Natural post-translational modifications of chemokines

Insights into the effect of protein glycosylation on carbohydrate substrate binding

The role of glycosylation in the binding of glycoproteins to carbohydrate substrates has not been well understood. The present study addresses this knowledge gap by elucidating the links between the glycosylation patterns of a model glycoprotein, a Family 1 carbohydrate-binding module (TrCBM1), and the thermodynamic and structural properties of its binding to different carbohydrate substrates using isothermal titration calorimetry and computational simulation. The variations in glycosylation patterns cause a gradual transition of the binding to soluble cellohexaose from an entropy-driven process to an enthalpy-driven one, a trend closely correlated with the glycan-induced shift of the predominant binding force from hydrophobic interactions to hydrogen bonding. However, when binding to a large surface of solid cellulose, glycans on TrCBM1 have a more dispersed distribution and thus have less adverse impact on the hydrophobic interaction forces, leading to overall improved binding. Unexpectedly, our simulation results also suggest an evolutionary role of O-mannosylation in transforming the substrate binding features of TrCBM1 from those of type A CBMs to those of type B CBMs. Taken together, these findings provide new fundamental insights into the molecular basis of the role of glycosylation in protein-carbohydrate interactions and are expected to better facilitate further studies in this area.

Purification of native CCL7 and its functional interaction with selected chemokine receptors

Chemokine receptors form a major sub-family of G protein-coupled receptors (GPCRs) and they are involved in a number of cellular and physiological processes related to our immune response and regulation. A better structural understanding of ligand-binding, activation, signaling and regulation of chemokine receptors is very important to design potentially therapeutic interventions for human disorders arising from aberrant chemokine signaling. One of the key limitations in probing the structural details of chemokine receptors is the availability of large amounts of purified, homogenous and fully functional chemokine ligands, and the commercially available products, are not affordable for in-depth structural studies. Moreover, production of uniformly isotope-labeled chemokines, for example, suitable for NMR-based structural investigation, also remains challenging. Here, we have designed a streamlined approach to express and purify the human chemokine CCL7 as well as its ¹⁵N-, ¹⁵N/¹³C-, ²H/¹⁵N/¹³C- isotope-labeled derivatives, at milligram levels using E. coli expression system. Purified CCL7 not only maintains a well-folded three-dimensional structure as analyzed using circular dichroism and ¹H/¹⁵N NMR but it also induces coupling of heterotrimeric G-proteins and β-arrestins for selected chemokine receptors in cellular system. We compared cAMP response induced by histidine tagged CCL7 and native CCL7 and found that modification of the N-terminus of CCL7 compromises its functionality. Our strategy presented here may be applicable to other chemokines and therefore, provide a potentially generic and cost-effective approach to produce chemokines in large amounts for functional and structural studies.

The Multitasking Potential of Alarmins and Atypical Chemokines

When the human genome was sequenced, it came as a surprise that it contains “only” 21,306 protein-coding genes. However, complexity and diversity are multiplied by alternative splicing, non-protein-coding transcripts, or post-translational modifications (PTMs) on proteome level. Here, we discuss how the multi-tasking potential of proteins can substantially enhance the complexity of the proteome further, while at the same time offering mechanisms for the fine-regulation of cell responses. Discoveries over the past two decades have led to the identification of “surprising” and previously unrecognized functionalities of long known cytokines, inflammatory mediators, and intracellular proteins that have established novel molecular networks in physiology, inflammation, and cardiovascular disease. In this mini-review, we focus on alarmins and atypical chemokines such as high-mobility group box protein-1 (HMGB-1) and macrophage migration-inhibitory factor (MIF)-type proteins that are prototypical examples of these classes, featuring a remarkable multitasking potential that allows for an elaborate fine-tuning of molecular networks in the extra- and intracellular space that may eventually give rise to novel “task”-based precision medicine intervention strategies.

Remodeling our concept of chemokine receptor function: From monomers to oligomers

The chemokines direct leukocyte recruitment in both homeostatic and inflammatory conditions, and are therefore critical for immune reactions. By binding to members of the class A G protein-coupled receptors, the chemokines play an essential role in numerous physiological and pathological processes. In the last quarter century, the field has accumulated much information regarding the implications of these molecules in different immune processes, as well as mechanistic insight into the signaling events activated through their binding to their receptors. Here, we will focus on chemokine receptors and how new methodological approaches have underscored the role of their conformations in chemokine functions. Advances in biophysical-based techniques show that chemokines and their receptors act in very complex networks and therefore should not be considered isolated entities. In this regard, the chemokine receptors can form homo- and heterodimers as well as oligomers at the cell surface. These findings are changing our view as to how chemokines influence cell biology, identify partners that regulate chemokine function, and open new avenues for therapeutic intervention.

