SUMOylation targets O-GlcNAcase to chaperone-mediated autophagy

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Biology

Background:

• O-GlcNAcase (OGA) is the primary enzyme removing intracellular O-GlcNAc modifications.
• OGA's regulatory mechanisms are not fully understood, despite its roles in cancer and stem cells.

Purpose of the Study:

• To investigate the small ubiquitin-like modifier (SUMO) modification of OGA.
• To elucidate the role of SUMOylation in OGA's cellular fate and the mechanism of chaperone-mediated autophagy (CMA) substrate selection.

Main Methods:

• SUMOylation analysis of OGA.
• Co-immunoprecipitation to study protein interactions (OGA-HSC70).
• Label-free quantitative mass spectrometry to identify interactomes and CMA clients.
• Site-directed mutagenesis to assess the SUMO-interacting motif (SIM) function in HSC70.

Main Results:

• OGA is SUMOylated at K358, targeting it for degradation via CMA.
• SUMOylation enhances the association between OGA and the CMA chaperone HSC70.
• A SUMO-interacting motif (SIM) on HSC70 is crucial for binding SUMOylated proteins and substrate selection in CMA.
• A proteome-wide pool of SUMO-mediated CMA clients was identified, including YEATS domain-containing two.

Conclusions:

• The SUMO-SIM interaction is a fundamental mechanism controlling substrate selectivity in chaperone-mediated autophagy.
• This study identifies a novel regulatory pathway for OGA and provides a framework for understanding SUMO-mediated CMA client selection.
• The findings have implications for understanding the pathophysiological roles of CMA.