title: Rab8-dependent recycling promotes endosomal cholesterol removal in normal and sphingolipidosis cells.
abstract: The mechanisms by which low-density lipoprotein (LDL)-cholesterol exits the endocytic circuits are not well understood. The process is defective in Niemann-Pick type C (NPC) disease in which cholesterol and sphingolipids accumulate in late endosomal compartments. This is accompanied by defective cholesterol esterification in the endoplasmic reticulum and impaired ATP-binding cassette transporter A1 (ABCA1)-dependent cholesterol efflux. We show here that overexpression of the recycling/exocytic Rab GTPase Rab8 rescued the late endosomal cholesterol deposition and sphingolipid mistrafficking in NPC fibroblasts. Rab8 redistributed cholesterol from late endosomes to the cell periphery and stimulated cholesterol efflux to the ABCA1-ligand apolipoprotein A-I (apoA-I) without increasing cholesterol esterification. Depletion of Rab8 from wild-type fibroblasts resulted in cholesterol deposition within late endosomal compartments. This cholesterol accumulation was accompanied by impaired clearance of LDL-cholesterol from endocytic circuits to apoA-I and could not be bypassed by liver X receptor activation. Our findings establish Rab8 as a key component of the regulatory machinery that leads to ABCA1-dependent removal of cholesterol from endocytic circuits.
authors.affiliation: Institute of Biomedicine/Anatomy, University of Helsinki, FI-00014 Helsinki, Finland.
authors.forename: Matts D
authors.initials: MD
authors.lastname: Linder
authors.forename: Riikka-Liisa
authors.initials: RL
authors.lastname: Uronen
authors.forename: Maarit
authors.initials: M
authors.lastname: Hölttä-Vuori
authors.forename: Peter
authors.initials: P
authors.lastname: van der Sluijs
authors.forename: Johan
authors.initials: J
authors.lastname: Peränen
authors.forename: Elina
authors.initials: E
authors.lastname: Ikonen
mesh_terms: D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism; D001692:Biological Transport; D002460:Cell Line; D002784:Cholesterol / Q000302:isolation & purification* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000819:agonists; D011992:Endosomes / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology* / Q000473:pathology*; D015870:Gene Expression; D006801:Humans; D000071518:Liver X Receptors; D008565:Membrane Proteins / Q000302:isolation & purification; D051379:Mice; D008807:Mice, Inbred BALB C; D009542:Niemann-Pick Diseases / Q000473:pathology*; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism; D015854:Up-Regulation; D020691:rab GTP-Binding Proteins / Q000172:deficiency / Q000302:isolation & purification / Q000378:metabolism*; D020695:rab4 GTP-Binding Proteins / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
chemical_list: D016632:Apolipoprotein A-I; D004268:DNA-Binding Proteins; D000071518:Liver X Receptors; D008565:Membrane Proteins; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D013107:Sphingolipids; D000090802:rab7 GTP-Binding Proteins; D002784:Cholesterol; C082377:RAB8A protein, human; D020691:rab GTP-Binding Proteins; D020695:rab4 GTP-Binding Proteins