Transient expression of recombinant ACKR4 (CCRL1) gene, an atypical chemokine receptor in human embryonic kidney (HEK 293) cells

ACKR4 also called CCX-CKR, CCRL1 as a member of atypical chemokine receptors, regulates the biological responses by clearance or transporting homeostatic chemokines such as CCL19, CCL21, CCL25, and CXCL13. Since these chemokines are involved in cancer development and metastasis, ACKR4 could have inhibition roles in cancer cell proliferation and invasion. Forming complexes with chemokine receptors by ACKR4 as in the case of hCXCR3 which lead to chemotaxis prevention is the other function of this protein is. However, as an atypical chemokine receptor, ACKR4 is less well-characterized compared to other members. Here, as the first step in understanding the molecular mechanisms of ACKR4 action, transfectants in HEK293T cell, was generated. In this study, ACKR4 coding sequence was cloned and human embryonic kidney 293T cells were used for recombinant production of ACKR4 protein. The liposome-mediated transfection with ACKR4 CDs, were detected in ACKR4 positive cells as early as 48 h post-transfection. The production of ACKR4 protein was confirmed using RT-PCR, dot blot, western blot, and flow cytometry. ACKR4 may represent a novel molecular target in cancer therapy, which might provide a chance for new therapeutic strategy. Therefore, the first step in the understanding of the molecular mechanisms of ACKR4 action is generation ACKR4-HEK293T recombinant cells.

Molecular and biochemical characterization of recombinant guinea pig tumor necrosis factor-alpha

Tumor necrosis factor alpha (TNF-α) is a cytokine which plays opposing roles in the context of infectious disease pathogenesis. TNF-α is essential for the development of a protective immune response to some pathogens, for example, Mycobacterium tuberculosis, by synergizing with other cytokines. However, exorbitant or uncontrolled TNF-α activity may also drive pathology and disease symptoms in many infectious diseases. In order to elucidate the beneficial and detrimental roles of TNF-α in tuberculosis (TB) and other diseases for which the guinea pig is the small animal model of choice, recombinant guinea pig (rgp)TNF-α has been produced using prokaryotic expression systems. However, it is unknown whether posttranslational modifications which cannot be made in the prokaryotic expression systems may be important for rgpTNF-α structure and function. Therefore, we carried out a comparative study by expressing rgpTNF-α in prokaryotic and eukaryotic expression systems and analyzed the eukaryotic-expressed rgpTNF-α for the presence of posttranslational modifications by subjecting it to NanoLC-MS/MS. We conclude that the eukaryotic-expressed rgpTNF-α lacks posttranslational modifications, and we found no significant difference in terms of the biological activity between prokaryotic- and eukaryotic-expressed rgpTNF-α. Taken together, results from our study show that a prokaryotic expression system can be used for generating large amounts of rgpTNF-α without concern for the biological integrity.

Chemokines in tumor progression and metastasis

Chemokines play a vital role in tumor progression and metastasis. Chemokines are involved in the growth of many cancers including breast cancer, ovarian cancer, pancreatic cancer, melanoma, lung cancer, gastric cancer, acute lymphoblastic leukemia, colon cancer, non-small lung cancer, non-hodgkin's lymphoma, etc. The expression of chemokines and their receptors is altered in many malignancies and leads to aberrant chemokine receptor signaling. This review focuses on the role of chemokines in key processes that facilitate tumor progression including proliferation, senescence, angiogenesis, epithelial mesenchymal transition, immune evasion and metastasis.

Leukocyte chemoattractant receptors in human disease pathogenesis

Combinations of leukocyte attractant ligands and cognate heptahelical receptors specify the systemic recruitment of circulating cells by triggering integrin-dependent adhesion to endothelial cells, supporting extravasation, and directing specific intratissue localization via gradient-driven chemotaxis. Chemoattractant receptors also control leukocyte egress from lymphoid organs and peripheral tissues. In this article, we summarize the fundamental mechanics of leukocyte trafficking, from the evolution of multistep models of leukocyte recruitment and navigation to the regulation of chemoattractant availability and function by atypical heptahelical receptors. To provide a more complete picture of the migratory circuits involved in leukocyte trafficking, we integrate a number of nonchemokine chemoattractant receptors into our discussion. Leukocyte chemoattractant receptors play key roles in the pathogenesis of autoimmune diseases, allergy, inflammatory disorders, and cancer. We review recent advances in our understanding of chemoattractant receptors in disease pathogenesis, with a focus on genome-wide association studies in humans and the translational implications of mechanistic studies in animal disease models.

