Nuclear translocation of IFN-gamma is an intrinsic requirement for its biologic activity and can be driven by a heterologous nuclear localization sequence

Disparate viral pandemics from COVID19 to monkeypox and beyond: a simple, effective and universal therapeutic approach hiding in plain sight

The field of antiviral therapeutics is fixated on COVID19 and rightly so as the fatalities at the height of the pandemic in the United States were almost 1,000,000 in a twelve month period spanning parts of 2020/2021. A coronavirus called SARS-CoV2 is the causative virus. Development of a vaccine through molecular biology approaches with mRNA as the inducer of virus spike protein has played a major role in driving down mortality and morbidity. Antivirals have been of marginal value in established infections at the level of hospitalization. Thus, the current focus is on early symptomatic infection of about the first five days. The Pfizer drug paxlovid which is composed of nirmatrelvir, a peptidomimetic protease inhibitor of SARS-CoV2 Mpro enzyme, and ritonavir to retard degradation of nirmatrelvir, is the current FDA recommended treatment of early COVID19. There is no evidence of broad antiviral activity of paxlovid against other diverse viruses such as the influenza virus, poxviruses, as well as a host of respiratory viruses. Although type I interferons (IFNs) are effective against SARS-CoV2 in cell cultures and in early COVID19 infections, they have not been broadly recommended as therapeutics for COVID19. We have developed stable peptidomimetics of both types I and II IFNs based on our noncanonical model of IFN signaling involving the C-terminus of the IFNs. We have also identified two members of intracellular checkpoint inhibitors called suppressors of cytokine signaling (SOCS), SOCS1 and SOCS3 (SOCS1/3), and shown that they are virus induced intrinsic virulence proteins with activity against IFN signaling enzymes JAK2 and TYK2. We developed a peptidomimetic antagonist, based on JAK2 activation loop, against SOCS1/3 and showed that it synergizes with the IFN mimetics for potent broad spectrum antiviral activity without the toxicity of intact IFN molecules. IFN mimetics and the SOCS1/3 antagonist should have an advantage over currently used antivirals in terms of safety and potency against a broad spectrum of viruses.

Dysregulation in IFN-γ signaling and response: the barricade to tumor immunotherapy

Interferon-gamma (IFN-γ) has been identified as a crucial factor in determining the responsiveness to immunotherapy. Produced primarily by natural killer (NK) and T cells, IFN-γ promotes activation, maturation, proliferation, cytokine expression, and effector function in immune cells, while simultaneously inducing antigen presentation, growth arrest, and apoptosis in tumor cells. However, tumor cells can hijack the IFN-γ signaling pathway to mount IFN-γ resistance: rather than increasing antigenicity and succumbing to death, tumor cells acquire stemness characteristics and express immunosuppressive molecules to defend against antitumor immunity. In this review, we summarize the potential mechanisms of IFN-γ resistance occurring at two critical stages: disrupted signal transduction along the IFNG/IFNGR/JAK/STAT pathway, or preferential expression of specific interferon-stimulated genes (ISGs). Elucidating the molecular mechanisms through which tumor cells develop IFN-γ resistance help identify promising therapeutic targets to improve immunotherapy, with broad application value in conjugation with targeted, antibody or cellular therapies.

Macrophages and neutrophils express IFNλs in granulomas from Mycobacterium tuberculosis-infected nonhuman primates

Granulomas are the hallmark of Mycobacterium tuberculosis (Mtb) infection. Cytokine-mediated signaling can modulate immune function; thus, understanding the cytokine milieu in granulomas is critical for understanding immunity in tuberculosis (TB). Interferons (IFNs) are important immune mediators in TB, and while type 1 and 2 IFNs have been extensively studied, less is known about type 3 IFNs (IFNλs) in TB. To determine if IFNλs are expressed in granulomas, which cells express them, and how granuloma microenvironments influence IFNλ expression, we investigated IFNλ1 and IFNλ4 expression in macaque lung granulomas. We identified IFNλ expression in granulomas, and IFNλ levels negatively correlated with bacteria load. Macrophages and neutrophils expressed IFNλ1 and IFNλ4, with neutrophils expressing higher levels of each protein. IFNλ expression varied in different granuloma microenvironments, with lymphocyte cuff macrophages expressing more IFNλ1 than epithelioid macrophages. IFNλ1 and IFNλ4 differed in their subcellular localization, with IFNλ4 predominantly localizing inside macrophage nuclei. IFNλR1 was also expressed in granulomas, with intranuclear localization in some cells. Further investigation demonstrated that IFNλ signaling is driven in part by TLR2 ligation and was accompanied by nuclear translocation of IFNλR1. Our data indicate that IFNλs are part of the granuloma cytokine milieu that may influence myeloid cell function and immunity in TB.

Expansion of fish CCL20_like chemokines by genome and local gene duplication: Characterisation and expression analysis of 10 CCL20_like chemokines in rainbow trout (Oncorhynchus mykiss)

Mammalian CCL20, or macrophage inflammatory protein-3α, can function as a homeostatic and inflammatory chemokine. In relation to the latter, it is responsible for the chemoattraction of lymphocytes and dendritic cells to mucosal immune sites under inflammatory and pathological conditions. CK1, CK8A and CK8B are rainbow trout (Oncorhynchus mykiss) CC chemokines that were reported previously to be phylogenetically related to mammalian CCL20. In the current study, an additional seven CCL20_L paralogues in rainbow trout are reported, that are divided into three subgroups and have been designated here as: CCL20_L1a (also referred to as CK1), CCL20_L1b1-2, CCL20_L2a (CK8A), CCL20_L2b (CK8B), CCL20_L3a, and CCL20_L3b1-4. Multiple CCL20_L genes were also identified in other salmonids that arose from both whole genome duplication and local gene duplication. Phylogenetic tree, homology and synteny analysis support that CCL20_L1-3 found in salmonids are also present in most teleosts arose from the 3 R whole genome duplication and in some species, local gene duplication. Like mammalian CCL20, rainbow trout CCL20_L molecules possess a high positive net charge with a pI of 9.34-10.16, that is reported to be important for antimicrobial activity. Rainbow trout CCL20_L paralogues are differentially expressed and in general highly expressed in mucosal tissues, such as gills, thymus and intestine. The expression levels of rainbow trout CCL20_L paralogues are increased during development and following PAMP/cytokine stimulation. For example, in RTS-11 cells CCL20_L3b1 and CCL20_L3b2 are highly up-regulated by LPS, Poly I:C, recombinant(r) IFNa and rIL-1β. Trout CCL20_L paralogues are also increased after Yersinia ruckeri infection or Poly I:C stimulation in vivo, with CCL20_L3b1 and CCL20_L3b2 again highly up-regulated. Overall, this is the first report of the complete CCL20 chemokine subfamily in rainbow trout, and the analysis of their expression and modulation in vitro and in vivo. These results suggest that teleosts possess divergent CCL20_L molecules that may have important roles in anti-viral/anti-bacterial defence and in mucosal immunity.

