title: Arf6 controls retromer traffic and intracellular cholesterol distribution via a phosphoinositide-based mechanism.
abstract: Small GTPases play a critical role in membrane traffic. Among them, Arf6 mediates transport to and from the plasma membrane, as well as phosphoinositide signalling and cholesterol homeostasis. Here we delineate the molecular basis for the link between Arf6 and cholesterol homeostasis using an inducible knockout (KO) model of mouse embryonic fibroblasts (MEFs). We find that accumulation of free cholesterol in the late endosomes/lysosomes of Arf6 KO MEFs results from mistrafficking of Niemann-Pick type C protein NPC2, a cargo of the cation-independent mannose-6-phosphate receptor (CI-M6PR). This is caused by a selective increase in an endosomal pool of phosphatidylinositol-4-phosphate (PI4P) and a perturbation of retromer, which controls the retrograde transport of CI-M6PR via sorting nexins, including the PI4P effector SNX6. Finally, reducing PI4P levels in KO MEFs through independent mechanisms rescues aberrant retromer tubulation and cholesterol mistrafficking. Our study highlights a phosphoinositide-based mechanism for control of cholesterol distribution via retromer.
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Marquer
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Huasong
authors.initials: H
authors.lastname: Tian
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Yi
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Jayson
authors.initials: J
authors.lastname: Bastien
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Dall'Armi
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: YoungJoo
authors.initials: Y
authors.lastname: Yang-Klingler
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Bowen
authors.initials: B
authors.lastname: Zhou
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Robin Barry
authors.initials: RB
authors.lastname: Chan
authors.affiliation: Department of Pathology and Cell Biology, Columbia University Medical Center, New York City, New York 10032, USA.
authors.forename: Gilbert
authors.initials: G
authors.lastname: Di Paolo
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000502:physiology*; D000818:Animals; D002784:Cholesterol / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D018345:Mice, Knockout; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D000089982:ADP-Ribosylation Factor 6; C497045:Npc2 protein, mouse; D018129:Phosphatidylinositol Phosphates; D017527:Receptor, IGF Type 2; D033921:Vesicular Transport Proteins; C037178:phosphatidylinositol 4-phosphate; D002784:Cholesterol; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse