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

J Immunol. 2008 Mar 15;180(6):3938-45. 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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


  • Contractile Proteins
  • FLNC protein, human
  • Filamins
  • Microfilament Proteins
  • Receptors, IgG