[Cytokines in bone diseases. What is cytokine?]

Cytokines have an essential role for cell-cell communication. They can regulate cell proliferation, differentiation, survival, and function. Interaction of cell surface receptor with cytokines is necessary for control of physiological responses. Activation of cytokine receptors transduces specific signal in the receptor-expressing cells, resulting that cytokines can regulate specific cell population. Thus, cytokines contribute directly or indirectly to morphogenesis, host defense and immune response, play critical roles for homeostasis and development.

Integrative genomic analyses on IL28RA, the common receptor of interferon-lambda1, -lambda2 and -lambda3

Interferon (IFN)-lambdas, including INF-lambda1, -lambda2, and -lambda3, are a newly described group of cytokines distantly related to the type I IFNs and IL-10 family members. IFN-lambda1, -lambda2, and -lambda3 bind to the same receptor (known as IL28RA) to exert their antiviral, antitumor and immunomodulatory effects. Here, we identified IL28RA genes from the genome of human, chimpanzee, macaque, orangutan, mouse, horse, rat, dog, chicken, and found that only one IL28RA existed in each genome. All the identified IL28RAs are single-pass type I membrane proteins except chicken IL28RA. They belong to the type II cytokine receptor family and contain one fibronectin type-III domain. We found human IL28RA was expressed in lymphs, testes, lymphoma, teratocarcinoma, pediatric pre-B cell acute lymphoblastic leukemia, germinal center B cells, embryonic stem cells, fetal lung, and also expressed in bladder, blood and breast cancers, glioma, head and neck cancer and lung cancer tissues. Three tumor-related transcriptional factor binding sites (AP-2, c-Jun and P53) were identified within the 1.0-kb regions upstream of the transcriptional start site of human IL28RA. Meta-analysis of the prognostic value of IL28RA genes in various cancers found that the expression of IL28RA was indeed related to the cancer prognosis in certain cancers. The STAT1 binding sites in the promoter region of IL28RA implied a specific mechanism for the amplifying effects of IFN-lambdas. The LyF-1 binding sites in the promoter region of IL28RA imply that IFN-lambdas were involved in the differentiation of early B and T cells.

Protein hormones and immunity

A number of observations and discoveries over the past 20 years support the concept of important physiological interactions between the endocrine and immune systems. The best known pathway for transmission of information from the immune system to the neuroendocrine system is humoral in the form of cytokines, although neural transmission via the afferent vagus is well documented also. In the other direction, efferent signals from the nervous system to the immune system are conveyed by both the neuroendocrine and autonomic nervous systems. Communication is possible because the nervous and immune systems share a common biochemical language involving shared ligands and receptors, including neurotransmitters, neuropeptides, growth factors, neuroendocrine hormones and cytokines. This means that the brain functions as an immune-regulating organ participating in immune responses. A great deal of evidence has accumulated and confirmed that hormones secreted by the neuroendocrine system play an important role in communication and regulation of the cells of the immune system. Among protein hormones, this has been most clearly documented for prolactin (PRL), growth hormone (GH), and insulin-like growth factor-1 (IGF-I), but significant influences on immunity by thyroid-stimulating hormone (TSH) have also been demonstrated. Here we review evidence obtained during the past 20 years to clearly demonstrate that neuroendocrine protein hormones influence immunity and that immune processes affect the neuroendocrine system. New findings highlight a previously undiscovered route of communication between the immune and endocrine systems that is now known to occur at the cellular level. This communication system is activated when inflammatory processes induced by proinflammatory cytokines antagonize the function of a variety of hormones, which then causes endocrine resistance in both the periphery and brain. Homeostasis during inflammation is achieved by a balance between cytokines and endocrine hormones.

High dynamic range characterization of the trauma patient plasma proteome

Although human plasma represents an attractive sample for disease biomarker discovery, the extreme complexity and large dynamic range in protein concentrations present significant challenges for characterization, candidate biomarker discovery, and validation. Herein we describe a strategy that combines immunoaffinity subtraction and subsequent chemical fractionation based on cysteinyl peptide and N-glycopeptide captures with two-dimensional LC-MS/MS to increase the dynamic range of analysis for plasma. Application of this "divide-and-conquer" strategy to trauma patient plasma significantly improved the overall dynamic range of detection and resulted in confident identification of 22,267 unique peptides from four different peptide populations (cysteinyl peptides, non-cysteinyl peptides, N-glycopeptides, and non-glycopeptides) that covered 3,654 different proteins with 1,494 proteins identified by multiple peptides. Numerous low abundance proteins were identified, exemplified by 78 "classic" cytokines and cytokine receptors and by 136 human cell differentiation molecules. Additionally a total of 2,910 different N-glycopeptides that correspond to 662 N-glycoproteins and 1,553 N-glycosylation sites were identified. A panel of the proteins identified in this study is known to be involved in inflammation and immune responses. This study established an extensive reference protein database for trauma patients that provides a foundation for future high throughput quantitative plasma proteomic studies designed to elucidate the mechanisms that underlie systemic inflammatory responses.

