suggest that the Gab1-SHP2-ERK1/2 signaling pathway comprises an inhibitory axis for IGF-I-dependent myogenic differentiation. [ABSTRACT FROM AUTHOR]

Interleukin 6 (IL-6), a pleiotropic cytokine, functions in cells through its interaction with its receptor complex, which consists of two ligand-binding α subunits and two signal-transducing subunits known as gp130. There is a wealth of studies on signals mediated by gp130, but its downregulation is less well understood. Here we found that IL-6 stimulation induced lysosome-dependent degradation of gp130, which correlated with an increase in the K63-linked polyubiquitination of gp130. The stimulation-dependent ubiquitination of gp130 was mediated by c-Cbl, an E3 ligase, which was recruited to gp130 in a tyrosine-phosphorylated SHP2-dependent manner. We also found that IL-6 induced a rapid translocation of gp130 from the cell surface to endosomal compartments. Furthermore, the vesicular sorting molecule Hrs contributed to the lysosomal degradation of gp130 by directly recognizing its ubiquitinated form. Deficiency of either Hrs or c-Cbl suppressed gp130 degradation, which leads to a prolonged and amplified IL-6 signal. Thus, our present report provides the first evidence for involvement of a c-Cbl/SHP2 complex in ubiquitination and lysosomal degradation of gp130 upon IL-6 stimulation. The lysosomal degradation of gp130 is critical for cessation of IL-6-mediated signaling. [ABSTRACT FROM AUTHOR]

Mast cells have key functions as effectors of immunoglobulin E–mediated allergic inflammatory diseases. Allergen stimulation induces Ca2+ influx and elicits the secretion of inflammatory mediators from mast cells. Here we show that the Ca2+-binding endoplasmic reticulum protein STIM1 is critical to mast cell function. STIM1-deficient fetal liver–derived mast cells had impaired Ca2+ influx mediated by the high-affinity immunoglobulin E receptor FcεRI and activation of the transcription factors NF-κB and NFAT. Mast cells lacking STIM1 also had much less degranulation and cytokine production after FcεRI stimulation. In addition, alterations in STIM1 expression affected the sensitivity of immunoglobulin E–mediated immediate-phase anaphylactic responses in vivo. Thus, STIM1 is key in promoting the Ca2+ influx that is essential for FcεRI-mediated mast cell activation and anaphylaxis. [ABSTRACT FROM AUTHOR]

Abstract: Leukemia inhibitory factor (LIF), a cardiac hypertrophic cytokine, increases L-type Ca2+ current (I CaL) via ERK-dependent and PKA-independent phosphorylation of serine 1829 in the Cav1.2 subunit. The signaling cascade through gp130 is involved in this augmentation. However, there are two major cascades downstream of gp130, i.e. JAK/STAT3 and SHP2/ERK. In this study, we attempted to clarify which of these two cascades plays a more important role. Knock-in mouse line, in which the SHP2 signal was disrupted (gp130F759/F759 group), and wild-type mice (WT group) were used. A whole-cell patch clamp experiment was performed, and intracellular Ca2+ concentration ([Ca2+] i transient) was monitored. The I CaL density and [Ca2+] i transient were measured from the untreated cells and the cells treated with LIF or IL-6 and soluble IL-6 receptor (IL-6+sIL-6r). Action potential duration (APD) was also recorded from the ventricle of each mouse, with or without LIF. Both LIF and IL-6+sIL-6r increased I CaL density significantly in WT (+27.0%, n =16 p <0.05, and +32.2%, n =15, p <0.05, respectively), but not in gp130F759/F759 (+9.4%, n =16, NS, and −6.1%, n =13, NS, respectively). Administration of LIF and IL-6+sIL-6r increased [Ca2+] i transient significantly in WT (+18.8%, n =13, p <0.05, and +32.0%, n =21, p <0.05, respectively), but not in gp130F759/F759 (−3.8%, n =7, NS, and −6.4%, n =10, NS, respectively). LIF prolonged APD80 significantly in WT (10.5±4.3%, n =12, p <0.05), but not in gp130F759/F759 (−2.1±11.2%, n =7, NS). SHP2-mediated signaling cascade is essential for the LIF and IL-6+sIL-6r-dependent increase in I CaL, [Ca2+] i transient and APD. [Copyright &y& Elsevier]

