Hexanediol: a chemical probe to investigate the material properties of membrane-less compartments

Abstract

Membrane-less compartments, such as P bodies and stress granules, play major roles in cell biology and disease. The dynamics and physical properties of these compart-ments are very diverse, ranging from liquid-like to solid-like behavior. Importantly, changes in compartment dynamics have been linked to changes in compartment func-tion or pathology. However, appropriate tools to investigate the physical properties of membrane-less compartments are still lacking. The aliphatic alcohol hexanediol has been proposed as a tool to differentiate between liquid-like and solid-like assemblies in living cells. We show that in vitro reconstituted compartments formed by the RNA-binding protein FUS are rapidly dissolved by hexanediol. In contrast, solid-like fibers of FUS, which have been linked to the disease amyotrophic lateral sclerosis (ALS), are resistant to hexanediol treatment, supporting the idea that hexanediol can differenti-ate between liquid-and solid-like assemblies. We further show that hexanediol can be used to examine the physical properties of membrane-less compartments in vivo. We find that hexanediol dissolves dynamic, liquid-like assemblies, such as P bodies, whereas solid-like assemblies, such as protein aggregates and cytoskeletal assemblies, are largely resistant to hexanediol. Finally, we report here that extended exposure of yeast and mammalian cells to hexanediol is cytotoxic and causes abnormal changes in cell mor-phology, which trigger the formation of aberrant assemblies. We therefore urge care in the use of hexanediol, especially when cells are exposed to hexanediol for extended times. In summary, we propose that hexanediol is a powerful tool to probe the physical properties of membrane-less compartments, but only if adequate controls are included and precautions are taken.