Haemopoietic receptors and helical cytokines

Exploring the landscape of synthetic IL-6-type cytokines

Interleukin-6 (IL-6)-type cytokines not only have key immunomodulatory functions that affect the pathogenesis of diseases such as autoimmune diseases, chronic inflammatory conditions, and cancer, but also fulfill important homeostatic tasks. Even though the pro-inflammatory arm has hindered the development of therapeutics based on natural-like IL-6-type cytokines to date, current synthetic trends might pave the way to overcome these limitations and eventually lead to immune-inert designer cytokines to aid type 2 diabetes and brain injuries. Those synthetic biology approaches include mutations, fusion proteins, and inter-cytokine swapping, and resulted in IL-6-type cytokines with altered receptor affinities, extended target cell profiles, and targeting of non-natural cytokine receptor complexes. Here, we survey synthetic cytokine developments within the IL-6-type cytokine family and discuss potential clinical applications.

Targeting IL-6 trans-signalling: past, present and future prospects

Interleukin-6 (IL-6) is a key immunomodulatory cytokine that affects the pathogenesis of diverse diseases, including autoimmune diseases, chronic inflammatory conditions and cancer. Classical IL-6 signalling involves the binding of IL-6 to the membrane-bound IL-6 receptor α-subunit (hereafter termed 'mIL-6R') and glycoprotein 130 (gp130) signal-transducing subunit. By contrast, in IL-6 trans-signalling, complexes of IL-6 and the soluble form of IL-6 receptor (sIL-6R) signal via membrane-bound gp130. A third mode of IL-6 signalling - known as cluster signalling - involves preformed complexes of membrane-bound IL-6-mIL-6R on one cell activating gp130 subunits on target cells. Antibodies and small molecules have been developed that block all three forms of IL-6 signalling, but in the past decade, IL-6 trans-signalling has emerged as the predominant pathway by which IL-6 promotes disease pathogenesis. The first selective inhibitor of IL-6 trans-signalling, sgp130, has shown therapeutic potential in various preclinical models of disease and olamkicept, a sgp130Fc variant, had promising results in phase II clinical studies for inflammatory bowel disease. Technological developments have already led to next-generation sgp130 variants with increased affinity and selectivity towards IL-6 trans-signalling, along with indirect strategies to block IL-6 trans-signalling. Here, we summarize our current understanding of the biological outcomes of IL-6-mediated signalling and the potential for targeting this pathway in the clinic.

Cytokimera GIL-11 rescued IL-6R deficient mice from partial hepatectomy-induced death by signaling via non-natural gp130:LIFR:IL-11R complexes

All except one cytokine of the Interleukin (IL-)6 family share glycoprotein (gp) 130 as the common β receptor chain. Whereas Interleukin (IL-)11 signal via the non-signaling IL-11 receptor (IL-11R) and gp130 homodimers, leukemia inhibitory factor (LIF) recruits gp130:LIF receptor (LIFR) heterodimers. Using IL-11 as a framework, we exchange the gp130-binding site III of IL-11 with the LIFR binding site III of LIF. The resulting synthetic cytokimera GIL-11 efficiently recruits the non-natural receptor signaling complex consisting of gp130, IL-11R and LIFR resulting in signal transduction and proliferation of factor-depending Ba/F3 cells. Besides LIF and IL-11, GIL-11 does not activate receptor complexes consisting of gp130:LIFR or gp130:IL-11R, respectively. Human GIL-11 shows cross-reactivity to mouse and rescued IL-6R^-/- mice following partial hepatectomy, demonstrating gp130:IL-11R:LIFR signaling efficiently induced liver regeneration. With the development of the cytokimera GIL-11, we devise the functional assembly of the non-natural cytokine receptor complex of gp130:IL-11R:LIFR.

An Emerging Role for Type I Interferons as Critical Regulators of Blood Coagulation

Type I interferons (IFNs) are central mediators of anti-viral and anti-bacterial host defence. Detection of microbes by innate immune cells via pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and cGAS-STING, induces the expression of type I IFN-stimulated genes. Primarily comprising the cytokines IFN-α and IFN-β, type I IFNs act via the type I IFN receptor in an autocrine or exocrine manner to orchestrate rapid and diverse innate immune responses. Growing evidence pinpoints type I IFN signalling as a fulcrum that not only induces blood coagulation as a core feature of the inflammatory response but is also activated by components of the coagulation cascade. In this review, we describe in detail recent studies identifying the type I IFN pathway as a modulator of vascular function and thrombosis. In addition, we profile discoveries showing that thrombin signalling via protease-activated receptors (PARs), which can synergize with TLRs, regulates the host response to infection via induction of type I IFN signalling. Thus, type I IFNs can have both protective (via maintenance of haemostasis) and pathological (facilitating thrombosis) effects on inflammation and coagulation signalling. These can manifest as an increased risk of thrombotic complications in infection and in type I interferonopathies such as systemic lupus erythematosus (SLE) and STING-associated vasculopathy with onset in infancy (SAVI). We also consider the effects on coagulation of recombinant type I IFN therapies in the clinic and discuss pharmacological regulation of type I IFN signalling as a potential mechanism by which aberrant coagulation and thrombosis may be treated therapeutically.

Molecular Actors of Inflammation and Their Signaling Pathways: Mechanistic Insights from Zebrafish

Inflammation is a hallmark of the physiological response to aggressions. It is orchestrated by a plethora of molecules that detect the danger, signal intracellularly, and activate immune mechanisms to fight the threat. Understanding these processes at a level that allows to modulate their fate in a pathological context strongly relies on in vivo studies, as these can capture the complexity of the whole process and integrate the intricate interplay between the cellular and molecular actors of inflammation. Over the years, zebrafish has proven to be a well-recognized model to study immune responses linked to human physiopathology. We here provide a systematic review of the molecular effectors of inflammation known in this vertebrate and recapitulate their modes of action, as inferred from sterile or infection-based inflammatory models. We present a comprehensive analysis of their sequence, expression, and tissue distribution and summarize the tools that have been developed to study their function. We further highlight how these tools helped gain insights into the mechanisms of immune cell activation, induction, or resolution of inflammation, by uncovering downstream receptors and signaling pathways. These progresses pave the way for more refined models of inflammation, mimicking human diseases and enabling drug development using zebrafish models.

