The N-end rule pathway regulates ER stress-induced clusterin release to the cytosol where it directs misfolded proteins for degradation
Sandeep Satapathy,
Holly Walker,
James Brown,
Yann Gambin,
Mark R. Wilson
Affiliations
Sandeep Satapathy
The Broad Institute of MIT and Harvard, Cambridge, MA 02139, USA; School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia; Molecular Horizons Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
Holly Walker
School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia; Molecular Horizons Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
James Brown
EMBL Australia Node in Single Molecule Science, and School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
Yann Gambin
EMBL Australia Node in Single Molecule Science, and School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
Mark R. Wilson
School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia; Molecular Horizons Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia; Corresponding author
Summary: Previous work suggests that cell stress induces release of the normally secreted chaperone clusterin (CLU) into the cytosol. We analyzed the localization of CLU in healthy and stressed cells, the mechanism of its cytosolic release, and its interactions with cytosolic misfolded proteins. Key results of this study are the following: (1) full-length CLU is released to the cytosol during stress, (2) the CLU N-terminal D1 residue is recognized by the N-end rule pathway and together with the enzyme ATE1 is essential for cytosolic release, (3) CLU can form stable complexes with cytosolic misfolded proteins and direct them to the proteasome and autophagosomes, and (4) cytosolic CLU protects cells from hypoxic stress and the cytosolic overexpression of an aggregation-prone protein. Collectively, the results suggest that enhanced cytosolic release of CLU is a stress response that can inhibit the toxicity of misfolded proteins and facilitate their targeted degradation via both autophagy and the proteasome.
