Immunologic relationship between platelet membrane glycoprotein GPIIb/IIIa and cell surface molecules expressed by a variety of cells

Abstract

A polyclonal antiserum to platelet membrane glycoprotein GPIIb/IIIa was used to detect antigenically related molecules on a diverse panel of human cells. Umbilical vein endothelial cells, erythroleukemic HEL cell, and diploid fetal lung GM1380 fibroblasts expressed GPIIb/IIIa-related molecules, as judged by immunofluorescence and immunoprecipitation of surface-labeled proteins. The GPIIb and BPIIIa subunits were both present and were of similar molecular weight in these cell types. These molecules were synthetic products of the cells, as shown by immunoprecipitation of intrinsically labeled proteins. Promyeloid U937 cells could be induced by 4β-phorbol 12-myristate 13-acetate to synthetize and express GPIIb/IIIa-related molecules on their cell surface. The GPIIb/IIIa-related molecules were not precisely identical in the various cell types, based on slight differences in electrophoretic mobility and their failure to react with monoclonal antibodies specific for each subunit of platelet GPIIb/IIIa. These results suggest the existence of a widely distributed family of GPIIb/IIIa-related molecules. This family of 'cytoadhesins' may share a common function in cellular adhesive reactions.