Filamin A stabilizes Fc gamma RI surface expression and prevents its lysosomal routing

• Published in: The Journal of immunology (1950) 2008-03, Vol.180 (6), p.3938-3945
• Main Authors: Beekman, Jeffrey M, van der Poel, Cees E, van der Linden, Joke A, van den Berg, Debbie L C, van den Berghe, Peter V E, van de Winkel, Jan G J, Leusen, Jeanette H W
• Format: Article
• Language: English
• Subjects: Animals; Cell Line, Tumor; Cell Membrane - genetics; Cell Membrane - immunology; Cell Membrane - metabolism; Cells, Cultured; Clone Cells; Contractile Proteins - deficiency; Contractile Proteins - genetics; Contractile Proteins - metabolism; Contractile Proteins - physiology; Filamins; Humans; Lysosomes - genetics; Lysosomes - immunology; Lysosomes - metabolism; Mice; Microfilament Proteins - deficiency; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Microfilament Proteins - physiology; Monocytes - immunology; Monocytes - metabolism; Protein Transport - genetics; Protein Transport - immunology; Receptors, IgG - biosynthesis; Receptors, IgG - genetics; Receptors, IgG - metabolism; Signal Transduction - genetics; Signal Transduction - immunology; Subcellular Fractions - immunology; Subcellular Fractions - metabolism; U937 Cells
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.180.6.3938

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.