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Deletions in the Cytoplasmic Domain of Platelet-Endothelial Cell Adhesion Molecule-1 (PECAM-1, CD31) Result in Changes in Ligand Binding Properties

Horace M. DeLisser, June Chilkotowsky, Horng-Chin Yan, Mildred L. Daise, Clayton A. Buck and Steven M. Albelda
The Journal of Cell Biology
Vol. 124, No. 1/2 (Jan., 1994), pp. 195-203
Stable URL: http://www.jstor.org/stable/1616222
Page Count: 9
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Deletions in the Cytoplasmic Domain of Platelet-Endothelial Cell Adhesion Molecule-1 (PECAM-1, CD31) Result in Changes in Ligand Binding Properties
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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.

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