Characterization of a novel signal transducing receptor on human T cells

Section: Discussionmentioning

confidence: 99%

“…has been shown to synergize with TCR for early steps in T cell activation and to stimulate a TCR-dependent Ca 2ϩ flux (7,8).…”

Section: Flag-mms and Cd8-mms Can Synergize With Cd3 For Plc␥ Phosphomentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Membrane Raft Association of CD47 Is Necessary for Actin Polymerization and Protein Kinase C θ Translocation in Its Synergistic Activation of T Cells

Rebres

Green

Reinhold

et al. 2001

“…T Cell Responses to Some CD47 Ligands Are CD47-independent-CD47 binding antibodies have been shown to act as both agonists and antagonists of specific CD47 responses (4,38). Therefore, the differences in responses to integrin ligands induced by B6H12 and FIRVVMYEGKK in Fig.…”

Section: A Cd47-binding Peptide Stimulatesmentioning

confidence: 99%

Regulation of Integrin Function by CD47 Ligands

Barazi

Cashel

et al. 2002

CD47 (integrin-associated protein) is an integral membrane protein that is required for granulocyte and T cell recruitment to sites of infection (1, 2), and its absence on red blood cells leads to their rapid macrophage-mediated clearance (3). CD47 may also function as a costimulator to regulate T cell activation, survival, and Th1 versus Th2 differentiation (4, 5). Endogenous ligands for the extracellular domain of CD47 include the secreted protein thrombospondin-1 (TSP1) 1 and potentially other members of the thrombospondin family, several integrins (6 -9), and some members of the signal-regulatory protein family (3, 10 -13). Engagement of CD47 by soluble ligands or signal-regulatory protein counter receptors modulates several cell signaling pathways, including activation of a heterotrimeric G protein (14).Although some signal transduction through CD47 is integrin-independent (4, 15, 16), association of CD47 with certain integrins was found to modulate their function to mediate cell adhesion or motility (6,8,9,17). In addition to its known functional and physical interactions with ␣ v ␤ 3 , ␣ IIb ␤ 3 , and ␣ 2 ␤ 1 integrins, several publications have suggested an association of CD47 with ␣ 4 ␤ 1 integrin. CD47 and ␣ 4 ␤ 1 were colocalized on microvilli of K562 erythroleukemia cells (18), and CD47-dependent arrest of T cells on inflammatory endothelium could be blocked by antibodies that prevent ␣ 4 ␤ 1 integrin binding to VCAM-1 (2). In the latter study, ligation of CD47 by TSP1 or signal-regulatory protein 1␣ was inferred to activate ␣ 4 ␤ 1 integrin on T cells, although this was not demonstrated either functionally or biochemically.We recently found that CD47 expression is required for stimulation of T cell motility and expression of MMP-2 stimulated by ␣ 4 ␤ 1 integrin ligands (19). An antibody to CD47 also blocked the motility response to an ␣ 4 ␤ 1 integrin ligand (19). Therefore, at least a functional interaction occurs between CD47 and ␣ 4 ␤ 1 integrin.We identified a binding site for ␣ 4 ␤ 1 integrin in the Nterminal domains of TSP1 and TSP2 (19), whereas two binding sites for CD47 have been localized to the C-terminal domain of TSP1 (for review, see Ref. 20). Thus, TSP1 could potentially regulate its own interaction with ␣ 4 ␤ 1 integrin through simultaneous interactions with CD47 and ␣ 4 ␤ 1 integrin on a T cell, analogous to the ability of soluble TSP1 to stimulate ␣ v ␤ 3 integrin-dependent melanoma cell adhesion to immobilized TSP1 (21).To define a molecular basis for functional cross-talk between these two receptors, we have examined the effect of CD47 ligands on the function of ␣ 4 ␤ 1 integrin in T cells and melanoma cells. We confirmed that ligation of CD47 can activate ␣ 4 ␤ 1 integrin function but unexpectedly found the mechanism of this activity to be CD47 ligand-dependent. We further show that CD47 ligation differentially activates and inactivates ␣ v ␤ 3 and ␣ 4 ␤ 1 in melanoma cells and ␣ 4 ␤ 1 and ␣ 5 ␤ 1 in Jurkat cells. Unexpectedly, but consistent with a recent report demonstrating C...

“…CD47 has been shown to bind to the C terminus of thrombospondin-1 (18), therefore suggesting a role in platelet activation. Anti-CD47 antibodies have also been used to implicate CD47 in T cell activation (19,20), T and B cell apoptosis (21,22), and stroma-supported erythropoiesis (23). Recently, CD47 has been shown to bind to P84 (also termed SIRP␣, Bit, SHPS-1, and MFR) (24 -26), and this interaction has been broadly implicated in the regulation of memory formation, macrophage multinucleation, B cell aggregation, and red blood cell self-recognition in mice (27,28).…”

mentioning

confidence: 99%

The Role of CD47 in Neutrophil Transmigration

Liu

Merlin

Burst

et al. 2001

172

CD47, a cell surface glycoprotein, plays an important role in modulating neutrophil (PMN) migration across endothelial and epithelial monolayers. Here we show that anti-CD47 monoclonal antibodies (mAbs) delay PMN migration across collagen-coated filters or T84 epithelial monolayers toward the chemoattractant formylmethionylleucylphenylalanine (fMLP). Despite delayed transmigration by anti-CD47 mAbs, the numbers of PMN migrating across in either condition were the same as in the presence of control non-inhibitory mAbs. Cell surface labeling and immunoprecipitation demonstrated upregulation of CD47 to the PMN cell surface with kinetics similar to those of the transmigration response. Subcellular fractionation studies revealed redistribution of CD47 from intracellular compartments that co-sediment with secondary granules to plasma membrane-containing fractions after fMLP stimulation. Experiments performed to investigate potential signaling pathways revealed that inhibition of tyrosine phosphorylation with genistein reversed the anti-CD47-mediated PMN migration delay, whereas inhibition of phosphatidylinositol 3-kinase only partially reversed anti-CD47 effects that correlated with a rapid increase in PMN cell surface CD47. Analysis of the contribution of epithelial-expressed CD47 to PMN transmigration revealed that PMN migration across CD47-deficient epithelial monolayers (CaCO2) was significantly increased after stable transfection with CD47. These results suggest that cell surface CD47 and downstream tyrosine phosphorylation signaling events regulate, in part, the rate of PMN migration during the inflammatory response.