Grb2-associated binder (Gab) family of scaffolding adaptor proteins coordinate signaling cascades downstream of growth factor and cytokine receptors. In the heart, among EGF family members, neuregulin-1β (NRG-1β, a paracrine factor produced from endothelium) induced remarkable tyrosine phosphorylation of Gab1 and Gab2 via erythroblastic leukemia viral oncogene (ErbB) receptors. We examined the role of Gab family proteins in NRG-1β/ErbB-mediated signal in the heart by creating cardiomyocyte-specific Gab1/Gab2 double knockout mice (DKO mice). Although DKO mice were viable, they exhibited marked ventricular dilatation and reduced contractility with aging. DKO mice showed high mortality after birth because of heart failure. In addition, we noticed remarkable endocardial fibroelastosis and increase of abnormally dilated vessels in the ventricles of DKO mice. NRG-1β induced activation of both ERK and AKT in the hearts of control mice but not in those of DKO mice. Using DNA microarray analysis, we found that stimulation with NRG-1β upregulated expression of an endothelium-stabilizing factor, angiopoietin 1, in the hearts of control mice but not in those of DKO mice, which accounted for the pathological abnormalities in the DKO hearts. Taken together, our observations indicated that in the NRG-1β/ErbB signaling, Gab1 and Gab2 of the myocardium are essential for both maintenance of myocardial function and stabilization of cardiac capillary and endocardial endothelium in the postnatal heart. [ABSTRACT FROM AUTHOR]

Grb2-associated binder (Gab) family of scaffolding adaptor proteins coordinate signaling cascades downstream of growth factor and cytokine receptors. In the heart, among EGF family members, neuregulin-1β (NRG-1β, a paracrine factor produced from endothelium) induced remarkable tyrosine phosphorylation of Gab1 and Gab2 via erythroblastic leukemia viral oncogene (ErbB) receptors. We examined the role of Gab family proteins in NRG-1β/ErbB-mediated signal in the heart by creating cardiomyocyte-specific Gab1/Gab2 double knockout mice (DKO mice). Although DKO mice were viable, they exhibited marked ventricular dilatation and reduced contractility with aging. DKO mice showed high mortality after birth because of heart failure. In addition, we noticed remarkable endocardial fibroelastosis and increase of abnormally dilated vessels in the ventricles of DKO mice. NRG-1β induced activation of both ERK and AKT in the hearts of control mice but not in those of DKO mice. Using DNA microarray analysis, we found that stimulation with NRG-1β upregulated expression of an endothelium-stabilizing factor, angiopoietin 1, in the hearts of control mice but not in those of DKO mice, which accounted for the pathological abnormalities in the DKO hearts. Taken together, our observations indicated that in the NRG-1β/ErbB signaling, Gab1 and Gab2 of the myocardium are essential for both maintenance of myocardial function and stabilization of cardiac capillary and endocardial endothelium in the postnatal heart. [ABSTRACT FROM AUTHOR]

IL-17-producing Th (Th17) comprise a distinct lineage of pro-inflammatory Th that are major contributors to autoimmune diseases. Treatment with IL-6 and transforming growth factor β (TGFβ) induces naive CD4+ T cells to generate Th17, which also requires expression of the IL-6/TGFβ target RORγt. We reported that IL-6 transduces two signaling pathways via tyrosine redidues of the signal transducer gp130: one depends on signal transducers and activators of transcription (STAT)-3 activation and the other on Src homology region 2 domain-containing phosphatase 2 (SHP2)/Grb2 associated binder (Gab)/mitogen-activated protein kinase (MAPK) activation. Here, we showed that CD4+ T cells carrying a mutant gp130 that transduces the SHP2/Gab/MAPK pathway but not the STAT3-mediated one failed to develop into Th17, while CD4+ T cells whose mutant gp130 transduces the STAT3 signal only generated Th17, indicating that IL-6 acts directly on T cells through the tyrosine residues of gp130 required for STAT3 activation to promote the development of Th17. Moreover, we found that gp130–STAT3 pathway is essential for Th17 development and for the expression of RORγt by using T cells specifically lacking gp130 and STAT3. Noteworthy is that the regulatory T cell (Treg) percentages and numbers were comparable between all mutant mice we tested in vivo, although we showed that IL-6–gp130–STAT3 pathway suppressed Treg development in vitro. Thus, we conclude that IL-6 acts directly to promote the development of Th17 by activating the T cell gp130–STAT3 pathway but has a minimum effect on Treg development at least in the steady state in vivo. Therefore, blockade of IL-6–gp130–STAT3 pathway in CD4+ T cells could be a good target for controlling unwanted Th17-mediated immune responses including autoimmune diseases. [ABSTRACT FROM PUBLISHER]

