Affinity modulation in platelet alpha 2 beta 1 following ligand binding.
In order to test for ligand-induced change in the affinity of platelet alpha 2 beta 1 to collagen we passaged labeled viable platelets through a column of fibrillar collagen and used stringent lysis conditions to remove all low-affinity receptors. A high affinity fraction left on the collagen could be eluted with DTT and 2% SDS. Antibodies raised against it Western-blotted alpha 2 beta 1. Functional tests performed with the antibodies confirmed the involvement of the high affinity proteins in platelet-collagen interactions attributed to alpha 2 beta 1: inhibition of collagen-specific platelet adhesion and aggregation. EDTA, chaotropic agents or low pH did not elute the high affinity fraction of alpha 2 beta 1. However, DTT followed by acetic acid did. Our data suggest that 1) ligand binding induces the formation of a new disulfide bond in a fraction of alpha 2 beta 1, 2) that this bond is intrareceptor and 3) that this change increases the affinity of the receptor to its ligand.
Gofer-Dadosh
N
N
Hemostasis Research Laboratory, Rabin Medical Center, Petah Tiqva, Israel.
Klepfish
A
A
Schmilowitz
H
H
Shaklai
M
M
Lahav
J
J
D001792:Blood Platelets / Q000378:metabolism*; D002846:Chromatography, Affinity; D003094:Collagen / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D016023:Integrins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008024:Ligands; D010973:Platelet Adhesiveness; D011485:Protein Binding; D038981:Receptors, Collagen
D016023:Integrins; D008024:Ligands; D038981:Receptors, Collagen; D003094:Collagen