Biomedical subjects

C Combadiere

Publications and source records attributed to C Combadiere.

23 records · Page 2Linked to original sources

PubMed1995

Cloning and functional expression of a human eosinophil CC chemokine receptor.

Eosinophils undergo chemotaxis, degranulate, and exhibit [C2+]i changes in response to the human CC chemokines macrophage inflammatory protein (MIP)-1 alpha, regulated on activation, normal T expressed and secreted (RANTES), and monocyte chemoattractant protein-3 (MCP-3), but the receptors involved have not been defined. We have isolated a human cDNA encoding the first eosinophil-selective chemokine receptor, designated CC chemokine receptor 3 (CC CKR3). CC CKR3 is a seven-transmembrane domain G protein-coupled receptor most closely related to the previously reported monocyte- and neutrophil-selective receptor CC CKR1 (also known as the MIP-1 alpha/RANTES receptor). When [Ca2+]i changes were monitored in stably transfected human embryonic kidney 293 cells, MIP-1 alpha and RANTES were both potent agonists for CC CKR3 and CC CKR1. However, MIP-1 beta was also an agonist for CC CKR3 but not CC CKR1; MCP-3 was an agonist for CC CKR1 but not CC CKR3. CC CKR3 may be one of the host factors responsible for selective recruitment of eosinophils to sites of inflammation.

Amino Acid Sequence↗

PubMed1995

Cloning, chromosomal localization, and RNA expression of a human beta chemokine receptor-like gene.

A human cDNA encoding a putative G protein-coupled receptor designated chemokine beta receptor-like 1 (CMKBRL1) was isolated from an eosinophilic leukemia library. Its deduced sequence is approximately 40% identical to previously cloned receptors for the beta chemokines macrophage inflammatory protein-1 alpha (MIP-1 alpha), RANTES, and monocyte chemoattractant protein-1 (MCP-1), which are chemoattractants for blood leukocytes, and is 83% identical to the product of the orphan rat cDNA RBS 11. Like the MIP-1 alpha/RANTES receptor, CMK-BRL1 is encoded by a small, single-copy gene that maps to chromosome 3p21 and is expressed in leukocytes. However, two screening assays with a broad panel of chemokines failed to identify its ligand. CMKBRL1 mRNA was detectable by Northern blot hybridization in neutrophils and monocytes, but not eosinophils, and was also found in eight solid organs that were tested with particularly high expression in brain. The RNA distribution of the known beta chemokine receptors was overlapping but distinct from that of CMKBRL1. MIP-1 alpha/RANTES receptor mRNA was detectable in neutrophils, monocytes, eosinophils, and in all eight solid organs tested, with particularly high expression in placenta, lung, and liver. MCP-1 receptor mRNA was found in monocytes, lung, liver, and pancreas. These results suggest that the ligand for the putative CMKBRL1 receptor is a beta chemokine that targets both neutrophils and monocytes. Moreover, the RNA distributions suggest that CMKBRL1, the MIP-1 alpha/RANTES receptor, and the MCP-1 receptor may have both overlapping and distinct biological roles.

Amino Acid Sequence↗

PubMed1994

Staurosporine up-regulates the expression of phorbol dibutyrate binding sites in human platelets.

Tumor-promoting phorbol esters bind to and activate protein kinase C (PKC). Staurosporine, a potent PKC inhibitor, interferes with PKC catalytic activity without altering phorbol ester binding sites in cell-free systems. We found that, unlike cell-free systems, treatment of intact platelets with staurosporine enhances the expression of phorbol 12, 13-dibutyrate (PDBu) binding sites. Incubation of platelets at 37 degrees with staurosporine (25 nM to 1 microM and 2 nM tritiated PDBu ([3H]PDBu) increased the amount of [3H]PDBu specifically bound to intact platelets by approximately 10 to 200% of control values. This effect was rapid and plateaued after 10 min of cell treatment. Scatchard analysis of the data showed that staurosporine (500 nM) significantly increased the total binding capacity Bmax from 42.9 +/- 15.4 x 10(3) to 78 +/- 7.3 x 10(3) sites per platelet and reduced the apparent dissociation constant value Kd from 30.8 +/- 8.6 nM to 9.4 +/- 3.4 nM. Enhanced PDBu binding capacity and affinity were also observed with human mononuclear and polymorphonuclear leukocytes. Fractionation of staurosporine-treated platelets showed an increased binding capacity of the particulate fraction (102%) and decreased binding capacity of the soluble fraction (60%) compared to controls, with no change in the affinity of PDBu binding to these fractions. Chelation of internal calcium with BAPTA did not significantly attenuate the staurosporine-mediated rise in PBDu binding but prevented the platelet-activating factor-induced response, indicating that cytosolic calcium does not play an important role in these staurosporine effects. These results show that, in addition to interfering with PKC protein-phosphorylating activity, staurosporine enhances PDBu binding affinity and capacity in intact platelets. This latter effect appears to be due to translocation of soluble PDBu binding sites, presumably PKC units.