Overview of the mechanisms regulating chemokine activity and availability

Physiological leukocyte homing and extravasation of leukocytes during inflammatory processes is directed by a number of proteins including adhesion molecules, proteases, cytokines and chemokines. Tight regulation of leukocyte migration is essential to ensure appropriate migration. A number of mechanisms exist that regulate leukocyte migration including up- or down-regulation of chemokine or chemokine receptor gene expression. However, chemokine availability in vivo also depends on the interaction of chemokines with specific glycosaminoglycans such as heparan sulfate on the surface of endothelial layers. Modification of the interaction of chemokines with these glycosaminoglycans alters the presentation of chemokines to chemokine receptors on circulating leukocytes. On top, binding of chemokines to atypical chemokine receptors that do not signal through G proteins affects chemokine availability on the endothelial layers. In addition to mechanisms that modulate chemokine availability, this review summarizes mechanisms that fine-tune chemokine function. These include synergy or antagonism between chemokines and alternative splicing of chemokine genes. Moreover, chemokines may be posttranslationally modified leading to molecules with enhanced or reduced potency to bind to G protein-coupled receptors or GAGs or generating chemokines with altered receptor specificity. Cross-talk between these different mechanisms generates a complex regulatory network that allows the organism to modulate leukocyte migration in a highly specific manner.

Activity of soluble aminopeptidase A and dipeptidyl peptidase IV and membrane-bound aminopeptidase B and pyroglutamyl peptidase I in adenoid hyperplasia, tonsillar hyperplasia and chronic tonsillitis

OBJECTIVE

To analyze soluble and membrane-bound peptidase activities in the tonsils and adenoids removed from patients with adenoid hyperplasia, tonsillar hyperplasia and chronic tonsillitis.

METHODS

A total of 48 tissue samples from patients undergoing adenoidectomy and tonsillectomy for adenoid hyperplasia, tonsillar hyperplasia or chronic tonsillitis were analyzed. The catalytic activity of a pool of peptidases in the soluble (dipeptidyl peptidase IV, aminopeptidase A, aminopeptidase N and cystinyl aminopeptidase) and membrane-bound (prolyl endopeptidase, aspartyl aminopeptidase, aminopeptidase B and pyroglutamyl peptidase I) fractions was measured fluorometrically.

RESULTS

The activity of membrane-bound aminopeptidase B was higher in cases of chronic tonsillitis and adenoid hyperplasia than in tonsillar hyperplasia, p=0.004. Soluble dipeptidyl peptidase IV and membrane-bound pyroglutamyl peptidase I were found to be more active in tissues from male chronic tonsillitis tissues, p<0.05, while membrane-bound aminopeptidase B activity was higher in tissues of females with tonsillar hyperplasia, p<0.001. In the case of chronic tonsillitis, soluble aminopeptidase A was found to have a higher level of activity in tissues from children than those from adults, p=0.005.

CONCLUSIONS

Our results suggest a potential role of soluble aminopeptidase A, soluble dipeptidyl peptidase IV, membrane-bound aminopeptidase B and membrane-bound pyroglutamyl peptidase I in the pathobiology of adenoid hyperplasia, tonsillar hyperplasia and chronic tonsillitis that is differently regulated as a function of gender. These finfings may modify in the future the clinical approach to these diseases.

Receptor oligomerization: a pivotal mechanism for regulating chemokine function

Since the first reports on chemokine function, much information has been generated on the implications of these molecules in numerous physiological and pathological processes, as well as on the signaling events activated through their binding to receptors. Despite these extensive studies, no chemokine-related drugs have yet been approved for use in patients with inflammatory or autoimmune diseases. This discrepancy between efforts and results has forced a re-evaluation of the chemokine field. We have explored chemokine receptor conformations at the cell surface and found that, as is the case for other G protein-coupled receptors, chemokine receptors are not isolated entities that are activated following ligand binding; rather, they are found as dimers and/or higher order oligomers at the cell surface, even in the absence of ligands. These complexes form organized arrays that can be modified by receptor expression and ligand levels, indicating that they are dynamic structures. The way in which these receptor complexes are stabilized modulates ligand binding, as well as their pharmacological properties and the signaling events activated. These conformations thus represent a mechanism that increases the broad variety of chemokine functions. Understanding these receptor interactions and their dynamics at the cell surface is thus critical for influencing chemokine function and could open up new possibilities for drug design.

Atypical chemokine receptors

Atypical chemokine receptors (ACRs) are cell surface receptors with seven transmembrane domains structurally homologous to chemokine G-protein coupled receptors (GPCRs). However, upon ligation by cognate chemokines, ACRs fail to induce classical signaling and downstream cellular responses characteristic for GPCRs. Despite this, by affecting chemokine availability and function, ACRs impact on a multitude of pathophysiological events and have emerged as important molecular players in health and disease. This review discusses individual characteristics of the currently known ACRs, highlights their similarities and differences and attempts to establish their group identity. It summarizes the progress made in mapping ACR expression, understanding their diverse in vitro and in vivo functions of ACRs and uncovering their contributions to disease pathogeneses.

Altered dipeptidyl peptidase IV and prolyl endopeptidase activities in chronic tonsillitis, tonsillar hyperplasia and adenoid hyperplasia

OBJECTIVE

To analyse peptidase activities in the removed tonsils and adenoids from patients with chronic tonsillitis, tonsillar hyperplasia and adenoid hyperplasia.

