Integrin-Generated Forces Lead to Streptavidin-Biotin Unbinding in Cellular Adhesions

• Type of Material: Article
• Authors: Carol Jurchenko, Emory University; Yuan Chang, Emory University; Yoshie Narui, Emory University; Yun Zhang, Emory University; Khalid Salaita, Emory University
• Language: English
• Date: 2014-04
• Publisher: Biophysical Society
• Publication Version: Final Published Version
• Copyright Statement: © 2014 by the Biophysical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
• Final Published Version (URL): http://dx.doi.org/10.1016/j.bpj.2014.01.049
• Title of Journal or Parent Work: Biophysical Journal
• ISSN: 0006-3495
• Volume: 106
• Issue: 7
• Start Page: 1436
• End Page: 1446
• Grant/Funding Information: K.S. is grateful for support from the NIH (R01-GM097399), the Alfred P. Sloan Research Fellowship, and the Army Research Office (62570EGII).; Research reported in this publication was supported in part by the NIH/NCI under award number P30CA138292.; The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
• Research Categories: Chemistry, General

Abstract

The interplay between chemical and mechanical signals plays an important role in cell biology, and integrin receptors are the primary molecules involved in sensing and transducing external mechanical cues. We used integrin-specific probes in molecular tension fluorescence microscopy to investigate the pN forces exerted by integrin receptors in living cells. The molecular tension fluorescence microscopy probe consisted of a cyclic Arg-Gly-Asp-D-Phe-Lys(Cys) (cRGDfK(C)) peptide tethered to the terminus of a polyethylene glycol polymer that was attached to a surface through streptavidin-biotin linkage. A fluorescence resonance energy transfer mechanism was used to visualize tension-driven extension of the polymer. Surprisingly, we found that integrin receptors dissociate streptavidin-biotin tethered ligands in focal adhesions within 60 min of cell seeding. Although streptavidin-biotin binding affinity is described as the strongest noncovalent bond in nature, and is ∼106 - 108 times larger than that of integrin-RGD affinity, our results suggest that individual integrin-ligand complexes undergo a marked enhancement in stability when the receptor assembles in the cell membrane. Based on the observation of streptavidin-biotin unbinding, we also conclude that the magnitude of integrin-ligand tension in focal adhesions can reach values that are at least 10 fold larger than was previously estimated using traction force microscopy-based methods.