Identification of cell-binding site of angiomodulin (AGM/TAF/Mac25) that interacts with heparan sulfates on cell surface

Abstract

Angiomodulin (AGM/TAF/mac25) is a 30-kDa glycoprotein that was identified as an integrin-independent cell adhesion protein secreted by human bladder carcinoma cells. AGM is highly accumulated in small blood vessels of tumor tissues. In the present study, we attempted to identify the cell surface receptor and the cell-binding site of AGM using ECV-304 human vascular endothelial cells and BALB/c3T3 mouse fibroblasts. Heparin, heparan sulfate, and dextran sulfate, but not chondroitin sulfate, inhibited both adhesion of the two cell lines to AGM-coated plates and binding of AGM to these cells. Treatment of cells with heparinase, but not chondroitinase, inhibited both cell adhesion to AGM and AGM binding to cells. These results strongly suggested that heparan sulfates are the major receptor for AGM. Furthermore, we determined a 20-amino acid sequence within AGM molecule as its major cell-binding site. The synthetic peptide for the cell-binding sequence showed cell adhesion activity comparable to that of AGM, and the activity was inhibited by heparin and heparan sulfate. The peptide competitively inhibited cell adhesion to AGM and the binding of AGM to cells. These results indicated that AGM binds to cells through interaction of the identified cell-binding sequence with heparan sulfates on cell surface. It was also found that the heparan sulfate-binding peptide inhibited the formation of capillary tube-like structures of vascular endothelial cells in culture.

Strong suppression of tumor growth by insulin‐like growth factor‐binding protein‐related protein 1/tumor‐derived cell adhesion factor/mac25

“…(9) It promotes weak cell adhesion, probably by binding cell surface heparan sulfate proteoglycans. (11) In accordance with the cell adhesion activity of IGFBP-rP1, IGFBP-rP1-expressing EJ-1 and DLD-1 cells more efficiently adhered to fibronectin and laminin-5 than their IGFBP-rP1-non-expressing counterparts. The cell adhesion activity of cancer cells was inversely correlated with their anchorageindependent growth ability.…”

“…It should also be noted that IGFBP-rP1 is highly expressed in blood vessels in tumor tissues (6) and high endothelial venule cells in lymphoid tissues. (32) IGFBP-rP1 is known to interact with many factors besides insulin and IGFs, such as type IV collagen, (6) syndecans or heparansulfates, (11)(12)(13) chemokines and interferon-γ-inducible protein 10. (33) Moreover, IGFBP-rP1 stimulates prostacyclin production.…”

“…interacting with cell-surface syndecans. (10)(11)(12) In the present study, we compared the cell adhesion efficiency of the pairs of EJ-1 and DLD-1 cell lines to fibronectin and laminin-5. These cells were suspended in serum-free medium and inoculated on plastic plates that had previously been coated with fibronectin or laminin-5.…”

“…(8) The protein product of IGFBP-rP1 was identified as a tumor-derived cell adhesion factor (TAF) from human bladder carcinoma cells (9) and as prostacyclin-stimulating factor from human fibroblasts. (7) The purified IGFBP-rP1 exerts a weak cell adhesion activity through heparan sulfate proteoglycans on the cell surface (10)(11)(12) and stimulates cell growth in culture medium containing insulin or IGFs. (6,13) Because this protein is highly accumulated in blood vessels of various human cancer tissues, it is also referred to as angiomodulin.…”

High Expression of IGFBP7 in Fibroblasts Induced by Colorectal Cancer Cells Is Co-Regulated by TGF-β and Wnt Signaling in a Smad2/3-Dvl2/3-Dependent Manner

“…At present, this is difficult to assess, because there is little research on the role of IGFBP7 in tumor stroma. IGFBP7 was found highly expressed in the vessels of glioma [34]; it can interact with extracellular matrix protein to induce the adhesion and migration of endothelial cells [35], [36]. Pen and colleagues also reported that IGFBP7 in endothelial cells can induce angiogenesis [18].…”