title: Engagement of spectrin and actin in capping of FcgammaRII revealed by studies on permeabilized U937 cells.
abstract: Plasma membrane receptors can undergo translocation in the plane of plasma membrane after binding of polyvalent ligands. Ligand/receptor clusters, named patches, can collect into a polar cap, presumably due to their association with the submembrane actin-based cytoskeleton. We found that the assembly of Fcgamma receptor II caps in human monocytic U937 cells was accompanied by the accumulation of spectrin and actin in the cap region. Permeabilization of cells with streptolysin O rendered capping sensitive to inhibition by phalloidin, an actin filament stabilizing agent. A rabbit antibody directed against the chicken erythrocyte alpha-subunit of spectrin, an actin- and membrane-binding protein, also blocked the capping in a dose dependent manner. The inhibition reached approximately 50% after 20 minutes of cell treatment with the antibody. Anti-alpha-spectrin targeted specifically its submembrane antigen, in contrast to unspecific antibodies which remained dispersed in the cell interior and had no influence on the cap assembly. Our results indicate an active engagement of spectrin and actin filaments in the capping of Fcgamma receptor II.
authors.affiliation: Department of Cell Biology, Nencki Institute of Experimental Biology, 3 Pasteur Street, Warsaw, 02-093, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Kwiatkowska
authors.forename: A
authors.initials: A
authors.lastname: Sobota
mesh_terms: D000199:Actins / Q000378:metabolism*; D000906:Antibodies / Q000494:pharmacology; D001426:Bacterial Proteins; D002463:Cell Membrane Permeability / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D006801:Humans; D007152:Immunologic Capping / Q000276:immunology*; D008856:Microscopy, Fluorescence; D010590:Phalloidine / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism*; D013049:Spectrin / Q000276:immunology / Q000378:metabolism*; D013301:Streptolysins / Q000494:pharmacology; D020298:U937 Cells; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000199:Actins; D000906:Antibodies; D001426:Bacterial Proteins; D017452:Receptors, IgG; D013301:Streptolysins; C025964:streptolysin O; D013049:Spectrin; D010590:Phalloidine; D014638:Vanadates