期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2002
卷号：99
期号：11
页码：7426-7431
DOI：10.1073/pnas.112194999
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Integrin activation states determine the ability of these receptors to mediate cell-matrix and cell-cell interactions. The prototypic example of this phenomenon is the platelet integrin, IIb{beta}3. In unstimulated platelets, IIb{beta}3 is inactive, whereas exposing platelets to an agonist such as ADP or thrombin enables IIb{beta}3 to bind ligands such as fibrinogen and von Willebrand factor. To study the regulation of integrin activation states at the level of single molecules, we developed a model system based on laser tweezers, enabling us to determine the rupture forces required to separate single ligand-receptor pairs by using either purified proteins or intact living cells. Here, we show that rupture forces of individual fibrinogen molecules and either purified IIb{beta}3 or IIb{beta}3 on the surface of living platelets were 60 to 150 pN with a peak yield strength of 80-100 pN. Platelet stimulation using either ADP or the thrombin receptor-activating peptide enhanced the accessibility but not the adhesion strength of single IIb{beta}3 molecules, indicating that there are only two states of IIb{beta}3 activation. Thus, we found it possible to use laser tweezers to measure the regulation of forces between individual ligand-receptor pairs on living cells. This methodology can be applied to the study of other regulated cell membrane receptors using the ligand-receptor yield strength as a direct measure of receptor activation/inactivation state.