METHODS

We have analyzed 48 tissue samples from patients undergoing tonsillectomy and adenoidectomy for chronic tonsillitis, tonsillar hyperplasia or adenoid hyperplasia. Tonsillectomy and adenoidectomy samples were collected and frozen for later enzyme analysis. The catalytic activity of a pool of peptidases (dipeptidyl peptidase IV, prolyl endopeptidase, aminopeptidase A, aminopeptidase N, aspartyl aminopeptidase, aminopeptidase B, neutral endopeptidase, pyroglutamyl peptidase I, puromycin-sensitive aminopeptidase and cystinyl aminopeptidase) was measured fluorometrically.

RESULTS

The activity of prolyl endopeptidase was higher in tonsillar hyperplasia and adenoid hyperplasia than in chronic tonsillitis. On the contrary, dipeptidyl peptidase IV activity was higher in chronic tonsillitis than in hypertrophic tissues. When data were stratified by age and gender, dipeptidyl peptidase IV was also found to be more active in adult and male chronic tonsillitis tissues. Inversely, dipeptidyl peptidase IV activity was higher in tissues of females with tonsillar hyperplasia.

CONCLUSIONS

These data indicate the involvement of dipeptidyl peptidase IV and prolyl endopeptidase in the mechanisms underlying chronic tonsillitis, tonsillar hyperplasia and adenoid hyperplasia.

Chemokine oligomerization and interactions with receptors and glycosaminoglycans: the role of structural dynamics in function

The first chemokine structure, that of IL-8/CXCL8, was determined in 1990. Since then, many chemokine structures have emerged. To the initial disappointment of structural biologists, the tertiary structures of these small proteins were found to be highly conserved. However, they have since proven to be much more interesting and diverse than originally expected. Somewhat like lego blocks, many chemokines oligomerize and there is significant diversity in their oligomeric forms and propensity to oligomerize. Chemokines not only interact with receptors where different oligomeric forms can induce different signaling responses, they also interact with glycosaminoglycans which can stabilize oligomers and other structures that would not otherwise form in solution. Although chemokine monomers and dimers yielded quickly to structure determination, structural information about larger chemokine oligomers, chemokines receptors, and complexes of chemokines with glycosaminoglycans and receptors has been more difficult to obtain, but recent breakthroughs suggest that this information will be forthcoming, especially with receptor structures. Equally important and challenging, will be efforts to correlate the structural information with function.

Copy number variation in chemokine superfamily: the complex scene of CCL3L-CCL4L genes in health and disease

Genome copy number changes (copy number variations: CNVs) include inherited, de novo and somatically acquired deviations from a diploid state within a particular chromosomal segment. CNVs are frequent in higher eukaryotes and associated with a substantial portion of inherited and acquired risk for various human diseases. CNVs are distributed widely in the genomes of apparently healthy individuals and thus constitute significant amounts of population-based genomic variation. Human CNV loci are enriched for immune genes and one of the most striking examples of CNV in humans involves a genomic region containing the chemokine genes CCL3L and CCL4L. The CCL3L-CCL4L copy number variable region (CNVR) shows extensive architectural complexity, with smaller CNVs within the larger ones and with interindividual variation in breakpoints. Furthermore, the individual genes embedded in this CNVR account for an additional level of genetic and mRNA complexity: CCL4L1 and CCL4L2 have identical exonic sequences but produce a different pattern of mRNAs. CCL3L2 was considered previously as a CCL3L1 pseudogene, but is actually transcribed. Since 2005, CCL3L-CCL4L CNV has been associated extensively with various human immunodeficiency virus-related outcomes, but some recent studies called these associations into question. This controversy may be due in part to the differences in alternative methods for quantifying gene copy number and differentiating the individual genes. This review summarizes and discusses the current knowledge about CCL3L-CCL4L CNV and points out that elucidating their complete phenotypic impact requires dissecting the combinatorial genomic complexity posed by various proportions of distinct CCL3L and CCL4L genes among individuals.

Changes in gingival crevicular fluid inflammatory mediator levels during the induction and resolution of experimental gingivitis in humans

AIM

The goal of this study is to characterize the changes in 33 biomarkers within the gingival crevicular fluid during the 3-week induction and 4-week resolution of stent-induced, biofilm overgrowth mediated, experimental gingivitis in humans.

METHODS

Experimental gingivitis was induced in 25 subjects for 21 days followed by treatment with a sonic powered toothbrush for 28 days. Clinical indices and gingival crevicular fluids were collected weekly during induction and biweekly during resolution. Samples were analysed using a bead-based multiplexing analysis for the simultaneous measurements of 33 biomarkers within each sample including cytokines, matrix-metalloproteinases (MMPs) and adipokines. Prostaglandin-E(2) was measured by enzyme-linked immunoadsorbant assay. Statistical testing using general linear models with structured covariance matrices were performed to compare stent to contralateral (non-stent) changes in clinical signs and in biomarker levels over time.