Dissecting Interleukin-6 Classic and Trans-signaling in Inflammation and Cancer

Interleukin-6 (IL-6) is a cytokine synthesized by many cells in the human body. IL-6 binds to a membrane-bound receptor (IL-6R), which is only present on hepatocytes, some epithelial cells, and some leukocytes. The complex of IL-6 and IL-6R binds to the ubiquitously expressed receptor subunit gp130, which forms a homodimer and thereby initiates intracellular signaling, e.g., the JAK/STAT and MAPK pathways. Proteases can cleave the membrane-bound IL-6R from the cell surface and generate a soluble IL-6R (sIL-6R), which retains its ability to bind IL-6. The IL-6/sIL-6R complex associates with gp130 and induces signaling even on cells which do not express the IL-6R. This paradigm has been called IL-6 trans-signaling, whereas signaling via the membrane-bound IL-6R is referred to as classic signaling. We have generated several molecular tools to differentiate between both pathways and to analyze the consequences of cellular IL-6 signaling in vivo. One of these tools is soluble gp130Fc, which selectively inhibits IL-6 trans-signaling. This protein under the WHO name Olamkicept has successfully undergone phase II clinical trials in patients with autoimmune diseases. Here, in this chapter, we describe several molecular tools to differentiate between IL-6 classic and trans-signaling and to analyze the consequences of cellular IL-6 signaling in vivo.

CRLF1 and CLCF1 in Development, Health and Disease

Cytokines and their receptors have a vital function in regulating various processes such as immune function, inflammation, haematopoiesis, cell growth and differentiation. The interaction between a cytokine and its specific receptor triggers intracellular signalling cascades that lead to altered gene expression in the target cell and consequent changes in its proliferation, differentiation, or activation. In this review, we highlight the role of the soluble type I cytokine receptor CRLF1 (cytokine receptor-like factor-1) and the Interleukin (IL)-6 cytokine CLCF1 (cardiotrophin-like cytokine factor 1) during development in physiological and pathological conditions with particular emphasis on Crisponi/cold-induced sweating syndrome (CS/CISS) and discuss new insights, challenges and possibilities arising from recent studies.

The two facets of gp130 signalling in liver tumorigenesis

The liver is a vital organ with multiple functions and a large regenerative capacity. Tumours of the liver are the second most frequently cause of cancer-related death and develop in chronically inflamed livers. IL-6-type cytokines are mediators of inflammation and almost all members signal via the receptor subunit gp130 and the downstream signalling molecule STAT3. We here summarize current knowledge on how gp130 signalling and STAT3 in tumour cells and cells of the tumour micro-environment drives hepatic tumorigenesis. We furthermore discuss very recent findings describing also anti-tumorigenic roles of gp130/STAT3 and important considerations for therapeutic interventions.

Therapeutic targeting of IL-6 trans-signaling

Interleukin-6 (IL-6) is a cytokine, which is involved in innate and acquired immunity, in neural cell maintenance and in metabolism. IL-6 can be synthesized by many different cells including myeloid cells, fibroblasts, endothelial cells and lymphocytes. The synthesis of IL-6 is strongly stimulated by Toll like receptors and by IL-1. Therefore, IL-6 levels in the body are high during infection and inflammatory processes. Moreover, IL-6 is a prominent growth factor of tumor cells and plays a major role in inflammation associated cancer. On target cells, IL-6 binds to an IL-6 receptor, which is not signaling competent. The complex of IL-6 and IL-6 receptor associate with a second receptor subunit, glycoprotein gp130, which dimerizes and initiates intracellular signaling. Cells, which do not express the IL-6 receptor are not responsive to IL-6. They can, however, be stimulated by the complex of IL-6 and a soluble form of the IL-6 receptor, which is generated by limited proteolysis and to a lesser extent by translation from an alternatively spliced mRNA. This process has been named IL-6 trans-signaling. This review article will explain the biology of IL-6 trans-signaling and the specific inhibition of this mode of signaling, which has been recognized to be fundamental in inflammation and cancer.

Historical overview of the interleukin-6 family cytokine

Interleukin-6 (IL-6) has been identified as a 26-kD secreted protein that stimulates B cells to produce antibodies. Later, IL-6 was revealed to have various functions that overlap with other IL-6 family cytokines and use the common IL-6 signal transducer gp130. IL-6 stimulates cells through multiple pathways, using both membrane and soluble IL-6 receptors. As indicated by the expanding market for IL-6 inhibitors, it has become a primary therapeutic target among IL-6 family cytokines. Here, we revisit the discovery of IL-6; discuss insights regarding the roles of this family of cytokines; and highlight recent advances in our understanding of regulation of IL-6 expression.

A cytokine receptor domeless promotes white spot syndrome virus infection via JAK/STAT signaling pathway in red claw crayfish Cherax quadricarinatus

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway is pivotal in immune responses for a variety of pathogens in both vertebrates and invertebrates. Domeless (Dome), as a unique cytokine receptor, involves in the upstream JAK/STAT pathway in invertebrates. In this study, the full-length cDNA sequence of a cytokine receptor Dome was identified from red claw crayfish Cherax quadricarinatus (named as CqDome), which contained an open reading frame of 4251 bp, encoding 1416 amino acids. The CqDome contained extracellular conservative domains of a signal peptide, two cytokine binding modules (CBM), three fibronectin-type-III-like (FN3) domains and a transmembrane region. Tissue distribution analysis showed that CqDome generally expressed in all the tissues selected with a high expression in hemocyte. The gene expression of both the viral immediately early gene (IE1) and a late gene envelope protein VP28 of white spot syndrome virus (WSSV) were significantly decreased after gene silencing of CqDome in crayfish haematopoietic tissue (Hpt) cells, indicating a key role of CqDome in promoting WSSV infection. Furthermore, the phosphorylation level of CqSTAT was significantly inhibited by gene silencing of CqDome in Hpt cells, indicating that CqDome participated in signal transduction of JAK/STAT pathway in red claw crayfish. These data together suggest that CqDome is likely to promote WSSV infection via JAK/STAT pathway, which sheds new light on further elucidation of the pathogenesis of WSSV.

Structural Understanding of Interleukin 6 Family Cytokine Signaling and Targeted Therapies: Focus on Interleukin 11

Cytokines are small signaling proteins that have central roles in inflammation and cell survival. In the half-century since the discovery of the first cytokines, the interferons, over fifty cytokines have been identified. Amongst these is interleukin (IL)-6, the first and prototypical member of the IL-6 family of cytokines, nearly all of which utilize the common signaling receptor, gp130. In the last decade, there have been numerous advances in our understanding of the structural mechanisms of IL-6 family signaling, particularly for IL-6 itself. However, our understanding of the detailed structural mechanisms underlying signaling by most IL-6 family members remains limited. With the emergence of new roles for IL-6 family cytokines in disease and, in particular, roles of IL-11 in cardiovascular disease, lung disease, and cancer, there is an emerging need to develop therapeutics that can progress to clinical use. Here we outline our current knowledge of the structural mechanism of signaling by the IL-6 family of cytokines. We discuss how this knowledge allows us to understand the mechanism of action of currently available inhibitors targeting IL-6 family cytokine signaling, and most importantly how it allows for improved opportunities to pharmacologically disrupt cytokine signaling. We focus specifically on the need to develop and understand inhibitors that disrupt IL-11 signaling.