Insights into teleost interferon-gamma biology: An update

Interferon-gamma (IFN-ϒ) is probably one of the most relevant cytokines orchestrating the immune response in vertebrates. Although the activities mediated by this molecule are well known in mammals, several aspects of the IFN-ϒ system in teleosts remain a riddle to scientists. Numerous studies support a potentially similar role of the fish IFN-ϒ signalling pathway in some well-described immunological processes induced by this cytokine in mammals. Nevertheless, the existence in some teleost species of duplicated ifng genes and an additional gene derived from ifng known as interferon-γ-related (ifngrel), among other things, raises new interesting questions about the mode of action of these various molecules in fish. Moreover, certain IFN-ϒ-mediated activities recently observed in mammals are still fully unknown in fish. Another attractive but mainly unexplored curious property of IFN-ϒ in vertebrates is its potential dual role depending on the type of pathogen. In addition, some aspects mediated by this molecule could favour the resolution of a bacterial infection but be harmful in the context of a viral disease, and vice versa. This review collects old and new aspects of IFN-ϒ research in teleosts and discusses new questions and pathways of investigation based on recent discoveries in mammals.

Noncanonical IFN Signaling, Steroids, and STATs: A Probable Role of V-ATPase

A small group of only seven transcription factors known as STATs (signal transducer and activator of transcription) are considered to be canonical determinants of specific gene activation for a plethora of ligand/receptor systems. The activation of STATs involves a family of four tyrosine kinases called JAK kinases. JAK1 and JAK2 activate STAT1 in the cytoplasm at the heterodimeric gamma interferon (IFNγ) receptor, while JAK1 and TYK2 activate STAT1 and STAT2 at the type I IFN heterodimeric receptor. The same STATs and JAKs are also involved in signaling by functionally different cytokines, growth factors, and hormones. Related to this, IFNγ-activated STAT1 binds to the IFNγ-activated sequence (GAS) element, but so do other STATs that are not involved in IFNγ signaling. Activated JAKs such as JAK2 and TYK2 are also involved in the epigenetics of nucleosome unwrapping for exposure of DNA to transcription. Furthermore, activated JAKs and STATs appear to function coordinately for specific gene activation. These complex events have not been addressed in canonical STAT signaling. Additionally, the function of noncoding enhancer RNAs, including their role in enhancer/promoter interaction is not addressed in the canonical STAT signaling model. In this perspective, we show that JAK/STAT signaling, involving membrane receptors, is essentially a variation of cytoplasmic nuclear receptor signaling. Focusing on IFN signaling, we showed that ligand, IFN receptor, the JAKs, and the STATs all undergo endocytosis and ATP-dependent nuclear translocation to promoters of genes specifically activated by IFNs. We argue here that the vacuolar ATPase (V-ATPase) proton pump probably plays a key role in endosomal membrane crossing by IFNs for receptor cytoplasmic binding. Signaling of nuclear receptors such as those of estrogen and dihydrotestosterone provides templates for making sense of the specificity of gene activation by closely related cytokines, which has implications for lymphocyte phenotypes.

[Traffic and signalisation of the leptin receptor]

Receptors are the master regulators conveying the information provided by the hormone from the extracellular environment to the intracellular milieu. As a result, the level of receptors at the cell surface can determine the signaling strength. Regulation of receptor trafficking to the cell surface or receptor retention processes in intracellular compartments are key mechanisms for leptin receptor (ObR) activity. An alteration of these mechanisms leads to the development of obesity. However, the canonical mechanism of plasma membrane receptors activation is challenged by the discovery that intracellular receptors also have their own signaling activity inside specific intracellular compartments. These intracellular receptors can trigger signaling that regulates a particular function, different from, or in continuity with, surface receptor signaling. We will address both these aspects by focusing particularly on the case of the leptin receptor (ObR), i.e., i) the regulation of its level of exposure to the cell surface and its impact on the development of obesity, and ii) the discovery of its location and signaling in some intracellular compartments.

Interferons type II and their receptors R1 and R2 in fish species: Evolution, structure, and function

Interferon gamma (IFN-γ) is one of the key players in the immune system of vertebrates. The evolution and properties of IFN-γ and its receptors in fish species are of special interest as they point to the origin of innate immunity in vertebrates. We studied the phylogeny, biophysical and structural properties of IFN-γ and its receptors. Our phylogeny analysis suggests the existence of two groups of IFN-γ related proteins, one specific for Acanthomorpha, the other for Cypriniformes, Characiformes and Siluriformes. The analysis further shows an ancient duplication of the gene for IFN-γ receptor 1 (IFN- γR1) and the parallel existence of the duplicated genes in all current teleost fish species. In contrast, only one gene can be found for receptor 2, IFN- γR2. The specificity of the interaction between IFN- γ and both types of IFN- γR1 was determined by microscale thermophoresis measurements of the equilibrium dissociation constants for the proteins from three fish species. The measured preference of IFN- γ for one of the two forms of receptor 1agrees with the bioinformatic analysis of the coevolution between IFN- γ and receptor 1. To elucidate structural relationships between IFN-γ of fish and other vertebrate species, we determined the crystal structure of IFN-γ from olive flounder (Paralichthys olivaceus, PoliIFN-γ) at crystallographic resolution of 2.3 Å and the low-resolution structures of Takifugu rubripes, Oreochromis niloticus, and Larimichthys crocea IFN-γ by small angle X-ray diffraction. The overall PoliIFN-γ fold is the same as the fold of the other known IFN- γ structures but there are some significant structural differences, namely the additional C-terminal helix G and a different angle between helices C and D in PoliIFN-γ.

