Reentrant liquid condensate phase of proteins is stabilized by hydrophobic and non-ionic interactions
Georg Krainer, Timothy J. Welsh, Jerelle A. Joseph, Jorge R. Espinosa, Sina Wittmann, Ella de Csilléry, Akshay Sridhar, Zenon Toprakcioglu, Giedre Gudiškytė, Magdalena A. Czekalska, William E. Arter, Jordina Guillén‐Boixet, Titus M. Franzmann, Seema Qamar, Peter St George‐Hyslop, Anthony A. Hyman, Rosana Collepardo‐Guevara, Simon Alberti, Tuomas P. J. Knowles
Abstract
Liquid-liquid phase separation of proteins underpins the formation of membraneless compartments in living cells. Elucidating the molecular driving forces underlying protein phase transitions is therefore a key objective for understanding biological function and malfunction. Here we show that cellular proteins, which form condensates at low salt concentrations, including FUS, TDP-43, Brd4, Sox2, and Annexin A11, can reenter a phase-separated regime at high salt concentrations. By bringing together experiments and simulations, we demonstrate that this reentrant phase transition in the high-salt regime is driven by hydrophobic and non-ionic interactions, and is mechanistically distinct from the low-salt regime, where condensates are additionally stabilized by electrostatic forces. Our work thus sheds light on the cooperation of hydrophobic and non-ionic interactions as general driving forces in the condensation process, with important implications for aberrant function, druggability, and material properties of biomolecular condensates.