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B Moser

Publications and source records attributed to B Moser.

At least 91 records · Page 5Linked to original sources
PubMed1995

Sequence variation of a novel heptahelical leucocyte receptor through alternative transcript formation.

Chemoattractants, including chemokines such as interleukin 8 (IL-8) and related proteins, activate leucocytes via seven-transmembrane-domain G-protein-coupled receptors. A cDNA for a novel receptor of this kind consisting of 327 amino acids was isolated from a human blood monocyte cDNA library. The polypeptide, termed monocyte-derived receptor 15 (MDR15), is an alternative form of the Burkitt's lymphoma receptor 1 (BLR1) encoded by a human Burkitt's lymphoma cDNA [Dobner, Wolf, Emrich and Lipp (1992) Eur. J. Immunol. 22, 2795-2799]. MDR15 and BLR1 cDNAs differ in the 5' region, where the open reading frame of MDR15 is shorter by 45 codons. Southern-blot analysis indicates that the two transcripts for MDR15 and BLR1 are encoded by the same gene. Northern-blot analysis using a probe that hybridizes with both mRNAs demonstrated high-level expression in chronic B-lymphoid leukaemia and non-Hodgkin's lymphoma cells and, to a lesser extent, peripheral blood monocytes and lymphocytes. Reverse transcription-PCR studies with MDR15- and BLR1-specific primers showed similar levels of transcripts for both receptors in RNA that was positive in Northern-blot analysis. MDR15 and BLR1 have high structural similarity to receptors for human IL-8 (about 40% amino acid identity) and other chemokines. However, none of a series of radiolabelled chemokines (IL-8, NAP-2, GRO alpha, PF4, IP10, MCP-1, MCP-2, MCP-3, I-309, RANTES and MIP-1 alpha) and other ligands (C3a and leukotriene B4) bound to Jurkat transfectants that stably expressed either MDR15 or BLR1 mRNA. The fact that MDR15 and BLR1 are expressed on leucocytes and show marked sequence similarity to chemokine receptors suggests the existence of as yet unidentified chemokines. Alternative transcript formation affecting the 5'-terminal part of the coding region may be a way to modify ligand-binding selectivity.

Alternative Splicing↗
PubMed1995

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).

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.

Cell Line↗
PubMed1995

A subset of striatopallidal neurons are Fos-immunopositive following acute monoamine depletion in the rat.

Experiments were conducted to characterise the Fos-immunopositive neurons that are observed in the dorsal rim of the striatum following monoamine depletion by the systemic administration of reserpine. Using a retrograde tract-tracer, some of these neurons could be shown to project to the globus pallidus but none were seen to project to the entopeduncular nucleus. In addition, these neurons were located in a region of both poor calbindin immunoreactivity and cholinesterase activity. It can be concluded that Fos levels are increased only in a subset of striatopallidal neurons following monoamine depletion. This subset of neurons is located in the dorsal region of the striatum where it has previously been shown that neurons can preferentially be induced to undergo apoptosis upon monoamine depletion.

Animals↗
PubMed1995

Structure-activity relationships of chemokines.

Structural analysis of chemokines has revealed that the alpha/beta structural-fold is highly conserved among both the CXC and CC chemokine classes. Although dimerization and aggregation is often observed, the chemokines function as monomers. The critical receptor binding regions are in the NH2-terminal 20 residues of the protein and are the least ordered in solution. The flexible NH2-terminal region is the most critical receptor binding site and a second site also exists in the loop that follows the two disulfides. The well-ordered regions are not directly involved in receptor binding but, along with the disulfides, they provide a scaffold that determines the conformation of the sites that are critical for receptor binding. These general requirements for function are common to all the chemokines. For the CC chemokines, receptor activation and receptor binding regions are separate within the 10 residue NH2-terminal region. This has allowed identification of high affinity analogs that do not activate the receptor and are potent antagonists.

Amino Acid Sequence↗
PubMed1995

Interleukin-8 and the chemokine family.

Two subfamilies of chemokines are distinguished depending on the arrangement of the first two of four conserved cysteines, which are either separated by one amino acid (CXC chemokines) or adjacent (CC chemokines). IL-8 and the other CXC chemokines act preferentially on neutrophils, while the CC chemokines (MCP-1, MCP-2, MCP-3, RANTES, MIP-1 alpha and MIP-1 beta) act on monocytes, but not neutrophils, and have additional activities toward basophil and eosinophil granulocytes, and T-lymphocytes. Several chemokine receptors have been identified, all of which belong to the seven-transmembrane-domain type and are coupled to G-proteins. The discovery of chemokines has provided the basis for the understanding of leukocyte recruitment and activation in inflammation and other disturbances of tissue homeostasis.

