WNK kinases sense molecular crowding and rescue cell volume via phase separation

• Published in: Cell Vol. 185; no. 24; pp. 4488 - 4506.e20
• Main Authors: Boyd-Shiwarski, Cary R., Shiwarski, Daniel J., Griffiths, Shawn E., Beacham, Rebecca T., Norrell, Logan, Morrison, Daryl E., Wang, Jun, Mann, Jacob, Tennant, William, Anderson, Eric N., Franks, Jonathan, Calderon, Michael, Connolly, Kelly A., Cheema, Muhammad Umar, Weaver, Claire J., Nkashama, Lubika J., Weckerly, Claire C., Querry, Katherine E., Pandey, Udai Bhan, Donnelly, Christopher J., Sun, Dandan, Rodan, Aylin R., Subramanya, Arohan R.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23-11-2022
• Subjects: biomolecular condensates; Cell Size; cell volume regulation; hyperosmotic stress; K-Cl cotransport; macromolecular crowding; Na-K-2Cl cotransport; phase separation; Phosphorylation; Protein Serine-Threonine Kinases; SLC12 cotransporter; WNK kinase; cell volume regulation; SLC12 cotransporter; phase separation; hyperosmotic stress; macromolecular crowding; Na-K-2Cl cotransport; K-Cl cotransport; WNK kinase; biomolecular condensates
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2022.09.042

When challenged by hypertonicity, dehydrated cells must recover their volume to survive. This process requires the phosphorylation-dependent regulation of SLC12 cation chloride transporters by WNK kinases, but how these kinases are activated by cell shrinkage remains unknown. Within seconds of cell exposure to hypertonicity, WNK1 concentrates into membraneless condensates, initiating a phosphorylation-dependent signal that drives net ion influx via the SLC12 cotransporters to restore cell volume. WNK1 condensate formation is driven by its intrinsically disordered C terminus, whose evolutionarily conserved signatures are necessary for efficient phase separation and volume recovery. This disorder-encoded phase behavior occurs within physiological constraints and is activated in vivo by molecular crowding rather than changes in cell size. This allows kinase activity despite an inhibitory ionic milieu and permits cell volume recovery through condensate-mediated signal amplification. Thus, WNK kinases are physiological crowding sensors that phase separate to coordinate a cell volume rescue response.
[Display omitted]
•Endogenous WNK1 forms hyperosmotic stress-induced condensates•The intrinsically disordered C-terminal domain mediates WNK1 phase separation•Phase behavior of the WNK1 CTD is evolutionarily conserved despite sequence divergence•WNK1 is a molecular crowding sensor and mediator of regulatory volume increase
WNK1 is a molecular crowding sensor that undergoes cell shrinkage-dependent phase separation to restore cell volume. This study provides a clear link between the intrinsically disordered region-mediated phase separation of a protein and cell physiology.