A Programmable DNA Origami Nanospring That Reports Dynamics of Single Integrin Motion, Force Magnitude and Force Orientation in Living Cells

Mechanical forcesare critical for regulating many biological processessuch as cell differentiation, proliferation, and death. Probing thecontinuously changing molecular force through integrin receptors providesinsights into the molecular mechanism of rigidity sensing in cells;however, the force information is still limited. Here, we built acoil-shaped DNA origami (DNA nanospring, NS) as a force sensor thatreports the dynamic motion of single integrins as well as the magnitudeand orientation of the force through integrins in living cells. Wemonitored the extension with nanometer accuracy and the orientationof the NS linked with a single integrin by the shape of the fluorescencespots. We used acoustic force spectroscopy to estimate the force-extensioncurve of the NS and determined the force with an & SIM;10% forceerror at a broad detectable range from subpicoNewtons (pN) to & SIM;50pN. We found single integrins tethered with the NS moved several tensof nanometers, and the contraction and relaxation speeds were loaddependent at less than & SIM;20 pN but robust over & SIM;20 pN.Fluctuations of the traction force orientation were suppressed withincreasing load. Our assay system is a potentially powerful tool forstudying mechanosensing at the molecular level.