Interferon gamma peptidomimetic targeted to interstitial myofibroblasts attenuates renal fibrosis after unilateral ureteral obstruction in mice

Renal fibrosis cannot be adequately treated since anti-fibrotic treatment is lacking. Interferon-γ is a pro-inflammatory cytokine with anti-fibrotic properties. Clinical use of interferon-γ is hampered due to inflammation-mediated systemic side effects. We used an interferon-γ peptidomimetic (mimγ) lacking the extracellular IFNγReceptor recognition domain, and coupled it to the PDGFβR-recognizing peptide BiPPB. Here we tested the efficacy of mimγ-BiPPB (referred to as “Fibroferon”) targeted to PDGFβR-overexpressing interstitial myofibroblasts to attenuate renal fibrosis without inducing inflammation-mediated side effects in the mouse unilateral ureter obstruction model.

Unilateral ureter obstruction induced renal fibrosis characterized by significantly increased α-SMA, TGFβ1, fibronectin, and collagens I and III protein and/or mRNA expression. Fibroferon treatment significantly reduced expression of these fibrotic markers. Compared to full-length IFNγ, anti-fibrotic effects of Fibroferon were more pronounced. Unilateral ureter obstruction-induced lymphangiogenesis was significantly reduced by Fibroferon but not full-length IFNγ. In contrast to full-length IFNγ, Fibroferon did not induce IFNγ-related side-effects as evidenced by preserved low-level brain MHC II expression (similar to vehicle), lowered plasma triglyceride levels, and improved weight gain after unilateral ureter obstruction.

In conclusion, compared to full-length IFNγ, the IFNγ-peptidomimetic Fibroferon targeted to PDGFβR-overexpressing myofibroblasts attenuates renal fibrosis in the absence of IFNγ-mediated adverse effects.

An Update on the Therapeutic Potential of Stem Cells

The seeming setbacks noted for stem cells underscore the need for experimental studies for safe and efficacious application to patients. Both clinical and experimental researchers have gained valuable knowledge on the characteristics of stem cells, and their behavior in different microenvironment. This introductory chapter focuses on adult mesenchymal stem cells (MSCs) based on the predominance in the clinic. MSCs can be influenced by inflammatory mediators to exert immune suppressive properties, commonly referred to as "licensing." Interestingly, while there are questions if other stem cells can be delivered across allogeneic barrier, there is no question on the ability of MSCs to provide this benefit. This property has been a great advantage since MSCs could be available for immediate application as "off-the-shelf" stem cells for several disorders, tissue repair and gene/drug delivery. Despite the benefit of MSCs, it is imperative that research continues with the various types of stem cells. The method needed to isolate these cells is outlined in this book. In parallel, safety studies are needed; particularly links to oncogenic event. In summary, this introductory chapter discusses several potential areas that need to be addressed for safe and efficient delivery of stem cells, and argue for the incorporation of microenvironmental factors in the studies. The method described in this chapter could be extrapolated to the field of chimeric antigen receptor T-cells (CAR-T). This will require application to stem cell hierarchy of memory T-cells.

Current prospects of type II interferon γ signaling and autoimmunity

Interferon γ (IFNγ) is a pleiotropic protein secreted by immune cells. IFNγ signals through the IFNγ receptor, a protein complex that mediates downstream signaling events. Studies into IFNγ signaling have provided insight into the general concepts of receptor signaling, receptor internalization, regulation of distinct signaling pathways, and transcriptional regulation. Although IFNγ is the central mediator of the adaptive immune response to pathogens, it has been shown to be involved in several non-infectious physiological processes. This review will provide an introduction into IFNγ signaling biology and the functional roles of IFNγ in the autoimmune response.

Molecular characterization and expression analysis of interferon-gamma in the large yellow croaker Larimichthys crocea

The large yellow croaker Larimichthys crocea is an important mariculture fish species in China, and the bacterium Vibrio harveyi (V. harveyi) and the ciliate protozoan Cryptocaryon irritans (C. irritans) are the two major pathogens in its aquaculture sector. Interferon-gamma (IFN-γ) plays important roles in regulating both innate and cell mediated immune responses as an inflammatory cytokine. In this study, we obtained the nucleotide sequence of IFN-γ from the large yellow croaker (LcIFN-γ). The phylogenetic relationship tree of 18 available IFN-γ genes was constructed based on their sequences. Expression analyses in 10 various tissues were conducted after the croaker challenged with V. harveyi and C. irritans, respectively. Real time PCR analysis showed that the expression of LcIFN-γ was observed broadly in health individuals. After injected with V. harveyi, the 10 tissues had a higher expression of IFN-γ at the first day (1 d); only spleen, muscle, intestine, heart and skin had higher expressions after infected with C. irritans at 1 d. Major immune tissues (skin, gill, head kidney and spleen) and detoxification tissue (liver) were sampled at 0 h, 6 h, 1 d, 2 d, 3 d, 4 d, 5 d and 7 d to understand the expression trends of LcIFN-γ after challenged with C. irritans. The expressions of LcIFN-γ in skin and gill (the primary immune organs) showed a clear correlative relationship with the life cycle of C. irritans.

