Carbohydrate recognition site of interleukin-2 in relation to cell proliferation

Ancient Cytokine Interleukin 15-Like (IL-15L) Induces a Type 2 Immune Response

Related interleukin-2, -15, and -15-like (IL-2, -15, and -15L) are ancient cytokines, with all three genes surviving in extant fish and some mammals. The present study is the first to identify IL-15L functions, namely in rainbow trout. In isolated trout splenocytes, and in vivo, purified recombinant IL-15L+IL-15Rα molecules induced expression of IL-4 and IL-13 homologs, which are markers of type 2 immunity. In contrast, trout IL-15 stimulated type 1 immunity markers, thus IL-15 and IL-15L can have opposing functions. Trout IL-15L was more dependent on "in trans" presentation by the receptor chain IL-15Rα than IL-15, and stimulated CD4^-CD8^-(IgM^-) lymphocytes from thymus and spleen. We propose an important role for IL-15L early in the type 2 immunity cytokine cascade. Trout IL-2 and IL-15 exhibited features reminiscent of their mechanistic and functional dichotomy observed in mammals; for example, IL-15 but not IL-2 required a receptor alpha chain (only IL-15Rα in the case of fish) for its stability, and only IL-15 was efficient in stimulating lymphocytes from mucosal tissues. Data suggest that IL-15L and IL-15 may be particularly effective in stimulating innate lymphocyte type 2 cells (ILC2) and natural killer (NK) cells, respectively, but further identification of the cell types is needed. An interesting finding different from in mammals was the efficient stimulation of CD4⁺CD8⁺ thymocytes by IL-2. In short, this study presents fundamental information on the evolution of the IL-2/15/15L cytokine family.

Pressuromodulation at the cell membrane as the basis for small molecule hormone and peptide regulation of cellular and nuclear function

Building on recent knowledge that the specificity of the biological interactions of small molecule hydrophiles and lipophiles across microvascular and epithelial barriers, and with cells, can be predicted on the basis of their conserved biophysical properties, and the knowledge that biological peptides are cell membrane impermeant, it has been further discussed herein that cellular, and thus, nuclear function, are primarily regulated by small molecule hormone and peptide/factor interactions at the cell membrane (CM) receptors. The means of regulating cellular, and thus, nuclear function, are the various forms of CM Pressuromodulation that exist, which include Direct CM Receptor-Mediated Stabilizing Pressuromodulation, sub-classified as Direct CM Receptor-Mediated Stabilizing Shift Pressuromodulation (Single, Dual or Tri) or Direct CM Receptor-Mediated Stabilizing Shift Pressuromodulation (Single, Dual or Tri) cum External Cationomodulation (≥3+ → 1+); which are with respect to acute CM receptor-stabilizing effects of small biomolecule hormones, growth factors or cytokines, and also include Indirect CM- or CM Receptor-Mediated Pressuromodulation, sub-classified as Indirect 1ary CM-Mediated Shift Pressuromodulation (Perturbomodulation), Indirect 2ary CM Receptor-Mediated Shift Pressuromodulation (Tri or Quad Receptor Internal Pseudo-Cationomodulation: SS 1+), Indirect 3ary CM Receptor-Mediated Shift Pressuromodulation (Single or Dual Receptor Endocytic External Cationomodulation: 2+) or Indirect (Pseudo) 3ary CM Receptor-Mediated Shift Pressuromodulation (Receptor Endocytic Hydroxylocarbonyloetheroylomodulation: 0), which are with respect to sub-acute CM receptor-stabilizing effects of small biomolecules, growth factors or cytokines. As a generalization, all forms of CM pressuromodulation decrease CM and nuclear membrane (NM) compliance (whole cell compliance), due to pressuromodulation of the intracellular microtubule network and increases the exocytosis of pre-synthesized vesicular endogolgi peptides and small molecules as well as nuclear-to-rough endoplasmic reticulum membrane proteins to the CM, with the potential to simultaneously increase the NM-associated chromatin DNA transcription of higher molecular weight protein forms, secretory and CM-destined, mitochondrial and nuclear, including the highest molecular weight nuclear proteins, Ki67 (359 kDa) and Separase (230 kDa), with the latter leading to mitogenesis and cell division; while, in the case of growth factors or cytokines with external cationomodulation capability, CM Receptor External Cationomodulation of CM receptors (≥3+ → 1+) results in cationic extracellular interaction (≥3+) with extracellular matrix heparan sulfates (≥3+ → 1+) concomitant with lamellopodesis and cell migration. It can be surmised that the modulation of cellular, and nuclear, function is mostly a reactive process, governed, primarily, by small molecule hormone and peptide interactions at the cell membrane, with CM receptors and the CM itself. These insights taken together, provide valuable translationally applicable knowledge.

