Selective autophagy inhibition through disruption of the PIK3C3-containing complex I.

The PIK3C3/VPS34-containing phosphatidylinositol 3-kinase (PtdIns3K) initiation complex (complex I) is necessary for macroautophagy/autophagy initiation and is comprised of PIK3R4/VPS15-PIK3C3/VPS34-BECN1-ATG14, while the endosomal trafficking complex (complex II) is necessary for vesicle trafficking and is comprised of PIK3R4/VPS15-PIK3C3/VPS34-BECN1-UVRAG. This composition difference was exploited to identify novel and specific autophagy inhibitors that disrupted the BECN1-ATG14 protein-protein interaction, without affecting vesicle trafficking. A cellular NanoBRET assay was implemented to identify these inhibitors, and one compound was able to successfully disrupt the BECN1-ATG14 interaction and inhibit autophagy, with limited impact on vesicle trafficking. These results reveal the first protein-protein interaction inhibitor targeting the autophagy initiation machinery and demonstrate the viability of targeting protein-protein interactions for the discovery of autophagy-specific modulators.