RESULTS

Gingivitis induction was associated with a significant 2.6-fold increase in interleukin 1-beta (IL-beta), a 3.1-fold increase in IL-1alpha and a significant decrease in multiple chemokines as well as MMPs-1, -3 and 13. All changes in clinical signs and mediators rebounded to baseline in response to treatment in the resolution phase.

CONCLUSIONS

Stent-induced gingivitis is associated with marked, but reversible increases in IL-alphaa and IL-1beta with suppression of multiple chemokines as well as selected MMPs.

Chemokines and chemokine receptors: new insights into cancer-related inflammation

Chemokines are involved in cellular interactions and tropism in situations frequently associated with inflammation. Recently, the importance of chemokines and chemokine receptors in inflammation associated with carcinogenesis has been highlighted. Increasing evidence suggests that chemokines are produced by tumor cells as well as by cells of the tumor microenvironment including cancer-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), endothelial cells, tumor-associated macrophages (TAMs) and more recently tumor-associated neutrophils (TANs). In addition to affecting tumor cell proliferation, angiogenesis and metastasis, chemokines also seem to modulate senescence and cell survival. Here, we review recent progress on the roles of chemokines and chemokine receptors in cancer-related inflammation, and discuss the mechanisms underlying chemokine action in cancer that might facilitate the development of novel therapies in the future.

Chemokine decoy receptors: structure-function and biological properties

Chemokines induce cell migration through the activation of a distinct family of structurally related heterotrimeric G protein-coupled receptors (GPCR). Over the last few years, several receptors in this family that recognize chemokines but do not induce cell migration have been identified. These "atypical" chemokine receptors are unable to activate transduction events that lead directly to cell migration, but appear nonetheless to play a nonredundant role in the control of leukocyte recruitment at inflammatory sites and in tumors by shaping the chemoattractant gradient, either by removing, transporting, or concentrating their cognate ligands.

The chemokine system in cancer biology and therapy

Chemokines are a key component of cancer-related inflammation. Chemokines and chemokine receptors are downstream of genetic events that cause neoplastic transformation and are components of chronic inflammatory conditions, which predispose to cancer. Components of the chemokine system affect in a cell autonomous or non-autonomous way multiple pathways of tumor progression, including: leukocyte recruitment and function; cellular senescence; tumor cell proliferation and survival; invasion and metastasis. Available information in preclinical and clinical settings suggests that the chemokine system represents a valuable target for the development of innovative therapeutic strategies.

On the origin of serum CD26 and its altered concentration in cancer patients

Dipeptidyl peptidase IV (DPP-IV), assigned to the CD26 cluster, is expressed on epithelial cells and lymphocytes and is a multifunctional or pleiotropic protein. Its peptidase activity causes degradation of many biologically active peptides, e.g. some incretins secreted by the enteroendocrine system. DPP-IV has, therefore, become a novel therapeutic target for inhibitors that extend endogenously produced insulin half-life in diabetics, and several reviews have appeared in recent months concerning the clinical significance of CD26/DPP-IV. Biological fluids contain relatively high levels of soluble CD26 (sCD26). The physiological role of sCD26 and its relation, if any, to CD26 functions, remain poorly understood because whether the process for CD26 secretion and/or shedding from cell membranes is regulated or not is not known. Liver epithelium and lymphocytes are often cited as the most likely source of sCD26. It is important to establish which tissue or organ is the protein source as well as the circumstances that can provoke an abnormal presence/absence or altered levels in many diseases including cancer, so that sCD26 can be validated as a clinical marker or a therapeutic target. For example, we have previously reported low levels of sCD26 in the blood of colorectal cancer patients, which indicated the potential usefulness of the protein as a biomarker for this cancer in early diagnosis, monitoring and prognosis. Through this review, we envisage a role for sCD26 and the alteration of normal peptidase capacity (in clipping enteroendocrine or other peptides) in the complex crosstalk between the lymphoid lineage and, at least, some malignant tumours.

Recognition versus adaptive up-regulation and degradation of CC chemokines by the chemokine decoy receptor D6 are determined by their N-terminal sequence

The chemokine decoy receptor D6 controls inflammatory responses by selective recognition and degradation of most CCR1 to CCR5 agonistic ligands. CCL14 is a homeostatic chemokine present at high concentrations in the serum with a weak agonist activity on CCR1. Under inflammatory conditions, plasmin and UPA-mediated truncation of 8 amino acids generates the potent CCR1/CCR3/CCR5 isoform CCL14(9-74), which is further processed and inactivated by dipeptidyl peptidase IV/CD26 that generates CCL14(11-74). Here we report that D6 efficiently binds both CCL14 and its truncated isoforms. Like other D6 ligands, the biologically active CCL14(9-74) induces adaptive up-regulation of D6 expression on the cell membrane and is rapidly and efficiently degraded. In contrast, the D6-mediated degradation of the biologically inactive isoforms CCL14(1-74) and CCL14(11-74) is very inefficient. Thus, D6 cooperates with CD26 in the negative regulation of CCL14 by the selective degradation of its biologically active isoform. Analysis of a panel of CC chemokines and their truncated isoforms revealed that D6-mediated chemokine degradation does not correlate with binding affinity. Conversely, degradation efficiency is positively correlated with D6 adaptive up-regulation. Sequence analysis indicated that a proline residue in position 2 of D6 ligands is dispensable for binding but crucial for D6 adaptive up-regulation and efficient degradation.

