Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10145 (IL-8)
 23,849 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown that platelet factor 4 (PF4), a platelet-specific CXC chemokine, can directly and specifically inhibit human megakaryocyte colony formation. We therefore hypothesized that PF4 might function as a negative autocrine regulator of megakaryocytopoiesis. Herein we present additional studies characterizing the inhibitory effect of CXC chemokines on human megakaryocyte development. We first corroborated our initial studies by showing that recombinant human (rH) PF4, like the native protein, inhibited megakaryocytopoiesis. We then examined the inhibitory properties of other CXC family members. Neutrophil activating peptide-2 (NAP-2), a naturally occurring N-terminally cleaved beta TG peptide, was found to inhibit megakaryocytopoiesis with two to three orders of magnitude greater potency than PF4. Structure function studies showed that an N-terminal mutation, which eliminated NAP-2's neutrophil activating properties (NAP-2E2-->A), also abrogated its ability to inhibit megakaryocyte development. Further investigations of this type demonstrated that a chimeric PF4 protein (AELR/PF4) in which PF4's N-terminus was replaced with the first four amino acids of NAP-2 was also a potent inhibitor of megakaryocytopoiesis. Interleukin (IL)-8, another CXC chemokine, and three CC chemokines (macrophage inhibitory protein-1 alpha [MIP-1 alpha], MIP-1 beta, and C10) also specifically inhibited megakaryocyte colony formation at NAP-2 equivalent doses. CXC and CC chemokine inhibition was additive suggesting that the effects might be mediated through a common pathway. The inhibitory effects of NAP-2 and MIP-1 alpha could not be overcome by adding physiologically relevant amounts of recombinant human megakaryocyte growth and development factor (MGDR) (50 ng/mL) to the cultures. Using Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR) based analyses, we documented mRNA expression of IL-8 receptor isoforms alpha and beta in total platelet RNA and in normal human megakaryocytes, respectively. Based on these results, we hypothesize that chemokines play a physiologic role in regulating megakaryocytopoiesis. Because chemokines are elaborated by ancillary marrow cells, both autocrine and paracrine growth control is suggested, the effects of which might be exerted, in part, through alpha and beta IL-8 receptors.
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PMID:Chemokine regulation of human megakaryocytopoiesis. 767 Jan 1

The CXC chemokine, IL-8, is a potent chemoattractant of neutrophils and binds to two distinct receptors, termed IL-8R1 and IL-8R2. These receptors share high affinity for IL-8, however, only IL-8R1 is specific for IL-8 whereas IL-8R2 binds other related chemokines, including GRO alpha with high affinity. Stable Jurkat transfectants were generated expressing either functional IL-8R1 or IL-8R2 (J-IL8R1 and J-IL8R2). Both J-IL8R1 and J-IL8R2 exhibited high affinity IL-8 binding (Kd 3-5 nM) with respective receptor densities of 23,000 +/- 3,000 and 18,500 +/- 1,500. Pre-treatment of both transfectants with 1.0 micrograms/ml B. pertussis toxin (PTx) resulted in inhibition of IL-8 mediated intracellular Ca2+ mobilisation and chemotaxis, without altering the receptor's affinity for its ligand. This indicates that both receptors couple to a PTx-sensitive G-protein. Further studies showed that IL-8R1 and IL-8R2 could mediate time-dependent phosphorylation of p42/p44 MAP-kinase. In both transfectants, phosphorylation was maximal at 1-2 min after IL-8 stimulation and could be inhibited by PTx. Stimulation of J-IL8R1 and J-IL8R2 with GRO alpha revealed that this chemokine was a more potent activator of MAP-kinase in J-IL8R2, an observation reflected in the high affinity binding of GRO alpha to IL-8R2. These studies indicate that chemokines are capable of activating protein kinases and with regards to PTx-sensitivity and MAP-kinase stimulation, no significant differences between IL-8R1 and IL-8R2 post-receptor signalling occur during cell activation by IL-8.
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PMID:A comparison of post-receptor signal transduction events in Jurkat cells transfected with either IL-8R1 or IL-8R2. Chemokine mediated activation of p42/p44 MAP-kinase (ERK-2). 775 May 73