Animals↗
PubMed1994

Structural requirements for interleukin-8 function identified by design of analogs and CXC chemokine hybrids.

Structure-activity relationships of human interleukin-8 (IL-8) were probed using chemically synthesized analogs with single or double amino acid substitutions, as well as hybrids derived by substituting IL-8 regions into IP10, a related protein that lacks IL-8 activity. The analogs were tested for functional activity by measuring induction of elastase release from human neutrophils and competition for binding of radiolabeled IL-8. The hybrid studies indicated that Gly31 and Pro32, as well as the NH2-terminal region from IL-8 are required to convert IP10 into a fully functional protein, suggesting that these elements are critical for IL-8 activity. Both disulfide bridges, linking residue 7 to 34 and residue 9 to 50, were critical for function, as shown by substituting the cysteine pairs with alpha-aminobutyric acid. Single conservative substitutions were generally accepted into the 10-22 region of IL-8, which contrasts with the ELR motif (residues 4-6), previously shown to be essential for activity. The importance of residues within the 10-15 region and the 17-22 region was demonstrated with hybrids. In addition, some of the 4-22 residues have structural roles that may be important; for example, Tyr13, Phe17, and Phe21 are involved in aromatic interactions in the IL-8 structure, and are also moderately sensitive to modification. Except for Cys50, the results argue against a role for the 36-72 region, including the COOH-terminal alpha-helix, in receptor binding. We conclude that the disulfide bridges and 30-35 turn provide a structural scaffold for the NH2-terminal region which includes the primary receptor-binding site (the ELR motif) and secondary binding and conformational determinants between residues 10 and 22.

Amino Acid Sequence↗
PubMed1994

Both interleukin-8 receptors independently mediate chemotaxis. Jurkat cells transfected with IL-8R1 or IL-8R2 migrate in response to IL-8, GRO alpha and NAP-2.

Neutrophil leukocytes, the target cells for interleukin-8 and related CXC chemokines, bear high numbers of two types of IL-8 receptors (IL-8R1 and IL-8R2). By cDNA transfection Jurkat cell lines were generated that stably express either IL-8R1 or IL-8R2 (J-IL8R1 and J-IL8R2). J-IL8R1 expressed 4,000 +/- 1,000 copies of IL-8R1, and bound IL-8 with high affinity (Kd 1-4 nM) and GRO alpha and NAP-2 with low affinity (Kd 200-500 nM). J-IL8R2 expressed 17,000 +/- 3,000 copies of IL-8R2, and bound all three chemokines with high affinity. Both transfectants showed a similar degree of chemotactic migration after stimulation with IL-8, GRO alpha and NAP-2. All three chemokines were equally potent as attractants of J-IL8R2, whereas IL-8 was 300 to 1,000-fold more potent than GRO alpha or NAP-2 as attractant of J-IL8R1. The potencies, therefore, agree with the affinities of the ligands to IL-8R1 and IL-8R2. Our results demonstrate that both IL-8 receptors function independently, and mediate chemotaxis in response to IL-8 and other CXC chemokines.

Animals↗
PubMed1994

Functional and ligand binding specificity of the rabbit neutrophil IL-8 receptor.

IL-8 mediates migration and activation of neutrophils. This study describes the functional and ligand binding specificity of the human intercrine peptides IL-8, neutrophil-activating peptide 2 (NAP-2), melanoma growth stimulatory activity (GRO), and platelet factor 4 (PF4) to rabbit neutrophils and mammalian cell lines transfected with rabbit IL-8 receptor cDNA (F3R). Rabbit neutrophil membranes bound 125I-labeled IL-8 and 125I-labeled NAP-2 but did not bind 125I-labeled GRO or 125I-labeled PF4. Rabbit neutrophils mobilized intracellular Ca2+ in response to IL-8 and NAP-2 but not to GRO or PF4. Monkey kidney cells (COS-7) and hamster lung fibroblasts (CCL-39) were transiently and stably transfected with the rabbit neutrophil IL-8 receptor F3R cDNA. COS-7 cells transfected with F3R cDNA bound 125I-labeled IL-8 but did not bind other IL-8-related peptides such as 125I-labeled NAP-2, 125I-labeled GRO, or 125I-labeled PF4. Furthermore, bound 125I-labeled IL-8 was only displaced by unlabeled IL-8 but not by unlabeled NAP-2, GRO alpha, or PF4. Consistent with this observation, stably transfected CCL 39 cells expressing F3R cDNA mobilized Ca2+ only in response to IL-8. We conclude that F3R cDNA encodes a functional IL-8 receptor isotype with strict ligand binding specificity for IL-8, that rabbit neutrophils do not bind human GRO alpha, and it is suggested that rabbit neutrophils contain in addition to the F3R protein another IL-8 receptor isotype with broad ligand specificity or a distinct NAP-2 receptor.

