Kinase Inhibitor-Induced Cell-Type Specific Vacuole Formation in the Absence of Canonical ATG5-Dependent Autophagy...

Area of Science:

• Cell Biology
• Molecular Pharmacology
• Cancer Research

Background:

• Pyridinyl-imidazole inhibitors, such as SB202190, targeting p38 MAPKα/β (MAPK14/MAPK11), have demonstrated cell-type specific defective autophagy, leading to vacuole formation, cell death, and tumor suppression.
• Previous research indicated that SB202190's vacuolation effect is an off-target phenomenon.

Purpose of the Study:

• To investigate the mechanism of SB202190-induced vacuole formation, specifically its independence from ATG5-mediated autophagy.
• To identify key regulators and modulators of this vacuolation process and its cell-type specificity.

Main Methods:

• Utilized autophagy-deficient and ATG5-knockout cell lines to assess vacuolation independent of canonical autophagy.
• Investigated the role of late-endosomal GTPase RAB7 in vacuole formation.
• Conducted a screen for vacuolation modulators, including sorafenib and ATR inhibitors (VE-821).
• Analyzed transcriptomics data from sensitive and resistant cell lines to identify a predictive gene expression signature.

Main Results:

• SB202190-induced vacuole formation occurs independently of ATG5-mediated autophagosome initiation, even in autophagy-deficient cells.
• RAB7 colocalizes with these vacuoles, and its GTP-binding activity is crucial for vacuolation.
• Sorafenib inhibits vacuolation and enhances SB202190 cytotoxicity; VE-821 phenocopies the vacuolation response.
• A gene expression signature distinguishing vacuole-forming from non-vacuole-forming cells was identified.

Conclusions:

• SB202190-induced vacuolation is an ATG5-independent, RAB7-dependent process.
• Modulators like sorafenib and VE-821 offer insights into regulating this phenotype.
• The identified gene signature may predict cellular sensitivity to these compounds, potentially revealing novel anti-cancer strategies.