Chemokine Receptor CXCR2 Activates Distinct Pathways for Chemotaxis and Calcium Mobilization.

Abstract

Cytokine-induced neutrophil chemoattractants (CINCs) are potent neutrophil chemotactic factors in rats and major mediators of acute inflammation.1-3) Four members of the CINC family have been identified: CINC-1, CINC-2a, CINC-2b, and CINC-3/macrophage inflammatory protein-2 (MIP-2).1) CINC-2a and CINC-2b differ only in the sequence of carboxy-terminal three amino acid residues and are produced by alternative splicing.4) CINCs show high degrees of sequence similarity to human GROs, interleukin 8 (IL-8), mouse KC, and mouse MIP-2 and belong to the CXC chemokine family. CINC-1 and CINC-2 show chemotactic activity comparable with that of CINC-3.5) Treatment of neutrophils with CINC-1 or CINC-2 inhibited the chemotactic activity of CINC-1 and CINC-2, but not that of CINC-3, whereas treatment with CINC-3 inhibited the activity of all CINCs.6) On the other hand, CINC-3 induced calcium mobilization more potently than CINC-1 and CINC-2, and desensitized calcium mobilization in neutrophils induced by CINC-1 and CINC-2.5) In addition, CINC-3 potently competed with the binding of 125 I-labeled CINC-3 Tyr, although CINC-1 competed only weakly. 7) To determine the biochemical basis for the differences in neutrophil responses to CINC-1/-2 versus CINC-3, we have cloned the gene encoding the receptor and identified rat CXCR2 as the common receptor for all CINCs.8) CXCR2 belongs to the family of G-proteincoupled receptors with seven transmembrane-spanning domains. Herein, we report the relationship between the biological activities of CINCs and G-protein usage. MATERIALS AND METHODSPreparation of Neutrophils Neutrophils were harvested from the peritoneal exudate 16 h after intraperitoneal injection of Krebs/Ringer bicarbonate solution containing 1% casein (120 ml/kg body weight of male Wistar rats), washed twice with Gey's balanced salt solution and twice with the assay buffer and then resuspended at a concentration of 10 7 cells/ml. 5)Pertussis Toxin Treatment Neutrophils were incubated with pertussis toxin (PTX, 1 mg/ml) at 37°C for 2 h in a humidified 5% CO 2 atmosphere and washed twice with the assay buffer. Measurement of Intracellular Free Calcium LevelsThe intracellular free calcium level in neutrophils was measured by the method described previously.5) Neutrophils were incubated with the calcium indicator fura-2 acetoxymethyl ester (2.5 mM) in Ca 2ϩ /Mg 2ϩ -free phosphate-buffered saline containing 10 mM HEPES, 0.25% bovine serum albumin, and 10 mM glucose (pH 7.4) for 30 min at 37°C. After incubation, the cells were washed twice and resuspended at 10 6 cells/ml with the buffer. In the presence of 1 mM CaCl 2 , fluorescence changes were monitored using a Hitachi F4500 fluorescence spectrophotometer at excitation wavelengths of 340 and 380 nm and an emission wavelength of 510 nm. Fura-2-loaded cells were stimulated with CINCs, then lysed with 0.1% Triton-X, and finally Ca 2ϩ was chelated with 6 mM EGTA. Intracellular calcium levels were calculated as described by Grynkiewicz et al. 9)Chemotaxis Assay in Vitro Chemotactic a...

Selective local PMN recruitment by CXCL1 or CXCL2/3 injection does not cause inflammatory pain

“…2F). In line with this finding, CXCR2 ligands were detected in serum of septic patients with CXCR2 down-regulation [55], impaired PMN migration in rats [56,57], and induced lysosomal degradation of CXCR2 in transfected cells [58]. Taken together, in our model, CXCL1 and CXCL2/3 caused selective PMN recruitment.…”

Ligand-independent CXCR2 Dimerization

“…This is proved by our observation that cell pretreatment with LY294002, which drastically eliminated Akt phosphorylation, did not abolish CXCL8-induced ERK1/2 phosphorylation. In contrast, both pathways are coupled to PTXsensitive G proteins as already described in other systems (42,43) but differently from others (39). It is interesting to note that the coexpression of two different CXCR2 mutations, one lacking the N-terminal (involved in chemokine binding) domain, Y49-CXCR2, and one lacking the whole C-terminal domain (involved in signaling), CXCR2-A315, did not restore cell signaling and chemotaxis, indicating that receptor activation upon agonist binding implicates an intramolecular mechanism.…”

Immune Antibodies and Helminth Products Drive CXCR2-Dependent Macrophage-Myofibroblast Crosstalk to Promote Intestinal Repair

“…3C ). Both CXCL2 and CXCL3 bind with high affinity to the chemokine receptor CXCR2 [ 32 ]. Thus, we studied the involvement of CXCR2 signaling in the positive effect of BMM-secreted factors on scratch wound closure by MF using the CXCR2 receptor antagonist SB265610.…”