Post-translational inhibition of IP-10 secretion in IEC by probiotic bacteria: impact on chronic inflammation

Background

Clinical and experimental studies suggest that the probiotic mixture VSL#3 has protective activities in the context of inflammatory bowel disease (IBD). The aim of the study was to reveal bacterial strain-specific molecular mechanisms underlying the anti-inflammatory potential of VSL#3 in intestinal epithelial cells (IEC).

Methodology/Principal Findings

VSL#3 inhibited TNF-induced secretion of the T-cell chemokine interferon-inducible protein (IP-10) in Mode-K cells. Lactobacillus casei (L. casei) cell surface proteins were identified as active anti-inflammatory components of VSL#3. Interestingly, L. casei failed to block TNF-induced IP-10 promoter activity or IP-10 gene transcription at the mRNA expression level but completely inhibited IP-10 protein secretion as well as IP-10-mediated T-cell transmigration. Kinetic studies, pulse-chase experiments and the use of a pharmacological inhibitor for the export machinery (brefeldin A) showed that L. casei did not impair initial IP-10 production but decreased intracellular IP-10 protein stability as a result of blocked IP-10 secretion. Although L. casei induced IP-10 ubiquitination, the inhibition of proteasomal or lysosomal degradation did not prevent the loss of intracellular IP-10. Most important for the mechanistic understanding, the inhibition of vesicular trafficking by 3-methyladenine (3-MA) inhibited IP-10 but not IL-6 expression, mimicking the inhibitory effects of L. casei. These findings suggest that L. casei impairs vesicular pathways important for the secretion of IP-10, followed by subsequent degradation of the proinflammatory chemokine. Feeding studies in TNF^ΔARE and IL-10^−/− mice revealed a compartimentalized protection of VSL#3 on the development of cecal but not on ileal or colonic inflammation. Consistent with reduced tissue pathology in IL-10^−/− mice, IP-10 protein expression was reduced in primary epithelial cells.

Conclusions/Significance

We demonstrate segment specific effects of probiotic intervention that correlate with reduced IP-10 protein expression in the native epithelium. Furthermore, we revealed post-translational degradation of IP-10 protein in IEC to be the molecular mechanism underlying the anti-inflammatory effect.

Distinct outcomes of Trypanosoma cruzi infection in hamsters are related to myocardial parasitism, cytokine/chemokine gene expression, and protein expression profile

BACKGROUND

Trypanosoma cruzi-infected outbred hamsters reproduce the range of different outcomes of Chagas disease noted in humans. We tested whether myocarditis, its mediators, and myocardial protein expression are related to the severity of the acute phase of T. cruzi infection in the hamster model.

METHODS

Myocardium left ventricles (LVs) obtained from Syrian hamsters infected with T. cruzi were collected 21 days after infection. Myocarditis and the T. cruzi nest/antigen area were analyzed by histological and morphometric analysis. Cytokine and chemokine messenger RNA (mRNA) expression was analyzed using real-time reverse-transcriptase polymerase chain reaction. Differentially expressed proteins were identified by 2-dimensional electrophoresis, followed by mass spectrometry.

RESULTS

While in the acute phase of infection, 50% of animals displayed weight loss and signs of acute-phase infection (hereafter referred to as "acute-phase signs" [APS]) (e.g., lethargy, vomiting, and diarrhea). Both the T. cruzi nest/antigen area and the expression of interferon-gamma, tumor necrosis factor-alpha, interleukin-10, and CCL3 mRNA were significantly increased in the LVs of animals with APS, compared with the LVs of animals without APS. Animals with APS, those without APS, and uninfected animals demonstrated distinct myocardial expression of contractile, stress response, and metabolism proteins.

CONCLUSIONS

The distinct outcomes of acute T. cruzi infection in Syrian hamsters are related to cardiac parasitism, cytokine expression, and changes in the expression of structural/contractile and stress response proteins that may be associated with alterations in the cardiomyocyte cytoskeleton.