Interleukins and STAT signaling

Metazoan cells secrete small proteins termed cytokines that execute a variety of biological functions essential for the survival of organisms. Binding of cytokines that belong to the hematopoietin- or interferon-family, to their cognate receptors on the surface of target cells, induces receptor aggregation, which in turn sequentially triggers tyrosine-phosphorylation-dependent activation of receptor-associated Janus-family tyrosine kinases (JAKs), receptors, and signal transducers and activators of transcription (STATs). Phosphorylated STATs form dimers that migrate to the nucleus, bind to cognate enhancer elements and activate transcription of target genes. Each cytokine activates a specific set of genes to execute its biological functions with a certain degree of redundancy. Cytokine signals are, in general, transient in nature. Therefore, under normal physiological conditions, initiation and attenuation of cytokine signals are tightly controlled via multiple cellular and molecular mechanisms. Aberrant activation of cytokine signaling pathways is, however, found under a variety of patho-physiological conditions including cancer and immune diseases.

Full house: 12 receptors for 27 cytokines

With the sequencing of the human genome nearing completion, it appears that all members of the class II cytokine receptor family (CRF2) have been identified and partially characterized. The entire family is composed of exactly one dozen members. Eleven of them combine as various heterodimers to transduce signals across the cellular membrane for 27 cytokines divided into four structurally related groups: 6 cytokines of the IL-10 family, 17 type I IFNs, 1 type II IFN and 3 IFN-lambdas. The last CRF2 member is the soluble receptor which can neutralize the action of one of the cytokines of the IL-10 family, IL-22. Although the extracellular domains of all CRF2 proteins reveal primary and structural homology, their intracellular domains are very dissimilar. Nevertheless, signaling events induced through various combinations of CRF2 subunits partially overlap, leading to the induction of overlapping but cytokine-specific biological activities.

G protein-coupled receptor genes in the FANTOM2 database

G protein-coupled receptors (GPCRs) comprise the largest family of receptor proteins in mammals and play important roles in many physiological and pathological processes. Gene expression of GPCRs is temporally and spatially regulated, and many splicing variants are also described. In many instances, different expression profiles of GPCR gene are accountable for the changes of its biological function. Therefore, it is intriguing to assess the complexity of the transcriptome of GPCRs in various mammalian organs. In this study, we took advantage of the FANTOM2 (Functional Annotation Meeting of Mouse cDNA 2) project, which aimed to collect full-length cDNAs inclusively from mouse tissues, and found 410 candidate GPCR cDNAs. Clustering of these clones into transcriptional units (TUs) reduced this number to 213. Out of these, 165 genes were represented within the known 308 GPCRs in the Mouse Genome Informatics (MGI) resource. The remaining 48 genes were new to mouse, and 14 of them had no clear mammalian ortholog. To dissect the detailed characteristics of each transcript, tissue distribution pattern and alternative splicing were also ascertained. We found many splicing variants of GPCRs that may have a relevance to disease occurrence. In addition, the difficulty in cloning tissue-specific and infrequently transcribed GPCRs is discussed further.

IFN-lambdas mediate antiviral protection through a distinct class II cytokine receptor complex

We report here the identification of a ligand-receptor system that, upon engagement, leads to the establishment of an antiviral state. Three closely positioned genes on human chromosome 19 encode distinct but paralogous proteins, which we designate interferon-lambda1 (IFN-lambda1), IFN-lambda2 and IFN-lambda3 (tentatively designated as IL-29, IL-28A and IL-28B, respectively, by HUGO). The expression of IFN-lambda mRNAs was inducible by viral infection in several cell lines. We identified a distinct receptor complex that is utilized by all three IFN-lambda proteins for signaling and is composed of two subunits, a receptor designated CRF2-12 (also designated as IFN-lambdaR1) and a second subunit, CRF2-4 (also known as IL-10R2). Both receptor chains are constitutively expressed on a wide variety of human cell lines and tissues and signal through the Jak-STAT (Janus kinases-signal transducers and activators of transcription) pathway. This receptor-ligand system may contribute to antiviral or other defenses by a mechanism similar to, but independent of, type I IFNs.

