GFP Stable Cell Line-MCF-7

Autophagy uses lysosomal regeneration to break down intracellular components and recycle nutrients. The study found an endosome-dependent phospholipid signaling route that connects PI3Kα signaling to lysosomal renewal during basal autophagy. INPP4B produces PI3Kα-derived PI(3)P on late endosomes, which is necessary for basal autophagy degradation but not for starvation-induced autophagy degradation. As late endosomes mature into endolysosomes, PI(3)P signaling is maintained and used as a substrate by the 5-kinase PIKfyve to produce PI(3,5)P2. PI(3,5)P2 recruits the SNX-BAR protein SNX2 to endolysosomes, where it stimulates lysosome regeneration. Inhibiting INPP4B/PIKfyve-dependent lysosomal regeneration reduces the autophagic clearance of protein aggregates in response to proteotoxic stress, which increases cytotoxicity. Under nutrient-sufficient conditions, PI3Kα, INPP4B, and PIKfyve play a sequential role in basal autophagic degradation and proteotoxic stress protection against endolysosomes through PI(3,5)P2-dependent lysosomal regeneration. These data suggest that endosomal maturation pathways connect PI3Kα signaling to lysosomal regeneration during basal autophagy.

Figure 1. The GFP-MCF-7 cell line was used to investigate the role of INPP4B in PI3Kα-dependent degradation of basal autophagy. Changes in the levels of autophagy markers, such as LC3B and p62, were analyzed by expressing GFP-INPP4B or GFP vectors to explore the effects of INPP4B on the autophagic process under different conditions and to assess the role of PI3Kα and Vps34 inhibitors. (Rodgers SJ, et al., 2022)