Mohr, J. M.; Kartashew, L.; Gretz, J.; Shankar, S.; Jung, S.; Kruss, S.; Erpenbeck, L.

Cells continuously generate and respond to mechanical forces across compartments, with the plasma membrane acting as a nanoscale interface for sensing and transmitting tension. How intracellular forces are translated into membrane tension during dynamic processes such as neutrophil extracellular trap (NET) formation remains unclear. Here, we combine the mechanosensitive fluorescent probe Flipper-TR with fluorescence lifetime imaging microscopy (FLIM) to map spatiotemporal changes in plasma membrane tension in living cells. After validation in HeLa and dHL-60 cells under osmotic perturbation, we apply this approach to primary human neutrophils undergoing NETosis. Membrane tension transiently increases during chromatin decondensation and nuclear swelling within 90 min and is followed by a marked decrease 30 min after membrane rupture. Prior to rupture, tension is spatially heterogeneous, indicating localized nanoscale mechanical regulation. Cholesterol depletion abolishes the transient increase and reduces heterogeneity without affecting overall NETosis kinetics. Together, these findings establish the plasma membrane as a dynamic nanoscale reporter of intracellular mechanical stress during NETosis.