IFN-γ in turtle: conservation in sequence and signalling and role in inhibiting iridovirus replication in Chinese soft-shelled turtle Pelodiscus sinensis

The IFN-γ gene was identified in a turtle, the Chinese soft-shelled turtle, Pelodiscus sinensis, with its genome consisting of 4 exons and 3 introns. The deduced amino acid sequence of this gene contains a signal peptide, an IFN-γ family signature motif (130)IQRKAVNELFPT, an NLS motif (155)KRKR and three potential N-glycosylation sites. As revealed by real-time quantitative PCR, the gene was constitutively expressed in all tested organs/tissues, with higher level observed in blood, intestine and thymus. An induced expression of IFN-γ at mRNA level was observed in peripheral blood leucocytes (PBLs) in response to in vitro stimulation of LPS and PolyI:C. The overexpression of IFN-γ in the Chinese soft-shelled turtle artery (STA) cell line resulted in the increase in the expression of transcriptional regulators, such as IRF1, IRF7 and STAT1, and antiviral genes, such as Mx, PKR, implying possibly the existence of a conserved signalling network and role for IFN-γ in the turtle. Furthermore, the infection of soft-shelled turtle iridovirus (STIV) in the cell line transfected with IFN-γ may cause the cell death as demonstrated with the elevated lactate dehydrogenase (LDH) level and cell mortality. However, the mechanism involved in the antiviral activity may require further investigation.

Steroid-like signalling by interferons: making sense of specific gene activation by cytokines

Many cytokines, hormones and growth factors use the JAK (Janus kinase)/STAT (signal transducer and activator of transcription) pathway for cell signalling and specific gene activation. In the classical model, ligand is said to interact solely with the receptor extracellular domain, which triggers JAK activation of STATs at the receptor cytoplasmic domain. Activated STATs are then said to carry out nuclear events of specific gene activation. Given the limited number of STATs (seven) and the activation of the same STATs by cytokines with different functions, the mechanism of the specificity of their signalling is not obvious. Focusing on IFNγ (interferon γ), we have shown that ligand, receptor and activated JAKs are involved in nuclear events that are associated with specific gene activation, where the receptor subunit IFNGR1 (IFNγ receptor 1) functions as a transcription/co-transcription factor and the JAKs are involved in key epigenetic events. RTKs (receptor tyrosine kinases) such as EGFR [EGF (epidermal growth factor) receptor] and FGFR [FGF (fibroblast growth factor) receptor] also undergo nuclear translocation in association with their respective ligands. EGFR and FGFR, like IFNGR1, have been shown to function as transcription/co-transcription factors. The RTKs also regulate other kinases that have epigenetic effects. Our IFNγ model, as well as the RTKs EGFR and FGFR, have similarities to that of steroid receptor signalling. These systems consist of ligand-receptor-co-activator complexes at the genes that they activate. The co-activators consist of transcription factors and kinases, of which the latter play an important role in the associated epigenetics. It is our view that signalling by cytokines such as IFNγ is but a variation of specific gene activation by steroid hormones.

Current thoughts on the therapeutic potential of stem cell

Stem cells are considered as potential therapy for inflammatory disorders, tissue repair, and gene delivery, among others. The heterogeneity of a disease and the underlying disorder of a patient bring up the question on the method by which stem cells should be delivered. This summary discusses potential complex interactions among mediators at sites to tissue insults with stem cells. The chapter selects mesenchymal stem cells (MSCs) as a model, although the discussion is relevant to all stem cells. The review examines how MSCs and their differentiated cells can develop cross communication with soluble factors and cells within the region of tissue damage. Inflammatory cytokines, IL-1, TNFα, and TGFβ are selected to explain how they can affect the responses of MSCs, while predisposing the stem cells to oncogenic event. By understanding the varied functions of MSCs, one will be able to intervene to form a balance in functions, ultimately to achieve safety and efficient application. Cytokines can affect the expression of pluripotent genes such as REST and Oct-4. REST is a critical gene in the decision of a cell to express or repress neural genes. Since cytokines can affect microRNAs, the review incorporates this family of molecules as mediators of cytokine effects. IFNγ, although an inflammatory mediator, is central to the expression of MHC-II on MSCs. Therefore, it is included to discuss its role in the transplantation of stem cells across allogeneic barrier. In summary, this chapter discusses several potential areas that need to be addressed for safe and efficient delivery of stem cells, and argue for the incorporation of microenvironmental factors in the studies.

Cytostatic effect of the hypothalamic cytokine PRP-1 is mediated by mTOR and cMyc inhibition in high grade chondrosarcoma

This study aimed to further elucidate the molecular mechanisms of antiproliferative action of proline rich polypeptide 1 (PRP-1) cytokine, produced by neurosecretory cells of the hypothalamus to be considered as alternative adjuvant therapy for metastatic chondrosarcoma, which does not respond to chemotherapy or radiation and currently without any effective treatment. Rapid cell proliferation assay of human primary cultures from high grade chondrosarcoma patients biopsies and human chondrosarcoma JJ012 cell line indicated 50 and 80% inhibition in PRP-1 treated samples correspondingly. Videomicroscopy detected that despite the treatment there are still dividing cells, meaning that cells are not in the state of dormancy, rather PRP-1 repressed the cell cycle progression, exhibited cytostatic effect. The mammalian target of rapamycin (mTOR) is an intracellular serine/threonine protein kinase that has a crucial role in a nutrient sensitive signaling pathway that regulates cell growth. Experiments with mTOR pathway after PRP-1 (10 μg/ml) treatment indicated statistically significant 30% inhibition of mTOR activity and its 56% inhibition in immunoprecipitates with PRP-1 concentrations effective for cell proliferation inhibition. Treatment with PRP- caused inhibition of mTOR and downstream target cMyc oncogenic transcription factor sufficient to trigger the cytostatic effect in high grade, but not in low grade chondrosarcomas. The fact that lower concentrations than 10 μg/ml peptide with cytostatic effect did not inhibit mTOR, but inhibited cMyc prompted us to assume that PRP-1 binds to two different receptors facilitating the antiproliferative effect.

