A member of the selectin family (gmp-140/padgem) is expressed on thrombin-stimulated rat platelets in vitro

• Published in: Comparative biochemistry and physiology. A, Comparative physiology Vol. 102; no. 2; pp. 265 - 271
• Main Authors: Winocour, P.D, Chignier, E, Parmentier, S, McGregor, J.L
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier B.V 1992; Elsevier
• Subjects: Biological and medical sciences; expression; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Immunohematology; man; PADGEM protein; Platelet immunology; platelets; selectin; stimulation; Human; Rat; Enzyme; Rodentia; Cell adhesion molecule; Thrombin; Glycoproteins; Monoclonal antibody; Cell surface; Vertebrata; Platelet; Mammalia; Cross reaction
• ISSN: 0300-9629
• DOI: 10.1016/0300-9629(92)90133-B

1. 1. Granule membrane protein (GMP-140) is an integral α-granule membrane glycoprotein, expressed on the surface of human platelets following degranulation, and is pan of a new family of adhesion molecules (selectins) related to the endothelial leukocyte adhesion molecule (ELAM-1) and to the lymphocyte homing receptors in man (Leu-8/TQ1) and in mouse (gp90 MEL-14). 2. 2. The cross-reactivity with rat platelets of the monoclonal antibodies (MAb), LYP20 and S12, directed against human GMP-140 was examined, with the purpose of assessing the homology of GMP-140 between human and rat platelets and of using positive MAbs to detect platelet activation in vivo in response to vascular disease in rats. 3. 3. By ELISA technique, LYP20 gave a greater OD reading with thrombin-stimulated rat platelets than with resting platelets. 4. 4. 125I-LYP20 bound significantly more to thrombin-stimulated rat platelets (3875 ± 750 molecules/ platelet) than to resting platelets (645 ± 240 molecules/platelet, P < 0.01) with 50% maximum binding at 0.13 ± 0.02 μg/ml; 125I-S12 did not bind to rat platelets. 5. 5. By fluorescence-activated flow cytometry there were significantly more fluorescent thrombin-stimulated platelets (56 ± 7% of total), compared with resting platelets (8 ± 1% of total, P < 0.001). 6. 6. Western blots of rat platelet lysates showed that LYP20 bound to a single band identified, under non-reducing conditions, as having the same apparent M r as GMP-140. 7. 7. LYP20 immunoprecipitated a protein which became radiolabelled on the surface of thrombin-activated rat platelets; S12 did not recognize any protein. 8. 8. It appears that LYP20 and S12 are directed against different epitopes on the GMP-140 molecule and that the LYP20 epitope, but not the S12 epitope, is preserved in GMP-140 in rat platelets. 9. 9. LYP20 can, therefore, be used as a marker of GMP-140 expression on activated platelets in vivo in rats.