ISS: Elucidating the role of integrin mechanotransduction in response to microgravity

Cells undergo surprising biological changes in microgravity. Under these conditions, cells alter their activities and the structure of their internal “skeleton,” known as the cytoskeleton. This is remarkable because the force of gravity on a single cell in microgravity is very small—roughly one million billionth the weight of a paperclip—and it is not clear how cells sense such tiny changes. This project tests the idea that the cytoskeleton and the proteins that anchor it to the outside environment act as “gravitational sensors.” To test this idea, the team will use an ultra-sensitive molecular force sensor to measure the tiny pulling forces that cells exert on their surroundings through adhesion receptors and see whether those forces change when gravity is altered. Success will enable precise measurements of cell forces aboard the International Space Station (ISS) and reveal fundamental mechanisms by which cells "feel" microgravity. This project investigates how microgravity affects integrin-mediated mechanotransduction, the cellular process by which mechanical forces are converted into biochemical signals. Integrins are transmembrane receptors that couple the extracellular matrix to the cytoskeleton and generate forces critical for cell adhesion, migration, and signaling. Prior work has shown that microgravity alters focal adhesion dynamics and cytoskeletal organization, but the underlying force changes and their signaling consequences remain unclear. To address this, the team will develop and deploy molecular tension fluorescence microscopy probes based on DNA hairpins and duplexes to quantify integrin forces under microgravity aboard the International Space Station. These probes provide piconewton-scale force sensitivity and enable long-term preservation of force signals in fixed samples. Ground-based and ISS-exposed cells will be cultured on force-calibrated substrates, fixed in orbit, and returned for post-flight super-resolution imaging. Using a multiplexed method developed by the team, Points Accumulation for Imaging in Nanoscale Topography or DNA-PAINT, the team will map the spatial distribution of force transmission and associated mechanotransduction proteins such as vinculin and YAP/TAZ. The project aims to (1) determine the minimum force required to activate integrin signaling under microgravity, (2) quantify integrin force profiles using reversible and irreversible DNA probes, and (3) characterize nanoscale focal adhesion organization in microgravity-exposed cells. This ISS-based study will uniquely isolate gravitational effects on force signaling, enabling high-resolution mechanistic insights into how cellular mechanics respond to changes in the external environment. The outcomes will advance both space biology and mechanobiology, informing therapies for diseases involving disrupted mechanotransduction. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.