ABSTRACT
STF-62247 was previously identified as a promising compound able to selectively target the loss of the tumor suppressor gene von Hippel-Lindau (VHL) in renal cell carcinomas. This present work investigates the effect of STF-62247 on the autophagic flux. Our investigations show that STF-62247 blocks late stages of autophagy through lysosomal disruption. Indeed, STF-62247 localizes at lysosomes and causes unregulated swelling of these acidic compartments in VHL-mutated cells, linking a potential role for VHL in lysosomal integrity. Knock-outs of BECN1 and ATG5 were able to rescue the viability of VHL-mutated cells in response to STF-62247 but did not rescue the lysosomal swelling. In fact, neutralizing the lysosomal pH by inhibiting the vacuolar H+-ATPase completely rescued this phenotype. Moreover, we show that STF-62247 disrupts endocytic routes and causes cathepsin D trafficking defects. This mechanistic study is the first to characterize STF-62447 as a novel lysosomotropic compound. Importantly, our study re-classifies STF-62247 as a blocker of later stages of autophagy and highlights its potential usage as a powerful new tool for endocytic and autophagy-related research.
- List of abbreviations
- AMPK
- AMP-activated protein kinase
- AO
- Acridine Orange
- AP
- Autophagosome
- ATG
- Autophagy-related gene
- BAF
- Bafilomyin A1
- ccRCC
- Clear cell renal cell carcinoma
- CTSD
- Cathepsin D
- KO
- Knock-out
- LTR
- Lysotracker Red
- LY
- Lucifer Yellow
- mTOR
- Mammalian target of Rapamycin
- STF
- STF-62247
- V-ATPase
- Vacuolar H+-ATPase pump
- VHL
- von Hippel-Lindau