The immunomodulating roles of glycoproteins in epithelial ovarian cancer

The complexity of the immune system demands an intricate defense mechanism by tumors. Ovarian and other tumors employ specific glycoproteins and the associated glycan sequences to modulate immune responses. Glycoproteins enable tumor cells that express or secrete these molecules to evade immune cell attack and induce the immune system to promote tumor growth. This review focuses first on the immune environment in ovarian cancer, and the mechanisms of activation and inhibition that immune cells undergo in order to either attack or ignore a target cell. Next we illustrate the immunomodulatory roles of ovarian cancer-associated glycans and glycoproteins in 1. preventing immune synapse formation, 2. serving as ligands of immune cell receptors, 3. scavenging cytokines and chemokines, and 4. participating in the formation of autoantibodies against the tumor. The importance of these immunomodulating strategies from the view points of understanding the tumor immunology of ovarian tumors, potential origin of such mechanisms, and specific strategies to circumvent the glycoconjugate-mediated suppression of immune responses is discussed in this review.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update covering the period 2001-2002

This review is the second update of the original review on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates that was published in 1999. It covers fundamental aspects of the technique as applied to carbohydrates, fragmentation of carbohydrates, studies of specific carbohydrate types such as those from plant cell walls and those attached to proteins and lipids, studies of glycosyl-transferases and glycosidases, and studies where MALDI has been used to monitor products of chemical synthesis. Use of the technique shows a steady annual increase at the expense of older techniques such as FAB. There is an increasing emphasis on its use for examination of biological systems rather than on studies of fundamental aspects and method development and this is reflected by much of the work on applications appearing in tabular form.

Perlecan: a major IL-2-binding proteoglycan in murine spleen

Although interleukin-2 (IL-2) is typically considered a soluble cytokine, our laboratory has shown that the availability of IL-2 in lymphoid tissues is regulated, in part, by an association with heparan sulfate glycosaminoglycan. Heparan sulfate is usually found in proteoglycan form, in which the heparan sulfate chains are covalently linked to a specific core protein. We now show that perlecan is one of the major IL-2-binding heparan sulfate proteoglycans in murine spleen. IL-2 binds perlecan via heparan sulfate chains, as enzymatic removal of heparan sulfate from splenic perlecan abolishes its ability to bind IL-2. Furthermore, we demonstrate that perlecan-bound IL-2 supports the proliferation of an IL-2-dependent cell line. Identification of perlecan as a major heparan sulfate proteoglycan that binds IL-2 has implications for both the localization and regulation of IL-2 in vivo.

IL-2 signals through Sgk1 and inhibits proliferation and apoptosis in kidney cancer cells

The interleukin-2 is a cytokine that is essential for lymphocytic survival and function. Ectopic expression of the IL-2 receptor in epithelial tissues has been reported previously, although the functional significance of this expression is still being investigated. We provided novel structural and functional information on the expression of the IL-2 receptor in kidney cancer cells and in other normal and neoplastic human epithelial tissues. In A-498 kidney cancer cells, we showed that IL-2 binding to its own receptor triggers a signal transduction pathway leading to the inhibition of proliferation and apoptosis. We found that the inhibition of proliferation is associated with Erk1/2 dephosphorylation, whereas the survival signals appear to be mediated by Sgk1 activation. This investigation focuses on the IL-2 induced regulation of Sgk1 and describes a role of the IL-2 receptor and Sgk1 in the regulation of epithelial tumor cell death and survival.

