Deletions in the cytoplasmic domain of platelet-endothelial cell adhesion molecule-1 (PECAM-1, CD31) result in changes in ligand binding properties

Abstract

Abstract. Platelet/endothelial cell adhesion molecule-1 (PECAM-1, CD31) is a member of the immunoglobulin superfamily present on platelets, endothelial cells, and leukocytes that may function as a vascular cell adhesion molecule. The purpose of this study was to examine the role of the cytoplasmic domain in PECAM-1 function. To accomplish this, wild-type and mutated forms of PECAM-1 cDNA were transfected into murine fibroblasts and the functional characteristics of the cells analyzed. Wild-type PECAM-1 localized to the cell-cell borders of adjacently transfected cells and mediated heterophilic, calcium-dependent L-cell aggregation that was inhibitable by a polyclonal and two monoclonal anti-PECAM-1 antibodies. A mutant protein lacking the entire cytoplasmic domain did not support aggregation or move to cell-cell borders. In contrast, both forms of PECAM-1 with partially truncated cytoplasmic domains (missing either the COOH-terminal third or two thirds of the cytoplasmic domain) localized to cell-cell borders in 3T3 cells in a manner analogous to the distribution seen in cultured endothelial cells. L-cells expressing these mutants demonstrated homophilic, calcium-independent aggregation that was blocked by the polyclonal anti-PECAM-1 antibody, but not by the two bioactive monoclonal antibodies. Although changes in the cytoplasmic domain of other receptors have been shown to alter ligand-binding affinity, to our knowledge, PECAM-1 is the first example of a cell adhesion molecule where changes in the cytoplasmic domain result in a switch in the basic mechanism of adhesion leading to different ligand-binding specificity. Variations in the cytoplasmic domain could thus be a potential mechanism for regulating PECAM-1 activity in vivo.

Alternative Splicing of a Specific Cytoplasmic Exon Alters the Binding Characteristics of Murine Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1)

“…Previous experiments showed that full-length huPECAM-1 promoted heterophilic aggregation in transfected L-cells in a divalent cation-dependent, heparin-sensitive manner (Albelda et al, 1991;Muller et al, 1992;DeLisser et al, 1993). In contrast, mutants of huPECAM-1 with partially truncated cytoplasmic domains mediated aggregation that was quite different in that it was homophilic, divalent cation-independent, and heparin-insensitive (DeLisser et al, 1994a). These findings raised the possibility that naturally occurring alternatively spliced forms of PECAM-1 might also function differently (Baldwin et al, 1994).…”

The Carboxyl-terminal Region of Biliary Glycoprotein Controls Its Tyrosine Phosphorylation and Association with Protein-tyrosine Phosphatases SHP-1 and SHP-2 in Epithelial Cells

“…Recent studies on PECAM-1 (platelet endothelial cell adhesion molecule-1) give credence to this suggestion (62)(63)(64): PECAM-1 is a member of the Ig superfamily and is responsible for contacts between leukocytes or platelets with the surface of endothelial cells. Indeed, the last 10 amino acids of Bgp1, surrounding Tyr-515, demonstrate striking homology to a region of 18 amino acids within PECAM-1, particularly those centered around Tyr-686 (Bgp1, SSPRATETVYSEVKKK; PECAM-1, LGTRATETVYSEIRKVDP).…”

The Protein-tyrosine Phosphatase SHP-2 Associates with Tyrosine-phosphorylated Adhesion Molecule PECAM-1 (CD31)

“…The cytoplasmic domain of adhesion molecules can control their function (52)(53)(54)(55)(56)(57). RBL-2H3 cells bind to fibronectin through integrin receptors resulting in cell spreading and a redistribution of the granules to the periphery of the cells (30,58).…”