Animals↗
PubMed1994

Cloning of a human seven-transmembrane domain receptor, LESTR, that is highly expressed in leukocytes.

Several chemotactic agonists including interleukin-8 (IL-8) and related cytokines have been shown to activate and attract leukocytes via seven-transmembrane domain, GTP-binding protein-coupled receptors. A cDNA clone, LESTR, encoding a protein of 352 amino acids, corresponding to a novel receptor of this type, was isolated from a human blood monocyte cDNA library. The sequence of the deduced protein, LESTR (leukocyte-derived seven-transmembrane domain receptor), has 92.6% identity with that of a recently reported bovine neuropeptide Y (NPY) receptor, boLCR1 (Rimland, J., Xin, W., Sweetnam, P., Saijoh, K., Nestler, E. J., and Duman, R. S. (1991) Mol. Pharmacol. 40, 869-875). LESTR, however, is more similar (> 34%) to the IL-8 receptors, IL-8R1 and IL-8R2, than to several NPY receptors of different origin (< 20%). In the monocyte library, LESTR cDNA fragments were about 20 times as frequent as cDNA coding for IL-8R1 and IL-8R2, and much higher levels of LESTR- than IL-8R-specific mRNA were found in human blood neutrophils and lymphocytes. LESTR transcripts, by contrast, were low or undetectable in several neuroblastoma cell lines that are widely used to study NPY functions. Transfected cells expressing high levels of LESTR mRNA did not bind radiolabeled NPY, IL-8, NAP-2, GRO alpha, PF4, IP10, MCP-1, MCP-3, MIP-1 alpha, HC14, I309, RANTES, C3a, or LTB4. NPY also failed to bind to neutrophils, monocytes, and lymphocytes, to elicit responses in vitro such as Ca2+ changes, shape change, chemotaxis, enzyme release, and the respiratory burst, and to induce leukocyte accumulation upon injection in rats and rabbits. Although the ligand for LESTR could not be identified among a large number of chemotactic cytokines, the high expression in white blood cells and the marked sequence relation to IL-8R1 and IL-8R2 suggest that LESTR may function in the activation of inflammatory cells.

Amino Acid Sequence↗
PubMed1994

Glutamate-induced apoptosis results in a loss of striatal neurons in the parkinsonian rat.

The motor symptoms of Parkinson's disease are caused by an increase in activity of striatal neurons which project to the globus pallidus. The discharge activity of these striatal cells is normally regulated by a balance between an inhibitory nigral dopamine input and an excitatory cortical glutamate input. The loss of nigrostriatal dopamine in Parkinson's disease allows the cortical glutamatergic input to dominate (see Fig. 1). Pharmacological or surgical manipulations which redress this imbalance in activity in the striatum, or prevent its propagation throughout the basal ganglia, alleviate the motor symptoms of Parkinsonism. We present evidence to suggest the existence of an endogenous mechanism which compensates for the striatal imbalance during the early stages of Parkinsonism. In the rat rendered parkinsonian by systemic administration of reserpine, selective deletion of striatal neurons was observed. The dying striatal neurons exhibited all of the morphological and biochemical hallmarks of apoptosis. This apoptotic cell death was blocked by either administration of glutamate antagonists or decortication. Our data demonstrate that unchecked endogenous glutamate can induce apoptosis of striatal projection neurons in vivo. This observation may have relevance to the neurophysiological mechanisms which maintain the balance of neural activity within the CNS and to the pathology of neurological diseases.

Animals↗
PubMed1994

Monocyte chemotactic proteins MCP-1, MCP-2, and MCP-3 are major attractants for human CD4+ and CD8+ T lymphocytes.