Citrullination of CXCL10 and CXCL11 by peptidylarginine deiminase: a naturally occurring posttranslational modification of chemokines and new dimension of immunoregulation

Interactions between chemokines and enzymes are vital in immunoregulation. Structural protein citrullination by peptidylarginine deiminase (PAD) has been associated with autoimmunity. In this report, we identified a novel naturally occurring posttranslational modification of chemokines, that is, the deimination of arginine at position 5 into citrulline of CXC chemokine ligand 10 (CXCL10) by rabbit PAD and human PAD2. Citrullination reduced (≥ 10-fold) the chemoattracting and signaling capacity of CXCL10 for CXC chemokine receptor 3 (CXCR3) transfectants; however, it did not affect CXCR3 binding. On T lymphocytes, though, citrullinated CXCL10 remained active but was again weaker than authentic CXCL10. PAD was also able to convert CXCL11, causing an impairment of CXCR3 signaling and T-cell activation, though less pronounced than for CXCL10. Similarly, receptor binding properties of CXCL11 were not altered by citrullination. However, deimination decreased heparin binding properties of both CXCL10 and CXCL11. Overall, chemokines are the first immune modulators reported of being functionally modified by citrullination. These data provide new structure-function dimensions for chemokines in leukocyte mobilization, disclosing an anti-inflammatory role for PAD. Additionally because citrullination has severe consequences for chemokine biology, this invites to reassess the involvement and impact of PAD and citrullinated peptides in inflammation, autoimmunity, and hematologic disorders.

MAIDS resistance-associated gene expression patterns in secondary lymphoid organs

Murine acquired immunodeficiency syndrome (MAIDS) is caused by exposure to murine leukemia virus and serves as a model to study human AIDS. In MAIDS-susceptible C57BL/6 mice, virus exposure leads to progressive immune deficiency, while resistant strains such as BALB/c recover from infection and develop protective immunity. The goal of this study was to identify early gene expression patterns that may be important in establishing this strain-specific differential response. Total RNA was isolated from spleens and pooled lymph nodes of both mouse strains at 3 and 7 days post virus infection. The complementary DNA generated from this RNA was hybridized to mouse oligonucleotide DNA microarrays using a strategy that controlled for inherent variability and highlighted only virus-induced changes. Fluorescent intensities were normalized and analyzed for statistically significant differential expression between strains across both time points and lymphoid organs. The majority of the resistance-associated genes was identified at day 3 post-infection and demonstrated the highest fold differences between strains, while more susceptibility-associated sequences were seen at 7 days post-infection. Among the most highly differentially expressed sequences seen at the earlier time point were genes related to protein metabolism, especially serine proteases. Differential patterns of chemokine-related genes were observed at the later time point. The overall pattern of expression suggests strain-specific differences in proteases and chemokines within secondary lymphoid organs shortly after infection influence the likelihood of disease progression.

The role of CXC chemokines and their receptors in cancer

Chemokines, or chemotactic cytokines, and their receptors have been discovered as essential and selective mediators in leukocyte migration to inflammatory sites and to secondary lymphoid organs. Besides their functions in the immune system, they also play a critical role in tumor initiation, promotion and progression. There are four subgroups of chemokines: CXC, CC, CX(3)C, and C chemokine ligands. The CXC or alpha subgroup is further subdivided in the ELR(+) and ELR(-) chemokines. Members that contain the ELR motif bind to CXC chemokine receptor 2 (CXCR2) and are angiogenic. In contrast, most of the CXC chemokines without ELR motif bind to CXCR3 and are angiostatic. An exception is the angiogenic ELR(-)CXC chemokine stromal cell-derived factor-1 (CXCL12/SDF-1), which binds to CXCR4 and CXCR7 and is implicated in tumor metastasis. This review is focusing on the role of CXC chemokines and their receptors in tumorigenesis, including angiogenesis, attraction of leukocytes to tumor sites and induction of tumor cell migration and homing in metastatic sites. Finally, their therapeutic use in cancer treatment is discussed.

Chemokines: novel targets for breast cancer metastasis

Recent studies have highlighted the possible involvement of chemokines and their receptors in breast cancer progression and metastasis. Chemokines and their receptors constitute a superfamily of signalling factors whose prognosis value in breast cancer progression remains unclear. We will examine here the expression pattern of chemokines and their receptors in mammary gland physiology and carcinogenesis. The nature of the cells producing chemokines or harboring chemokine receptors appears to be crucial in certain conditions for example, the infiltration of the primary tumor by leukocytes and angiogenesis. In addition, chemokines, their receptors and the interaction with glycosaminoglycan (GAGs) are key players in the homing of cancer cells to distant metastasis sites. Several lines of evidence, including in vitro and in vivo models, suggest that the mechanism of action of chemokines in cancer development involves the modulation of proliferation, apoptosis, invasion, leukocyte recruitment or angiogenesis. Furthermore, we will discuss the regulation of chemokine network in tumor neovascularity by decoy receptors. The reasons accounting for the deregulation of chemokines and chemokine receptors expression in breast cancer are certainly crucial for the comprehension of chemokine role in breast cancer and are in several cases linked to estrogen receptor status. The targeting of chemokines and chemokine receptors by antibodies, small molecule antagonists, viral chemokine binding proteins and heparins appears as promising tracks to develop therapeutic strategies. Thus there is significant interest in developing strategies to antagonize the chemokine function, and an opportunity to interfere with metastasis, the leading cause of death in most patients.