Zinc is an essential trace element required for enzymatic activity and for maintaining the conformation of many transcription factors; thus, zinc homeostasis is tightly regulated. Although zinc affects several signaling molecules and may act as a neurotransmitter, it remains unknown whether zinc acts as an intracellular second messenger capable of transducing extracellular stimuli into intracellular signaling events. In this study, we report that the cross-linking of the high affinity immunoglobin E receptor (Fcε receptor I [Fcε RI]) induced a release of free zinc from the perinuclear area, including the endoplasmic reticulum in mast cells, a phenomenon we call the zinc wave. The zinc wave was dependent on calcium influx and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase activation. The results suggest that the zinc wave is involved in intracellular signaling events, at least in part by modulating the duration and strength of FcεRI-mediated signaling. Collectively, our findings indicate that zinc is a novel intracellular second messenger. [ABSTRACT FROM AUTHOR]

Patients with Omenn syndrome (OS) have hypomorphic RAG mutations and develop varying manifestations of severe combined immunodeficiency. It is not known which symptoms are caused directly by the RAG mutations and which depend on other polymorphic genes. Our current understanding of OS is limited by the lack of an animal model. In the present study, we identified a C57BL/10 mouse with a spontaneous mutation in, and reduced activity of, RAG1. Mice bred from this animal contained high numbers of memory-phenotype T cells and experienced hepatosplenomegaly and eosinophilia, had oligoclonal T cells, and demonstrated elevated levels of IgE, major symptoms of OS. Depletion of CD4+ T cells in the mice caused a reduction in their IgE levels. Hence these "memory mutant" mice are a model for human OS; many symptoms of their disease were direct results of the Rag hypomorphism and some were caused by malfunctions of their CD4+ T cells. [ABSTRACT FROM AUTHOR]

Patients with Omenn syndrome (OS) have hypomorphic RAG mutations and develop varying manifestations of severe combined immunodeficiency. It is not known which symptoms are caused directly by the RAG mutations and which depend on other polymorphic genes. Our current understanding of OS is limited by the lack of an animal model. In the present study, we identified a C57BL/10 mouse with a spontaneous mutation in, and reduced activity of, RAG1. Mice bred from this animal contained high numbers of memory-phenotype T cells and experienced hepatosplenomegaly and eosinophilia, had oligoclonal T cells, and demonstrated elevated levels of IgE, major symptoms of OS. Depletion of CD4+ T cells in the mice caused a reduction in their IgE levels. Hence these ‘memory mutant’ mice are a model for human OS; many symptoms of their disease were direct results of the Rag hypomorphism and some were caused by malfunctions of their CD4+ T cells. [ABSTRACT FROM AUTHOR]

Dendritic cells (DC) play a central role in immune responses by presenting antigenic peptides to CD4+ T cells through MHCII molecules. Here, we demonstrate a TRIF–GEFH1–RhoB pathway is involved in MHCII surface expression on DC. We show the TRIF (TIR domain-containing adapter inducing IFNβ)- but not the myeloid differentiation factor 88 (MyD88)-dependent pathway of lipopolysaccharide (LPS)-signaling in DC is crucial for the MHCII surface expression, followed by CD4+ T-cell activation. LPS increased the activity of RhoB, but not of RhoA, Cdc42, or Rac1/2 in a manor dependent on LPS-TRIF- but not LPS-Myd88-signaling. RhoB colocalized with MHCII+ lysosomes in DC. A dominant-negative (DN) form of RhoB (DN-RhoB) or RhoB's RNAi in DC inhibited the LPS-induced MHCII surface expression. Moreover, we found GEFH1 associated with RhoB, and DN-GEFH1 or GEFH1's RNAi suppressed the LPS-mediated RhoB activation and MHCII surface expression. DN-RhoB attenuated the DC's CD4+ T-cell stimulatory activity. Thus, our results provide a molecular mechanism relating how the MHCII surface expression is regulated during the maturation stage of DC. The activation of GEFH1-RhoB through the TRIF-dependent pathway of LPS in DC might be a critical target for controlling the activation of CD4+ T cells. [ABSTRACT FROM AUTHOR]

