Polymerization of MIP-1 chemokine (CCL3 and CCL4) and clearance of MIP-1 by insulin-degrading enzyme.

Macrophage inflammatory protein-1 (MIP-1), MIP-1α (CCL3) and MIP-1ß (CCL4) are chemokines crucial for immune responses towards infection and inflammation. Both MIP-1α and MIP-1ß form high-molecular-weight aggregates. Our crystal structures reveal that MIP-1 aggregation is a polymerization process and human MIP-1α and MIP-1ß form rod-shaped, double-helical polymers. Biophysical analyses and mathematical modelling show that MIP-1 reversibly forms a polydisperse distribution of rod-shaped polymers in solution. Polymerization buries receptor-binding sites of MIP-1α, thus depolymerization mutations enhance MIP-1α to arrest monocytes onto activated human endothelium. However, same depolymerization mutations render MIP-1α ineffective in mouse peritoneal cell recruitment. Mathematical modelling reveals that, for a long-range chemotaxis of MIP-1, polymerization could protect MIP-1 from proteases that selectively degrade monomeric MIP-1. Insulin-degrading enzyme (IDE) is identified as such a protease and decreased expression of IDE leads to elevated MIP-1 levels in microglial cells. Our structural and proteomic studies offer a molecular basis for selective degradation of MIP-1. The regulated MIP-1 polymerization and selective inactivation of MIP-1 monomers by IDE could aid in controlling the MIP-1 chemotactic gradient for immune surveillance.

Biochemical analysis of matrix metalloproteinase activation of chemokines CCL15 and CCL23 and increased glycosaminoglycan binding of CCL16.

Leukocyte migration and activation is orchestrated by chemokines, the cleavage of which modulates their activity and glycosaminoglycan binding and thus their roles in inflammation and immunity. Early research identified proteolysis as a means of both activating or inactivating CXC chemokines and inactivating CC chemokines. Recent evidence has shown activating cleavages of the monocyte chemoattractants CCL15 and CCL23 by incubation with synovial fluid, although the responsible proteases could not be identified. Herein we show that CCL15 is processed in human synovial fluid by matrix metalloproteinases (MMPs) and serine proteases. Furthermore, a family-wide investigation of MMP processing of all 14 monocyte-directed CC chemokines revealed that each is precisely cleaved by one or more MMPs. By MALDI-TOF-MS, 149 cleavage sites were sequenced including the first reported instance of CCL1, CCL16, and CCL17 proteolysis. Full-length CCL15-(1-92) and CCL23-(1-99) were cleaved within their unique 31 and 32-amino acid residue extended amino termini, respectively. Unlike other CCL chemokines that lose activity and become receptor antagonists upon MMP cleavage, the prominent MMP-processed products CCL15-(25-92, 28-92) and CCL23-(26-99) are stronger agonists in calcium flux and Transwell CC receptor transfectant and monocytic THP-1 migration assays. MMP processing of CCL16-(1-97) in its extended carboxyl terminus yields two products, CCL16-(8-77) and CCL16-(8-85), with both showing unexpected enhanced glycosaminoglycan binding. Hence, our study reveals for the first time that MMPs activate the long amino-terminal chemokines CCL15 and CCL23 to potent forms that have potential to increase monocyte recruitment during inflammation.

Chemokine N-terminal-derived peptides differentially regulate signaling by the receptors CCR1 and CCR5.

Inflammatory chemokines are often elevated in disease settings, where the largest group of CC-chemokines are the macrophage inflammatory proteins (MIP), which are promiscuous for the receptors CCR1 and CCR5. MIP chemokines, such as CCL3 and CCL5 are processed at the N terminus, which influences signaling in a highly diverse manner. Here, we investigate the signaling capacity of peptides corresponding to truncated N termini. These 3-10-residue peptides displayed weak potency but, surprisingly, retained their signaling on CCR1. In contrast, none of the peptides generated a signal on CCR5, but a CCL3-derived tetrapeptide was a positive modulator boosting the signal of several chemokine variants on CCR5. In conclusion, chemokine N termini can be mimicked to produce small CCR1-selective agonists, as well as CCR5-selective modulators.