Controlling Nuclear Jaks and Stats for Specific Gene Activation by Ifn γ and Other Cytokines: A Possible Steroid-like Connection

The mechanism of specific gene activation by cytokines that use JAK/STAT signalling pathway is unknown. There are four different types of JAKs and seven different types of STATs. In the classical model of signaling, ligand interacts solely with the receptor extracellular domain, which triggers JAK activation at the receptor cytoplasmic domain. Activated STATs are then said to carry out nuclear events of specific gene activation, including associated epigenetic changes that cause heterochromatin destabilization. Ligand, receptor, and JAKs play no further role in the classical model. Given the limited number of STATs and the activation of the same STATs by cytokines with different functions, the mechanism of the specificity of their signalling is not obvious. Focusing on gamma interferon (IFNγ), we have shown that ligand, receptor, and activated JAKs are involved in nuclear events that are associated with specific gene activation. In this model, receptor subunit IFNGR1 functions as a transcription/cotranscription factor and the JAKs are involved in key epigenetic events that are required for specific gene activation. The model has implications for gene activation in cancer as well as stem cell differentiation.

CD56+ T cells inhibit hepatitis C virus replication in human hepatocytes

CD56(+) T cells are abundant in liver and play an important role in defense against viral infections. However, the role of CD56(+) T cells in control of hepatitis C virus (HCV) infection remains to be determined. We investigated the noncytolytic anti-HCV activity of primary CD56(+) T cells in human hepatocytes. When HCV Japanese fulminant hepatitis-1 (JFH-1)-infected hepatocytes were co-cultured with CD56(+) T cells or incubated in media conditioned with CD56(+) T cell culture supernatants (SN), HCV infectivity and replication were significantly inhibited. The antibodies to interferon (IFN)-gamma or IFN-gamma receptor could largely block CD56(+) T cell-mediated anti-HCV activity. Investigation of mechanism(s) responsible for CD56(+) T cell-mediated noncytolytic anti-HCV activity showed that CD56(+) T SN activated the multiple elements of janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway and enhanced the expression of IFN regulatory factors (IRFs) 1, 3, 7, 8, and 9, resulting in the induction of endogenous IFN-alpha/beta expression in hepatocytes. Moreover, CD56(+) T SN treatment inhibited the expression of HCV-supportive micro RNA (miRNA)-122 and enhanced the levels of anti-HCV miRNA-196a in human hepatocytes.

CONCLUSION

These findings provide direct in vitro evidence at cellular and molecular levels that CD56(+) T cells may have an essential role in innate immune cell-mediated defense against HCV infection. (HEPATOLOGY 2009.).

Interferon gamma is recognised by importin alpha/beta: enhanced nuclear localising and transactivation activities of an interferon gamma mimetic

Interferon (IFN) gamma's ability to localise in the nucleus and function in gene activation has been known for some time, although the role of the conventional nuclear transporting importin molecules is unclear. Here, we demonstrate for the first time the direct recognition of IFNgamma and an IFNgamma mimetic peptide by IMPalpha and the IMPalpha/beta heterodimer, where the IFNgamma mimetic shows higher affinity. Significantly, this correlates well both with in vivo ability to target green fluorescent protein to the nucleus in transfected cells as determined by quantitative confocal laser scanning microscopy, as well as GAS promoter activity of a luciferase reporter. This has important implications for IFNgamma's anti-viral action, and the potential use of the IFNgamma mimetic in antiviral therapies.

Influence of IFN-gamma and its receptors in human breast cancer

BACKGROUND

Interferons are a group of proteins that trigger multiple responses including prevention of viral replication, inhibition of cell growth, and modulation of cell differentiation. In different mammary carcinoma cell lines IFNgamma induces growth arrest at mid-G1. At the present there are no in vivo studies in human breast. The aim of this study was to investigate the expression patterns of IFNgamma and its two receptors (IFNgamma-Ralpha and IFNgamma-Rbeta) by Western blot and immunohistochemistry, in order to elucidate its role in the different types of human breast cancer (in situ and infiltrative).

METHODS

Immunohistochemical and semiquantitative study of IFNgamma, its receptors types (IFNgamma-Ralpha and IFNgamma-Rbeta), cell proliferation (proliferating cell nuclear antigen, also named PCNA), and apoptosis (TUNEL method) was carried between the three breast groups (fibrocystic lesions, in situ tumors and infiltrating tumors).

RESULTS

In the three groups of patients, IFNgamma and IFNgamma-Ralpha immunoreactions appeared in the cytoplasm while IFNgamma-Rbeta also was found in the nucleus. The optical density to IFNgamma was higher in in situ carcinoma than in benign and infiltrating tumors. When we observed IFNgamma-Ralpha, the optical density was lower in infiltrating carcinoma than in benign and in situ tumors (the higher density). To IFNgamma-Rbeta, the optical density was similar in the three group samples. In tumor samples PCNA and TUNEL index was significantly higher; than in benign diseases. PCNA index increased with the malignance. No significant differences were found between cancer types to TUNEL. IFNgamma could be a potential therapeutic tool in breast cancer. However, tumor cells are able to escape from the control of this cytokine in the early tumor stages; this is probably due to a decreased expression of IFNgamma, or also to an alteration of either its receptors or some transduction elements.

CONCLUSION

We conclude that the decrease in the % positive samples that expressed IFNgamma and IFNgamma-Ralpha together with the nuclear localization of IFNgamma-Rbeta, could be a tumoral cell response, although perhaps insufficient to inhibit the uncontrolled cell proliferation. Perhaps, IFNgamma might be unable to activate p21 to stop the cell cycle, suggesting a possible participation in breast cancer development.

