title: In vivo, Pikfyve generates PI(3,5)P2, which serves as both a signaling lipid and the major precursor for PI5P.
abstract: Mutations that cause defects in levels of the signaling lipid phosphatidylinositol 3,5-bisphosphate [PI(3,5)P(2)] lead to profound neurodegeneration in mice. Moreover, mutations in human FIG4 predicted to lower PI(3,5)P(2) levels underlie Charcot-Marie-Tooth type 4J neuropathy and are present in selected cases of amyotrophic lateral sclerosis. In yeast and mammals, PI(3,5)P(2) is generated by a protein complex that includes the lipid kinase Fab1/Pikfyve, the scaffolding protein Vac14, and the lipid phosphatase Fig4. Fibroblasts cultured from Vac14(-/-) and Fig4(-/-) mouse mutants have a 50% reduction in the levels of PI(3,5)P(2), suggesting that there may be PIKfyve-independent pathways that generate this lipid. Here, we characterize a Pikfyve gene-trap mouse (Pikfyve(β-geo/β-geo)), a hypomorph with ~10% of the normal level of Pikfyve protein. shRNA silencing of the residual Pikfyve transcript in fibroblasts demonstrated that Pikfyve is required to generate all of the PI(3,5)P(2) pool. Surprisingly, Pikfyve also is responsible for nearly all of the phosphatidylinositol-5-phosphate (PI5P) pool. We show that PI5P is generated directly from PI(3,5)P(2), likely via 3'-phosphatase activity. Analysis of tissues from the Pikfyve(β-geo/β-geo) mouse mutants reveals that Pikfyve is critical in neural tissues, heart, lung, kidney, thymus, and spleen. Thus, PI(3,5)P(2) and PI5P have major roles in multiple organs. Understanding the regulation of these lipids may provide insights into therapies for multiple diseases.
authors.affiliation: Departments of Cell and Developmental Biology, Division of Pediatric Cardiology, Department of Pediatrics and Communicable Diseases, and Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Zolov
authors.forename: Dave
authors.initials: D
authors.lastname: Bridges
authors.forename: Yanling
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wei-Wei
authors.initials: WW
authors.lastname: Lee
authors.forename: Ellen
authors.initials: E
authors.lastname: Riehle
authors.forename: Rakesh
authors.initials: R
authors.lastname: Verma
authors.forename: Guy M
authors.initials: GM
authors.lastname: Lenk
authors.forename: Kimber
authors.initials: K
authors.lastname: Converso-Baran
authors.forename: Thomas
authors.initials: T
authors.lastname: Weide
authors.forename: Roger L
authors.initials: RL
authors.lastname: Albin
authors.forename: Alan R
authors.initials: AR
authors.lastname: Saltiel
authors.forename: Miriam H
authors.initials: MH
authors.lastname: Meisler
authors.forename: Mark W
authors.initials: MW
authors.lastname: Russell
authors.forename: Lois S
authors.initials: LS
authors.lastname: Weisman
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology; D008565:Membrane Proteins; D051379:Mice; D008817:Mice, Mutant Strains; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D018129:Phosphatidylinositol Phosphates / Q000096:biosynthesis* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D012333:RNA, Messenger; C525133:Vac14 protein, mouse; C106336:phosphatidylinositol 3,5-diphosphate; C113567:phosphatidylinositol 5-phosphate; C116930:Pikfyve protein, mouse