LIMD1 phase separation contributes to cellular mechanics and durotaxis by regulating focal adhesion dynamics in response to force

The mechanical environement affects cell morphology, differentiation and motility. The ability of cells to follow gradients of extracellular matrix stiffness-durotaxis has been implicated in development, fibrosis, and cancer. Cells sense and respond to extra-cellular mechanical cues through cell-matrix adhesions. Interestingly, the maturation of focal adhesions (FAs) is reciprocally force-dependent. How biomechanical cues dictate the status of cell motility and how FAs coordinate force sensing and self-organization remain enigmatic. LIMD1, a member of the LIM domain proteins, localizes to the FAs and has been reported to negatively regulate the Hippo-YAP pathway in response to tension. Here we identify the force sensitive recruitment of LIMD1 to the FAs. We discover that LIMD1 regulates cell spreading, maintains FA dynamics and cellular force, and is critical for durotaxis. Intriguingly, LIMD1 selectively recruits late but not early FA proteins through phase separation at the FAs under force. We suggest a model in which localization of LIMD1 to the FAs, triggered by mechanical force, serves as a phase separation hub for assembling and organizing late FA proteins, allowing for effective FA maturation and efficient cellular mechano-transduction.