TRIMming down autophagy in breast cancer

Area of Science:

• Cellular Biology
• Molecular Mechanisms
• Metabolic Pathways

Background:

• Macroautophagy (autophagy) is a vital lysosome-dependent metabolic recycling pathway conserved across species.
• ULK1 is essential for initiating autophagy but is rapidly degraded during nutrient starvation, necessitating tight control mechanisms.
• The precise regulation of the ULK1 complex remains incompletely understood.

Purpose of the Study:

• To elucidate the roles of novel ULK1 complex binding proteins, TRIM27 and STK38L, in autophagy regulation.
• To investigate the mechanisms by which TRIM27 and STK38L control ULK1 activity and levels.
• To establish the physiological relevance of the identified regulatory axis in disease contexts.

Main Methods:

• Investigated the interaction of TRIM27 and STK38L with the ULK1 complex.
• Analyzed ubiquitination and proteasomal degradation of ULK1.
• Examined the role of STK38L phosphorylation in ULK1 regulation.
• Utilized TRIM27 knockout mouse models.
• Assessed autophagy levels in breast cancer models.

Main Results:

• TRIM27 maintains basal autophagy via ULK1 ubiquitination and proteasomal degradation.
• TRIM27 and STK38L collaboratively restrain excessive autophagy during starvation.
• TRIM27 activates STK38L, which phosphorylates ULK1, promoting its hyper-ubiquitination by TRIM27.
• TRIM27 knockout mice exhibit increased basal autophagy.
• The STK38L-TRIM27-ULK1 axis has physiological relevance in breast cancer.

Conclusions:

• TRIM27 and STK38L function as a rheostat, controlling ULK1 levels and thereby modulating autophagy.
• The STK38L-TRIM27-ULK1 axis represents a potential therapeutic target for modulating autophagy in various diseases.
• Understanding this regulatory axis provides new insights into controlling cellular metabolism and survival.