Molecular mimicry of human cytokine and cytokine response pathway genes by KSHV.

Four virus proteins similar to two human macrophage inflammatory protein (MIP) chemokines, interleukin-6 (IL-6), and interferon regulatory factor (IRF) are encoded by the Kaposi's sarcoma-associated herpesvirus (KSHV) genome. vIL-6 was functional in B9 proliferation assays and primarily expressed in KSHV-infected hematopoietic cells rather than KS lesions. HIV-1 transmission studies showed that vMIP-I is similar to human MIP chemokines in its ability to inhibit replication of HIV-1 strains dependent on the CCR5 co-receptor. These viral genes may form part of the response to host defenses contributing to virus-induced neoplasia and may have relevance to KSHV and HIV-I interactions.

Crystal structure of viral macrophage inflammatory protein I encoded by Kaposi's sarcoma-associated herpesvirus at 1.7A.

Viral macrophage inflammatory protein I (vMIP-I) is a chemokine encoded by the Kaposi's sarcoma-associated herpesvirus (KSHV) that selectively activates the CC chemokine receptor 8 (CCR8), for which the endogenous ligand is CCL1. The crystal structure of vMIP-I was determined at 1.7A for comparison with other chemokines, especially those that bind CCR8, such as vMIP-II from KSHV, a CCR8 antagonist and the closest homolog (40% identical). vMIP-I has a typical chemokine fold consisting of an extended N-terminal loop, followed by a three-stranded antiparallel beta-sheet and a C-terminal alpha-helix. The four molecules in the asymmetric unit comprise two MIP-1beta-like dimers. Electrostatic surface representations of CCR8-binding chemokines reveal only minor areas of correlating surface potential, which must be reconciled with promiscuity in receptor and glycosaminoglycan (GAG) binding. In addition, the biological relevance of chemokine oligomerization is examined by comparing the oligomeric states of all chemokine structures deposited to date in the RCSB PDB.

Structure of human MIP-3alpha chemokine.

The structure of the human macrophage inflammatory protein-3alpha (MIP-3alpha) has been determined at 1.81 angstroms resolution by X-ray crystallography. The dimer crystallized in the tetragonal space group I4, with unit-cell parameters a = b = 83.99, c = 57.20 angstroms. The crystals exhibit two molecules in the asymmetric unit. The structure was solved by the molecular-replacement method and the model was refined to a conventional R value of 20.6% (R(free) = 25.7%). MIP-3alpha possesses the same monomeric structure as previously described for other chemokines. However, in addition to limited structural changes in the beta1-beta2 hairpin of monomer B, the electron density is fully defined for a few extra residues at the N- and C-termini of monomer A and the C-terminus of monomer B compared with MIP-3alpha in space group P6(1). As the N-terminal and loop regions have been shown to be critical for receptor binding and signaling, this additional structural information may help in determining the basis of the CCR6 selectivity of MIP-3alpha.

Design and synthesis of novel chemokine analogs derived from vMIP-II.

Stepwise solid phase synthesis using the Fmoc chemistry is reported for a panel of 71-residue and novel unnatural chemokine analogs derived from vMIP-II. This demonstrates the feasibility of using this synthetic method to generate de novo designed protein ligand molecules to study the biology and pharmacology of chemokine receptors.

Directed cell migration via chemoattractants released from degradable microspheres.

Chemotaxis, cell migration directed by spatial concentration gradients of chemoattractant molecules, is critical for proper function of the immune system. Materials capable of generating defined chemoattractant gradients via controlled release may be useful for the design of improved vaccines and immunotherapies that draw specific cells to an immunization site. To this end, we encapsulated formyl-Nle-Leu-Phe-Nle-Tyr-Lys (fN'LFN'YK) peptides or macrophage inflammatory protein-3alpha (MIP-3alpha or CCL20) in degradable poly(lactide-co-glycolide) microspheres that provided sustained release for more than 2 weeks in vitro. fN'LFN'YK and MIP-3alpha chemoattract dendritic cells (DCs), the key antigen-presenting cells involved in generation of primary immune responses, and their precursors, monocytes. Using an in vitro videomicroscopy migration assay, we detected strong chemotaxis of human monocytes and monocyte-derived DCs through 3D collagen gels toward microspheres releasing fN'LFN'YK. Similarly, microparticles releasing MIP-3alpha were able to attract mouse bone marrow-derived dendritic cells. Strikingly, prolonged attraction of DCs from distances up to 500 microm from the source to the point of contact with individual microspheres was observed. Such microspheres could be of general interest for the design of vaccines that promote adaptive immunity and as a platform for studying the biology of chemotaxis in vitro and in vivo.

