title: Oxysterol-binding protein ORP3 rescues the Amyotrophic Lateral Sclerosis-linked mutant VAPB phenotype.
abstract: A mutation in VAPB causes a familial form of Amyotrophic Lateral Sclerosis. The mutant protein (VAPB-P56S) is aggregate prone and blocks retrograde traffic from the endoplasmic reticulum (ER) Golgi intermediate compartment (ERGIC) including trafficking to the nuclear envelope (NE). Here we report a morphological screen where overexpression of oxysterol binding protein-related protein-3 (ORP3) rescued the mutant VAPB phenotype. It resolved the mutant VAPB-induced membrane expansions, restored solubility of the mutant protein in non-ionic detergent, and restored trafficking of Emerin to the NE. Knockdown of ORP3 or VAPB increased the intracellular level of phosphatidylinositol 4-phosphate (PtdIns4P). Decreasing PtdIns4P levels by inhibiting its synthesis reduced the severity of the mutant VAPB-induced membrane expansions and restored Emerin trafficking to the NE. Thus, VAPB and its interacting partners cooperatively regulate protein trafficking through the ERGIC by modulating PtdIns4P levels.
authors.affiliation: Ottawa Hospital Research Institute Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5.
authors.forename: Angie
authors.initials: A
authors.lastname: Darbyson
authors.affiliation: Ottawa Hospital Research Institute Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5. Electronic address: jngsee@uottawa.ca.
authors.forename: Johnny K
authors.initials: JK
authors.lastname: Ngsee
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D050556:Fatty Acid-Binding Proteins; D006367:HeLa Cells; D006801:Humans; D010641:Phenotype; D014407:Tumor Cells, Cultured; D033921:Vesicular Transport Proteins / Q000235:genetics* / Q000378:metabolism; D000098825:Oxysterol Binding Proteins
chemical_list: D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D033921:Vesicular Transport Proteins; C471934:OSBPL3 protein, human; D000098825:Oxysterol Binding Proteins; C496748:VAPB protein, human
keywords: Amyotrophic Lateral Sclerosis; Endoplasmic reticulum Golgi intermediate compartment (ERGIC); Nuclear envelope; Oxysterol binding protein-related protein; Phosphatidylinositol 4-phosphate