Platelets with 10% of the normal amount of glycoprotein VI have an impaired response to collagen that results in a mild bleeding tendency.
Platelet glycoprotein VI (GPVI), a 62kD membrane protein, has been identified as one of the platelet receptors for collagen, since GPVI-deficient platelets exhibit abnormal responses to collagen and an abnormal bleeding tendency. We report a female patient with a mild bleeding history whose platelets expressed 10% GPVI of normal platelets. Shape change, aggregation and ATP release of the patient's platelets were completely absent in response to 1-5 micrograms/ml collagen but present normally in response to ADP and Ca2+ ionophore A23187. Adhesion of the patient's platelets to coated collagen was mildly affected (40-60% of normal platelets) in spite of only 10% expression of GPVI. Flow cytometrical studies revealed that the patient's platelets expressed normal amounts of the GPIa/IIa complex. These results suggest that platelet GPVI is less involved in adhesion to collagen than shape change and aggregation induced by collagen.
Arai
M
M
Department of Clinical Pathology, Tokyo Medical College, Japan.
Yamamoto
N
N
Moroi
M
M
Akamatsu
N
N
Fukutake
K
K
Tanoue
K
K
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000097:blood; D015703:Antigens, CD / Q000097:blood; D001792:Blood Platelets / Q000737:chemistry* / Q000187:drug effects / Q000473:pathology; D018955:CD36 Antigens; D000001:Calcimycin / Q000494:pharmacology; D002448:Cell Adhesion / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D006474:Hemorrhagic Disorders / Q000097:blood*; D006801:Humans; D015151:Immunoblotting; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010980:Platelet Membrane Glycoproteins / Q000032:analysis; D013915:Thrombasthenia / Q000097:blood
D015703:Antigens, CD; D018955:CD36 Antigens; D010980:Platelet Membrane Glycoproteins; D000001:Calcimycin; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003094:Collagen