Glycoprotein VI oligomerization in cell lines and platelets.
BACKGROUND
Glycoprotein VI (GPVI) is a physiologic receptor for collagen expressed at the surface of platelets and megakaryocytes. Constitutive dimerization of GPVI has been proposed as being necessary for the interaction with collagen, although direct evidence of dimerization has not been reported in cell lines or platelets.


OBJECTIVE
To investigate oligomerization of GPVI in transfected cell lines and in platelets under non-stimulated conditions.


RESULTS
By using a combination of molecular and biochemical techniques, we demonstrate that GPVI association occurs at the surface of transfected 293T cells under basal conditions, through an interaction at the extracellular domain of the receptor. Bioluminescence resonance energy transfer was used to confirm oligomerization of GPVI under these conditions. A chemical crosslinker was used to detect constitutive oligomeric forms of GPVI at the surface of platelets, which contain the Fc receptor (FcR) gamma-chain.


CONCLUSIONS
The present results directly demonstrate GPVI-FcR gamma-chain oligomerization at the surface of the platelet, and thereby add to the growing evidence that oligomerization of GPVI may be a prerequisite for binding of the receptor to collagen, and therefore for proper functioning of platelets upon vascular damage.
Berlanga
Oscar
O
Institute of Biomedical Research, Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Bori-Sanz
Teresa
T
Institute of Biomedical Research, Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
James
John R
JR
Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, University of Oxford, Oxford OX3 9DS, UK.
Frampton
Jon
J
Institute of Biomedical Research, Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Davis
Simon J
SJ
Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, University of Oxford, Oxford OX3 9DS, UK.
Tomlinson
Michael G
MG
Institute of Biomedical Research, Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Watson
Steve P
SP
Institute of Biomedical Research, Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
D001483:Base Sequence; D001704:Biopolymers / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism*; D002460:Cell Line; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*
D001704:Biopolymers; D017931:DNA Primers; D010980:Platelet Membrane Glycoproteins