IFN mimetic as a therapeutic for lethal vaccinia virus infection: possible effects on innate and adaptive immune responses

We have developed small peptide mimetics of IFN-gamma that can bypass the poxvirus virulence factor B8R protein, which binds to intact IFN-gamma and prevents its interaction with receptor extracellular domain. Thus, these peptides inhibit vaccinia virus replication in cell culture where intact IFN-gamma is ineffective. We demonstrate here that the mouse IFN-gamma-mimetic peptide, IFN-gamma(95-132), protects C57BL/6 mice against overwhelming lethal vaccinia virus infection. The mimetic peptide was synthesized with an attached lipophilic group for penetration of cell plasma membrane. Injection of mimetic i.p. before and at the time of intranasal (10(6) PFU) or i.p. (10(7) PFU) challenge with virus resulted in complete protection at 200 microg of mimetic and 40-60% protection at 5 microg of mimetic. Initiation of treatment of mice with IFN-gamma mimetic up to 2 days postinfection resulted in complete protection against death, whereas initiation of treatment at 6 days postinfection resulted in 40% protection. Administration of mimetic by the oral route also completely protected mice against the intranasal route of a lethal dose of vaccinia virus challenge. In addition to its direct antiviral effect, the mimetic also possessed adjuvant effects in boosting humoral and cellular immunity to vaccinia virus. The combination of antiviral and adjuvant effects by the IFN mimetic probably plays a role in its potent anti-vaccinia virus properties. These results suggest an effective therapeutic against ongoing, lethal poxvirus infections that taps into innate and adaptive host defenses.

EGFR signaling pathway in breast cancers: from traditional signal transduction to direct nuclear translocalization

Aberrant epidermal growth factor receptor (EGFR) signaling is a major characteristic of many human malignancies including breast cancer. Since the discovery of EGF in 1960's and its receptor in 1980's, our understanding of the EGF/EGFR pathway has been significantly advanced and consequently, EGFR is considered as a major oncogenic factor and an attractive therapeutic target. The well-established traditional function of EGFR is known to transmit extra-cellular mitogenic signals, such as EGF and transforming growth factor-alpha (TGF-alpha), through activating a number of downstream signaling cascades. These include signaling modules that involve phospholipase C-gamma, Ras, and phosphatidylinositol-3 kinase (PI-3K). In cancer cells, the common outcomes following the activation of the EGFR-mediated downstream pathways are altered gene activities, leading to un-controlled tumor proliferation and apoptosis. Interestingly, emerging evidences suggest the existence of a direct mode of the EGFR pathway that is distinct from the traditional transduction pathway. This new mode of EGFR signaling involves cellular transport of EGFR from the cell-surface to the cell nucleus, association of nuclear EGFR complex with gene promoters, and transcriptional regulation of the target genes. Although the nature and pathological consequences of the nuclear EGFR pathway remain elusive, accumulating evidences suggest its association with increased tumor cell proliferation and poor survival rate in breast cancer patients. While several anti-EGFR agents are being tested in breast cancer patients clinically and others under pre-clinical development, a better understanding of the traditional and the nuclear EGFR pathways will facilitate the identification of patients that are likely to respond to these agents as well as future development of more effective anti-EGFR therapeutic interventions.

Nuclear-cytoplasmic transport of EGFR involves receptor endocytosis, importin beta1 and CRM1

Many receptor tyrosine kinases (RTKs) can be detected in the cell nucleus, such as EGFR, HER-2, HER-3, HER-4, and fibroblast growth factor receptor. EGFR, HER-2 and HER-4 contain transactivational activity and function as transcription co-factors to activate gene promoters. High EGFR in tumor nuclei correlates with increased tumor proliferation and poor survival in cancer patients. However, the mechanism by which cell-surface EGFR translocates into the cell nucleus remains largely unknown. Here, we found that EGFR co-localizes and interacts with importins alpha1/beta1, carriers that are critical for macromolecules nuclear import. EGFR variant mutated at the nuclear localization signal (NLS) is defective in associating with importins and in entering the nuclei indicating that EGFR's NLS is critical for EGFR/importins interaction and EGFR nuclear import. Moreover, disruption of receptor internalization process using chemicals and forced expression of dominant-negative Dynamin II mutant suppressed nuclear entry of EGFR. Additional evidences suggest an involvement of endosomal sorting machinery in EGFR nuclear translocalization. Finally, we found that nuclear export of EGFR may involve CRM1 exportin as we detected EGFR/CRM1 interaction and markedly increased nuclear EGFR following exposure to leptomycin B, a CRM1 inhibitor. Collectively, these data suggest the importance of receptor endocytosis, endosomal sorting machinery, interaction with importins alpha1/beta1, and exportin CRM1 in EGFR nuclear-cytoplasmic trafficking. Together, our work sheds light into the nature and regulation of the nuclear EGFR pathway and provides a plausible mechanism by which cells shuttle cell-surface EGFR and potentially other RTKs through the nuclear pore complex and into the nuclear compartment.

Tracking STAT nuclear traffic

Accurate cellular localization is crucial for the effective function of most signalling molecules and nuclear translocation is central to the function of transcription factors. The passage of large molecules between the cytoplasm and nucleus is restricted, and this restriction affords a mechanism to regulate transcription by controlling the access of transcription factors to the nucleus. In this Review, we focus on the signal transducer and activator of transcription (STAT) family of transcription factors. The regulation of the nuclear trafficking of STAT-family members is diverse. Some STAT proteins constitutively shuttle between the nucleus and cytoplasm, whereas others require tyrosine phosphorylation for nuclear localization. In either case, the regulation of nuclear trafficking can provide a target for therapeutic intervention.

The gamma interferon (IFN-gamma) mimetic peptide IFN-gamma (95-133) prevents encephalomyocarditis virus infection both in tissue culture and in mice

We have demonstrated previously that the C-terminal gamma interferon (IFN-gamma) mimetic peptide consisting of residues 95 to 133 [IFN-gamma(95-133)], which contains the crucial IFN-gamma nuclear localization sequence (NLS), has antiviral activity in tissue culture. Here we evaluate the efficacy of this peptide and its derivatives first in vitro and then in an animal model of lethal viral infection with the encephalomyocarditis (EMC) virus. Deletion of the NLS region from the IFN-gamma mimetic peptide IFN-gamma(95-133) resulted in loss of antiviral activity. However, the NLS region does not have antiviral activity in itself. Replacing the NLS region of IFN-gamma(95-133) with the NLS region of the simian virus 40 large T antigen retains the antiviral activity in tissue culture. IFN-gamma(95-133) prevented EMC virus-induced lethality in mice in a dose-dependent manner compared to controls. Mice treated with IFN-gamma(95-133) had no or low EMC virus titers in their internal organs, whereas control mice had consistently high viral titers, especially in the heart tissues. Injection of B8R protein, which is encoded by poxviruses as a defense mechanism to neutralize host IFN-gamma, did not inhibit IFN-gamma(95-133) protection against a lethal dose of EMC virus, whereas mice treated with rat IFN-gamma were not protected. The data presented here show that the IFN-gamma mimetic peptide IFN-gamma(95-133) prevents EMC virus infection in vivo and in vitro and may have potential against other lethal viruses, such as the smallpox virus, which encodes the B8R protein.

