Investigating the biophysical mechanisms of integrin-based adhesion at the cellular and single-molecule level
Abstract/Contents
- Abstract
- Integrins mediate cell adhesion to the extracellular matrix and enable the construction of complex, multicellular organisms, yet fundamental aspects of integrin-based adhesion remain poorly understood. Notably, recent estimates of the load experienced by integrins span two orders of magnitude, a discrepancy arising from limitations inherent to existing techniques. Thus, it is unclear if integrin-based adhesion, and by extension mechanotransduction, reflects a disproportionate contribution by only a few integrins bearing large forces, or is instead a collective phenomenon reflecting the cumulative output of many weaker interactions. We used FRET-based molecular tension sensors (MTSs) to directly measure the distribution of forces experienced by individual integrins in living cells. We find that the majority of integrins transmit relatively modest forces of less than 7 pN, and that a large proportion of these integrins bear minimal loads of less than 3 pN. This finding suggests that most integrins are tensioned to well below their load-bearing capacities. In addition, load-bearing integrins are not exclusively localized to adhesion structures; integrins exerting low forces outside of discernible adhesions contribute a significant fraction of the cell's total traction and are sufficient for maintaining adhesion. Further, we developed MTSs presenting the full fibronectin type III 9th and 10th domains which includes the synergy site, a secondary binding site thought to reinforce the fibronectin- α5β1 integrin bond. Our data indicate that the synergy site does not increase the force per integrin, but does increase the relative contribution of α5β1 integrin in mediating adhesion. Further, our data indicate that the synergy site is critical for the cell's ability to resist detachment when exposed to externally applied load. In total, these data suggest that a substantial population of bound but minimally tensioned integrins, aided by synergy site-mediated mechanical reinforcement, can provide cells and tissues with physical resiliency. Finally, we tested the hypothesis that loads are apportioned differently on distinct integrin types (here, α5β1 and αv-class). Surprisingly, our data indicate minimal differences in the amount of force transmitted by either α5β1 and αv-class integrins. Instead, our data are consistent with a model in which different integrin subtypes play distinct roles in organizing adhesion structure and dynamics.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Chang, Alice Chun-Chii |
|---|---|
| Associated with | Stanford University, Department of Chemical Engineering. |
| Primary advisor | Dunn, Alexander Robert |
| Thesis advisor | Dunn, Alexander Robert |
| Thesis advisor | Lin, Michael Z |
| Thesis advisor | Swartz, James R |
| Advisor | Lin, Michael Z |
| Advisor | Swartz, James R |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Alice Chun-Chii Chang. |
|---|---|
| Note | Submitted to the Department of Chemical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Alice Chun-Chii Chang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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