The Role of Interleukins in Colorectal Cancer

Despite great progress has been made in treatment strategies, colorectal cancer (CRC) remains the predominant life-threatening malignancy with the feature of high morbidity and mortality. It has been widely acknowledged that the dysfunction of immune system, including aberrantly expressed cytokines, is strongly correlated with the pathogenesis and progression of colorectal cancer. As one of the most well-known cytokines that were discovered centuries ago, interleukins are now uncovering new insights into colorectal cancer therapy. Herein, we divide currently known interleukins into 6 families, including IL-1 family, IL-2 family, IL-6 family, IL-8 family, IL-10 family and IL-17 family. In addition, we comprehensively reviewed the oncogenic or antitumour function of each interleukin involved in CRC pathogenesis and progression by elucidating the underlying mechanisms. Furthermore, by providing interleukins-associated clinical trials, we have further driven the profound prospect of interleukins in the treatment of colorectal cancer.

Prolactin Acts on Myeloid Progenitors to Modulate SMAD7 Expression and Enhance Hematopoietic Stem Cell Differentiation into the NK Cell Lineage

Numerous cell types modulate hematopoiesis through soluble and membrane bound molecules. Whether developing hematopoietic progenitors of a particular lineage modulate the differentiation of other hematopoietic lineages is largely unknown. Here we aimed to investigate the influence of myeloid progenitors on CD34+ cell differentiation into CD56+ innate lymphocytes. Sorted CD34+ cells cultured in the presence of stem cell factor (SCF) and FMS-like tyrosine kinase 3 ligand (FLT3L) give rise to numerous cell types, including progenitors that expressed the prolactin receptor (PRLR). These CD34+PRLR+ myeloid-lineage progenitors were derived from granulocyte monocyte precursors (GMPs) and could develop into granulocytes in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. Moreover, CD34+PRLR+ myeloid progenitors lacked lymphoid developmental potential, but when stimulated with prolactin (PRL) they increased the differentiation of other CD34+ cell populations into the NK lineage in a non-contact dependent manner. Both mRNA and protein analyses show that PRL increased mothers against decapentaplegic homolog 7 (SMAD7) in CD34+PRLR+ myeloid cells, which reduced the production of transforming growth factor beta 1 (TGF-β1), a cytokine known to inhibit CD56+ cell development. Thus, we uncover an axis whereby CD34+PRLR+ GMPs inhibit CD56+ lineage development through TGF-β1 production and PRL stimulation leads to SMAD7 activation, repression of TGF-β1, resulting in CD56+ cell development.

Recent Advances in Electrochemical and Optical Biosensors Designed for Detection of Interleukin 6

Interleukin 6 (IL-6), being a major component of homeostasis, immunomodulation, and hematopoiesis, manifests multiple pathological conditions when upregulated in response to viral, microbial, carcinogenic, or autoimmune stimuli. High fidelity immunosensors offer real-time monitoring of IL-6 and facilitate early prognosis of life-threatening diseases. Different approaches to augment robustness and enhance overall performance of biosensors have been demonstrated over the past few years. Electrochemical- and fluorescence-based detection methods with integrated electronics have been subjects of intensive research due to their ability to offer a better signal-to-noise ratio, high specificity, ultra-sensitivity, and wide dynamic range. In this review, the pleiotropic role of IL-6 and its clinical significance is discussed in detail, followed by detection schemes devised so far for their quantitative analysis. A critical review on underlying signal amplification strategies and performance of electrochemical and optical biosensors is presented. In conclusion, we discuss the reliability and feasibility of the proposed detection technologies for commercial applications.

Identification of prognostic genes in the acute myeloid leukemia microenvironment

The tumor microenvironment (TME) has a strong influence on the progression, therapeutic response, and clinical outcome of acute myeloid leukemia (AML), one of the most common hematopoietic malignancies in adults. In this study, we identified TME-related genes associated with AML prognosis. Gene expression profiles from AML patients were downloaded from TCGA database, and immune and stromal scores were calculated using the ESTIMATE algorithm. Immune scores were correlated with clinical features such as FAB subtypes and patient's age. After categorizing AML cases into high and low score groups, an association between several differentially expressed genes (DEGs) and overall survival was identified. Functional enrichment analysis of the DEGs showed that they were primarily enriched in the immune response, inflammatory response, and cytokine activity, and were involved in signaling processes related to hematopoietic cell lineage, B cell receptor, and chemokine pathways. Two significant modules, dominated respectively by CCR5 and ITGAM nodes, were identified from the PPI network, and 20 hub genes were extracted. A total of 112 DEGs correlated with poor overall survival of AML patients, and 11 of those genes were validated in a separate TARGET-AML cohort. By identifying TME-associated genes, our findings may lead to improved prognoses and therapies for AML.

Activating mutations of the gp130/JAK/STAT pathway in human diseases

Cytokines of the interleukin-6 (IL-6) family are involved in numerous physiological and pathophysiological processes. Dysregulated and increased activities of its members can be found in practically all human inflammatory diseases including cancer. All cytokines activate several intracellular signaling cascades, including the Jak/STAT, MAPK, PI3K, and Src/YAP signaling pathways. Additionally, several mutations in proteins involved in these signaling cascades have been identified in human patients, which render these proteins constitutively active and result in a hyperactivation of the signaling pathway. Interestingly, some of these mutations are associated with or even causative for distinct human diseases, making them interesting targets for therapy. This chapter describes the basic biology of the gp130/Jak/STAT pathway, summarizes what is known about the molecular mechanisms of the activating mutations, and gives an outlook how this knowledge can be exploited for targeted therapy in human diseases.

The role of the interleukin (IL)-6/IL-6 receptor axis in cancer

Interleukin-6 (IL-6) is a pleiotropic cytokine that activates a classic signalling pathway upon binding to its membrane-bound receptor (IL-6R). Alternatively, IL-6 may 'trans-signal' in a manner that is facilitated by its binding to a soluble derivative of the IL-6 receptor (sIL-6R). Resultant signal transduction is, respectively, driven by the association of IL-6/IL-6R or IL-6/sIL-6R complex with the membrane-associated signal transducer, gp130 (Glycoprotein 130). Distinct JAK (Janus tyrosine kinase)/STAT (signal transducers and activators of transcription) and other signalling pathways are activated as a consequence. Of translational relevance, overexpression of IL-6 has been documented in several neoplastic disorders, including but not limited to colorectal, ovarian and breast cancer and several haematological malignancies. This review attempts to summarise our current understanding of the role of IL-6 in cancer development. In short, these studies have shown important roles for IL-6 signalling in tumour cell growth and survival, angiogenesis, immunomodulation of the tumour microenvironment, stromal cell activation, and ultimate disease progression. Given this background, we also consider the potential for therapeutic targeting of this system in cancer.