A chimeric MIP-1alpha/RANTES protein demonstrates the use of different regions of the RANTES protein to bind and activate its receptors.

Human RANTES (CCL5) and MIP-1alpha (CCL3) bind and activate several CC chemokine receptors. RANTES is a high-affinity ligand for CCR1 and CCR5, and it binds CCR3 with moderate affinity and CCR4 with low affinity. MIP-1alpha has similar binding characteristics to RANTES except that it does not bind to CCR3. Here we have generated a chimera of human MIP-1alpha and RANTES, called MIP/RANTES, consisting of the eight amino terminal residues of MIP-1alpha preceding the CC motif, and the remainder of the sequence is RANTES. The chimera is able to induce chemotaxis of human monocytes. MIP/RANTES has >100-fold reduction in binding to CCR1 and does not bind to CCR3 but retains full, functional binding to CCR5. It has equivalent affinity for CCR5 to MIP-1alpha and RANTES, binding with an IC(50) of 1.12 nM, and is able to mobilize calcium and induce endocytosis of CCR5 in PBMC in a manner equi-potent to RANTES. It also retains the ability to inhibit R5 using HIV-1 strains. Therefore, we conclude that the amino terminus of RANTES is not involved in CCR5 binding, but it is essential for CCR1 and CCR3.

Chemical modification of a variant of human MIP-1alpha; implications for dimer structure.

A sequence variant of human MIP-1alpha, in which Asp26 has been replaced by Al alpha, has been chemically modified by the addition of 13C-labeled methyl groups at each of the lysine residues and the N-terminus. The sites of methylation have been verified by a combination of MALDI-TOF mass spectrometric experiments and tryptic digestion followed by N-terminal mapping. The effect of the modification on the structure and activity of the protein have been determined by analytical ultra-centrifugation, 13C NMR spectroscopy and receptor binding studies. The results of these experiments suggest that huMIP-alpha D26A (BB10010), when present as a dimer, adopts a globular structure, like MCP-3, rather than the elongated or cylindrical structure determined for dimers of huMIP-1beta and RANTES.

The solution structure of the anti-HIV chemokine vMIP-II.

We report the solution structure of the chemotactic cytokine (chemokine) vMIP-II. This protein has unique biological activities in that it blocks infection by several different human immunodeficiency virus type 1 (HIV-1) strains. This occurs because vMIP-II binds to a wide range of chemokine receptors, some of which are used by HJV to gain cell entry. vMIP-II is a monomeric protein, unlike most members of the chemokine family, and its structure consists of a disordered N-terminus, followed by a helical turn (Gln25-Leu27), which leads into the first strand of a three-stranded antiparallel beta-sheet (Ser29-Thr34; Gly42-Thr47; Gln52-Asp56). Following the sheet is a C-terminal alpha-helix, which extends from residue Asp60 until Gln68. The final five residues beyond the C-terminal helix (Pro70-Arg74) are in an extended conformation, but several of these C-terminal residues contact the first beta-strand. The structure of vMIP-II is compared to other chemokines that also block infection by HIV-1, and the structural basis of its lack of ability to form a dimer is discussed.

Macrophage inflammatory protein-1.

Macrophage inflammatory protein (MIP)-1alpha was identified 15 years ago as the first of now four members of the MIP-1 CC chemokine subfamily. These proteins termed CCL3 (MIP-1alpha), CCL4 (MIP-1beta), CCL9/10 (MIP-1delta), and CCL15 (MIP-1gamma) according to the revised nomenclature for chemokines are produced by many cells, particularly macrophages, dendritic cells, and lymphocytes. MIP-1 proteins, which act via G-protein-coupled cell surface receptors (CCR1, 3, 5), e.g. expressed by lymphocytes and monocytes/macrophages (MPhi), are best known for their chemotactic and proinflammatory effects but can also promote homoeostasis. The encouraging results of preclinical studies in murine models of inflammation, i.e. asthma, arthritis, or multiple sclerosis, have led to the development of potent CCR3 and 5 antagonists, some of which are currently being tested in first clinical trials.

