Complement receptor type three (CD11b/CD18) of human polymorphonuclear leukocytes recognizes fibrinogen.

Abstract

Human polymorphonuclear leukocytes (PMN) have previously been shown to bind to aggregates of fibrin and to fibrinogen-coated surfaces. During their interactions with fibrinogen-coated surfaces, PMN make such close contact with the surface that a portion of the secreted elastase activity is protected from macromolecular protease inhibitors in the surrounding medium. Here we show that the receptor on PMN that mediates this interaction is complement receptor type 3 (CR3; CD11b/CD18), a molecule previously identified as a receptor for the complement protein fragment C3bi. Monoclonal antibodies against CR3 that block the binding of C3bi also block the binding of PMN to fibrinogen-coated surfaces and the formation of a protected compartment. The region of fibrinogen recognized by CR3 lies at the carboxyl terminus of the y chain, since peptides based on this sequence effectively inhibit the binding of PMN to fibrinogen-coated surfaces. These peptides also block the binding of C3bi-coated erythrocytes to CR3, thus indicating that a single binding site is used for binding both C3bi and fibrinogen. Sequence analysis shows strong structural similarity between this region of fibrinogen and other known ligands of CR3. These studies thus indicate that CR3 functions as a receptor not only for C3bi but also for fibrinogen.Several observations suggest that polymorphonuclear leukocytes (PMN) bind specifically to fibrin and may be involved in dissolution of clots. PMN can be found concentrated in fibrin deposits in vivo (1, 2), aggregates of fibrin are phagocytosed by PMN in vivo (1, 2), and radioiodinated aggregates of fibrin bind avidly to PMN in vitro (3). Recently, we have observed that during migration across fibrinogen-coated surfaces in response to chemotactic stimuli, PMN release elastase that degrades the fibrinogen (4). Degradation of surface-bound fibrinogen by elastase is completely inhibited by the low molecular weight inhibitor MeO-Suc-Ala2-ProVal-CH2Cl (AAPVCK) but degradation cannot be completely inhibited by high molecular weight inhibitors such as soybean trypsin inhibitor (SBTI). The elastase appears to be protected from inhibitory proteins in the surrounding medium by sequestration in a compartment formed between the PMN and the substrate similar to the compartment that forms between macrophages and substrates coated with IgG or the complement protein C3 (5). This supposition is strengthened by the observation that fluoresceinated fibrinogen is lost from the substrate in patches that correspond to the margins of spread PMN (S.D.W., unpublished observations).Here we examine the receptors on PMN that mediate adhesion to fibrinogen and the formation of the protected compartment. We find that adhesion to fibrinogen-coated surfaces is inhibited by peptides derived from the carboxyl terminus of the 'y chain of fibrinogen. This is the same region that is recognized by the Peptides. Peptide L10 (LGGAKQAGDV), based on residues 402-411 of the y chain of human fibrinogen, was synthesized by Peninsula Laborato...

Short exposure of intestinal epithelial cells to TNF-α and histamine induces Mac-1-mediated neutrophil adhesion independent of protein synthesis

“…Neither RGD peptide (0.01-1 mg/mL) nor heparinase (0.01-1 IU/mL) treatment of HT29 cells affected neutrophil adhesion to TNF-␣ (5 h and 30 min)-and histamine (30 min)-stimulated HT29 cells (data not shown). These results suggest that heparin-like glycosaminoglycans and extracellular matrix proteins containing RGD sequences that are reported to be recognized by Mac-1 [31][32][33] are unlikely to be involved in neutrophil-HT29 cell interactions.…”

“…Thus, it is unclear whether sugar chains such as sialic acids and N-glycans of intestinal epithelial cells are mainly involved in Mac-1-mediated neutrophil adhesion to HT29 cells. Furthermore, epithelial counter-receptor for neutrophil Mac-1 does not seem to be a GPI-anchored type protein, and heparin like glycosaminoglycans, and extracellular matrix protein containing RGD sequences that are reported to be recognized by Mac-1 [31][32][33], is unlikely involved in neutrophil-HT29 cell interactions.…”

“…In addition, to examine the involvement of heparin-like glycosaminoglycans and extracellular matrix proteins containing RGD sequences in neutrophil-HT29 cell interactions, HT29 cells were stimulated with TNF-␣ (5 h and 30 min) or histamine (30 min) in the presence of 0.01-1 IU/mL of heparinase III in FBS-free medium, or adhesion assay was performed in the presence of 0.01-1 mg/mL RGD peptide [31][32][33].…”

Expression of a structural domain of the β2 subunit essential for αMβ2 ligand recognition

“…␣ M ␤ 2 recognizes a multiplicity of protein ligands including the complement C3 fragment iC3b [9,13], ICAM-1 [14], and the coagulation proteins fibrinogen [15] and Factor X [16]. Currently, we hypothesize that interactive sites in both the ␣ and ␤ subunits coordinate the binding of ligand and cations to comprise the ligand binding pocket.…”

Entactin stimulates neutrophil adhesion and chemotaxis through interactions between its Arg-Gly-Asp (RGD) domain and the leukocyte response integrin.

“…PMN adhesion was assayed in 72-well Terasaki plates (Nunc HLA plates 7651 1; Thomas Scientific, Swedesboro, NJ) using a modification of the procedure described by Wright et al (31 ).…”