The AB loop of oncostatin M (OSM) determines species-specific signaling in humans and mice

The pleiotropic interleukin-6 (IL-6)-type cytokine oncostatin M (OSM) signals in multiple cell types, affecting processes such as cell differentiation, hematopoiesis, and inflammation. In humans, OSM exerts its effects through activation of either of two different heterodimeric receptor complexes, formed by glycoprotein 130 (gp130) and either OSM receptor (OSMR) or leukemia inhibitory factor receptor (LIFR). In contrast, the mouse OSM orthologue acts mainly through dimers containing OSMR and gp130 and shows limited activity through mouse LIFR. Despite their structural similarity, neither human nor mouse OSM signal through the other species' OSMR. The molecular basis for such species-specific signaling, however, remains poorly understood. To identify key molecular features of OSM that determine receptor activation in humans and mice, we generated chimeric mouse-human cytokines. Replacing regions within binding site III of murine OSM with the human equivalents showed that the cytokine's AB loop was critical for receptor selection. Substitutions of individual amino acids within this region demonstrated that residues Asn-37, Thr-40, and Asp-42 of the murine cytokine were responsible for limited LIFR activation and absence of human OSMR/LIFR signaling. In human OSM, Lys-44 appeared to be the main residue preventing mouse OSMR activation. Our data reveal that individual amino acids within the AB loop of OSM determine species-specific activities. These mutations might reflect a key step in the evolutionary process of this cytokine, in which receptor promiscuity gives way to ligand-receptor specialization.

The AB loop and D-helix in binding site III of human Oncostatin M (OSM) are required for OSM receptor activation

Oncostatin M (OSM) and leukemia inhibitory factor (LIF) are closely related members of the interleukin-6 (IL-6) cytokine family. Both cytokines share a common origin and structure, and both interact through a specific region, termed binding site III, to activate a dimeric receptor complex formed by glycoprotein 130 (gp130) and LIF receptor (LIFR) in humans. However, only OSM activates the OSM receptor (OSMR)-gp130 complex. The molecular features that enable OSM to specifically activate the OSMR are currently unknown. To define specific sequence motifs within OSM that are critical for initiating signaling via OSMR, here we generated chimeric OSM-LIF cytokines and performed alanine-scanning experiments. Replacement of the OSM AB loop within OSM's binding site III with that of LIF abrogated OSMR activation, measured as STAT3 phosphorylation at Tyr-705, but did not compromise LIFR activation. Correspondingly, substitution of the AB loop and D-helix in LIF with their OSM counterparts was sufficient for OSMR activation. The alanine-scanning experiments revealed that residues Tyr-34, Gln-38, Gly-39, and Leu-45 (in the AB loop) and Pro-153 (in the D-helix) had specific roles in activating OSMR but not LIFR signaling, whereas Leu-40 and Cys-49 (in the AB loop), and Phe-160 and Lys-163 (in the D-helix) were required for activation of both receptors. Because most of the key amino acid residues identified here are conserved between LIF and OSM, we concluded that comparatively minor differences in a few amino acid residues within binding site III account for the differential biological effects of OSM and LIF.

Interleukin-6 Family Cytokines

The interleukin (IL)-6 family cytokines is a group of cytokines consisting of IL-6, IL-11, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), oncostatin M (OSM), cardiotrophin 1 (CT-1), cardiotrophin-like cytokine (CLC), and IL-27. They are grouped into one family because the receptor complex of each cytokine contains two (IL-6 and IL-11) or one molecule (all others cytokines) of the signaling receptor subunit gp130. IL-6 family cytokines have overlapping but also distinct biologic activities and are involved among others in the regulation of the hepatic acute phase reaction, in B-cell stimulation, in the regulation of the balance between regulatory and effector T cells, in metabolic regulation, and in many neural functions. Blockade of IL-6 family cytokines has been shown to be beneficial in autoimmune diseases, but bacterial infections and metabolic side effects have been observed. Recent advances in cytokine blockade might help to minimize such side effects during therapeutic blockade.

Dissecting Interleukin-6 Classic- and Trans-Signaling in Inflammation and Cancer

Interleukin-6 is a cytokine synthesized by many cells in the human body. IL-6 binds to a membrane bound IL-6R, which is only present on hepatocytes, some epithelial cells and some leukocytes. The complex of IL-6 and IL-6R binds to the ubiquitously expressed receptor subunit gp130, which forms a homodimer and thereby initiates intracellular signaling via the JAK/STAT and the MAPK pathways. IL-6R expressing cells can cleave the receptor protein to generate a soluble IL-6R (sIL-6R), which can still bind IL-6 and can associate with gp130 and induce signaling even on cells, which do not express IL-6R. This paradigm has been called IL-6 trans-signaling whereas signaling via the membrane bound IL-6R is referred to as classic signaling. We have generated several molecular tools to differentiate between IL-6 classic- and trans-signaling and to analyze the consequence of cellular IL-6 signaling in vivo.

Interleukin-6 as a Multifunctional Regulator: Inflammation, Immune Response, and Fibrosis

Interleukin 6 (IL-6) is a 184-amino acid protein cytokine that is produced by many types of cells and is expressed during states of cellular stress, such as inflammation, infection, wound sites, and cancer. IL-6 levels may increase several thousand-fold in these states and may help to coordinate the response to dysregulation of tissue homeostasis. IL-6 acts through a membrane-bound IL-6 receptor (mIL-6R), which, together with a second receptor, glycoprotein 130 (gp130), leads to the initiation of intracellular signaling (classic signaling). Given that IL-6R is expressed on only a few types of cells, though all cells express gp130, direct stimulation by IL-6 is limited to cells that express mIL-6R. However, IL-6R is also produced as a soluble, secreted protein that, together with IL-6, can stimulate all gp130-expressing cells by a process termed IL-6 trans-signaling. IL-6 trans-signaling can be blocked without affecting IL-6 classic signaling through mIL-6R. IL-6 has major effects on the adaptive and innate immune system and on mesenchymal and stromal responses during inflammation. It promotes the development of pathogenic T-helper 17 T cells and the maturation of B lymphocytes. Many innate immune cells, neutrophils, and monocytes/macrophages produce and respond to IL-6, resulting in autocrine feedback loops that amplify inflammation. IL-6 has been implicated in the pathogenesis of fibrotic diseases in which IL-6 trans-signaling has been shown to stimulate the proliferation of fibroblasts and the release of procollagen and fibronectin.