Clipping, shedding and RIPping keep immunity on cue

Exposure to infectious agents elicits defense mechanisms that necessitate a timely immune response. The immediate delivery of essential cues for immune activation is provided, in part, by proteolytic processing. A large repertoire of molecules orchestrates the activation, migration, and effector function of immune cells. The diversity of this repertoire matches well with the broad array of substrates that can be cleaved by proteinases, and many of these substrates are proving to be essential for proper immune-cell function. Here, we discuss how two specific classes of metal-dependent proteinases, the matrix metalloproteinases and the disintegrin metalloproteinases, have consequences well beyond classical cell-matrix and cell-cell interactions and motility, and we review their roles in immune-cell maturation, clonal expansion, and cytotoxic functions.

Selective Isolation of N-Blocked Peptides by Isocyanate-Coupled Resin

We developed a method for selective isolation of N-blocked peptides from a complex mixture such as an enzymatic digest of a protein. The approach is based on a newly designed isocyanate-resin (resin-NCO), which specifically reacts with alpha-amino or imino groups. This method, then, permits the isolation of N-blocked peptides, even those containing Lys, from a peptide mixture as intact forms by trapping N-free peptides via covalent bonding to the resin-NCO. The present study demonstrates the performance of this method for the selective isolation of N-blocked peptides by applying it to several peptide mixtures, including proteolytic digests.

Role of chemokines in the endometrium and in embryo implantation

PURPOSE OF REVIEW

Chemokines are well known for their roles in the immune system; convincing evidence has emerged demonstrating a broader role for chemokines in the endometrium, particularly during embryo implantation. This review highlights the evidence on newly defined roles for chemokines in the endometrium during embryo implantation, with particular focus on those chemokines expressed by the endometrium.

RECENT FINDINGS

The highly regulated temporal and spatial expression of chemokines in the endometrium leads not only to specific recruitment and activation of appropriate leucocytes but also coordinates the precisely orchestrated invasion of trophoblasts through the decidua and maternal vasculature. Results to date implicate chemokine signalling at the maternal-foetal interface in important processes during implantation and placentation, such as leucocyte recruitment and controlled trophoblast invasion. Unravelling such actions of chemokines in the endometrium has provided new insights into these complex processes.

SUMMARY

Disturbances of chemokine production, processing, or actions are likely to contribute to dysfunction of implantation and placentation, with implications for early pregnancy loss and disturbed placental and foetal development. More research into altered chemokine function in such conditions may provide leads for new clinical interventions.

Role of chemokines for the localization of leukocyte subsets in the kidney

Chemokines comprise a family of structurally related chemotactic proteins. They bind to about 20 corresponding receptors. Chemokines provide a general communication system for cells, and regulate lymphocyte migration under normal (homeostatic) and inflammatory conditions. Chemokines organize microenvironments in lymphoid tissue, lymphoid organogenesis, and participate in vascular and lymphatic angiogenesis. Expressed at the site of injury in the kidney, chemokines are involved in the recruitment of specific leukocyte subsets to particular renal compartments. Here we summarize recent data on chemokine biology with a focus on the role of chemokines in the recruitment of neutrophils (polymorphonuclear leukocytes), monocytes/macrophages, dendritic cells, T cells, including regulatory T cells, and B cells in renal inflammation.

Chemokine sequestration by atypical chemokine receptors

Leucocyte migration is essential for robust immune and inflammatory responses, and plays a critical role in many human diseases. Chemokines, a family of small secreted protein chemoattractants, are of fundamental importance in this process, directing leucocyte trafficking by signalling through heptahelical G-protein-coupled receptors expressed by the migrating cells. However, several mammalian chemokine receptors, including D6 and CCX-CKR (ChemoCentryx chemokine receptor), do not fit existing models of chemokine receptor function, and do not even appear to signal in response to chemokine binding. Instead, these 'atypical' chemokine receptors are biochemically specialized for chemokine sequestration, acting to regulate chemokine bioavailability and thereby influence responses through signalling-competent chemokine receptors. This is of critical importance in vivo, as mice lacking D6 show exaggerated cutaneous inflammatory responses and an increased susceptibility to the development of skin cancer. CCX-CKR, on the other hand, is predicted to modulate homoeostatic lymphocyte and dendritic cell trafficking, key migratory events in acquired immune responses that are directed by CCX-CKR-binding chemokines. Thus studies on 'atypical' chemokine receptors are revealing functional and biochemical diversity within the chemokine receptor family and providing insights into novel mechanisms of chemokine regulation.