The responses of lymphocytes to six CC chemokines--MCP-1, MCP-2, MCP-3, MIP-1 alpha, MIP-1 beta, and RANTES--were studied using cloned human CD4+ and CD8+ T cells. All CC chemokines tested induced migration of both types of lymphocytes, whereas two CXC chemokines used as controls, IL-8 and IP-10, were inactive. The monocyte chemotactic proteins (MCP-1, MCP-2, and MCP-3) showed a typically bimodal concentration dependence, and were considerably more effective than MIP-1 alpha, MIP-1 beta, or RANTES. All CC chemokines also induced a rapid and transient rise in cytosolic free Ca2+ in either type of T cell. The rise was prevented by Bordetella pertussis toxin treatment, indicating that G-protein-coupled receptors are involved in signaling. It was most pronounced with MCP-1 and MCP-3, which is in agreement with the efficacy of these chemokines as chemoattractants. The responses to MCP-2, MIP-1 alpha, MIP-1 beta, and RANTES were weaker, and no changes were obtained on stimulation with IL-8 or IP-10. Freshly isolated human blood lymphocytes were also tested, but neither migration nor Ca2+ changes were observed. Low numbers of high-affinity receptors for MCP-1 were found on CD4+ and CD8+ cells ( < 900 per cell, Kd < 1 nM), and desensitization experiments showed that MCP-1, MCP-2, and MCP-3 share receptors. Owing to their superior effectiveness on CD4+ and CD8+ T cells, the monocyte chemotactic proteins could play a major role in the recruitment of activated T lymphocytes.

CD4-Positive T-Lymphocytes↗
PubMed1993

Constitutive expression of interleukin-8 and its receptor in human myeloid and lymphoid leukemia.

Interleukin-8 (IL-8), a member of the family of small inducible cytokines, is mainly known for its striking neutrophil-activating properties. Constitutive IL-8 production is negligible in normal leukocytes. We examined expression of IL-8 and its receptor in purified leukemic cells from patients with untreated acute myeloblastic leukemia (AML) and lymphoid leukemias. In the majority of cases (18 of 26 AML, 8 of 15 lymphoid leukemias), the cells constitutively expressed IL-8 mRNA transcripts. In all but 3 of these cases, IL-8 mRNA-expressing cells secreted biologically active IL-8 protein. Immunocytochemical analysis showed intracellular IL-8 (5% to 90% of total cells), demonstrating that the leukemic cells themselves rather than contaminants (monocytes or lymphocytes) were the source of IL-8. Ten of 25 AML samples expressed IL-8 receptor mRNA and, with 1 exception, the IL-8 receptor expressing cells also produced its ligand. In contrast, all lymphoid leukemias were negative. Furthermore, frequent coexpression of IL-8 and IL-1 beta transcripts was seen in both AML and lymphoid leukemia samples, whereas fewer cases coexpressed IL-8 and either macrophage colony-stimulating factor or granulocyte-macrophage colony-stimulating factor. In leukemic cells expressing the IL-8 receptor, IL-8 induced cytosolic free calcium changes, indicating activation of the classical signaling pathway. These results suggest that IL-8 may have biologic activities in hematopoiesis.

Blotting, Southern↗
PubMed1993

Expression of transcripts for two interleukin 8 receptors in human phagocytes, lymphocytes and melanoma cells.

Two cDNAs coding for distinct interleukin 8 (IL-8) receptors, IL-8R1 [Murphy and Tiffany (1991) Science 253, 1280-1283] and IL-8R2 [Holmes, Lee, Kuang, Rice and Wood (1991) Science 253, 1278-1280] have been reported, and biochemical studies on human neutrophils have revealed two proteins (p70 and p44) that bind IL-8 with high affinity [Moser, Schumacher, von Tscharner, Clark-Lewis and Baggiolini (1991), J. Biol. Chem. 266, 10666-10671]. We have cloned the cDNA coding for IL-8R1 from a library of differentiated HL-60 cells. Transfection of this cDNA into Jurkat cells resulted in the expression of high-affinity binding for IL-8 and two related cytokines, GRO alpha and neutrophil-activating peptide 2 (Kd 0.5-1.0 nM). Northern-blot analysis with the IL-8R1 cDNA as probe revealed abundant expression of transcripts of different size in human neutrophils and low-level expression of a single RNA species in HL-60 cells differentiated with dimethyl sulphoxide and retinoic acid. Because of the extensive nucleotide sequence similarity of the cDNAs for IL-8R1 and IL-8R2, the reverse-transcription PCR method was used for analysis of RNA expression in myeloid and lymphoid cells, 19 cell lines established from human primary melanomas or metastases, two melanocyte and one fibroblast cell lines. IL-8R1 mRNA transcripts were expressed at high levels in neutrophils, and to a lesser extent in blood monocytes and the myeloid cell lines, HL-60 and AML 193, but were not found in THP-1 cells, lymphocytes and Jurkat cells. IL-8R2 mRNA transcripts, by contrast, were found in all blood cells and related cell lines, as well as in all melanoma, melanocyte and fibroblast cell lines tested. As for IL-8R1, IL-8R2 mRNA expression was highest in neutrophils. These results suggest that IL-8R1 and IL-8R2 may both be involved in neutrophil activation by IL-8 and related cytokines, and presumably correspond to p70 and p44, the receptors that were identified biochemically. Possible IL-8 functions on lymphocytes and melanoma cells, e.g. chemotaxis and proliferation, must be independent of IL-8R1 and may be mediated by IL-8R2.

