Hsp70 exhibits a liquid-liquid phase separation ability and chaperones condensed FUS against amyloid aggregation
Yichen Li, Jinge Gu, Chen Wang, Jiaojiao Hu, Shenqing Zhang, Cong Liu, Shengnan Zhang, Yanshan Fang, Dan Li
Abstract
Hsp70 is a key molecular chaperone in the protein quality control system to safeguard protein homeostasis in cells. Previous studies have shown that Hsp70 chaperones TDP-43, a pathogenic protein associated with amyotrophic lateral sclerosis (ALS), in nuclear bodies and prevents it from the pathological aggregation. In this work, we report that Hsp70 undergoes liquid-liquid phase separation, chaperones FUS, another ALS-linked pathogenic protein, in stress granules (SGs), and prevents condensed FUS from amyloid aggregation. Knock-down of Hsp70 does not influence SG assembly but results in the liquid-to-solid transition in SGs. NMR experiments further reveal Hsp70 predominantly uses its C-terminal substrate-binding domain to interact with the low complexity domain of FUS, which represents a mechanism distinct from that interacting with TDP-43. These findings suggest that Hsp70 is widely involved in chaperoning the physiological dynamics of various membrane-less organelles and adopts different mechanisms to prevent the pathological aggregation of different proteins.