Overexpression of the erythropoietin receptor in RAMA 37 breast cancer cells alters cell growth and sensitivity to tamoxifen

Erythropoietin (EPO) is the main regulator of erythropoiesis, and its receptor (EPOR) is expressed in various tissues, including tumors. Expression of EPOR in breast cancer tissue has been shown to correlate with expression of the estrogen receptor (ER). However, EPOR promotes proliferation in an EPO-independent manner. In patients with breast cancer, EPOR is associated with impaired tamoxifen response in ER-positive tumors, but not in ER-negative tumors. Furthermore, a positive correlation between EPOR/ER status and increased local cancer recurrence has been demonstrated, and EPOR expression is associated with G-protein coupled ER (GPER). Herein, we assessed the effects of EPOR on cell physiology and tamoxifen response in the absence of EPO stimulation using two cell lines that differ only in their EPOR expression status: RAMA 37 cells (low EPOR expression) and RAMA 37-28 cells (high EPOR expression). Alterations in cell growth, morphology, response to tamoxifen cytotoxicity, and EPOR-activated signal transduction were observed. RAMA 37 cells showed higher proliferation capacity without tamoxifen treatment, while RAMA 37-28 cells were more resistant to tamoxifen and proliferated more rapidly in the presence of tamoxifen. EPOR overexpression induced cell-morphology changes upon tamoxifen treatment, which resulted in the production of cell protrusions and subsequent cell death. Short-term treatment with tamoxifen (6 h) prompted RAMA 37 cells to acquired longer protrusions than RAMA 37-28 cells, which indicated a pre-apoptotic stage. Furthermore, prolonged treatment with tamoxifen (72 h) caused a greater reduction in RAMA 37 cell numbers, which indicated a higher rate of cell death. RAMA 37-28 cells showed prolonged activation of AKT signaling. We propose sustained AKT phosphorylation in EPOR-overexpressing cells as a mechanism that can lead to EPOR-induced tamoxifen resistance.

Synthekines are surrogate cytokine and growth factor agonists that compel signaling through non-natural receptor dimers

Cytokine and growth-factor ligands typically signal through homo- or hetero-dimeric cell surface receptors via Janus Kinase (JAK/TYK), or Receptor Tyrosine Kinase (RTK)-mediated trans-phosphorylation. However, the number of receptor dimer pairings occurring in nature is limited to those driven by natural ligands encoded within our genome. We have engineered synthethic cytokines (synthekines) that drive formation of cytokine receptor dimer pairings that are not formed by endogenous cytokines and that are not found in nature, and which activate distinct signaling programs. We show that a wide range of non-natural cytokine receptor hetero-dimers are competent to elicit a signaling output. We engineered synthekine ligands that assembled IL-2Rβ/IL-4Rα or IL-4Rα/IFNAR2 receptor heterodimers, that do not occur naturally, triggering signaling and functional responses distinct from those activated by the endogenous cytokines IL-2, IL-4, and IFN. Furthermore, hybrid synthekine ligands that dimerized a JAK/STAT cytokine receptor with a receptor tyrosine kinase (RTK) also elicited a signaling response. Synthekines represent a new family of synthetic ligands with pre-defined receptors, but 'orphan' functions, that enable the full combinatorial scope of dimeric signaling receptors encoded within the human genome to be exploited for basic research and drug discovery.

Characterization, promoter analysis and expression of the interleukin-6 gene in blunt snout bream, Megalobrama amblycephala

Interleukin-6 (IL-6) is one of the most important multifunctional cytokines, playing essential roles in mediating the innate and adaptive immune responses. In this study, il-6 gene and its promoter from blunt snout bream, Megalobrama amblycephala, were characterized, and its expression at the transcript level in healthy fish and after bacterial infection was determined by quantitative real-time PCR. The results showed that the M. amblycephala il-6 (Mamil-6) cDNA had an ORF of 699 bp, encoding 232 amino acids, and contained 9 instable motifs in the 3' UTR. The deduced MamIL-6 possessed a 24-amino acid signal peptide and was located in the cytoplasm. Although sequence alignment and phylogenetic analysis revealed that IL-6 is poorly conserved in vertebrates, the protein and genomic structure of il-6 gene was well conserved. Analysis of the Mamil-6 promoter revealed the presence of a conserved TATA box and six major cis-regulatory elements, including C/EBPβ (NF-IL6), AP-1, CRE, GRE, GATA and NF-κB binding sites. In healthy fish, Mamil-6 was the most abundant in the spleen. After Aeromonas hydrophila infection, Mamil-6 was significantly up-regulated in all 6 immune-related tissues examined, suggesting that Mamil-6 plays an important role in the blunt snout bream immune system.

Biological role of granulocyte macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF) on cells of the myeloid lineage

M-CSF and GM-CSF are 2 important cytokines that regulate macrophage numbers and function. Here, we review their known effects on cells of the macrophage-monocyte lineage. Important clues to their function come from their expression patterns. M-CSF exhibits a mostly homeostatic expression pattern, whereas GM-CSF is a product of cells activated during inflammatory or pathologic conditions. Accordingly, M-CSF regulates the numbers of various tissue macrophage and monocyte populations without altering their "activation" status. Conversely, GM-CSF induces activation of monocytes/macrophages and also mediates differentiation to other states that participate in immune responses [i.e., dendritic cells (DCs)]. Further insights into their function have come from analyses of mice deficient in either cytokine. M-CSF signals through its receptor (CSF-1R). Interestingly, mice deficient in CSF-1R expression exhibit a more significant phenotype than mice deficient in M-CSF. This observation was explained by the discovery of a novel cytokine (IL-34) that represents a second ligand of CSF-1R. Information about the function of these ligands/receptor system is still developing, but its complexity is intriguing and strongly suggests that more interesting biology remains to be elucidated. Based on our current knowledge, several therapeutic molecules targeting either the M-CSF or the GM-CSF pathways have been developed and are currently being tested in clinical trials targeting either autoimmune diseases or cancer. It is intriguing to consider how evolution has directed these pathways to develop; their complexity likely mirrors the multiple functions in which cells of the monocyte/macrophage system are involved.

The role of interleukin-6 signaling in nervous tissue

The cytokine interleukin-6 (IL-6) plays a critical role in the pathogenesis of inflammatory disorders and in the physiological homeostasis of neural tissue. Profound neuropathological changes, such as multiple sclerosis (MS), Parkinson's and Alzheimer's disease are associated with increased IL-6 expression in brain. Increased nocturnal concentrations of serum IL-6 are found in patients with impaired sleep whereas IL-6-deficient mice spend more time in rapid eye movement sleep associated with dreaming. IL-6 is crucial in the differentiation of oligodendrocytes, regeneration of peripheral nerves and acts as a neurotrophic factor. It exerts its cellular effects through two distinct pathways which include the anti-inflammatory pathway involving the membrane-bound IL-6 receptor (IL-6R) expressed on selective cells, including microglia, in a process known as classical signaling that is also critical for bacterial defense. In classical signaling binding of IL-6 to the membrane-bound IL-6R activates the β-receptor glycoprotein 130 (gp130) and subsequent down-stream signaling. The alternative, rather pro-inflammatory pathway, shown to mediate neurodegeneration in mice, termed trans-signaling, depends on a soluble form of the IL-6R that is capable of binding IL-6 to stimulate a response on distal cells that express gp130. A naturally occurring soluble form of gp130 (sgp130) has been identified that can specifically bind and neutralize the IL-6R/IL-6 complex. Thus, trans-signaling is blocked but classical signaling is completely unaffected. A modified, recombinant dimerized version of sgp130 (sgp130Fc) has successfully been used to block inflammatory processes in mice and may also be used in the clarification of IL-6 trans-signaling in neurological diseases.

