Phosphatidylinositol-5-phosphate 4-kinases regulate cellular lipid metabolism by facilitating autophagy

Lundquist, Mark R., Goncalves, Marcus D., Loughran, Ryan M., Possik, Elite, Vijayaraghavan, Tarika, Yang, Annan, Pauli, Chantal, Ravi, Archna, Verma, Akanksha, Yang, Zhiwei, Johnson, Jared L., Wong, Jenny C.Y., Ma, Yilun, Hwang, Katie Seo Kyoung, Weinkove, David, Divecha, Nullin, Asara, John M., Elemento, Olivier, Rubin, Mark A., Kimmelman, Alec C., Pause, Arnim, Cantley, Lewis C. and Emerling, Brooke M. (2018) Phosphatidylinositol-5-phosphate 4-kinases regulate cellular lipid metabolism by facilitating autophagy. Molecular Cell, 70 (3), 531–544.e9. (doi:10.1016/j.molcel.2018.03.037).

Abstract

While the majority of phosphatidylinositol-4, 5-bisphosphate (PI-4, 5-P₂) in mammalian cells is generated by the conversion of phosphatidylinositol-4-phosphate (PI-4-P) to PI-4, 5-P₂, a small fraction can be made by phosphorylating phosphatidylinositol-5-phosphate (PI-5-P). The physiological relevance of this second pathway is not clear. Here, we show that deletion of the genes encoding the two most active enzymes in this pathway, Pip4k2a and Pip4k2b, in the liver of mice causes a large enrichment in lipid droplets and in autophagic vesicles during fasting. These changes are due to a defect in the clearance of autophagosomes that halts autophagy and reduces the supply of nutrients salvaged through this pathway. Similar defects in autophagy are seen in nutrient-starved Pip4k2a^−/−Pip4k2b^−/− mouse embryonic fibroblasts and in C. elegans lacking the PI5P4K ortholog. These results suggest that this alternative pathway for PI-4, 5-P₂ synthesis evolved, in part, to enhance the ability of multicellular organisms to survive starvation. Lundquist et al. reveal a critical evolutionarily conserved function of the PI5P4K family of enzymes in autophagy. PI5P4Ks generate PI-4, 5-P₂ from the minor lipid PI-5-P and are required for autophagosome-lysosome fusion during metabolic stress. Importantly, this study sheds light on the anti-cancer mechanism of PI5P4K inhibition.

This record has no associated files available for download.

Contributors

Download statistics