Zinc is a trace element that is essential for the function of many enzymes and transcription factors. Zinc deficiency results in defects in innate and acquired immune responses. However, little is known about the mechanism(s) by which zinc affects immune cell function. Here we show that stimulation with the Toll-like receptor 4 agonist lipopolysaccharide (LPS) altered the expression of zinc transporters in dendritic cells and thereby decreased intracellular free zinc. A zinc chelator mimicked the effects of LPS, whereas zinc supplementation or overexpression of the gene encoding Zip6, a zinc transporter whose expression was reduced by LPS, inhibited LPS-induced upregulation of major histocompatibility complex class II and costimulatory molecules. These results establish a link between Toll-like receptor signaling and zinc homeostasis. [ABSTRACT FROM AUTHOR]

Abstract: Mice having a point mutation of IL-6 signal transducer, gp130, named gp130F759 induced a rheumatoid arthritis-like disease. The disease induction is totally dependent on mature lymphocytes, since no arthritis-like disease induced in a double mutant between gp130F759 and RAG2KO mice. We prepared several other double mutants including gp130F759/IgMKO, gp130F759/CD8KO, gp130F759/CIITAKO and gp130F759/CD4KO and analyzed the development of the arthritis. We found that development of the disease attenuated in gp130F759/CIITAKO and gp130F759/CD4KO, suggesting the MHC class II-restricted CD4+ T cells are important for the disease development. We showed memory/activated phenotype of CD4+ T cells increased in gp130F759 mice. Since activation of CD4+ T cells is mainly controlled by dendritic cells (DC) in vivo, we investigated this feature of DC in gp130F759 mice. We isolated DCs from superficial lymph nodes and observed that IL-6-mediated signaling suppresses maturation of DCs in vivo. However, total number of DCs in vivo significantly increased in gp130F759 mice compared with wild type controls. Thus, we hypothesize that the rheumatoid arthritis-like disease in gp130F759 mice is induced by an interaction between CD4+ T cells and DC under gp130F759 signal regulation. [Copyright &y& Elsevier]

Summary: We found IL-6-STAT3 pathway suppresses MHC class II (MHCII) expression on dendritic cells (DCs) and attenuates T cell activation. Here, we showed that IL-6-STAT3 signaling reduced intracellular MHCII αβ dimmer, Ii, and H2-DM levels in DCs. IL-6-mediated STAT3 activation decreased cystatin C level, an endogenous inhibitor of cathepsins, and enhanced cathepsin activities. Importantly, cathepsin S inhibitors blocked reduction of MHCII αβ dimer, Ii, and H2-DM in the IL-6-treated DCs. Overexpression of cystatin C suppressed IL-6-STAT3-mediated increase of cathepsin S activity and reduction of MHCII αβ dimer, Ii, and H2-DM levels in DCs. Cathepsin S overexpression in DCs decreased intracellular MHCII αβ dimer, Ii, and H2-DM levels, LPS-mediated surface expression of MHCII and suppressed CD4+ T cell activation. IL-6-gp130-STAT3 signaling in vivo decreased cystatin C expression and MHCII αβ dimer level in DCs. Thus, IL-6-STAT3-mediated increase of cathepsin S activity reduces the MHCII αβ dimer, Ii, and H2-DM levels in DCs, and suppresses CD4+ T cell-mediated immune responses. [Copyright &y& Elsevier]

Severe acute respiratory syndrome (SARS) has become a global public health emergency. p38 mitogen-activated protein kinase (MAPK) and its downstream targets are activated in SARS coronavirus (SARS-CoV)-infected Vero E6 cells and activation of p38 MAPK enhances the cytopathic effects of SARS-CoV infection. In addition, weak activation of Akt cannot prevent SARS-CoV infection-induced apoptosis in Vero E6 cells. In the present study, we demonstrated that signal transducer and activator of transcription (STAT) 3, which is constitutively phosphorylated at tyrosine (Tyr)-705 and slightly phosphorylated at serine (Ser)-727 in Vero E6 cells, was dephosphorylated at Tyr-705 on SARS-CoV infection. In addition to phosphorylation of p38 MAPK in virus-infected cells, other MAPKs, i.e., extracellular signal-regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase (JNK), were phosphorylated. Although inhibitors of ERK1/2 and JNK (PD98059 and SP600125) had no effect on phosphorylation status of STAT3, inhibitors of p38 MAPK (SB203580 and SB202190) partially inhibited dephosphorylation of STAT3 at Tyr-705. Tyr-705-phosphorylated STAT3 was localized mainly in the nucleus in mock infected cells, whereas STAT3 disappeared from the nucleus in virus-infected cells. As STAT3 acts as an activator of transcription in the nucleus, these results suggest that STAT3 lacks its activity on transcription in SARS-CoV-infected Vero E6 cells. [Copyright &y& Elsevier]