Signaling via the CytoR/JAK/STAT/SOCS pathway: Emergence during evolution

Cell-cell signaling represents an essential hallmark of multicellular organisms, which necessarily require a means of communicating between different cell populations, particularly immune cells. Cytokine receptor signaling through the Janus kinase/Signal Transducer and Activator of Transcription/Suppressor of Cytokine Signaling (CytoR/JAK/STAT/SOCS) pathway embodies one important paradigm by which this is achieved. This pathway has been extensively studied in vertebrates and protostomes and shown to play fundamental roles in development and function of immune and other cells. However, our understanding of the origins of the individual pathway components and their assembly into a functional pathway has remained limited. This study examined the origins of each component of this pathway through bioinformatics analysis of key extant species. This has revealed step-wise accretion of individual components over a large evolutionary time-frame, but only in bilateria did a series of innovations allow their final coalescence to form a complete pathway. Assembly of the CytoR/JAK/STAT pathway has followed the retrograde model of pathway evolution, whereas addition of the SOCS component has adhered to the patchwork model.

Systematic Review of Pharmacological Properties of the Oligodendrocyte Lineage

Oligodendrogenesis and oligodendrocyte precursor maturation are essential processes during the course of central nervous system development, and lead to the myelination of axons. Cells of the oligodendrocyte lineage are generated in the germinal zone from migratory bipolar oligodendrocyte precursor cells (OPCs), and acquire cell surface markers as they mature and respond specifically to factors which regulate proliferation, migration, differentiation, and survival. Loss of myelin underlies a wide range of neurological disorders, some of an autoimmune nature—multiple sclerosis probably being the most prominent. Current therapies are based on the use of immunomodulatory agents which are likely to promote myelin repair (remyelination) indirectly by subverting the inflammatory response, aspects of which impair the differentiation of OPCs. Cells of the oligodendrocyte lineage express and are capable of responding to a diverse array of ligand-receptor pairs, including neurotransmitters and nuclear receptors such as γ-aminobutyric acid, glutamate, adenosine triphosphate, serotonin, acetylcholine, nitric oxide, opioids, prostaglandins, prolactin, and cannabinoids. The intent of this review is to provide the reader with a synopsis of our present state of knowledge concerning the pharmacological properties of the oligodendrocyte lineage, with particular attention to these receptor-ligand (i.e., neurotransmitters and nuclear receptor) interactions that can influence oligodendrocyte migration, proliferation, differentiation, and myelination, and an appraisal of their therapeutic potential. For example, many promising mediators work through Ca²⁺ signaling, and the balance between Ca²⁺ influx and efflux can determine the temporal and spatial properties of oligodendrocytes (OLs). Moreover, Ca²⁺ signaling in OPCs can influence not only differentiation and myelination, but also process extension and migration, as well as cell death in mature mouse OLs. There is also evidence that oligodendroglia exhibit Ca²⁺ transients in response to electrical activity of axons for activity-dependent myelination. Cholinergic antagonists, as well as endocannabinoid-related lipid-signaling molecules target OLs. An understanding of such pharmacological pathways may thus lay the foundation to allow its leverage for therapeutic benefit in diseases of demyelination.

The biology of interleukin-27 reveals unique pro- and anti-inflammatory functions in immunity

Interleukin (IL)-27 is a multifaceted heterodimeric cytokine with pronounced pro- and anti-inflammatory as well as immunoregulatory functions. It consists of the two subunits p28/IL-30 and Epstein Bar virus-induced protein 3 (EBI3). EBI3 functions as a soluble α-receptor, and IL-27 can therefore directly activate its target cells through a heterodimer of glycoprotein 130 (gp130) and WSX-1. Being a heterodimeric cytokine that signals through gp130, IL-27 is either grouped into the IL-6 or the IL-12 family of cytokines. Originally identified as an IL-12-like cytokine that induces proliferation of CD4+ T cells and production of IFN-γ more than ten years ago, subsequent research revealed a much broader role of IL-27 in inflammation, cancer development and regulation and differentiation of immune cells. In this review, we summarize the current biochemical and molecular knowledge about the signal transduction of IL-27. Based on this, we highlight functional overlaps and plasticity with other cytokines and cytokine receptors of the IL-6/IL-12 superfamily, and describe the important role of IL-27 with regard to the differentiation of T cells, infections and cancer development. We further discuss IL-27 as a therapeutic target and how specific blockade of this cytokine could be achieved.

Muscular interleukin-6 differentially regulates skeletal muscle adaptation to high-fat diet in a sex-dependent manner

Interleukin-6 (IL-6) is now known to be not only a major cytokine controlling the immune system but also basic physiological variables such as body weight and metabolism. We recently reported that muscle-specific interleukin-6 deletion influences body weight and body fat in a sex-dependent manner in mice. When compared with littermate floxed controls, males gained less weight whereas females gained more weight after a 12-week high-fat diet treatment (HFD). We herewith report gender-differences of HFD treatment on fast and slow skeletal muscle in muscle-specific IL-6 deficient mice. While gross muscle architecture was normal, in males, HFD resulted in an increased proportion of medium-large size myofibers which was prevented by muscle IL-6 deletion. No modifications of fiber size were observed in females. HFD induced a fiber-type switching in tibialis muscle, increasing the proportion of fast-oxidative fibers and decreasing the fast-glycolytic fibers in female mice which were dependent on muscle IL-6. No changes of fiber types were detected in males. Finally, HFD was associated with increased collagen deposition in both sexes and muscle types. However, this effect was only associated to the presence of muscular IL-6 only on the slow soleus muscle in males. The results demonstrate sex-dependent effects of both HFD and muscle IL-6 deficiency in skeletal muscle.

Innate immune regulation by STAT-mediated transcriptional mechanisms

The term innate immunity typically refers to a quick but non-specific host defense response against invading pathogens. The innate immune system comprises particular immune cell populations, epithelial barriers, and numerous secretory mediators including cytokines, chemokines, and defense peptides. Innate immune cells are also now recognized to play important contributing roles in cancer and pathological inflammatory conditions. Innate immunity relies on rapid signal transduction elicited upon pathogen recognition via pattern recognition receptors (PRRs) and cell:cell communication conducted by soluble mediators, including cytokines. A majority of cytokines involved in innate immune signaling use a molecular cascade encompassing receptor-associated Jak protein tyrosine kinases and STAT (signal transducer and activator of transcription) transcriptional regulators. Here, we focus on roles for STAT proteins in three major innate immune subsets: neutrophils, macrophages, and dendritic cells (DCs). While knowledge in this area is only now emerging, understanding the molecular regulation of these cell types is necessary for developing new approaches to treat human disorders such as inflammatory conditions, autoimmunity, and cancer.

Identification of a JAK/STAT pathway receptor domeless from Pacific white shrimp Litopenaeus vannamei

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway was known to participate in dozens of immune responses in organisms. Domeless, first identified in Drosophila melanogaster, is a unique receptor involved in invertebrate JAK/STAT pathway. In this study, a cytokine receptor (LvDOME) was identified in Litopenaeus vannamei. The LvDOME cDNA was 5178bp in length with an Open Reading Frame (ORF) of 4191bp. LvDOME contained two cytokine binding modules (CBMs) and three fibronectin-type-III-like (FNIII) domains, similar to most vertebrate IL-6 receptors. LvDOME was expressed highest in shrimp muscle and could be up-regulated in the late stage of white spot syndrome virus (WSSV) infection. LvDOME could significantly enhance the activity of the WSSV wsv069 gene promoter through acting on the STAT-binding motif, suggesting LvDOME could activate the JAK/STAT pathway. Moreover, knockdown of LvDOME resulted in lower cumulative mortality of shrimps and less WSSV copies, suggesting LvDOME may be hijacked by WSSV to benefit virus replication. To our knowledge, this is the first report on the receptor of JAK/STAT pathway in shrimp.

Tuning cytokine receptor signaling by re-orienting dimer geometry with surrogate ligands

Most cell-surface receptors for cytokines and growth factors signal as dimers, but it is unclear whether remodeling receptor dimer topology is a viable strategy to "tune" signaling output. We utilized diabodies (DA) as surrogate ligands in a prototypical dimeric receptor-ligand system, the cytokine Erythropoietin (EPO) and its receptor (EpoR), to dimerize EpoR ectodomains in non-native architectures. Diabody-induced signaling amplitudes varied from full to minimal agonism, and structures of these DA/EpoR complexes differed in EpoR dimer orientation and proximity. Diabodies also elicited biased or differential activation of signaling pathways and gene expression profiles compared to EPO. Non-signaling diabodies inhibited proliferation of erythroid precursors from patients with a myeloproliferative neoplasm due to a constitutively active JAK2V617F mutation. Thus, intracellular oncogenic mutations causing ligand-independent receptor activation can be counteracted by extracellular ligands that re-orient receptors into inactive dimer topologies. This approach has broad applications for tuning signaling output for many dimeric receptor systems.

Erythropoietin as a new therapeutic opportunity in brain inflammation and neurodegenerative diseases

Highly expressed Erythropoietin Receptor (EPO-R) has been detected in several nonhematopoietic hypoxic cells, including cells from different brain areas in response to many different types of cell injury. In brain, hypoxia-ischemia (HI) can induce a wide spectrum of biologic responses, where inflammation and apoptosis are the main protagonists. Inflammation, as a primary brain insult, can induce a chronic hypoxic condition, producing the continuous cycle of inflammation-hypoxia that increases the apoptotic-cell number. It has also been demonstrated that administration of erythropoietin (EPO) prevented the neuronal death induced by HI, as well as the induction of lipid peroxidation in the hippocampus in a rodent model of Alzheimer's disease. Anti-apoptotic, anti-inflammatory, anti-oxidant, and/or cell-proliferative effects of EPO, have been observed in all type of cells expressing EPO-R, resulting in a potential tool for neuroprotection, neuroreparation, or neurogenesis of brain damaged areas. The nasal route is an alternative way of drugs administration that has been successfully exploited for bypassing the blood brain barrier, and subsequently delivering EPO and other molecules to central nervous system. Intranasal administration of EPO could be a new therapeutic opportunity in several brain damages that includes hypoxia, inflammation, neurodegenerative process, and apoptosis.

Biology of IL-27 and its role in the host immunity against Mycobacterium tuberculosis

IL-27, a heterodimeric cytokine of IL-12 family, regulates both innate and adaptive immunity largely via Jak-Stat signaling. IL-27 can induce IFN-γ and inflammatory mediators from T lymphocytes and innate immune cells. IL-27 has unique anti-inflammatory properties via both Tr1 cells dependent and independent mechanisms. Here the role and biology of IL-27 in innate and adaptive immunity are summarized, with special interest with immunity against Mycobacterium tuberculosis.

Insights into cytokine-receptor interactions from cytokine engineering

Cytokines exert a vast array of immunoregulatory actions critical to human biology and disease. However, the desired immunotherapeutic effects of native cytokines are often mitigated by toxicity or lack of efficacy, either of which results from cytokine receptor pleiotropy and/or undesired activation of off-target cells. As our understanding of the structural principles of cytokine-receptor interactions has advanced, mechanism-based manipulation of cytokine signaling through protein engineering has become an increasingly feasible and powerful approach. Modified cytokines, both agonists and antagonists, have been engineered with narrowed target cell specificities, and they have also yielded important mechanistic insights into cytokine biology and signaling. Here we review the theory and practice of cytokine engineering and rationalize the mechanisms of several engineered cytokines in the context of structure. We discuss specific examples of how structure-based cytokine engineering has opened new opportunities for cytokines as drugs, with a focus on the immunotherapeutic cytokines interferon, interleukin-2, and interleukin-4.

Erythropoietin and cancer: the unintended consequences of anemia correction

Until 1990, erythropoietin (EPO) was considered to have a single biological purpose and action, the stimulation of red blood cell growth and differentiation. Slowly, scientific and medical opinion evolved, beginning with the discovery of an effect on endothelial cell growth in vitro and the identification of EPO receptors (EPORs) on neuronal cells. We now know that EPO is a pleiotropic growth factor that exhibits an anti-apoptotic action on numerous cells and tissues, including malignant ones. In this article, we present a short discussion of EPO, receptors involved in EPO signal transduction, and their action on non-hematopoietic cells. This is followed by a more detailed presentation of both pre-clinical and clinical data that demonstrate EPO’s action on cancer cells, as well as tumor angiogenesis and lymphangiogenesis. Clinical trials with reported adverse effects of chronic erythropoiesis-stimulating agents (ESAs) treatment as well as clinical studies exploring the prognostic significance of EPO and EPOR expression in cancer patients are reviewed. Finally, we address the use of EPO and other ESAs in cancer patients.