Synthesis and characterization of fluorescent and photoactivatable MIP-1alpha ligands and interactions with chemokine receptors CCR1 and CCR5.

Photoaffinity and fluorescent analogues of the 70-amino acid chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) were designed, synthesized, characterized, and applied to probe MIP-1alpha interactions with the chemokine receptors CCR1 and CCR5. The photoactivatable MIP-1alpha ligand, BP-MIP-1alpha, and the fluorescent ligand, Flu-MIP-1alpha were prepared by selective chemical coupling of p-benzoylphenylthiocarbamyl or fluoresceinthiocarbamyl, respectively, at the N-terminus of MIP-1alpha. Both ligands BP-MIP-1alpha and Flu-MIP-1alpha retained high binding affinity and agonist potency at CCR1 and CCR5. Photoaffinity labeling of CCR1 and CCR5 receptors stably expressed in CHO cells resulted in specific covalent attachment of [(125)I]BP-MIP-1alpha and production of protein complexes of 54 and 48 kDa, respectively, on SDS-PAGE. This represents the first photo-cross-linking between a chemokine and its receptor. Flu-MIP-1alpha selectively labeled CCR1 or CCR5 receptors expressed in CHO cells and was used to characterize receptor binding domains. When bound to CCR1 or CCR5 receptors, the fluorescence signal of Flu-MIP-1alpha was quenched by collision with iodide indicating that the N-terminal end of MIP-1alpha is accessible to the solvent. These data strongly suggest that the N-terminal end of MIP-1alpha interacts with domains of CCR1 or CCR5 receptors located at the extracellular surface. The photoactivatable BP-MIP-1alpha described here should prove valuable for the identification of contact sites on receptors by photoaffinity labeling experiments.

Herpesvirus saimiri transformation of HIV type 1 suppressive CD8+ lymphocytes from an HIV type 1-infected asymptomatic individual.

CD8+ T lymphocytes from HIV+ individuals can potently suppress HIV-1 replication in a noncytolytic manner. This suppression appears to be multifactorial and the molecules contributing have not been fully elucidated. As an approach to this question we used herpesvirus saimiri (HVS) to transform CD8+ T lymphocytes from an HIV+ asymptomatic donor to a continuously growing, activation-independent, IL-2-dependent phenotype. The transformed cell population, termed CD8(HVS), had an activated phenotype, contained HVS sequences, did not shed infectious HVS virus, and was polyclonal. The CD8(HVS) cells, despite the absence of detectable CTL activity, potently suppressed HIV-1 production by both autologous and heterologous CD4+ cells from infected donors. The CD8(HVS) cells in coculture also suppressed virus production from PBMCs acutely infected with syncytium-inducing (SI) strains or NSI primary isolates of HIV-1. The supernatants from the CD8(HVS) cells and their concentrates derived from these supernatants were suppressive to NSI primary isolates of HIV-1 but not to SI strains. Fractionation of these concentrates showed that the suppressive activity was associated with low molecular mass (6500- to 19,300-Da) protein species. Western blotting and ELISA indicated that the CC chemokines MIP-1alpha, MIP-1beta, and RANTES were present in these fractions. Antibody-blocking studies with antibodies to the CC chemokines indicated that a significant portion of the soluble HIV-suppressive activity was due to these molecules. However, these experiments also suggested the inhibitory activity of the CD8(HVS) cells in coculture is not due exclusively to the CC chemokines. The HVS-transformed cells provide a useful tool for the study of noncytolytic CD8+ T lymphocyte-mediated suppression of HIV-1.

Distinct chemotactic and angiogenic activities of peptides derived from Kaposi's sarcoma virus encoded chemokines.

