A Hemidesmosome-to-Cytoplasm Translocation of Small Heat Shock Proteins Provides Immediate Protection against Heat Stress.

Small heat shock proteins (sHSPs) are important regulators for maintaining protein homeostasis in response to stresses. However, the strategies used by constitutively expressed sHSPs to control their activities in normal versus stressed conditions are still not fully understood. Here we show that the constitutively expressed HSP-43 in the C. elegans epidermis is stored within the basal C. elegans hemidesmosomes (CeHDs) under normal conditions and is rapidly released into the cytoplasm to exert protective functions upon heat stress. The association with CeHDs protects HSP-43 from degradation or toxic cytoplasmic aggregation in unstressed situations. Our study reveals a rapid and specific translocation-based heat shock response of the sHSPs working through hemidesmosomes. It refreshes our knowledge about the stress-resistant functions of stable cellular adhesions and provides insight into the activity-control strategies of sHSPs. It also underlines the importance of structural integrity of the cells on stress resistance and damage control.