Interaction of platelet glycoprotein V with glycoprotein Ib-IX regulates expression of the glycoproteins and binding of von Willebrand factor to glycoprotein Ib-IX in transfected cells.
The goal of the present study was to determine whether platelet glycoprotein (GP) V interacts directly with the von Willebrand factor receptor GP Ib-IX and, if so, whether it affects the expression and function of this receptor. A melanoma cell line that does not contain actin-binding protein was transfected with the cDNAs coding for GP V and for each of the three subunits of GP Ib-IX. GP V co-immunoprecipitated and co-localized with GP Ib-IX. Although GP V could be expressed in the absence of GP Ib-IX, the amount incorporated in the membrane was markedly increased when GP Ib-IX was present. Similarly, there was an enhanced expression of GP Ib-IX on the cell surface in the presence of GP V. The binding affinity of botrocetin-induced von Willebrand factor to GP Ib-IX was unaffected by the presence or absence of GP V. However, the binding capacity was increased by the presence of GP V. We conclude that GP V interacts directly with GP Ib-IX, that GP V must associate with GP Ib-IX to be efficiently expressed in the membrane, and that GP V increases the binding capacity of the cells for von Willebrand factor by enhancing the surface expression of the GP Ib-IX complex.
Meyer
S C
SC
Children's Hospital Oakland Research Institute, California 94609, USA.
Fox
J E
JE
D000911:Antibodies, Monoclonal; D005786:Gene Expression Regulation; D006801:Humans; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D014162:Transfection; D014407:Tumor Cells, Cultured; D014841:von Willebrand Factor / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D010980:Platelet Membrane Glycoproteins; D014841:von Willebrand Factor