Therapeutic uses of anti-interleukin-6 receptor antibody

Cytokine-targeted therapy has generated a paradigm shift in the treatment of several immune-mediated diseases. Interleukin-6 (IL-6), which was initially identified as B-cell stimulatory factor 2, is a prototypical cytokine with wide-ranging biological effects on immune cells such as B and T cells, on hepatocytes, hematopoietic cells, vascular endothelial cells and on many others. IL-6 is thus crucially involved in the regulation of immune responses, hematopoiesis and inflammation. When infections and tissue injuries occur, IL-6 is promptly synthesized and performs a protective role in host defense against such stresses and traumas. However, excessive production of IL-6 during this emergent process induces potentially fatal complications, including systemic inflammatory response syndrome (SIRS), and dysregulated, persistently high expression of IL-6 causes the onset or development of various chronic immune-mediated disorders. For these reasons, IL-6 blockade was expected to become a novel therapeutic strategy for various diseases characterized by IL-6 overproduction. Indeed, worldwide clinical trials of tocilizumab, a humanized anti-IL-6 receptor monoclonal antibody, have successfully proved its outstanding efficacy against rheumatoid arthritis, juvenile idiopathic arthritis and Castleman disease, leading to the approval of tocilizumab for the treatment of these diseases. Moreover, various reports regarding off-label use of tocilizumab strongly suggest that it will be widely applicable for acute, severe complications such as SIRS and cytokine-release syndrome and other refractory chronic immune-mediated diseases.

Pierced Lasso Bundles are a new class of knot-like motifs

A four-helix bundle is a well-characterized motif often used as a target for designed pharmaceutical therapeutics and nutritional supplements. Recently, we discovered a new structural complexity within this motif created by a disulphide bridge in the long-chain helical bundle cytokine leptin. When oxidized, leptin contains a disulphide bridge creating a covalent-loop through which part of the polypeptide chain is threaded (as seen in knotted proteins). We explored whether other proteins contain a similar intriguing knot-like structure as in leptin and discovered 11 structurally homologous proteins in the PDB. We call this new helical family class the Pierced Lasso Bundle (PLB) and the knot-like threaded structural motif a Pierced Lasso (PL). In the current study, we use structure-based simulation to investigate the threading/folding mechanisms for all the PLBs along with three unthreaded homologs as the covalent loop (or lasso) in leptin is important in folding dynamics and activity. We find that the presence of a small covalent loop leads to a mechanism where structural elements slipknot to thread through the covalent loop. Larger loops use a piercing mechanism where the free terminal plugs through the covalent loop. Remarkably, the position of the loop as well as its size influences the native state dynamics, which can impact receptor binding and biological activity. This previously unrecognized complexity of knot-like proteins within the helical bundle family comprises a completely new class within the knot family, and the hidden complexity we unraveled in the PLBs is expected to be found in other protein structures outside the four-helix bundles. The insights gained here provide critical new elements for future investigation of this emerging class of proteins, where function and the energetic landscape can be controlled by hidden topology, and should be take into account in ab initio predictions of newly identified protein targets.

Biochemical efficacy of vitamin D in ameliorating endocrine and metabolic disorders in diabetic rats

CONTEXT

Due to the biochemical role of vitamin D (Vit D) in the endocrine system, especially its potential anti-inflammatory and immune-modulating properties, there is an increased interest in its potential role in the prevention and control of diabetes mellitus.

OBJECTIVE

This study evaluated the potential therapeutic efficacy of Vit D in averting the detrimental effects of both types of diabetes mellitus.

MATERIALS AND METHODS

A total of 50 male Wistar rats were allotted into five groups: a placebo group; a nongenetic model of type 1 diabetes in rats (T1D), injected with a single dose of streptozotocin (STZ; 65 mg/kg, ip); a nongenetic model of type 2 diabetes in rats (T2D), given a short-term high-fat diet followed by a single low dose of STZ (35 mg/kg, ip); fourth and fifth groups that were gastrogavaged with Vit D (10 IU/kg) three days after the induction of T1D and T2D, respectively, which was continued daily throughout the experiment.

RESULTS

Vit D (10 IU/kg/60 days) significantly (p < 0.05) decreased fasting plasma glucose, ketoacidosis (decreased non-esterified fatty acid and β-hydroxyl butyric acid), pro-inflammatory interleukin-6, HbA1c in T1D and T2D and insulin resistance index by 33% in T2D. Interestingly, Vit D significantly (p < 0.05) increased fasting plasma insulin by 144% in T1D, plasma Ca level, insulin sensitivity index, and β-cell function index in T1D and T2D.

DISCUSSION AND CONCLUSION

Vit D ameliorated the deleterious biochemical impact of diabetes mellitus, likely by increasing insulin secretion and sensitivity, ameliorating the β-cell function, and decreasing the number of pro-inflammatory cytokines and insulin resistance.

Challenging the state of the art in protein structure prediction: Highlights of experimental target structures for the 10th Critical Assessment of Techniques for Protein Structure Prediction Experiment CASP10

For the last two decades, CASP has assessed the state of the art in techniques for protein structure prediction and identified areas which required further development. CASP would not have been possible without the prediction targets provided by the experimental structural biology community. In the latest experiment, CASP10, more than 100 structures were suggested as prediction targets, some of which appeared to be extraordinarily difficult for modeling. In this article, authors of some of the most challenging targets discuss which specific scientific question motivated the experimental structure determination of the target protein, which structural features were especially interesting from a structural or functional perspective, and to what extent these features were correctly reproduced in the predictions submitted to CASP10. Specifically, the following targets will be presented: the acid-gated urea channel, a difficult to predict transmembrane protein from the important human pathogen Helicobacter pylori; the structure of human interleukin (IL)-34, a recently discovered helical cytokine; the structure of a functionally uncharacterized enzyme OrfY from Thermoproteus tenax formed by a gene duplication and a novel fold; an ORFan domain of mimivirus sulfhydryl oxidase R596; the fiber protein gene product 17 from bacteriophage T7; the bacteriophage CBA-120 tailspike protein; a virus coat protein from metagenomic samples of the marine environment; and finally, an unprecedented class of structure prediction targets based on engineered disulfide-rich small proteins.

Multifarious determinants of cytokine receptor signaling specificity

Cytokines play crucial roles in regulating immune homeostasis. Two important characteristics of most cytokines are pleiotropy, defined as the ability of one cytokine to exhibit diverse functionalities, and redundancy, defined as the ability of multiple cytokines to exert overlapping activities. Identifying the determinants for unique cellular responses to cytokines in the face of shared receptor usage, pleiotropy, and redundancy will be essential in order to harness the potential of cytokines as therapeutics. Here, we discuss the biophysical (ligand-receptor geometry and affinity) and cellular (receptor trafficking and intracellular abundance of signaling molecules) parameters that contribute to the specificity of cytokine bioactivities. Whereas the role of extracellular ternary complex geometry in cytokine-induced signaling is still not completely elucidated, cytokine-receptor affinity is known to impact signaling through modulation of the stability and kinetics of ternary complex formation. Receptor trafficking also plays an important and likely underappreciated role in the diversification of cytokine bioactivities but it has been challenging to experimentally probe trafficking effects. We also review recent efforts to quantify levels of intracellular signaling components, as second messenger abundance can affect cytokine-induced bioactivities both quantitatively and qualitatively. We conclude by discussing the application of protein engineering to develop therapeutically relevant cytokines with reduced pleiotropy and redirected biological functionalities.