Base Sequence↗
PubMed1993

Platelet factor 4 binds to interleukin 8 receptors and activates neutrophils when its N terminus is modified with Glu-Leu-Arg.

Amino acid deletion and mutagenesis experiments have indicated that the sequences Glu-Leu-Arg (ELR) preceding the first cysteine at the N terminus of interleukin 8 (IL-8) is required for receptor binding and neutrophil activation. Platelet factor 4 (PF4) is structurally related to IL-8 (35% sequence identity) but lacks the N-terminal ELR sequence and comparable effects on neutrophils. We introduced the ELR sequence at the N terminus of PF4 and found that the modified protein was a potent neutrophil activator and attractant. On the other hand, when the ELR sequence was introduced into the corresponding positions of two other proteins related to IL-8, gamma-interferon-inducible protein IP10 and monocyte chemoattractant protein 1, neither of them acquired neutrophil-activating properties, indicating that besides ELR additional structural determinants of IL-8 and PF4 are important for binding to IL-8 receptors. The conservation of these binding determinants suggests that PF4 may have evolved from a neutrophil activating protein.

Amino Acid Sequence↗
PubMed1993

Interleukin-8 antagonists generated by N-terminal modification.

We have previously shown that the residues Glu4-Leu5-Arg6 (ELR) preceding the first cysteine at the N terminus of the 72-residue form of interleukin-8 (IL-8) are essential for receptor binding and neutrophil activation (Clark-Lewis, I., Schumacher, C., Baggiolini, M., and Moser, B. (1991) J. Biol. Chem. 266, 23128-23134). We have now synthesized a series of analogs of IL-8(4-72), the truncated form of IL-8 with the N-terminal sequence ELRC, as potential IL-8 antagonists. Among 26 analogs with deletions or amino acid replacements in the ELR region several inhibited IL-8 function. The most potent were IL-8(6-72), with Arg6 at the N terminus, and IL-8,AAR(7-72) with N-terminal Ala4-Ala5 instead of Glu4-Leu5. They inhibited IL-8 receptor binding, exocytosis (IC50 0.3 microM), as well as chemotaxis and the respiratory burst. Inhibition was restricted to responses elicited by IL-8, GRO alpha, or NAP-2, and no effect was observed when the unrelated agonists fMet-Leu-Phe or C5a were used as stimuli. These results demonstrate that selective antagonists that prevent or attenuate the action of IL-8 and its related chemotactic cytokines are obtained by modification of the ELR sequence at the N terminus.

Amino Acid Sequence↗
PubMed1992

High- and low-affinity binding of GRO alpha and neutrophil-activating peptide 2 to interleukin 8 receptors on human neutrophils.

GRO alpha and neutrophil-activating peptide 2 (NAP-2), like their analog interleukin 8 (IL-8), are considered to be inflammatory mediators since they recruit and activate neutrophil leukocytes. After introduction of tyrosines by substitution for other residues at the C terminus, GRO alpha and NAP-2 were labeled with 125I and used for binding studies. A total of 60,000-90,000 receptors per neutrophil were found for either ligand. Of these 30-45% were of high affinity with a mean Kd value of 0.3 and 0.7 nM for GRO alpha and NAP-2, respectively, and 55-70% of low affinity (Kd = 30 nM). Two proteins of approximately 70 kDa and 44 kDa (p70 and p44) were specifically cross-linked with labeled GRO alpha, NAP-2, and IL-8. Unlabeled IL-8 fully inhibited this cross-linking and the binding of labeled GRO alpha or NAP-2 to the high-affinity sites on neutrophils or neutrophil membranes. Treatment of membranes with digitonin resulted in the preferential solubilization of a single receptor species, corresponding to p44, that bound GRO alpha and NAP-2 with low affinity (Kd = 30 nM) and IL-8 with high affinity (Kd = 0.4 nM). Exposure of neutrophil membranes to 100 microM guanosine 5'-[gamma-thio]triphosphate led to a 75-fold increase of the Kd in approximately 60% of the IL-8 receptors. High-affinity receptors for GRO alpha and NAP-2 were similarly affected. In contrast, guanosine 5'-[gamma-thio]triphosphate had no effect on the binding of IL-8 to p44 solubilized by digitonin. These results demonstrate that human neutrophils bear two classes of receptors for GRO alpha, NAP-2, and IL-8 (p70 and p44) that may differ in their mode of interaction with GTP regulatory proteins.

Cell Membrane↗