Interleukin-8 (IL-8), a member of the CXC chemokine family, is a key activator of neutrophils. We have previously shown that two novel CC chemokine-like properties, namely monocyte chemoattraction and binding to CC CKR-1, are introduced into IL-8 by mutating Leu25 to the conserved tyrosine present in CC chemokines. To further investigate the role of this position in receptor selectivity, we have mutated Leu25 to cysteine. The protein folds correctly with two disulfide bonds and a free thiol group at Cys25. This mutant behaves overall like wild-type IL-8, with little change in neutrophil chemotaxis and IL-8 receptor binding, and has no effect on CC CKR-1. These data are consistent with cysteine being approximately isosteric with the natural amino acid leucine. However, modification of the cysteine by addition of a fluorescent N-methyl-N-(2-N-methyl, N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)aminoethyl)acetamido (NBD) group lowers potency in neutrophil chemotaxis and affinity in IL-8 receptor binding assays by 2 orders of magnitude. This Leu25 --> Cys-NBD mutant introduces monocyte chemoattractant activity and the ability to displace 125I-labeled macrophage inflammatory protein-1 alpha from the recombinant CC CKR-1 receptor. Additionally, we show a specific interaction between the fluorescent mutant and the N-terminal 34-amino acid peptide from CC CKR-1. This confirms the importance of this region in IL-8 in receptor binding and in conferring specificity between CXC and CC chemokines. Circular dichroism spectra of the IL-8 mutants having CC chemokine-like activity show a consistent drop in alpha-helical content compared with the spectra for wild-type IL-8. This suggests that distortion of the C-terminal helix may play a role in chemokine receptor-ligand selectivity.
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PMID:A molecular switch of chemokine receptor selectivity. Chemical modification of the interleukin-8 Leu25 --> Cys mutant. 862 14

Interleukin-8 (IL-8), a CXC chemokine, is known to bring about chemotaxis and activation of neutrophils through high affinity binding to at least two distinct receptors, receptor-A and receptor-B. The IL-8 homolog melanoma growth stimulating activity (MGSA) is also active toward neutrophils. In contrast to IL-8, MGSA binds receptor-B with high affinity and binds receptor-A with approximately 400-fold lower affinity. Using the structure of IL-8 (Clore et al.(1990) Biochemistry, 29, 1689-1696; Baldwin et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 502-506) and the NMR-determined structure of MGSA (Fairbrother et al. (1994) J. Mol. Biol. 242, 252-270), we designed variants of both IL-8 and MGSA to investigate the basis of specificity for binding of these chemokines to the IL-8 receptors. The most outstanding structural difference between IL-8 and MGSA lies in the loop preceding the first beta-strand. When the corresponding (shorter) loop from MGSA was swapped into IL-8, both receptor-A and receptor-B binding affinities were significantly (>300-fold) reduced. However, with additional mutations that affect packing interactions, an IL-8 variant specific for receptor-B binding was produced. Conversely, when the same loop from IL-8 was swapped into MGSA, receptor-B binding was maintained with only a approximately 30-fold reduction in receptor-A affinity. Again, mutations affecting packing of the loop yielded a MGSA variant with high affinity for both receptors, like IL-8. Finally, we show, through point mutations in a monomeric IL-8 framework, that individual side chain substitutions can affect receptor specificity.
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PMID:Exchanging interleukin-8 and melanoma growth-stimulating activity receptor binding specificities. 866 82

Interleukin-8 (IL-8), growth-related oncogene (GRO) alpha, GRObeta, GROgamma, neutrophil-activating peptide-2 (NAP-2), epithelial cell-derived neutrophil activating peptide- 78 (ENA-78), and granulocyte chemoattractant protein-2 are potent neutrophil chemoattractants 40-90% identical in amino acid sequence that comprise a subgroup of human CXC chemokines defined by the conserved sequence motif glutamic acid-leucine-arginine (ELR). Two human chemotactic receptor subtypes for IL-8, named IL-8 receptors (IL8R) A and B, have been cloned. They are 78% identical in amino acid sequence, coexpressed in neutrophils, and distinguished by their different selectivities for GROalpha and NAP-2. Their selectivity for other ELR+ CXC chemokines has not been previously reported. By measuring calcium flux in human embryonic kidney 293 cells transfected with plasmids encoding IL8RA or IL8RB, we have now defined receptor selectivity for GRObeta, GROgamma, and ENA-78. The rank order of agonist potency, based on inspection of the mean effective concentration values (EC50), for IL8RB was GROgamma (1 nM) > IL-8 (4 nM) approximately GROalpha (5 nM) approximately GRObeta (4 nM) approximately NAP-2 (7 nM) > ENA-78 (11 nM), and for IL8RA was IL-8 (4 nM) >>> ENA-78 (40 nM) approximately NAP-2 (45 nM) > GROalpha (63 nM) approximately GROgamma (65 nM) >> GRObeta. The maximal response of IL8RA to IL-8 was at least 2-fold greater than the other five chemokines. All six agonists for IL8RB competed for high affinity 125I-IL-8, -GROalpha, -NAP-2, and -ENA-78 binding sites at IL8RB. GROalpha, GRObeta, GROgamma, NAP-2, and ENA-78 competed weakly for the high affinity IL-8 binding site at IL8RA. Thus, IL8RA and IL8RB are both highly selective for IL-8 and have similar sequences but differ dramatically in their selectivity for all other ELR+ CXC chemokines tested. These findings have important implications for developing novel neutrophil-specific anti-inflammatory drugs directed against the CXC chemokine signaling system.
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PMID:The CXC chemokines growth-regulated oncogene (GRO) alpha, GRObeta, GROgamma, neutrophil-activating peptide-2, and epithelial cell-derived neutrophil-activating peptide-78 are potent agonists for the type B, but not the type A, human interleukin-8 receptor. 870 98

