18 October 2004 Identification of stepped changes of binding affinity during interactions between the disintegrin rhodostomin and integrin αIIbβ3 in living cells using optical tweezers
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Abstract
Integrin receptors serve as both mechanical links and signal transduction mediators between the cell and its environment. Experimental evidence demonstrates that conformational changes and lateral clustering of the integrin proteins may affect their binding to ligands and regulate downstream cellular responses; however, experimental links between the structural and functional correlations of the ligand-receptor interactions are not yet elucidated. In the present report, we utilized optical tweezers to measure the dynamic binding between the snake venom rhodostomin, coated on a microparticle and functioned as a ligand, and the membrane receptor integrin alpha(IIb)beta(3) expressed on a Chinese Hamster Ovary (CHO) cell. A progressive increase of total binding affinity was found between the bead and CHO cell in the first 300 sec following optical tweezers-guided contact. Further analysis of the cumulative data revealed the presence of "unit binding force" presumably exerted by a single rhodostomin-integrin pair. Interestingly, two such units were found. Among the measurements of less total binding forces, presumably taken at the early stage of ligand-receptor interactions, a unit of 4.15 pN per molecule pair was derived. This unit force dropped to 2.54 pN per molecule pair toward the later stage of interactions when the total binding forces were relatively large. This stepped change of single molecule pair binding affinity was not found when mutant rhodostomin proteins were used as ligands (a single unit of 1.81 pN per pair was found). These results were interpreted along with the current knowledge about the conformational changes of integrins during the "molecule activation" process.
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Chia-Fen Hsieh, Chia-Fen Hsieh, Bo-Jui Chang, Bo-Jui Chang, Chyi-Huey Pai, Chyi-Huey Pai, Hsuan-Yi Chen, Hsuan-Yi Chen, Sien Chi, Sien Chi, Long Hsu, Long Hsu, Jin-Wu Tsai, Jin-Wu Tsai, Chi-Hung Lin, Chi-Hung Lin, } "Identification of stepped changes of binding affinity during interactions between the disintegrin rhodostomin and integrin αIIbβ3 in living cells using optical tweezers", Proc. SPIE 5514, Optical Trapping and Optical Micromanipulation, (18 October 2004); doi: 10.1117/12.558653; https://doi.org/10.1117/12.558653
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