The vMIPs are chemokine-like proteins expressed by the Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) during the lytic phase of viral infection. vMIP-I activates CCR8, a chemokine receptor expressed by Th2 lymphocytes and cultured monocytes. vMIP-II is an agonist for CCR3, a receptor expressed by eosinophils, and an antagonist for several other chemokine receptors. Both are highly angiogenic in the chick chorio-allantoic membrane. We designed and tested three 26-mer peptides, derived from vMIP-I (pK-I), from vMIP-II (pK-II) and from the control MIP-1alpha (pM), spanning key residues of chemokines. pK-I, pK-II and pM all were able to activate a strong chemotactic response in monocytes, higher than parental vMIP-I and II. This corresponded to induction of calcium fluxes in these cells, typical of chemokines. Interestingly, pK-II and pM were also active on PMN neutrophils. In vivo studies (matrigel sponge and rabbit cornea models) showed that pK-I retains the strong angiogenic potential exerted by vMIP-I, while pK-II and pM induced an inflammatory response, probably mediated by PMN recruitment. Our observations indicate that chemokine-derived peptides can show biological activity at pharmacological concentrations. pK-I, in particular, displays the angiogenic activity of full-length vMIP-I, while all peptides appear to have acquired additional properties, stimulating new cellular targets.

High-sensitivity analysis and sequencing of peptides and proteins by quadrupole ion trap mass spectrometry.

This paper describes experience with the commercially available LCQ quadrupole ion trap mass spectrometer applied to the off-line analysis of peptides and proteins. The standard front end of the electrospray probe was replaced with a micromanipulator which, with the aid of a magnifying device, allowed the use of a variety of miniaturized spraying interfaces. The low sample consumption and extended analysis times of these devices were ideally suitable to obtain improved results in terms of sensitivity and mass accuracy. This needed a careful optimization of the number of ions stored inside the trap (ion target parameter) and required spectrum averaging of many scans. A method is presented for the mathematical fitting of ZoomScan spectra to theoretical isotopic distributions, which allowed the mass determination of large peptides with more accuracy than that achieved by conventional deconvolution algorithms. A very simple on-line desalting configuration is also described which needed no external micro-high-performance liquid chromatographic pumps, and can be easily mounted using the built-in syringe delivery system of the LCQ. This set-up allowed extended analysis times of 'in-gel' protein digests in subpicomole amounts. Finally, the multiple fragmentation capabilities of the ion trap were found to be extremely useful for the analysis of peptide modifications such as phosphorylation and for sequencing individual peptides from highly complex MHC-bound peptide pools.

Phenolic derivatives from Wigandia urens with weak activity against the chemokine receptor CCR5.

Three compounds, 2,3-dihydroxy-4-methoxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran (1), 8-methoxy-2-methyl-2-(4-methyl-3-pentenyl)-2H-1-benzopyran-6-ol (2) and 4-methoxy-3-(3-methyl-2-butenyl)-benzoic acid (3), have been isolated from Wigandia urens. The structures of compounds 1, 2 and 3 were determined from spectroscopic data and showed activity in a CCR5 assay with IC(50) values of 33, 46 and 26 muM respectively.

Variation in CD4+ T and CD8+ T lymphocyte subpopulations in bovine mammary gland secretions during lactating and non-lactating periods.

Mammary gland secretions (MGS) of dairy cows at different stages of lactation were studied by immunofluorescence cytometry for T lymphocyte subpopulations using monoclonal antibodies. During early and late lactation, the mean ratio of CD4+/CD8+ T lymphocytes in the MGS was 0.5 and 0.8, respectively. A large proportion of the CD8+ cells coexpressed the activation molecule, ACT2. These results indicate that CD8+ ACT2+ cells constituted the major phenotype in the T lymphocytes throughout lactation. In the mammary gland of cows in which drying off was induced, however, the proportion of CD8+ ACT2+ cells decreased, resulting in the increase of the CD4+/ CD8+ ratio in the MGS. At the late non-lactation stage, the ratio reached a maximal level of 2.5-4.0, which was similar to or higher than that found in the peripheral blood. This selective increase of CD4+/CD8+ cell ratio correlated with an increase in the concentrations of total cells in the MGS. This high CD4+/CD8+ cell ratio during the drying off stage rapidly decreased just before parturition, correlating with the decrease in concentrations of total cells in the MGS, reaching the lowest level at early lactation. The cells isolated at the non-lactation stage produced the cytokines IL-2 and IL-4 at a level much higher than those of cells isolated at lactation stages, and the increases were correlated with the CD4+ T lymphocyte proportions.

