Novel CD47-dependent intercellular adhesion modulates cell migration

Abstract

CD47 is a ubiquitously expressed plasma membrane protein, also known as Integrin Associated Protein, that modulates cell adhesion both through alteration of the avidity of integrin binding and through interaction with its own ligands, the extracellular matrix protein thrombospondin (TSP) and the plasma membrane response regulator SIRPalpha1. We now show that CD47 expression on fibroblasts can induce intercellular adhesion resulting in cell aggregation in the absence of active integrins, SIRPalpha1 binding, and detectable TSP. CD47-expressing cells preferentially bind to other CD47-expressing cells, and intercellular adhesion requires stimulation by serum or a CD47-binding peptide from TSP. Cell-cell adhesion is inhibited by pertussis toxin and C. difficile toxin B, and both adherent and aggregating CD47-expressing fibroblasts have more rac in the GTP bound state than CD47-deficient cells. Spontaneous migration of Jurkat lymphocytes through a fibroblast monolayer is decreased by fibroblast expression of CD47, consistent with an increased barrier function of the CD47 expressing cells. The lymphocyte chemoattractant SDF-1alpha stimulates migration of Jurkat cells through this monolayer only if both the lymphocytes and fibroblasts express CD47, and the inhibition of migration by a CD47-interacting peptide from TSP similarly requires CD47 expression on both cell types. Thus, signaling dependent on both heterotrimeric and rho family GTPases can induce CD47 to participate in cell-cell interactions independent of known ligands that enhance intercellular adhesion and modulate cell migration.

Phylogenetic Divergence of CD47 Interactions with Human Signal Regulatory Protein α Reveals Locus of Species Specificity

“…The species specificity seen here with CHO-displayed CD47 (Fig. 4) seems not to be simple allor-none as previously reported (54,55); the interaction depends strongly on the density of molecules and their glycosylation status ( Figs. 1 and 2).…”

“…We tested the effects of seven changes (humans to cows) in fragment II and demonstrated a 70% reduction in the apparent binding constant for human SIRP␣. Only one of the identified seven amino acids (Asn 55 ) is conserved between mouse and human CD47, making results from both strategies consistent. The lack of any reduction in SIRP␣ binding when two glycosylation-related changes (N55R and D62N; hFII ⌬2 cCD47) were combined suggests that these two residues are probably less important for binding than the other five changes.…”

CD47 Deficiency Protects Mice from Lipopolysaccharide-Induced Acute Lung Injury and Escherichia coli Pneumonia

“…In the in vivo setting, there are several other factors (cytokines, cell-cell interactions, blood flow, and ventilation) that are not modeled by the in vitro studies. For example, impairment of engagement with ligands in the endothelial and epithelial cells in the CD47 Ϫ/Ϫ neutrophils may reduce neutrophil sequestration, adhesion, and transmigration (28). However, the exact mechanism requires further investigation.…”

The use of CD47-modified biomaterials to mitigate the immune response

“…CD47, also known as integrin-associated protein, is a ubiquitously expressed pentatransmembrane protein that has known physiological roles in cell attachment, spreading and immune evasion. [36][37][38][39] In addition to functioning as a ligand for SIRPa, which will be discussed below, CD47 interacts with several other proteins. Within the same cell, CD47 can form a multiprotein complex with the following integrin heterodimers: a II b 3 , a v b 3 , and a 2 b 1 .…”