Typing of multiple single nucleotide polymorphisms in cytokine and receptor genes using SNaPshot

Associations have been described between polymorphisms in cytokine genes and severity of autoimmune diseases, outcome of infectious disease, and outcome following transplantation. Many methods now exist for typing single nucleotide polymorphisms (SNPs) and these can be applied to typing cytokine gene and cytokine receptor gene variation. A system for typing multiple cytokine and receptor gene polymorphisms using a primer extension method, SNaPshot (Applied Biosystems, Foster City, CA, USA), has been assessed. The development of this methodology may enable other laboratories to type for cytokine SNPs in different populations and facilitate research into the effect of genetic polymorphism in the cytokine network in transplantation and disease.

International Union of Pharmacology. XXX. Update on chemokine receptor nomenclature

An update of the International Union of Pharmacology nomenclature for chemokines is outlined, defining one new receptor type, CXCR6, and disqualifying the putative receptor, CCR11.

Molecular cloning of a human novel type I cytokine receptor related to delta1/TSLPR

In a search for a human sequence related to a recently identified type I cytokine receptor delta1, which turned out to be a receptor subunit for a cytokine called TSLP, we have now identified a novel human type I cytokine receptor from a human T lymphocyte cDNA library. The deduced amino acid sequence of 371 residues has a typical signal sequence and a membrane-spanning region. The mature protein is predicted to have a molecular mass of 39,698 Da. The N-terminal extracellular region contains two fibronectin type III-like domains, four conserved cysteine residues, and a WSXWS box-like motif. The C-terminal intracellular region contains box 1 and box 2-like motifs. Thus, it has common characteristics of type I cytokine receptor family members, and we tentatively termed this protein CRLF2, which stands for cytokine receptor-like factor 2. Northern blot analysis revealed CRLF2 mRNA in liver, kidney, heart, and skeletal muscle. The fetal liver also expresses CRLF2 transcripts. The gene for CRLF2 was mapped to the pseudoautosomal region, Xp22.3 and Yp11.3 by FISH analysis, a region where genes encoding the IL-3 receptor alpha and the GM-CSF receptor alpha chains are also located. The biological function of this newly identified receptor is now under investigation.

Cloning and characterization of IL-22 binding protein, a natural antagonist of IL-10-related T cell-derived inducible factor/IL-22

The class II cytokine receptor family includes the receptors for IFN-alphabeta, IFN-gamma, IL-10, and IL-10-related T cell-derived inducible factor/IL-22. By screening genomic DNA databases, we identified a gene encoding a protein of 231 aa, showing 33 and 34% amino acid identity with the extracellular domains of the IL-22 receptor and of the IL-20R/cytokine receptor family 2-8, respectively, but lacking the transmembrane and cytoplasmic domains. A lower but significant sequence identity was found with other members of this family such as the IL-10R (29%), cytokine receptor family 2-4/IL-10Rbeta (30%), tissue factor (26%), and the four IFN receptor chains (23-25%). This gene is located on chromosome 6q24, at 35 kb from the IFNGR1 gene, and is expressed in various tissues with maximal expression in breast, lungs, and colon. The recombinant protein was found to bind IL-10-related T cell-derived inducible factor/IL-22, and to inhibit the activity of this cytokine on hepatocytes and intestinal epithelial cells. We propose to name this natural cytokine antagonist IL-22BP for IL-22 binding protein.

Signaling by type I and II cytokine receptors: ten years after

Discovered during the past ten years, Janus kinases and signal transducers and activators of transcription have emerged as critical elements in cytokine signaling and immunoregulation. Recently, knockout mice for all the members of these families have been generated, with remarkably specific outcomes. Equally exciting is the discovery of a new class of inhibitors, the suppressor of cytokine signaling family. The phenotypes of mice deficient in these molecules are also striking, underscoring the importance of negative regulation in cytokine signaling.

[Signal of the cytoplasmic regions of leukemia inhibitory factor receptor (LIFR) alpha-subunit and gp130 involves Stat3 activation in leukemic U937 cells]

OBJECTIVE

In order to understand the mechanism of proliferation and differentiation of leukemia cells, we investigate the relation between the cytoplasmic regions LIFR alpha-subunit and gp130 and the transcription activator Stat3 in human leukemic U937 cells.

