title: Ncr1p, the yeast ortholog of mammalian Niemann Pick C1 protein, is dispensable for endocytic transport.
abstract: The Niemann Pick C1 protein localizes to late endosomes and plays a key role in the intracellular transport of cholesterol in mammalian cells. Cholesterol and other lipids accumulate in a lysosomal or late endosomal compartment in cells lacking normal NPC1 function. Other than accumulation of lipids, defects in lysosomal retroendocytosis, sorting of a multifunctional receptor and endosomal movement have also been detected in NPC1 mutant cells. Ncr1p is an ortholog of NPC1 in the budding yeast Saccharomyces cerevisiae. In this study, we show that Ncr1p is a vacuolar membrane protein that transits through the biosynthetic vacuolar protein sorting pathway, and that it can be solubilized by Triton X-100 at 4 degrees C. Using well-established assays, we demonstrate that the absence of Ncr1p had no effect on fluid phase and receptor- mediated endocytosis, biosynthetic delivery to the vacuole, retrograde transport from endosome to Golgi and ubiquitin- and nonubiquitin-dependent multivesicular body sorting. We conclude that Ncr1p does not have an essential role in known endocytic transport pathways in yeast.
authors.affiliation: Department of Biochemistry, National University of Singapore, Singapore 119260.
authors.forename: Shaochong
authors.initials: S
authors.lastname: Zhang
authors.forename: Jihui
authors.initials: J
authors.lastname: Ren
authors.forename: Hongzhe
authors.initials: H
authors.lastname: Li
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhang
authors.forename: Jeffery S
authors.initials: JS
authors.lastname: Armstrong
authors.forename: Alan L
authors.initials: AL
authors.lastname: Munn
authors.forename: Hongyuan
authors.initials: H
authors.lastname: Yang
mesh_terms: D002268:Carboxypeptidases / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D006056:Golgi Apparatus / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D014617:Vacuoles / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D008562:Membrane Glycoproteins; C490168:NCR1 protein, S cerevisiae; C087335:PEP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D002268:Carboxypeptidases