Functional characterization of recombinant rat macrophage inflammatory protein-1 alpha and mRNA expression in pulmonary inflammation.

Chemokines are important inflammatory mediators that function by activating and recruiting leukocytes to an inflamed tissue. We have recently cDNA cloned the rat chemokine macrophage inflammatory protein-1 alpha (MIP-1 alpha) (1). In the present study, we characterize the biological function of recombinant MIP-1 alpha protein and describe expression of its mRNA both in vitro and in a rat model of lung inflammation. In vitro rat rMIP-1 alpha protein was chemotactic for both polymorphonuclear leukocytes (PMNs) and macrophages with maximal activity at 50 nM for both cell types. In in vivo studies, we found that intratracheal instillation of 1 and 5 micrograms of rMIP-1 alpha resulted in a significant (P < 0.05) influx of cells, primarily monocytes/macrophages, into the airspace of the lungs after 6 h. Mean numbers of lavagable PMNs were not elevated significantly (P < 0.05) for either dose of MIP-1 alpha. As a model of inflammation, rats were intratracheally instilled with 0.1 mg/kg bacterial lipopolysaccharide (LPS). Bronchoalveolar lavage (BAL) was performed 3 h later. Instillation of LPS resulted in an acute neutrophilia, but no significant change in lavagable macrophages. BAL cells from control animals (saline instilled) displayed no basal mRNA expression of either MIP-1 alpha or MIP-2 (positive control). In contrast, both MIP-1 alpha and MIP-2 mRNA levels increased markedly in BAL cells from rats instilled with LPS. The rat alveolar macrophage cell line (NR8383) also showed increased MIP-1 alpha mRNA levels in response to LPS (10 micrograms/ml) with a maximal increase after 6-8 h. The induction of MIP-1 alpha mRNA expression by LPS in NR8383 cells was attenuated by cotreatment with the antioxidants N-acetylcysteine and dimethylsulfoxide, suggesting that the induction of MIP-1 alpha mRNA by LPS is mediated via the generation of reactive oxygen species. We conclude that MIP-1 alpha is a potent chemoattractant for macrophages in vivo, and its mRNA expression in macrophages and BAL cells in response to inflammatory stimuli suggests a fundamental role in acute pulmonary inflammation.

Analysis of surface properties of human cancer cells using derivatized beads.

Standard histochemical analysis of cells and tissues generally involves procedures that utilize a relatively small number of probes such as dyes, and generally requires hours or days to process. Our laboratory has developed a novel method for histochemical surveys of cell surface properties that utilizes a large number of probes (derivatized agarose beads) and takes seconds or minutes to accomplish. In this study, 4 human cell lines (CCL-255 (LS123) human colon cancer cells that are non-tumorigenic in nude mice; CRL-1459 (CCD-18CO) human colon endothelial cells that are non-malignant; CCL-220 (COLO 320DM) human colon cancer cells that are tumorigenic in nude mice; and HTB-171 (NCI H446) human lung carcinoma cells) were tested for their ability to bind to agarose beads derivatized with 51 different molecules. There were statistically significant differences in binding of the 4 cell types to all of the 51 types of beads, but 15 types of beads showed dramatic differences in binding to one or more of the 4 cell types. For example, only HTB-171 (NCI H446) bound to p-aminophenyl-beta-D-glucopyranoside-derivatized beads and only CCL-220 (COLO 320DM) bound to L-tyrosine-derivatized beads. The specificity of cell-bead binding was examined by performing assays in the presence or absence of exogenously added compounds in hapten-type of inhibition experiments. This assay, that utilizes large numbers of novel probes, may help in the development of new libraries of surface properties of specific cell types, with differing degrees of malignancy, that at this time could not be developed by using other available technologies.