Gamma chain receptor interleukins: evidence for positive selection driving the evolution of cell-to-cell communicators in the mammalian immune system

The interleukin-2 receptor (IL-2R) gamma chain, or common gamma chain (gammac), is the hub of a protein interaction network in the mammalia that is central to defense against disease. It is the indispensable subunit of the functional receptor complexes for a group of interleukins known as the gamma-chain-dependent interleukins (IL-2, IL-4, -7, -9, -15, and -21). The gammac links these proteins through their interaction with it and their competition for its recruitment. The gammac-dependent interleukins also interact with each other to either enhance or suppress expression through manipulation of expression of receptor subunits. Given the influence of protein-protein interactions on evolution, such as those documented for many genes including the reproductive proteins of the sperm and egg coat, here we have asked whether there is a common thread in the evolution of these interleukins. Our findings indicate that positive selection has acted by fixing a large number of amino acid replacement mutations in every single one of these interleukins, this adaptive evolution is also observed in a lineage-specific manner. Crucially, however, there does not appear to have ever been an instance of adaptive evolution in the gammac chain itself, thereby providing an insight into the evolution of this hub protein. These findings highlight the importance of adaptive evolutionary events in the evolution of this central network in the immune system and suggest underlying causes for differences in defense responses in the mammalia.

The carbohydrate recognition by cytokines modulates their physiological activities

A variety of cytokines have been reported to be able to recognize specific carbohydrate moieties. To date, the role of carbohydrate recognition in cytokine function has been analyzed for several cytokines, including fibroblast growth factor (FGF), tumor necrosis factor (TNF)-alpha, and interleukin (IL)-2. The FGF family and their receptors have been found to recognize a heparan sulfate proteoglycan, which generates rigid complexes that induce signal transduction. We have found that IL-2 recognizes a high-mannose type glycan on the alpha subunit of the IL-2 receptor as well as a peptide portion of this subunit. Blocking this carbohydrate-IL-2 interaction diminished IL-2-induced signaling and T-cell proliferation. We have also shown that TNF-alpha recognizes the second mannose 6-phosphate diester of the glycan portion of glycosylphosphatidylinositol (GPI)-anchored glycoproteins. Blocking this GPI-anchored glycan-TNF-alpha interaction abrogates TNF-alpha-induced apoptosis. We aim to increase the number of cytokines which modulate their functions through the unique carbohydrate recognition, and open the way to systematically elucidate the biological functions of cytokine-carbohydrate interaction in immune system.

Recognition by TNF-alpha of the GPI-anchor glycan induces apoptosis of U937 cells

Tumor necrosis factor-alpha (TNF-alpha) binds to TNF-alpha receptors (TNFR) to produce a hexameric (TNF-alpha)(3)-(TNFR)(3) structure that stimulates apoptosis. We found by using ELISA that TNF-alpha binds to the glycosylphosphatidylinositol (GPI) anchor glycans of carcinoembryonic antigen, human placental alkaline phosphatase (hAP), and Tamm-Horsfall glycoprotein. These binding abilities were inhibited by 10(-6)M mannose-6-phosphate. Treatment of hAP with mild acid and phosphatase, which releases the N-acetylglucosamine (GlcNAc) beta1 -->phosphate-->6 residue from the GPI-anchor glycan of hAP, abrogated the binding of TNF-alpha to hAP. Thus, TNF-alpha binds to the GlcNAcbeta1-->phosphate-->6Man residue in GPI-anchor glycans. To investigate whether the carbohydrate-binding ability of TNF-alpha is related to its physiological functions, human lymphoma U937 cells were used. TNF-alpha stimulates U937 cell apoptosis in a dose-dependent manner and the presence of mannose-6-phosphate inhibited this. TNF-alpha-dependent tyrosine phosphorylation of several proteins in U937 cells was also diminished by mannose-6-phosphate. Phosphatidylinositol-specific phospholipase C-pretreatment also inhibited this tyrosine phosphorylation. These data suggest that TNF-alpha stimulates U937 cell apoptosis by forming a high-affinity nanomeric (TNF-alpha)(3)-(TNFR)(3)-(GPI-anchored glycan)(3) complex. The GPI-anchored glycoprotein involved remains to be identified.

