title: Filamin A stabilizes Fc gamma RI surface expression and prevents its lysosomal routing.
abstract: Filamin A, or actin-binding protein 280, is a ubiquitously expressed cytosolic protein that interacts with intracellular domains of multiple receptors to control their subcellular distribution, and signaling capacity. In this study, we document interaction between FcgammaRI, a high-affinity IgG receptor, and filamin A by yeast two-hybrid techniques and coimmunoprecipitation. Both proteins colocalized at the plasma membrane in monocytes, but dissociated upon FcgammaRI triggering. The filamin-deficient cell line M2 and a filamin-reconstituted M2 subclone (A7), were used to further study FcgammaRI-filamin interactions. FcgammaRI transfection in A7 cells with filamin resulted in high plasma membrane expression levels. In filamin-deficient M2 cells and in filamin RNA-interference studies, FcgammaRI surface expression was consistently reduced. FcgammaRI localized to LAMP-1-positive vesicles in the absence of filamin as shown by confocal microscopy indicative for lysosomal localization. Mouse IgG2a capture experiments suggested a transient membrane expression of FcgammaRI before being transported to the lysosomes. These data support a pivotal role for filamin in FcgammaRI surface expression via retention of FcgammaRI from a default lysosomal pathway.
authors.affiliation: Immunotherapy Laboratory, Department of Immunology, University Medical Center, Ultrech, The Netherland.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Beekman
authors.forename: Cees E
authors.initials: CE
authors.lastname: van der Poel
authors.forename: Joke A
authors.initials: JA
authors.lastname: van der Linden
authors.forename: Debbie L C
authors.initials: DL
authors.lastname: van den Berg
authors.forename: Peter V E
authors.initials: PV
authors.lastname: van den Berghe
authors.forename: Jan G J
authors.initials: JG
authors.lastname: van de Winkel
authors.forename: Jeanette H W
authors.initials: JH
authors.lastname: Leusen
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D002999:Clone Cells; D003285:Contractile Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D064448:Filamins; D006801:Humans; D008247:Lysosomes / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D021381:Protein Transport / Q000235:genetics / Q000276:immunology; D017452:Receptors, IgG / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D013347:Subcellular Fractions / Q000276:immunology / Q000378:metabolism; D020298:U937 Cells
chemical_list: D003285:Contractile Proteins; C578661:FLNC protein, human; D064448:Filamins; D008840:Microfilament Proteins; D017452:Receptors, IgG