Biology of chemokine and classical chemoattractant receptors: differential requirements for adhesion-triggering versus chemotactic responses in lymphoid cells.

Abstract

Abstract. Several chemoattractant receptors can support agonist-induced, integrin-dependent arrest of rolling neutrophils in inflamed venules in vivo, as well as subsequent crawling into tissues. It has been hypothesized that receptors of the Goq-linked chemoattractant subfamilies, especially receptors for chemokines, may mediate parallel activation-dependent arrest of homing lymphocyte subsets. However, although several chemokines can attract subsets of B or T cells, robust chemoattractant triggering of resting lymphocyte adhesion to vascular ligands has not been observed. To study the biology of individual leukocyte chemoattractant receptors in a defined lymphoid environment, mouse L1/2 pre-B cells and/or human Jurkat T cells were transfected with et (IL-8 receptor A) or 13 (MIPltx/CC-CKR-1) chemokine receptors, or with the classical chemoattractant C5a (C5aR) or formyl peptide receptors (fPR). All receptors supported robust agonistdependent a4131 integrin-mediated adhesion of lymphocytes to VCAM-1. L1/2 cells cotransfected with fPR and 137 integrin were also induced to bind MAdCAM-1, suggesting common mechanisms coupling chemoattractant receptors to activation of distinct integrins. Adhesion was rapid but transient, with spontaneous reversion to unstimulated levels within 5 min after peak binding. When observed under flow conditions, et4131-mediated arrest occurred within seconds after initiation of contact and rolling of IL-8RA transfectants on a VCAM-1/IL-8 co-coated surface; and arrest reversed spontaneously after a mean of 5 min with a return to rolling behavior. Each of the receptors also conferred agonist-specific chemotaxis; however, whereas strong adhesion required simultaneous occupancy of many receptors with maximal responses above the Ka, chemotaxis in each case was suppressed at high agonist concentrations. The findings indicate that et and 13 chemokine as well as classical chemoattractant receptors can trigger robust adhesion as well as directed migration of lymphoid cells, but that the requirements for and kinetics of adhesion triggering and chemotaxis are distinct, thus permitting their independent regulation. They suggest that the discordance between proadhesive and chemoattractant responses of circulating lymphocytes to many chemokines may reflect quantitative aspects of receptor expression and/or coupling rather than qualitative differences in receptor signaling.HODOPSIN-related Goq-linked 7 transmembrane "serpentine" receptors of the chemoattractant subfamily have been implicated in many aspects of leukocyte behavior, notably including the regulation of leukocyte adhesion, locomotion, and chemotaxis.

Discrete Steps in Binding and Signaling of Interleukin-8 with Its Receptor

“…It has been shown that the stimulation of IL-8 receptor transfectants by IL-8 causes transient integrin activation (24). It was found that 5A12, 7D9, and 6C6 were able to inhibit IL-8-induced VCAM-1 binding of the CXCR1 or CXCR2 transfectants by 35-50% (data not shown).…”

“…Chimeric CXCR1/2-For stable transfectants, the murine pre-B lymphoma cell line (L1-2) was used and transfected as described (24,25 Antibodies and Flow Cytometry, Isolation of Neutrophils-Anti-CXCR1 and -CXCR2 antibodies were generated as described (23). In addition, two previously reported (21) anti-CXCR2 mAbs, 10H2.12.1 (ATCC HB-11494) and 4D1.5.7 (ATCC HB-11495) were used for the purpose of comparison.…”

“…The IL-8-induced adhesion of CXCR1 or CXCR2 transfectants to VCAM-1 were carried out similarly to what was described (24). Cells were labeled with BCECF-AM (Molecular Probes, Eugene, OR) and preincubated with various concentrations of mAbs for 5-10 min.…”

The Carboxyl Tail of Protease-activated Receptor-1 Is Required for Chemotaxis

“…Migration Assay-Migration of BaF3 cells was assessed using the Transwell assay system as described previously (5,22). Briefly, cells were washed and resuspended in RPMI 1640 containing 0.2% bovine serum albumin and 10 mM HEPES buffer at a density of 5 ϫ 10 6 cells/ml.…”

IL-10 stimulatory effects on human NK cells explored by gene profile analysis

“…By contrast, microarray results showed that IL-10 increased mRNA levels of adhesion/migration-related genes such as L-selectin, VEGF receptor-1, t-PA, HM74, formyl peptide receptor-1 and lipoxin A4 receptor (Figure 3). The last three genes are involved in the synthesis of peptide receptors [38][39][40] that mediates leukocyte chemotaxis by binding peptides derived from protein degrada- tion occurring in damaged/diseased areas. 41 The overexpression of these receptors might play an important role in NK cell migration in response to the liberation of danger signals (eg peptides) freed in the tumor microenvironment.…”