Abstract
AG-1 is a monoclonal antibody that binds to human platelets and causes aggregation and secretion. Previous work has established that these responses result from phospholipase C-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2). To determine the mechanism by which this ligand induces signals for platelet activation, we performed a series of experiments examining the platelet binding site for AG-1. AG-1 immunoprecipitates from radioiodinated human platelet plasma membranes a protein of Mr 21,000. AG-1 immunoprecipitated proteins separated by SDS-PAGE, transferred to nitrocellulose, and incubated with [α32P]GTP demonstrate binding of the radiolabeled GTP to the Mr 21,000 protein. A 100-fold molar excess of unlabeled GTP inhibits completely this binding of [α32P]GTP. These results indicate that AG-1 interacts with a low Mr GTP-binding protein on the surface of platelets and suggests that either the protein recognized by AG-1 or a coprecipitating molecule of similar Mr is a low Mr GTP-binding protein that may function in platelet extracellular signal transduction.
Original language | English (US) |
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Pages (from-to) | 1252-1257 |
Number of pages | 6 |
Journal | Biochemical and biophysical research communications |
Volume | 171 |
Issue number | 3 |
DOIs | |
State | Published - Sep 28 1990 |
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Molecular Biology
- Cell Biology