Phosphatidylinositol-5-Phosphate 4-Kinases Regulate Cellular Lipid Metabolism By Facilitating Autophagy

• DOI: 10.1016/j.molcel.2018.03.037
• Publication Date: 2018-05-03T20:34:18Z
• Authors: Mark R. Lundquist; Marcus D. Goncalves; Ryan M. Loughran; Elite Possik; Tarika Vijayaragh...; Annan Yang; Chantal Pauli; Archna Ravi; Akanksha Verma; Zhiwei Yang; Jared L. Johnson; Jenny C.Y. Wong; Yilun Ma; Katie Seo-Kyoung ...; David Weinkove; Nullin Divecha; John M. Asara; Olivier Elemento; Mark A. Rubin; Alec C. Kimmelman; Arnim Pause; Lewis C. Cantley; Brooke M. Emerling
• Keywords: 0301 basic medicine; 570; Autophagosomes; 610; Fasting; Fibroblasts; Lipid Metabolism; Cell Line; Mice; Phosphotransferases (Alcohol Group Acceptor); 03 medical and health sciences; HEK293 Cells; Liver; Phosphatidylinositol Phosphates; Autophagy; Animals; Humans; Caenorhabditis elegans; Signal Transduction

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.