Human platelet glycoprotein V: its role in enhancing expression of the glycoprotein Ib receptor.
Platelet adhesion to an injured blood vessel wall is a critical initiating step in hemostasis mediated by a four member receptor complex (glycoprotein Ib/V/IX) interacting with plasma von Willebrand factor (vWF). The function of the GPV subunit within this complex is presently undefined. To study the role of glycoprotein (GP) V within the GPIb receptor complex, we transfected the GPV subunit gene into a hematopoietic cell line that constitutively expresses the other three subunits (human erythroleukemia [HEL] cells). Using flow cytometry, we found transfected GPV was surface expressed in HEL cells; this, in turn, led to increased surface expression of the ligand-binding GPIb alpha and GPIX subunits. Radioligand binding assays showed that GPV-transfected HEL cells bound more vWF than their non- or mock-transfected counterparts. We employed confocal microscopy of GPV-transfected HEL cells to show that GPV colocalizes with GPIb alpha on the cell surface. These findings suggest that the GPV subunit plays a role within the GPIb receptor complex by enhancing Ib alpha surface expression.
Calverley
D C
DC
Hematology Section, Seattle Veterans Affairs Medical Center, Seattle, WA 98108, USA.
Yagi
M
M
Stray
S M
SM
Roth
G J
GJ
D002462:Cell Membrane / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D018613:Microscopy, Confocal; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014162:Transfection
D046911:Macromolecular Substances; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; C028254:von Willebrand factor receptor