Several studies have shown that CC chemokines attract T lymphocytes, and that CD45RO+, memory phenotype cells are considered to be the main responders. The results, however, have often been contradictory and the role of lymphocyte activation and proliferation has remained unclear. Using CD45RO+ blood lymphocytes cultured under different stimulatory conditions, we have now studied chemotaxis as well as chemokine receptor expression. Expression of the RANTES/MIP-1 alpha receptor (CC-CKR1) and the MCP-1 receptor (CC-CKR2) was highly correlated with migration toward RANTES, MCP-1, and other CC chemokines, and was strictly dependent on the presence of IL-2 in the culture medium. Migration and receptor expression were rapidly downregulated when IL-2 was withdrawn, but were fully restored when IL-2 was added again. The effect of IL-2 could be partially mimicked by IL-4, IL-10, or IL-12, but not by IL-13, IFN gamma, IL-1 beta, TNF-alpha, or by exposure to anti-CD3, anti-CD28 or phytohemagglutinin. Activation of fully responsive lymphocytes through the TCR/CD3 complex and CD28 antigen actually had the opposite effect. It rapidly downregulated receptor expression and consequent migration even in the presence of IL-2. In contrast to the effects on CC chemokine receptors, stimulation of CD45RO+ T lymphocytes with IL-2 neither induced the expression of the CXC chemokine receptors, IL8-R1 and IL8-R2, nor chemotaxis to IL-8. The prominent role of IL-2 in CC chemokine responsiveness of lymphocytes suggests that IL-2-mediated expansion is a prerequisite for the recruitment of antigen-activated T cells into sites of immune and inflammatory reactions.
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PMID:Interleukin-2 regulates CC chemokine receptor expression and chemotactic responsiveness in T lymphocytes. 876 Jul 84

Chemokines are a family of small proteins that are present in a variety of inflammatory conditions and have been shown to activate and recruit a wide variety of cell types. They bind to a family of seven transmembrane G-protein-coupled receptors. Models for the interaction of the chemokines with their receptors suggest a two-step mechanism. Initially, the main body of the chemokine interacts with the outside of the receptor (Site 1), and this interaction directs receptor selectivity. Subsequently, the flexible amino-terminus of the chemokine interacts with the receptor core (Site 2) to initiate the signaling response. Mutagenesis studies of IL-8, the archetypal CXC chemokine, show that altering the protein on the third beta-sheet can change the receptor selectivity from that of a CXC chemokine and introduce CC chemokine activity-confirming the role of this region in Site 1. Mutagenesis studies of the amino-terminal region of IL-8 showed that a tripeptide, ELR, was essential for the interaction with Site 2. We have shown, using synthetic peptides and site-directed mutagenesis, that the amino-terminus of RANTES is important in the signaling response (Site 2). Mutations that alter only the interaction with Site 2 are capable of binding the receptor and not signaling and are therefore potential antagonists. Such antagonists have now been made by several groups, for a number of the chemokine receptors, and are active at nanomolar concentrations. These can now be used to test the hypothesis that antagonism of chemokine receptors will lead to a reduction in inflammation in vivo.
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PMID:The Molecular Basis of the Chemokine/Chemokine Receptor Interaction-Scope for Design of Chemokine Antagonists 881 52

