Novel and conventional inhibitors of canonical autophagy differently affect LC3‐associated phagocytosis

Abstract

In autophagy, LC3-positive autophagophores fuse and encapsulate the autophagic cargo in a double-membrane structure. In contrast, lipidated LC3 (LC3-II) is directly formed at the phagosomal membrane in LC3-associated phagocytosis (LAP). In this study, we dissected the effects of autophagy inhibitors on LAP. SAR405, an inhibitor of VPS34, reduced levels of LC3-II and inhibited LAP. In contrast, the inhibitors of endosomal acidification bafilomycin A1 and chloroquine increased levels of LC3-II, due to reduced degradation in acidic lysosomes. However, while bafilomycin A1 inhibited LAP, chloroquine did not. Finally, EACC, which inhibits the fusion of autophagosomes with lysosomes, promoted LC3 degradation possibly by the proteasome. Targeting LAP with small molecule inhibitors is important given its emerging role in infectious and autoimmune diseases.

Iron regulates contrasting toxicity of uropathogenic Eschericia coli in macrophages and epithelial cells

“…Collectively with LC3 staining and that XL1 blue and MG1655 reside in single membrane vacuoles while ST999 resides in double membrane vacuoles (Figure 4A), suggests that XL1 blue and MG1566 were internalized via LC3 associated phagocytosis (LAP) while ST999 induces xenophagy [61]. In LAP, LC3 is directly recruited to the limiting membrane of the vacuoles in LAP, resulting in efficient phagosome-lysosome fusion and degradation of the cargo as has been reported previously for other bacterial pathogens [65,66].…”

Lipid and protein content profiling of isolated native autophagic vesicles

“…Concurrently, only a minor fraction was decorated exclusively by one ATG8 protein, which was possibly due to insufficient antibody binding and/or the presence of nonautophagic vesicles, such as LC3‐associated phagosomes (Sanjuan et al , 2007 ). However, we treated cells with bafilomycin A 1 prior to isolation, which resulted in the substantial accumulation of autophagic vesicles within cells and, moreover, reduced the recruitment of LC3 to nonautophagic lipidation processes (Florey et al , 2015 ; Stempels et al , 2022 ). This substantiated the clear predominance of autophagic vesicles within isolate fractions of WT HeLa cells.…”

Macrophage-evading and tumor-specific apoptosis inducing nanoparticles for targeted cancer therapy

“…Tumor cells take up nanoparticles by pinocytosis, including macropinocytosis, clathrin-mediated, caveolin-mediated and clathrin/caveolae-independent endocytosis 52 , whereas macrophages uptake nanoparticles not only through pinocytosis, but also via phagocytosis 52 , 53 . As an autophagy inhibitor, CQ prevents lysosome acidification and decreases LC3-associated phagocytosis 54 . Thus, the inhibition of phagocytosis by CQ could result in the superior uptake reduction of nanoparticles in macrophages.…”