Zebrafish signal transducer and activator of transcription 3 (STAT3) controls the cell movements during gastrulation. Here, we show that noncell-autonomous activity of STAT3 signaling in gastrula organizer cells controls the polarity of neighboring cells through Dishevelled-RhoA signaling in the Wnt-planar cell polarity (Wnt- PCP) pathway. In STAT3-depleted embryos, although all the known molecules in the Wnt-PCP pathway were expressed normally, the RhoA activity in lateral mesendodermal cells was down-regulated, resulting in severe cell polarization defects in convergence and extension movements identical to Strabismus-depleted embryos. Cell-autonomous activation of Wnt-PCP signaling by δN- dishevelled rescued the defect in cell elongation, but not the orientation of lateral mesendodermal cells in STAT3- depleted embryos. The defect in the orientation could be rescued by transplantation of shield cells having noncell- autonomous activity of STAT3 signaling. These results suggest that the cells undergoing convergence and extension movement may sense the gradient of signaling molecules, which are expressed in gastrula organizer by STAT3 and noncell-autonomously activate PCP signaling in neighboring cells during zebrafish gastrulation. [ABSTRACT FROM AUTHOR]

sax1/nkx1.2 and sax2/nkx1.1 are members of the evolutionally conserved NK-1 homeobox gene family. sax1/nkx1.2 is reported to be expressed in the central nervous system during early and late neurogenesis in the chick and mouse, but the expression of sax2/nkx1.1 has not been reported. We isolated zebrafish cDNAs for sax1/nkx1.2 and sax2/nkx1.1 and examined their expression. In zebrafish, unlike chick and mouse, sax1/nkx1.2 was expressed in the prospective medial floor plate from the mid-gastrula period and was dependent on Nodal signaling. From the early segmentation period, sax1/nkx1.2 was also expressed in the posterior neuroectoderm. sax2/nkx1.1 was expressed in the prospective extraocular muscles, mesencephalic neurons residing along the tract of the posterior commissure, ventral neurons in the hindbrain, and interneurons in the spinal cord. [Copyright &y& Elsevier]

Ciliary neurotrophic factor (CNTF) has been known to inhibit the differentiation of presumptive rod photoreceptor cells; however, the underlying mechanisms have remained to be elucidated. We demonstrated that STAT3 activation, but not SHP2 activation, is responsible for the CNTF/gp130 signaling that inhibits expression of Rhodopsin and its upstream activator, crx, in the retinal explants derived from P0 mice (P0 retinal explants), utilizing STAT3-deficient retina and electroporation of dominant-negative form of STAT3 (STAT3F). We also demonstrated that STAT3 activation in presumptive rod photoreceptor cells at E18.5 is rapidly downregulated at P0, when Rhodopsin expression starts during retinal development. Persistent STAT3 activation in the P0 retinal explants prevented Rhodopsin expression and rapid upregulation of crx expression. STAT3-deficient retinas did not exhibit precocious rod photoreceptor cell differentiation as a whole, although they occasionally exhibited precocious upregulation of crx mRNA. Thus, we conclude that downregulation of STAT3 activation is required, but insufficient, for rod photoreceptor cell differentiation in the postnatal retina. [Copyright &y& Elsevier]

Vertebrate gastrulation is a critical step in the establishment of body plan. During gastrulation, epithelial-mesenchymal transition (EMT) occurs. EMT is one of the central events of embryonic development, organ and tissue regeneration, and cancer metastasis. Signal transducers and activators of transcription (STATs) mediate biological actions such as cell proliferation, differentiation and survival in response to cytokines and growth factors, in a variety of biological processes. STATs are also important in EMT during gastrulation, organogenesis, wound healing and cancer progression. We previously showed that STAT3 is activated in the organizer during zebrafish gastrulation and its activity is essential for gastrulation movements. The requirement for STAT3 is cell-autonomous for the anterior migration of gastrula organizer cells, and non-cell-autonomous for the convergence of neighbouring cells. The molecular mechanisms of STAT's action in EMT, however, are unknown. Here we identify LIV1, a breast-cancer-associated zinc transporter protein, as a downstream target of STAT3 that is essential and sufficient for STAT3's cell-autonomous role in the EMT of zebrafish gastrula organizer cells. Furthermore, we demonstrate that LIV1 is essential for the nuclear localization of zinc-finger protein Snail, a master regulator of EMT. These results establish a molecular link between STAT3, LIV1 and Snail in EMT. [ABSTRACT FROM AUTHOR]