METHODS

The cytoplasmic domain was each truncated from the LIFR alpha-subunit and gp130. The truncated forms of LIFR alpha-subunit(gp190EX) and gp130 (gp130EX) which can compete with the wild type receptor for binding to leukemia inhibitory factor (LIF) were expressed on the membrane of U937 cells. The level of Stat 3 and its phosphorylation were estimated by immunoblotting.

RESULTS

The increased level of Stat3 and its decreased tyrosine phosphorylation were detected in each group of gp130EX and gp190EX as compared with that in the wild type receptor subunit group.

CONCLUSION

The cytoplasmic domains of both LIFR alpha subunit and gp130 involve the induction of Stat3 phosphorylation in U937 cells.

Cytoplasmic and nuclear cytokine receptor complexes

Much of our understanding on how hormones and cytokines transmit their message into the cell is based on the receptor activation at the plasma membrane. Many experimental in vitro models have established the paradigm for cytokine action based upon such activation of their cell surface receptor. The signaling from the plasma membrane activated cytokine receptor is driven to the nucleus by a rapid ricochet of protein phosphorylation, ultimately integrated as a differentiative, proliferative, or transcriptional message. The Janus kinase (JAK)--signal transducers and activators of transcription (STAT) pathway that was first thought to be cytokine receptor specific now appears to be activated by other noncytokine receptors. Also, evidence is accumulating showing that cytokines modulate the signal transduction machinery of the tyrosine kinase receptors and that of the heterotrimeric guanosine triphosphate (GTP)-binding protein-coupled receptors. Thus cytokine receptor signaling has become much more complex than originally hypothesized, challenging the established model of specificity of the action of a given cytokine. This review is focused on another level of complexity emerging within cytokine receptor superfamily signaling. Over the past 10 years, data from different laboratories have shown that cytokines and their receptors localize to intracellular compartments including the nucleus, and, in some cases, biological responses have been correlated with this unexpected location, raising the possibility that cytokines act as their own messenger through inter-actions with nuclear proteins. Thus, the interplay between cytokine receptor engagement and cellular signaling turns out to be more dynamic than originally suspected. The mechanisms and regulations of intracellular translocation of the cytokines, their receptors, and their signaling proteins are discussed in the context that such compartmentalization provides some of the specificity of the responses mediated by each cytokine.

[Classification of cytokine receptor superfamily and signal transduction--structural feature and functional property]

Cytokines are groups of protein mediators that are involved in cell to cell communication and are classified into several distinct families based on their receptor structures. The class I cytokine receptor family includes most of interleukins and colony stimulating factors receptors and shares a conserved extracellular motif with homology to the fibronectin type III domain. While they do not have any intrinsic enzymatic activity, they bind a member of JAK family kinases. The receptors form a homo- or hetero-multimer by cytokine binding and activate the JAKs associated with the receptor. There are some groups of cytokines which exhibit similar functions by sharing the same receptor subunit.

Leptin receptor signal transduction: OBRa and OBRb of fa type

We report herein the characterization of activities of signal transduction for three types of leptin receptors (OBRs) from rats, the OBRa, OBRb, and OBRb with fa mutation (OBRb-fa), by measurement of the levels of tyrosine phosphorylation of STAT3 (signal transducers and activators of transcription 3) and MAPK (mitogen-activated protein kinase), which are induced by leptin stimulation of CHO cells stably expressing the OBR (CHO-OBRb, CHO-OBRa, or CHO-OBRb-fa cells). As the result of leptin stimulation, enhanced levels of tyrosine phosphorylation of STAT3 and MAPK were detected in CHO-OBRb cells. In CHO-OBRb-fa cells, enhancement levels for both were lower than those in CHO-OBRb cells. In CHO-OBRa cells, only the phosphorylation of MAPK was detected. These data suggest that these reduced signaling activities cause obesity in fa/fa rats and that OBRa, which has been generally thought to be inactive at signaling, actually transmits signals through the MAPK pathway.

Cloning and characterization of a novel class I cytokine receptor

The human gp130 cDNA sequence was used as a query to search an expressed sequence tag database (dbEST) to identify cDNA sequences with similarity to the cytokine class I receptor family. A novel class I cytokine receptor was identified in a human infant brain cDNA library and was named WSX-1. Full-length cDNA sequences for human and murine WSX-1 were isolated and characterized. The WSX-1 cDNA encodes a 636 amino acid transmembrane protein with an extracellular domain of 482 amino acids and a cytoplasmic domain of 96 amino acids. The structure of the WSX-1 protein most closely resembles that of gp130. Northern blot analysis indicates high levels of expression in thymus, spleen, lymph node, and peripheral blood leukocytes, suggesting a role for WSX-1 in modulation of the immune response.

