Thy-1 (CD90) Is an Interacting Partner for CD97 on Activated Endothelial Cells

Abstract

Leukocyte recruitment in response to inflammatory signals is governed, in part, by binding to Thy-1 (CD90) on activated endothelial cells (EC). In this study, we characterized the adhesion G-protein coupled receptor CD97, present on peripheral myeloid cells, as a novel interacting partner for Thy-1. CD97 was upregulated on polymorphonuclear cells (PMNC) of patients with psoriasis. In psoriatic skin lesions, CD97+ myeloid cells colocalized with Thy-1+ EC of small vessels in microabscesses, suggesting an interaction between CD97 and Thy-1 that was further examined by adhesion and protein-binding assays. PMNC and cell lines stably overexpressing CD97 adhered specifically to Thy-1+–activated human dermal EC, Thy-1+ CHO cells, and immobilized Thy-1 protein. Binding of the CD97+ CHO clones correlated with their CD97 expression level. Soluble CD97 bound specifically to immobilized Thy-1 protein, as well as Thy-1+–activated EC and CHO cells. In all assays, cellular adhesion or protein binding was blocked partially by CD97 and Thy-1–blocking mAb. Our data suggested that CD97 interacts via its stalk with Thy-1 because mAb directed to the stalk of CD97 showed stronger blocking compared with mAb to its epidermal growth factor-like domains, and binding was calcium independent. Moreover, soluble CD97 without the stalk and soluble EMR2, containing highly homologous epidermal growth factor-like domains but a different stalk, failed to bind. In summary, binding of leukocytes to activated endothelium mediated by the interaction of CD97 with Thy-1 is involved in firm adhesion of PMNC during inflammation and may play a role in the regulation of leukocyte trafficking to inflammatory sites.

Shear Stress–Dependent Downregulation of the Adhesion-G Protein–Coupled Receptor CD97 on Circulating Leukocytes upon Contact with Its Ligand CD55

“…A role of CD97 as receiver of local stromal and matrix adhesive codes would fit with its ability to engage with various ligands at low affinity. Besides CD55, CD97 binds the glycosaminoglycan dermatan sulfate, the integrin a5b1, and Thy-1/CD90 through different sites within the extracellular subunit (12,13,20). Similar characteristics have been reported for GPR56, an aGPCR expressed by neurons, various malignant cells, and cytotoxic lymphocytes (2,44).…”

“…CD55 interacts with the N-terminal epidermal growth factor (EGF)-like domains of CD97 (6)(7)(8), an aGPCR broadly expressed by hematopoietic and nonhematopoietic cells (9)(10)(11). Subsequently identified aGPCR ligands were dermatan sulfate, a5b1 integrin, tissue transglutaminase 2, phosphatidylserine, LPS, C1q, lasso/teneurin-2, collagen III, and Thy-1/CD90 (12)(13)(14)(15)(16)(17)(18)(19)(20). Evidence was obtained that aGPCRs have a role in cell positioning and tissue organization in various organ systems (21,22); however, in the strictest sense, aGPCRs are still functional orphans.…”

CD97 inhibits cell migration in human fibrosarcoma cells by modulating TIMP‐2/MT1‐ MMP/MMP‐2 activity – role of GPS autoproteolysis and functional cooperation between the N‐ and C‐terminal fragments

“…Several binding partners, including CD55 [37], chondroitin sulfate B [38], a5b1 and avb3 integrins [30], and Thy-1 (CD90) [39], which interact with different binding sites, have been identified for CD97. As similar phenotypes were seen in cells expressing CD97(EGF125) and CD97 (EGF1-5) isoforms, this suggests that CD55 and chondroitin sulfate B, which specifically bind the short and long CD97 isoforms, respectively, are probably not involved in these processes.…”

Adhesion G Protein-Coupled Receptors: Signaling, Pharmacology, and Mechanisms of Activation

“…This interaction has been extensively studied and shown to have a variety of effects on cell adhesion, cell motility, and carcinoma invasiveness but at present there is no evidence that this interaction can activate G protein-coupled signaling by CD97 (Mustafa et al, 2004;Liu et al, 2005). Moreover, the N terminus of GPR124 has been shown to facilitate adhesion by binding to both glycosaminoglycans and integrins (Vallon and Essler, 2006), and Thy-1 (CD90) has recently been shown to interact with CD97 to regulate polymorphonuclear cell adhesion (Wandel et al, 2012), but no corresponding signaling effects have been reported for these interactions.…”