Project Summary Mechanisms of Mechanotransduction by LIM Domain Proteins Mechanical forces are essential to controlling the shape, movement and even many aspects of cell physiology. Changes in the environment mechanics or defects in cellular mechanoresponse are implicated in a plethora of diseases including atherosclerosis, heart failure and cancer. A major challenge is to understand mechanotransduction - the mechanisms by which mechanical information is detected and communicated to pathways that control cell behavior. The LIM super family of proteins, which contain one or more LIM domains, represents a large number of putative mechanosensitive cellular proteins that are involved in physiological mechanotransduction pathways. Understanding how the LIM domains function to detect and transmit information about mechanical stress will result in a deeper understanding of mechanotransduction-based signaling, which is important for developing strategies of disease treatment and organ regeneration. This proposal leverages an innovative combination of cell biophysics, biochemistry molecular cell biology, live cell imaging and mathematical modeling to investigate the mechanism by which LIM domains sense mechanical stimuli in the actin cytoskeleton and, in turn, initiate YAP/TAZ mechanotransduction signaling. We recently discovered that a large number of LIM domains exhibit force-sensitive binding to actin filaments. Here we propose to: (1) identify the mechanism by which LIM proteins are recruited to mechanically stressed actin filaments, (2) determine how the LIM sequence enables specificity in force-dependent recruitment within the actin cytoskeleton and (3) elucidate how the mechanosensing by LIM protein LIMD1 initiates the YAP/TAZ mechanotransduction pathway. These studies have the potential to demonstrate a highly conserved mechanism of cell mechanosensing, and the methodologies will establish a novel strategy for tackling cell mechanotransduction.