Classification of cytokines according to the receptor code

A simple classification of cytokines is presented. It is based on voluminous information available from published papers of many outstanding researchers of the cytokines and their receptors and/or summarized by experts in this field. The cytokines are divided into 7 families according to their receptor code. Such arrangement of apparently different cytokines may explain the biological significance of pleiotropy and redundancy. Furthermore, it may stimulate the development of the comprehensive classification of cytokines together with classical hormones, neuromediators, neuromodulators and related substances that participate in complex biological communication system.

Dual oncostatin M (OSM) receptors. Cloning and characterization of an alternative signaling subunit conferring OSM-specific receptor activation

Oncostatin M (OSM) is a cytokine whose structural and functional features are similar to other members of the interleukin (IL)-6 family of cytokines (IL-6, IL-11, leukemia inhibitory factor (LIF), granulocyte colonystimulating factor, ciliary neurotrophic factor, and cardiotrophin-1), many of which utilize gp130 as a common receptor subunit. A biologically active OSM receptor has been previously described that consists of a heterodimer of leukemia inhibitory factor receptor (LIFR) and gp130. This LIFR.gp130 complex is also a functional receptor for LIF. We have cloned and characterized an alternative subunit (OSMRbeta) for an OSM receptor complex (a heterodimer of gp130 and OSMRbeta) that is activated by OSM but not by LIF. The signaling capability of specific receptor subunit combinations was analyzed by independent assays measuring cell proliferation or induction of acute phase protein synthesis. Our results demonstrate that both LIF and OSM cause tyrosine phosphorylation and activation of the gp130.LIFR combination, but the gp130.OSMRbeta complex is activated by OSM only. OSM-induced cellular responses, initiated through low affinity binding to gp130, are mediated by two heterodimeric receptor complexes that utilize alternative signal transducing subunits that confer different cytokine specificities to the receptor complex.

Keratinocytes and cytokine/growth factors

Cytokines are polypeptide growth factors produced by most nucleated cells in the body, including epithelial cells, keratinocytes, and Langerhans cells in the skin. Cytokines can be classified into interleukins, tumor necrosis factors, chemokines, colony-stimulating factor, interferons, and growth factors. Like classic hormones, cytokines bind to specific receptors to transmit their messages to target cells. Cytokine receptors can be divided into three cytokine receptor superfamilies: the immunoglobulin superfamily, the hematopoietin family, and the tumor necrosis factor family. Following cytokine/cytokine-receptor binding (first messenger), a signal transduction pathway is initiated. Factors affecting homeostasis in the skin and oral mucosa include a delicate balance between cytokines/cytokine-receptors and their antagonists. An imbalance in these variables can influence the development of cutaneous and oral diseases-such as lichen planus, autoimmune disorders, and some neoplastic processes- and can affect wound healing. Potential uses of cytokines include cancer and antiviral therapy.

[The classes, structures, functions and signaling transduction of cytokine receptors]

There are many kinds of cytokine receptors that belong to different receptor families. Most cytokine receptors function as: (1) receptor tyrosine kinase and tyrosine-kinase-associated receptor; (2) receptor serine/threonine kinase; (3) G-protein linked receptor. Following binding with cytokines and activation, the receptors trigger different cascade of intracellular protein phosphorylation to transduction signals, thereby altering the cell's pattern of gene expression and leading to biological effects.

Cytokine mediators of immunity and inflammation

The remarkable advances in molecular and cell biology occurring over the past four decades have served the cause of surgical science well. Our understanding of basic disease mechanisms and insights into potential new therapeutic strategies have occurred at a staggering pace. Perhaps nowhere in surgical biology are these mechanistic insights and therapeutic prospects more evident than in research defining the cytokine mediators of inflammation, injury, and repair. These proteins are secreted to some degree by virtually all immune cell types as well as by a diverse array of other nucleated cells, and their functions encompass a regulatory role on and among many components of the immune system. Such intense interest is well deserved because abnormalities or dysregulation of tissue and wound repair as well as of natural (innate) or specific (acquired) immune function underlie much of the morbidity and mortality associated with surgical practice. Indeed, it is evident that the insights gained from the study of such inflammatory mediators cross virtually every specialty of surgery, from the acute sequelae of severe injury and invasive infection to the chronic manifestations of benign and malignant processes.