LAUSR

Significance A cell must be able to measure whether the lipid membranes that surround its insides are stretched. Currently, mechanosensitive ion channels are the best-studied class of membrane tension sensors, but recent work suggests that peripheral membrane enzymes that gauge nuclear confinement or swelling during cell migration or upon tissue injury constitute a second class. The mechanosensitivity of these enzymes derives from their calcium-dependent (“C2-like”) membrane-interaction domains. Although these can be found in many important signaling proteins, they have remained virtually unstudied as mechanotransducers. How membrane tension controls these domains and what features render them mechanosensitive is unclear. Here, we show that membrane tension-sensing by C2-like domains is mediated by a synergy between mechanosensitive calcium-binding and membrane insertion. When nuclear membranes are stretched, the peripheral membrane enzyme cytosolic phospholipase A2 (cPLA2) binds via its calcium-dependent C2 domain (cPLA2-C2) and initiates bioactive lipid signaling and tissue inflammation. More than 150 C2-like domains are encoded in vertebrate genomes. How many of them are mechanosensors and quantitative relationships between tension and membrane recruitment remain unexplored, leaving a knowledge gap in the mechanotransduction field. In this study, we imaged the mechanosensitive adsorption of cPLA2 and its C2 domain to nuclear membranes and artificial lipid bilayers, comparing it to related C2-like motifs. Stretch increased the Ca2+ sensitivity of all tested domains, promoting half-maximal binding of cPLA2 at cytoplasmic resting-Ca2+ concentrations. cPLA2-C2 bound up to 50 times tighter to stretched than to unstretched membranes. Our data suggest that a synergy of mechanosensitive Ca2+ interactions and deep, hydrophobic membrane insertion enables cPLA2-C2 to detect stretched membranes with antibody-like affinity, providing a quantitative basis for understanding mechanotransduction by C2-like domains.