IFN-gamma and its receptor subunit IFNGR1 are recruited to the IFN-gamma-activated sequence element at the promoter site of IFN-gamma-activated genes: evidence of transactivational activity in IFNGR1

We have shown previously that IFN-gamma and one of its receptor subunits, IFNGR1, are translocated to the nucleus, together with STAT1alpha as one macromolecular complex, via the classical importin-dependent pathway. In this study, we have identified the nuclear targets of IFN-gamma and IFNGR1. By chromatin immunoprecipitation followed by PCR, IFN-gamma, its receptor subunit IFNGR1, and STAT1alpha were found to be associated with the IFN-gamma-activated sequence (GAS) in the promoter of two of the genes stimulated by IFN-gamma. Immunoprecipitated chromatin also showed the association of the IFN-gamma, IFNGR1, and STAT1alpha on the same DNA sequence. Examination of nuclear extracts from WISH cells treated with IFN-gamma revealed the specific binding of IFN-gamma, IFNGR1, and STAT1alpha to biotinylated GAS nucleotide sequence. Association of IFN-gamma, IFNGR1, and STAT1alpha with the GAS promoter was also demonstrated by EMSA. Transfection with a GAS-luciferase gene together with the IFNGR1 and nonsecreted IFN-gamma resulted in enhanced reporter activity. In addition, IFNGR1 fused to the yeast GAL4 DNA binding domain resulted in enhanced transcription from a GAL4 response element, suggesting the presence of a trans activation domain in IFNGR1. Our observations put IFN-gamma and its receptor subunit, IFNGR1, in direct contact with the promoter region of IFN-gamma-activated genes with associated increased activity, thus suggesting a transcriptional/cotranscriptional role for IFN-gamma/IFNGR1 as well as a possible role in determining the specificity of IFN-gamma action.

Peptide mimetics of gamma interferon possess antiviral properties against vaccinia virus and other viruses in the presence of poxvirus B8R protein

We have developed peptide mimetics of gamma interferon (IFN-gamma) that play a direct role in the activation and nuclear translocation of STAT1alpha transcription factor. These mimetics do not act through recognition by the extracellular domain of IFN-gamma receptor but rather bind to the cytoplasmic domain of the receptor chain 1, IFNGR-1, and thereby initiate the cellular signaling. Thus, we hypothesized that these mimetics would bypass the poxvirus virulence factor B8R protein that binds to intact IFN-gamma and prevents its interaction with the receptor. Human and murine IFN-gamma mimetic peptides were introduced into an adenoviral vector for intracellular expression. Murine IFN-gamma mimetic peptide was also expressed via chemical synthesis with an attached lipophilic group for penetration of cell plasma membrane. In contrast to intact human IFN-gamma, the mimetics did not bind poxvirus B8R protein, a homolog of the IFN-gamma receptor extracellular domain. Expression of B8R protein in WISH cells did not block the antiviral effect of the mimetics against encephalomyocarditis or vesicular stomatitis virus, while the antiviral activity of human IFN-gamma was neutralized. Consistent with the antiviral activity, the upregulation of MHC class I molecules on WISH cells by the IFN-gamma mimetics was not affected by B8R protein, while IFN-gamma-induced upregulation was blocked. Finally, the mimetics, but not IFN-gamma, inhibited vaccinia virus replication in African green monkey kidney BSC-40 cells. The data presented demonstrate that small peptide mimetics of IFN-gamma can avoid the B8R virulence factor for poxviruses and, thus, are potential candidates for antivirals against smallpox virus.

Nuclear interaction of EGFR and STAT3 in the activation of the iNOS/NO pathway

Epidermal growth factor receptor (EGFR) exists in the nucleus of highly proliferative cells where it functions as a transcription factor. Although EGFR has transactivational activity, it lacks a DNA binding domain and, therefore, may require a DNA binding transcription cofactor for its transcriptional function. Here, we report that EGFR physically interacts with signal transducers and activators of transcription 3 (STAT3) in the nucleus, leading to transcriptional activation of inducible nitric oxide synthase (iNOS). In breast carcinomas, nuclear EGFR positively correlates with iNOS. This study describes a mode of transcriptional control involving cooperated efforts of STAT3 and nuclear EGFR. Our work suggests that the deregulated iNOS/NO pathway may partly contribute to the malignant biology of tumor cells with high levels of nuclear EGFR and STAT3.

Novel Prognostic Value of Nuclear Epidermal Growth Factor Receptor in Breast Cancer

Epidermal growth factor receptor (EGFR) has been detected in the nucleus of cancer cells and primary tumors for decades. While localized in the nucleus, EGFR functions as a transcriptional regulator resulting in the activation of the cyclin D1 gene. Despite nuclear accumulation of EGFR is linked to increased DNA synthesis and proliferative potential, the pathological significance of nuclear EGFR, however, remains uninvestigated. Furthermore, expression of EGFR has not provided a consistent predictive value for survival of breast cancer patients. Here, we analyzed 130 breast carcinomas via immunohistochemical analyses for the levels of nuclear and non-nuclear EGFR. We found 37.7% of the cohort immunostained positively for nuclear EGFR and 6.9% with high levels of expression. Importantly, Kaplan-Meier survival analysis and log-rank test revealed a significant inverse correlation between high nuclear EGFR and overall survival (P = 0.009). Expression of nuclear EGFR correlated positively with increased levels of cyclin D1 and Ki-67, both are indicators for cell proliferation. In contrast, expression of non-nuclear EGFR did not significantly correlate with those of cyclin D1 and Ki-67 or the overall survival rate. In addition, we analyzed 37 oral squamous carcinomas for EGFR expression and found 24.3% of the cases to contain moderate/high levels of nuclear EGFR. Taken together, our findings indicate pathological significance of nuclear EGFR and may have important clinical implication.