Major royal jelly protein 3 modulates immune responses in vitro and in vivo

We have recently shown that royal jelly has potent antiallergic properties in a mouse model of immediate hypersensitivity. However, it is still unclear which components of royal jelly exhibit antiallergic activity. In this study, we have screened for antiallergic factors in royal jelly based on inhibition of IL-4 production by anti-CD3 stimulated spleen cells derived from OVA/alum-immunized mice. Using a series of column chromatographies, we purified a 70 kDa glycoprotein, major royal jelly protein 3 (MRJP3), that suppresses IL-4 production. In in vitro experiments, MRJP3 suppressed the production of not only IL-4 but also that of IL-2 and IFN-gamma by T cells concomitant with inhibition of proliferation. The MRJP3-mediated suppression of IL-4 production was also evident when lymph node cells from OVA/alum-immunized mice were stimulated with OVA plus antigen presenting cells. We next examined the purified suppressive factor on OVA/alum-induced allergic responses in mice. Interestingly, in spite of the antigenicity of MRJP3 itself as an extraneous foreign protein, intraperitoneal administration of MRJP3 inhibited serum anti-OVA IgE and IgG1 levels in immunized mice. In addition, heat-treated soluble MRJP3 treatment reduced its antigenicity while maintaining its inhibitory effects on antibody responses to OVA. These results indicate that MRJP3 can exhibit potent immunoregulatory effects in vitro and in vivo. Furthermore, considering the intriguing immunomodulatory effects of MRJP3, it may be of clinical significance to design MRJP3-derived antiallergic peptides by identifying the associated polypeptide regions.

Propagation and control of T cell responses by heparan sulfate-bound IL-2

IL-2, a cytokine produced by T cells, is a key regulator of immune responses and T cell homeostasis. Controlling the availability of IL-2 is consequently of significant import to the immune system. Like other cytokines, IL-2 is thought to function as a soluble agonist, transiently present when secreted in response to appropriate stimuli. In this study, we show that the most salient properties of IL-2, propagation and control of T cell responses, are mediated in vivo by bound and not free cytokine and specifically by heparan sulfate-bound IL-2. These findings necessitate a new look at how IL-2 regulates immune responses and support the notion that the microenvironment plays a determining role in modulating the character of immune responses.

Detection of ghost cells in the standard alkaline comet assay is not a good measure of apoptosis

The single cell gel electrophoresis assay, or Comet assay, is a powerful tool for measurement of DNA strands breaks, oxidative damage, and alkali labile sites, and the assay was recently modified to detect DNA cross-links. It has also been proposed as a measure of apoptosis since apoptotic cells are suspected to result in total migration of the DNA from the nucleus into the tail. Cells with this appearance are called ghost cells, clouds, hedgehogs, or NDCN (nondetectable cell nuclei). The aim of this study was to determine if ghost cells can be used to measure apoptosis in the standard alkaline comet assay. To answer this question, we made use of two cell lines: CTLL-2 cells that can enter apoptosis upon addition of apoptosis stimuli or IL-2 deprivation, and CTLL-2 bcl2 cells that are protected from apoptosis due to the overexpression of the apoptosis inhibitor gene bcl2. The two cell lines were treated with cytotoxins (nongenotoxic apoptosis inducers, nongenotoxic necrotic agents) or genotoxins. They were also subjected to growth factor withdrawal, which induced apoptosis in the CTLL-2 cell line. The level of apoptosis was measured by the Annexin V-FITC method in parallel with performing the Comet assay. The results obtained in the two cell lines suggest that apoptotic or necrotic death does not correlate well with the detection of ghost cells, presumably because these cells are lost upon electrophoresis. A variant of the alkaline Comet assay that was performed without electrophoresis (halo method) was able to efficiently detect cells undergoing apoptosis, but it was unable to clearly distinguish between apoptosis and genotoxic damage.

Functional convergence of invertebrate and vertebrate cytokine-like molecules based on a similar lectin-like activity

It is generally accepted that the action of cytokines results from their binding to specific receptors. However, many cytokines possess lectin-like activity that may be essential for the expression of their full biological activities. This review focuses on the physiological relevance of the lectin-like activity of cytokines during the innate immune response in mammals, using TNF as an illustrative example. Moreover, we will show that TNF displays functional analogies with a defense molecule from the earthworm Eisenia foetida termed CCF. These analogies are not reflected by primary sequence homology between CCF and TNF but are particularly based on a similar lectin-like activity/domain. Hence, from a phylogenetic point of view, the lectin-like activity/domain of CCF and TNF may represent an essential recognition mechanism that has been functionally conserved during the innate immune response of invertebrates and vertebrates as a result of convergent evolution.