Alkaloids↗

PubMedDate not supplied

A comparison of the priming effect of phorbol myristate acetate and phorbol dibutyrate on fMet-Leu-Phe-induced oxidative burst in human neutrophils.

Phorbol esters such as phorbol myristate acetate (PMA) and phorbol dibutyrate (PDBU) are generally considered to have similar effects through a similar mechanism, i.e. protein kinase C (PKC) activation. We recently suggested that this was not the case in human neutrophils. To identify further differences between the two phorbol esters, we compared their priming effects on fMet-Leu-Phe-induced superoxide anion (O2-) production, cytosolic PKC activity and binding of fMet-Leu-Phe. Priming could be initiated with a low (0.2 nM) concentration of both PDBU and PMA. Their effects on the pattern of fMet-Leu-Phe-induced superoxide production were similar in both Ca2(+)-containing and Ca2(+)-free medium. PDBU, like PMA, abolished the Ca2+ dependency of fMet-Leu-Phe-induced O2- production in a dose-dependent manner. In cytochalasin B-treated cells and in the presence of Ca2+, priming with PDBU or PMA did not alter the enhancing effect of cytochalasin B on fMet-Leu-Phe-induced O2- production. In Ca2(+)-free medium, priming abolished the Ca2+ dependency of fMet-Leu-Phe stimulation in cytochalasin B-treated cells. Cytochalasin B, however, enhanced the effect of PMA but not that of PDBU. Priming with PDBU was not associated under any experimental conditions with a decrease in cytosolic PKC activity, or an increase in PKM activity before or after fMet-Leu-Phe stimulation. Furthermore, priming effects were abolished by cell washing but not by H-7 or staurosporine, which are potent PKC inhibitors. PDBU, in contrast to PMA, increased fMet-Leu-Phe binding to PMNs through a decrease in the dissociation constant and induced degranulation of specific granules as measured by the release of vitamin B12 binding protein. These findings show that the priming effects of PDBU differ in certain respects from those of PMA, namely with regard to its synergism with cytochalasin B and the expression of fMet-Leu-Phe receptors. In addition, priming concentrations of PDBU, like PMA, did not alter cytosolic PKC activity in fMet-Leu-Phe-stimulated neutrophils.

Cells, Cultured↗

PubMedDate not supplied

Dissimilarities in superoxide anion production by human neutrophils stimulated by phorbol myristate acetate or phorbol dibutyrate.

Phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-dibutyrate (PDBU) are known to translocate protein kinase C (PKC) and to induce superoxide anion (O2-.) production in human neutrophils. They are thus currently used to probe the role of PKC in O2-. production. We show here that under certain conditions, O2-. production induced by PMA is not associated with a decrease in cytosolic PKC activity, whereas these two events are associated after PDBU stimulation. (1) In the presence of extracellular calcium (1 mM), O2-. production was related to the concentration of PMA. PMA induced O2-. production at all the concentrations studied, but this was not associated with a decrease in cytosolic PKC levels up to 5 ng/ml PMA (50% maximum O2-. production). (2) Under PDBU stimulation, even at very low O2-. production levels, cytosolic PKC decreased and the decrease as well as the O2-. production were related to the concentration of PDBU. (3) For a given decrease in cytosolic PKC, O2-. production induced by PMA was much greater than that induced by PDBU. (4) In calcium-free medium, O2-. production induced by low concentrations of PMA (up to 5 ng/ml) was lower than that observed in the presence of 1 mM calcium, whereas modifications of cytosolic PKC activity were similar. (5) Cytochalasin B had no effect on PMA-induced O2-. production, regardless of the calcium content of the medium, and had no effect on the decrease in cytosolic PKC. On the contrary, following PDBU stimulation, cytochalasin B increased O2-. production, regardless of the medium, but induced a larger decrease in cytosolic PKC when Ca2+ was present. (6) Preincubation of PMN with 100 microM H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) before stimulation with PMA or PDBU led to similar inhibition of O2-. production whatever the degree of decrease in cytosolic PKC activity. These findings show that, in contrast to PDBU, O2-. production induced by PMA is not always related to cytosolic PKC activity.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