Trafficking and signaling pathways of nuclear localizing protein ligands and their receptors

Interaction of ligands such as epidermal growth factor and interferon-gamma with the extracellular domains of their plasma membrane receptors results in internalization followed by translocation into the nucleus of the ligand and/or receptor. There has been reluctance, however, to ascribe signaling importance to this, the focus instead being on second messenger pathways, including mobilization of kinases and inducible transcription factors (TFs). The latter, however, fails to explain the fact that so many ligands stimulate the same second messenger cascades/TFs, and yet show distinct gene activation profiles. This is particularly apt in the case of the seven STAT TFs that are held to be the mediators of the distinct cellular functions of over 60 ligands. The current review focuses on five representative nuclear localizing ligands for which there is documentation of translocation into the cytosol and nucleus through well-characterized pathways, in addition to a role in gene activation by ligand/receptor in the nucleus.

Interferon-gamma: an overview of signals, mechanisms and functions

Interferon-gamma (IFN-gamma) coordinates a diverse array of cellular programs through transcriptional regulation of immunologically relevant genes. This article reviews the current understanding of IFN-gamma ligand, receptor, signal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophage function during infection. The current model for IFN-gamma signal transduction is discussed, as well as signal regulation and factors conferring signal specificity. Cellular effects of IFN-gamma are described, including up-regulation of pathogen recognition, antigen processing and presentation, the antiviral state, inhibition of cellular proliferation and effects on apoptosis, activation of microbicidal effector functions, immunomodulation, and leukocyte trafficking. In addition, integration of signaling and response with other cytokines and pathogen-associated molecular patterns, such as tumor necrosis factor-alpha, interleukin-4, type I IFNs, and lipopolysaccharide are discussed.

The ins and outs of STAT1 nuclear transport

There is an inherent elegance in being in the right place at the right time. The STAT1 transcription factor possesses regulatory signals that ensure its distribution to the right cellular location at the right time. Latent STAT1 resides primarily in the cytoplasm, and there it responds to hormone signaling through tyrosine phosphorylation by Janus kinases or growth factor receptors. After phosphorylation, STAT1 dimerizes, and this conformational change reveals a nuclear import signal that is recognized by a specific nuclear import carrier. In the nucleus, the STAT1 dimer dissociates from the import carrier and binds to specific DNA target sites in the promoters of regulated genes. STAT1 is subsequently dephosphorylated in the nucleus by a constitutively active tyrosine phosphatase, leading to its dissociation from DNA. A nuclear export signal of STAT1 appears to be masked when dimers are bound to DNA, but it becomes accessible to the CRM1 export carrier after dissociation from DNA. CRM1 binds STAT1 and transports the transcription factor back to the cytoplasm. Studies show that the regulatory trafficking signals that guide the nuclear import and export of STAT1 reside within its DNA binding domain. The location of these signals indicates that their function has coevolved with the ability of STAT1 to bind DNA and regulate gene expression. The nuclear import and subsequent recycling of STAT1 to the cytoplasm are integral to its function as a signal transducer and activator of transcription.

The role of IFNgamma nuclear localization sequence in intracellular function

Intracellularly expressed interferon gamma (IFNgamma) has been reported to possess biological activity similar to that of IFNgamma added to cells. This study addresses the mechanisms for such similar biological effects. Adenoviral vectors were used to express a non-secreted form of human IFNgamma or a non-secreted mutant form in which a previously demonstrated nuclear localization sequence (NLS), 128KTGKRKR134, was replaced with alanines at K and R positions. With the vector expressing non-secreted wild-type IFNgamma, biological responses normally associated with extracellular IFNgamma, such as antiviral activity and MHC class I upregulation, were observed, although the mutant IFNgamma did not possess biological activity. Intracellular human IFNgamma possessed biological activity in mouse L cells, which do not recognize extracellularly added human IFNgamma. Thus, the biological activity was not due to leakage of IFNgamma to the surroundings and subsequent interaction with the receptor on the cell surface. Biological function was associated with activation of STAT1alpha and nuclear translocation of IFNgamma, IFNGR1 and STAT1alpha. Immunoprecipitation of cellular extracts with antibody to the nuclear transporter NPI-1 showed the formation of a complex with IFNgamma-IFNGR1-STAT1alpha. To provide the physiological basis for these effects we show that extracellularly added IFNgamma possesses intracellular signaling activity that is NLS dependent, as suggested by our previous studies, and that this activity occurs via the receptor-mediated endocytosis of IFNgamma. The data are consistent with previous observations that the NLS of extracellularly added IFNgamma plays a role in IFNgamma signaling.

Lipid vector for the delivery of peptides towards intracellular pharmacological targets

The ability of single-chain lipopeptides to gain access to cellular compartments other than those related to degradation/recycling was first deduced from their capacity to deliver peptide antigens into MHC-class I loading mechanisms. The ability of lipopeptides to escape complete endosome degradation was further illustrated by the selective inhibition of different protein kinase C isoenzymes and, more recently, the presentation of agonistic activity towards the interferon gamma receptor. Taken together, several independent results indicate that modification of a peptide by a single lipid chain confers upon it intracellular trafficking properties that can be used to deliver functional cargo peptides into living cells; the endoplasmic reticulum, cytosolic protease activity, sites of kinase activity, or even the signalling pathway associated with cytokine stimulation, all appear accessible to peptide modified by a single lipidic moiety. In this context, the interferon gamma receptor can be considered as a very discriminative pharmacological model, useful for the comparative evaluation of the cellular delivery of lipopeptides, as it allows the unambiguous tracking of their intact delivery into a wide range of cellular compartments. This model is now being used to probe the influence of the nature of the lipid moiety on the trafficking properties of lipopeptides.