The mechanisms by which chemokines bind and signal through their receptors are complex and poorly understood. In the present study, we sought to dissect these processes and to map important functional domains of the two CXC chemokine (interleukin-8) receptors, CXCR1 (formally IL-8RA) and CXCR2 (formally IL-8RB), using blocking monoclonal antibodies (mAbs) to the receptors and a series of chimeras between CXCR1 and CXCR2. A panel of specific mAbs against CXCR1 or CXCR2, generated by immunizing mice with transfectants expressing either receptor, were shown to effectively block IL-8- and/or growth-related oncogene alpha (GROalpha) -mediated ligand binding, chemotaxis, elastase release, and VCAM-1 binding in CXCR1 and CXCR2 transfectants and/or human neutrophils. Of particular interest was an anti-CXCR1 mAb, 7D9, that inhibited chemotaxis, elastase release, and VCAM-1 binding but had no detectable effects on ligand binding. The epitopes of these blocking mAbs were mapped by using a series of CXCR1/2 chimera transfectants and synthetic peptides. Most of the anti-CXCR1 antibodies, except 7D9, mapped to the amino acid sequence WDFDDL (CXCR1 residues 10-15), and all the anti-CXCR2 antibodies mapped to the amino acid sequence FEDFW (CXCR2 residues 6-10). The epitope of mAb 7D9 mainly involved a region within the first 45 residues of CXCR1, and it appeared to be conformation-sensitive. These results support a model in which the binding and signaling of IL-8 with its receptor occur in at least two discrete steps involving distinct domains of the receptor. This model is consistent with the notion that discrete conformational changes of the receptor secondary to ligand binding are required to trigger various biological responses. Moreover, the ligand binding and chemotaxis properties of each CXCR1/2 chimeric receptor to IL-8 and GROalpha were determined. It was found that each is distinct in its ability to confer ligand binding and chemotactic response to IL-8 and GROalpha, and two conclusions could be made. 1) The N-terminal segment of CXCR1 is a dominant determinant of receptor subtype selectivity, consistent with previous studies using rabbit/human CXCR1/2 chimeras; and 2) the specificity determinant for GROalpha binding in CXCR2 involves sequences in the N terminus, distal to the first 15 residues, as well as other parts of the receptor.
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PMID:Discrete steps in binding and signaling of interleukin-8 with its receptor. 894 Jan 21

Rat CINC/Gro is a 72 residue chemotactic factor of neutrophils, and a member of the CXC chemokine family, that includes IL-8 and MGSA/GRO. Although the three-dimensional structure of CINC/Gro had previously been determined to be that of a dimer with 200 mM NaCl, it was shown on both ultracentrifugation analysis and 1H-NMR spectral analysis that CINC/Gro exists mainly as a monomer at a physiological concentration, similar to other proteins belonging to this family. By reducing the NaCl concentration, the equilibrium could be shifted to the monomer, making it possible to observe the monomer and dimer resonances in 1H-NMR spectra. There were no significant chemical shift changes of alpha protons in the beta sheet between the monomer and dimer, suggesting that the beta sheet structure was retained in the monomer. Instead, the chemical shift changes of a protons were significant at I18 and K21, which are located in the long loop region interacting with the alpha helix, and V59 at the beginning of the a helix, indicating structural changes in the relative positions of the alpha helix and beta sheet.
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PMID:Subunit association and monomer structure of CINC/Gro revealed by 1H-NMR. 919 22

Human neutrophils express two interleukin (IL)-8 receptors, CXC chemokine receptor (CXCR) 1 and CXCR2. IL-8 with changes to the NH2-terminal ELR motif can block IL-8-induced neutrophil functions (Moser, B., Dewald, B., Barella, L., Schumacher, C., Baggiolini, M., and Clark-Lewis, I. (1993) J. Biol. Chem. 268, 7125-7128). We have now examined the effect of NH2-terminally modified analogs of IL-8, GROalpha, and PF4 on CXCR1 and CXCR2 independently. Using stable Jurkat transfectants expressing either CXCR1 or CXCR2, it was shown that analogs derived from IL-8 bound both IL-8 receptors with similar affinity and could block IL-8-induced Ca2+ mobilization. By contrast, analogs of GROalpha and PF4, (R)GROalpha and (R)PF4, bound only CXCR2 with high affinity and blocked Ca2+ mobilization induced only via CXCR2. The differential effect on CXCR1 and CXCR2 was also demonstrated in studies with isolated neutrophils. Thus (R)GROalpha and (R)PF4 inhibited only the GROalpha but not the IL-8-stimulated elastase release, and these two analogs had no effect on IL-8-elicited superoxide generation, a response that is mediated by CXCR1 but not by CXCR2. These results show that CXCR2 selective receptor antagonists can be generated based upon the secondary binding determinants of GROalpha and PF4. They also highlight the primary importance of CXCR1 in chemokine-mediated release of granule enzymes and superoxide generation. The selective antagonists described may be used in future studies on IL-8 receptor signaling to define distinct steps leading to various functional responses induced in neutrophils via CXCR1 and CXCR2.
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PMID:Chemokine antagonists that discriminate between interleukin-8 receptors. Selective blockers of CXCR2. 919 14


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