A platelet alpha-granule membrane protein (GMP-140) is expressed on the plasma membrane after activation.
We have previously characterized a monoclonal antibody, S12, that binds only to activated platelets (McEver, R.P., and M.N. Martin, 1984, J. Biol. Chem., 259:9799-9804). It identifies a platelet membrane protein of Mr 140,000, which we have designated as GMP-140. Using immunocytochemical techniques we have now localized this protein in unstimulated and thrombin-stimulated platelets. Polyclonal antibodies to purified GMP-140 were used to enhance the sensitivity of detection. Nonpermeabilized, unstimulated platelets, incubated with anti-GMP-140 antibodies, and then with IgG-gold probes, showed very little label for GMP-140 along their plasma membranes. In contrast, thrombin-stimulated platelets exhibited at least a 50-fold increase in the amount of label along the plasma membrane. On frozen thin sections of unstimulated platelets we observed immunogold label along the alpha-granule membranes. We also employed the more sensitive technique of permeabilizing with saponin unstimulated platelets in suspension, and then incubating the cells with polyclonal anti-GMP-140 antibodies and Fab-peroxidase conjugate. Alpha-granule membranes showed heavy reaction product, but no other intracellular organelles were specifically labeled. These results demonstrate that GMP-140 is an alpha-granule membrane protein that is expressed on the platelet plasma membrane during degranulation.
P E
PE
Stenberg
R P
RP
McEver
M A
MA
Shuman
Y V
YV
Jacques
D F
DF
Bainton
D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D008970:Molecular Weight; D019007:P-Selectin; D010974:Platelet Aggregation
D000911:Antibodies, Monoclonal; D006023:Glycoproteins; D008565:Membrane Proteins; D019007:P-Selectin