Biogenesis of the vitronectin receptor in human endothelial cell: evidence that the vitronectin receptor and GPIIb-IIIa are synthesized by a common mechanism.
Human endothelial cells express a membrane glycoprotein alpha beta heterodimer similar to the human platelet glycoprotein IIb-IIIa complex (GPIIb-IIIa). This noncovalently associated complex is the vitronectin receptor (VNR). These two receptors belong to the cytoadhesin family and share the same beta subunit. They express different recognition specificities: platelet GPIIb-IIIa is a receptor for fibrinogen, fibronectin, and von Willebrand factor (vWF), whereas VNR is a receptor for vitronectin, and is possibly a receptor for fibrinogen and vWF. We analyzed the biosynthesis of the endothelial cell VNR. Our data show that VNR alpha is a two-chain protein which is biosynthesized as a single-chain precursor: the pro-VNR alpha. Pro-VNR alpha forms a complex with VNR beta, and this association occurs prior to the Golgi-mediated processing of the oligosaccharide side chains. Mature VNR beta is glycosylated by not fully processed oligosaccharide side chains because it remains endoglycosidase H (endo H) sensitive, even when the complex is expressed on the cell surface. This characteristic appears as a common feature for the members of the cytoadhesin family. These results indicate that although VNR and GPIIb-IIIa are biosynthesized in different cells, their expression is controlled by similar mechanisms, providing further support for the concept that the cytoadhesin family constitutes a distinct group of adhesion receptors.
Polack
B
B
Laboratoire d'Hématologie/DRF/LBIO, INSERM U217, Centre d'Etudes Nucléaires de Grenoble, France.
Duperray
A
A
Troesch
A
A
Berthier
R
R
Marguerie
G
G
D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000502:physiology*; D006023:Glycoproteins / Q000502:physiology*; D006596:Hexosaminidases / Q000494:pharmacology; D006801:Humans; D046911:Macromolecular Substances; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D010980:Platelet Membrane Glycoproteins / Q000096:biosynthesis*; D011233:Precipitin Tests; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011971:Receptors, Immunologic / Q000502:physiology*; D019030:Receptors, Vitronectin; D014415:Tunicamycin / Q000494:pharmacology; D019096:Vitronectin
D006023:Glycoproteins; D046911:Macromolecular Substances; D010980:Platelet Membrane Glycoproteins; D011971:Receptors, Immunologic; D019030:Receptors, Vitronectin; D019096:Vitronectin; D014415:Tunicamycin; D006596:Hexosaminidases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase