Platelet activation results in a redistribution of glycoprotein IV (CD36).
To investigate the possibility that thrombin and/or other platelet activators change the platelet surface expression of glycoprotein IV (GPIV, CD36), we used a panel of five GPIV-specific monoclonal antibodies (OKM5, 5F1, FA6-152, 8A6, and F13) directed against different epitopes. All these antibodies bound to resting platelets in a concentration-dependent and saturable manner, as determined by flow cytometry of washed platelets. Thrombin (1 U/mL) induced an approximately twofold increase in the platelet surface binding of each of these monoclonal antibodies. Immunofluorescence microscopy demonstrated an internal pool of GPIV that, after thrombin stimulation, redistributed to the platelet surface. In a whole-blood flow-cytometric assay, alpha-thrombin and the thromboxane A2 analogue U46619 each resulted in an approximately twofold increase in the platelet surface binding of OKM5, whereas ADP had a more modest effect, and collagen and epinephrine had little effect. The activation-induced up-regulation of the platelet OKM5 epitope occurred in vivo as demonstrated by flow cytometric analysis of whole blood emerging from a standardized skin puncture site. In summary, both in vitro and in vivo platelet activation results in increased platelet surface expression of GPIV, as a result of a redistribution of GPIV from an internal pool.
Michelson
A D
AD
Department of Pediatrics, University of Massachusetts Medical School, Worcester 01655.
Wencel-Drake
J D
JD
Kestin
A S
AS
Barnard
M R
MR
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000911:Antibodies, Monoclonal / Q000097:blood; D015703:Antigens, CD / Q000097:blood*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D018955:CD36 Antigens; D006801:Humans; D007223:Infant; D015539:Platelet Activation / Q000502:physiology*; D010980:Platelet Membrane Glycoproteins / Q000097:blood*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D016024:Receptors, Cytoadhesin / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018955:CD36 Antigens; D010980:Platelet Membrane Glycoproteins; D011450:Prostaglandin Endoperoxides, Synthetic; D016024:Receptors, Cytoadhesin; D014662:Vasoconstrictor Agents; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D013917:Thrombin