A patient with platelets deficient in glycoprotein VI that lack both collagen-induced aggregation and adhesion.
Molecular level studies on platelets deficient in collagen-induced aggregation provide evidence for identifying possible platelet collagen receptors. We investigated platelets from a patient with mild bleeding time prolongation, but otherwise normal coagulation data. Her platelets lacked collagen-induced aggregation and adhesion, but retained normal aggregation and release by other agonists. Labeling her platelets with 125I or 3H and analysis by SDS-PAGE/autoradiography showed normal levels of glycoproteins Ia, Ib, IIa, IIb, IIIa, and IV. However, there were significantly decreased incorporations of both radioactivities into a 61-kD membrane glycoprotein (GP), which was identified as GPVI from its mobility on unreduced-reduced, two-dimensional SDS-PAGE. Sugiyama et al. (1987. Blood. 69: 1712) reported that the serum from an idiopathic thrombocytopenic purpura (ITP) patient contained an antibody against a 62-kD platelet protein. Our patient's platelets lacked the antigen for the ITP patient's antibody, demonstrating that the ITP serum contains a specific antibody against GPVI. The patient's parents' platelets contained approximately 50% the normal amount of GPVI, but still had normal collagen-induced aggregation and adhesion. The patient's platelets did not bind to types I and III collagen fibrils. Our results suggest that GPVI functions as a collagen receptor.
Moroi
M
M
Department of Biochemistry II, Jichi Medical School, Tochigi, Japan.
Jung
S M
SM
Okuma
M
M
Shinmyozu
K
K
D000328:Adult; D001345:Autoradiography; D001792:Blood Platelets / Q000502:physiology*; D003094:Collagen / Q000378:metabolism / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D007106:Immune Sera; D015151:Immunoblotting; D008970:Molecular Weight; D010973:Platelet Adhesiveness / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects*; D010980:Platelet Membrane Glycoproteins / Q000032:analysis / Q000172:deficiency*; D011696:Purpura, Thrombocytopenic / Q000276:immunology
D007106:Immune Sera; D010980:Platelet Membrane Glycoproteins; D003094:Collagen