title: The Joubert Syndrome Protein Inpp5e Controls Ciliogenesis by Regulating Phosphoinositides at the Apical Membrane.
abstract: Phosphoinositides, a family of phosphorylated derivatives of phosphatidylinositol (PtdIns), are tightly regulated both temporally and spatially by PtdIns phosphatases and kinases. Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) cause Joubert syndrome, a human disorder associated with numerous ciliopathic defects, including renal cyst formation, linking phosphoinositides to ciliopathies. However, the molecular mechanism by which INPP5E-mediated PtdIns signaling regulates ciliogenesis and cystogenesis is unclear. Here, we utilized an in vivo vertebrate model of renal cystogenesis to show that Inpp5e enzymatic activity at the apical membrane directs apical docking of basal bodies in renal epithelia. Knockdown or knockout of inpp5e led to ciliogenesis defects and cystic kidneys in zebrafish. Furthermore, knockdown of inpp5e in embryos led to defects in cell polarity, cortical organization of F-actin, and apical segregation of PtdIns(4,5)P2and PtdIns(3,4,5)P3Knockdown of the ezrin gene, which encodes an ezrin/radixin/moesin (ERM) protein that crosslinks PtdIns(4,5)P2and F-actin, phenocopied inpp5e knockdowns. Notably, overexpression of the ezrin gene rescued inpp5e morphants. Finally, treatment with the PI 3-kinase inhibitor LY294002, which decreases PtdIns(3,4,5)P3levels, rescued the cellular, phenotypic, and renal functional defects in inpp5e-knockdown embryos. Together, our data indicate that Inpp5e functions as a key regulator of cell polarity in the renal epithelia, by inhibiting PtdIns(3,4,5)P3and subsequently stabilizing PtdIns(4,5)P2and recruiting Ezrin, F-actin, and basal bodies to the apical membrane, and suggest a possible novel approach for treating human ciliopathies.
authors.affiliation: Department of Molecular and Cell Biology, Tongji University School of Life Sciences and Technology, Shanghai, China.
authors.forename: Wenyan
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Molecular and Cell Biology, Tongji University School of Life Sciences and Technology, Shanghai, China.
authors.forename: Miaomiao
authors.initials: M
authors.lastname: Jin
authors.affiliation: Department of Molecular and Cell Biology, Tongji University School of Life Sciences and Technology, Shanghai, China.
authors.forename: Ruikun
authors.initials: R
authors.lastname: Hu
authors.affiliation: Department of Molecular and Cell Biology, Tongji University School of Life Sciences and Technology, Shanghai, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Molecular and Cell Biology, Tongji University School of Life Sciences and Technology, Shanghai, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut; and.
authors.forename: Shiaulou
authors.initials: S
authors.lastname: Yuan
authors.affiliation: Department of Molecular and Cell Biology, Tongji University School of Life Sciences and Technology, Shanghai, China; yingcao@tongji.edu.cn.|Tongji University and Shanghai Changzheng Hospital Joint Research Center for Translational Medicine, Changzheng Hospital, Shanghai, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Cao
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics; D000818:Animals; D002462:Cell Membrane / Q000502:physiology*; D002531:Cerebellum / Q000002:abnormalities; D002923:Cilia / Q000502:physiology; D005124:Eye Abnormalities / Q000235:genetics; D006801:Humans; D052177:Kidney Diseases, Cystic / Q000235:genetics; D010716:Phosphatidylinositols / Q000502:physiology*; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000502:physiology*; D012160:Retina / Q000002:abnormalities; D015027:Zebrafish; D000099182:Phosphoinositide 5-Phosphatases
chemical_list: D010716:Phosphatidylinositols; D010744:Phosphoric Monoester Hydrolases; D000099182:Phosphoinositide 5-Phosphatases
keywords: Inpp5e; cilia; phosphoinositides; polycystic kidney disease