Novel Analysis Method for Condensate Wetting Identifies Charge-Dependent Tau-Membrane Interactions

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Condensed biomolecular phases are fundamental compartments in cells and play intricate roles for cellular organization. Although often referred to as “membraneless organelles,” evidence has emerged that condensates associate with membranes through wetting interactions, which are physiologically important but not well understood. Here we report a novel method that provides a detailed description of how condensates interact with surfaces. Combining technically advantageous flat membranes and reconstituted condensates, we developed an accurate method that automatically analyzes the three-dimensional geometry of single, μ m -sized condensates acquired as multicondensate confocal image stacks using 96-well plates. We validated our computational routine by quantifying wetting of and condensates for precisely controlled solution and supported lipid membrane biochemistries. Further, we applied our method to analyze the wetting of condensates formed from the Alzheimer disease-associated protein tau in its phosphorylated and nonphosphorylated forms. Our results demonstrate that both membrane charge and tau posttranslational modifications affect wetting and that our method allows building a systematic, quantitative wetting database, which catalogues conditions controlling wetting in multiple dimensions. We anticipate that upscaled in a high-throughput pipeline, our screening approach will efficiently support efforts to construct a comprehensive wetosome database, which will unravel the mechanisms underlying condensate-membrane interactions and, thus, decipher the molecular grammar governing wetting.