title: Ligand-dependent localization and function of ORP-VAP complexes at membrane contact sites.
abstract: Oxysterol-binding protein/OSBP-related proteins (ORPs) constitute a conserved family of sterol/phospholipid-binding proteins with lipid transporter or sensor functions. We investigated the spatial occurrence and regulation of the interactions of human OSBP/ORPs or the S. cerevisiae orthologs, the Osh (OSBP homolog) proteins, with their endoplasmic reticulum (ER) anchors, the VAMP-associated proteins (VAPs), by employing bimolecular fluorescence complementation and pull-down set-ups. The ORP-VAP interactions localize frequently at distinct subcellular sites, shown in several cases to represent membrane contact sites (MCSs). Using established ORP ligand-binding domain mutants and pull-down assays with recombinant proteins, we show that ORP liganding regulates the ORP-VAP association, alters the subcellular targeting of ORP-VAP complexes, or modifies organelle morphology. There is distinct protein specificity in the effects of the mutants on subcellular targeting of ORP-VAP complexes. We provide evidence that complexes of human ORP2 and VAPs at ER-lipid droplet interfaces regulate the hydrolysis of triglycerides and lipid droplet turnover. The data suggest evolutionarily conserved, complex ligand-dependent functions of ORP-VAP complexes at MCSs, with implications for cellular lipid homeostasis and signaling.
authors.affiliation: Minerva Foundation Institute for Medical Research, Biomedicum 2U, Tukholmankatu 8, 00290, Helsinki, Finland.
authors.forename: Marion
authors.initials: M
authors.lastname: Weber-Boyvat
authors.forename: Henriikka
authors.initials: H
authors.lastname: Kentala
authors.forename: Johan
authors.initials: J
authors.lastname: Peränen
authors.forename: Vesa M
authors.initials: VM
authors.lastname: Olkkonen
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005816:Genetic Complementation Test; D006801:Humans; D006868:Hydrolysis; D066292:Lipid Droplets / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D046912:Multiprotein Complexes / Q000378:metabolism*; D034622:RNA Interference; D011987:Receptors, Steroid / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*; D015003:Yeasts; D000098825:Oxysterol Binding Proteins
chemical_list: D006631:Amine Oxidase (Copper-Containing); D015815:Cell Adhesion Molecules; D046912:Multiprotein Complexes; D011987:Receptors, Steroid; D011994:Recombinant Proteins; D014280:Triglycerides; C461064:OSBPL2 protein, human; D000098825:Oxysterol Binding Proteins; C076668:AOC3 protein, human