title: The role of the PI(3,5)P2kinase TbFab1 in endo/lysosomal trafficking in Trypanosoma brucei.
abstract: Protein trafficking through endo/lysosomal compartments is critically important to the biology of the protozoan parasite Trypanosoma brucei, but the routes material may take to the lysosome, as well as the molecular factors regulating those routes, remain incompletely understood. Phosphoinositides are signaling phospholipids that regulate many trafficking events by recruiting specific effector proteins to discrete membrane subdomains. In this study, we investigate the role of one phosphoinositide, PI(3,5)P2in T. brucei. We find a low steady state level of PI(3,5)P2in bloodstream form parasites comparable to that of other organisms. RNAi knockdown of the putative PI(3)P-5 kinase TbFab1 decreases the PI(3,5)P2pool leading to rapid cell death. TbFab1 and PI(3,5)P2both localize strongly to late endo/lysosomes. While most trafficking functions were intact in TbFab1 deficient cells, including both endocytic and biosynthetic trafficking to the lysosome, lysosomal turnover of an endogenous ubiquitinylated membrane protein, ISG65, was completely blocked suggesting that TbFab1 plays a role in the ESCRT-mediated late endosomal/multivesicular body degradative pathways. Knockdown of a second component of PI(3,5)P2metabolism, the PI(3,5)P2phosphatase TbFig4, also resulted in delayed turnover of ISG65. Together, these results demonstrate an essential role for PI(3,5)P2in the turnover of ubiquitinylated membrane proteins and in trypanosome endomembrane biology.
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA. Electronic address: julia.gilden@gmail.com.
authors.forename: Julia K
authors.initials: JK
authors.lastname: Gilden
authors.affiliation: Department of Microbiology Immunology, School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, USA. Electronic address: khanumae@buffalo.edu.
authors.forename: Khan
authors.initials: K
authors.lastname: Umaer
authors.affiliation: Department of Microbiology Immunology, School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, USA. Electronic address: emiliakr@buffalo.edu.
authors.forename: Emilia K
authors.initials: EK
authors.lastname: Kruzel
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA. Electronic address: ohecht@wisc.edu.
authors.forename: Oliver
authors.initials: O
authors.lastname: Hecht
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA. Electronic address: renanocorrea@gmail.com.
authors.forename: Renan O
authors.initials: RO
authors.lastname: Correa
authors.affiliation: Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA. Electronic address: john.mansfield@wisc.edu.
authors.forename: John M
authors.initials: JM
authors.lastname: Mansfield
authors.affiliation: Department of Microbiology Immunology, School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, USA. Electronic address: jdbangs@buffalo.edu.
authors.forename: James D
authors.initials: JD
authors.lastname: Bangs
mesh_terms: D011992:Endosomes / Q000201:enzymology* / Q000378:metabolism; D008247:Lysosomes / Q000201:enzymology* / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D021381:Protein Transport; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000378:metabolism
chemical_list: D018129:Phosphatidylinositol Phosphates; C106336:phosphatidylinositol 3,5-diphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor)
keywords: Endosome; Invariant surface protein 6; Lysosome; PI(3,5)P(2); Trypanosome