Cholesterol depletion by MβCD enhances membrane tension, its heterogeneity and affects cellular integrity

Cholesterol depletion in cells by MβCD remodels the plasma membrane’s mechanics and its interactions with the underlying cytoskeleton. Decoupling the two effects and studying various alterations to the membrane’s mechanical parameters is important for understanding cholesterol’s role in cellular response to stress. By mapping membrane height fluctuations in single cells, we report that MβCD treatment reduces temporal fluctuations and flattens out the membrane – but does not supress activity-driven fluctuations. We find that membrane tension increase contributes most to the altered fluctuations, among the multiple mechanical parameters computed. Maps also reveal an enhanced long-range heterogeneity within single cells, both in amplitude of fluctuations and membrane tension on cholesterol depletion. To check if this alters the tenacity of membrane to mechanical stress we use hypo-osmotic shock. We find that on MβCD treatment, cells are more prone to rupture than control cells, and this is not hindered by actomyosin perturbations. We report increased rupture sizes on cholesterol depletion and argue that, together, this indicates decreased lysis and line tension. Therefore, we show that cholesterol depletion directly affects cell membranes not only by enhancing membrane-cytoskeleton interactions, but also by increasing membrane tension while reducing lysis tension – hence making cells prone to rupture.