title: The R-Ras interaction partner ORP3 regulates cell adhesion.
abstract: Oxysterol-binding protein (OSBP)-related protein 3 (ORP3) is highly expressed in epithelial, neuronal and hematopoietic cells, as well as in certain forms of cancer. We assessed the function of ORP3 in HEK293 cells and in human macrophages. We show that ORP3 interacts with R-Ras, a small GTPase regulating cell adhesion, spreading and migration. Gene silencing of ORP3 in HEK293 cells results in altered organization of the actin cytoskeleton, impaired cell-cell adhesion, enhanced cell spreading and an increase of beta1 integrin activity--effects similar to those of constitutively active R-Ras(38V). Overexpression of ORP3 leads to formation of polarized cell-surface protrusions, impaired cell spreading and decreased beta1 integrin activity. In primary macrophages, overexpression of ORP3 leads to the disappearance of podosomal structures and decreased phagocytotic uptake of latex beads, consistent with a role in actin regulation. ORP3 is phosphorylated when cells lose adhesive contacts, suggesting that it is subject to regulation by outside-in signals mediated by adhesion receptors. The present findings demonstrate a new function of ORP3 as part of the machinery that controls the actin cytoskeleton, cell polarity and cell adhesion.
authors.affiliation: Department of Molecular Medicine, National Public Health Institute, Biomedicum, FI-00251 Helsinki, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Lehto
authors.forename: Mikko I
authors.initials: MI
authors.lastname: Mäyränpää
authors.forename: Teijo
authors.initials: T
authors.lastname: Pellinen
authors.forename: Pekka
authors.initials: P
authors.lastname: Ihalmo
authors.forename: Sanna
authors.initials: S
authors.lastname: Lehtonen
authors.forename: Petri T
authors.initials: PT
authors.lastname: Kovanen
authors.forename: Per-Henrik
authors.initials: PH
authors.lastname: Groop
authors.forename: Johanna
authors.initials: J
authors.lastname: Ivaska
authors.forename: Vesa M
authors.initials: VM
authors.lastname: Olkkonen
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology; D022081:Cell Surface Extensions / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D050556:Fatty Acid-Binding Proteins; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D010587:Phagocytosis / Q000502:physiology; D010766:Phosphorylation; D018631:ras Proteins / Q000378:metabolism*; D000098825:Oxysterol Binding Proteins
chemical_list: D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D019012:Integrin beta1; D018631:ras Proteins; C471934:OSBPL3 protein, human; D000098825:Oxysterol Binding Proteins; C085929:RRAS protein, human