title: Small, mobile FcepsilonRI receptor aggregates are signaling competent.
abstract: Crosslinking of IgE-bound FcepsilonRI triggers mast cell degranulation. Previous fluorescence recovery after photobleaching (FRAP) and phosphorescent anisotropy studies suggested that FcepsilonRI must immobilize to signal. Here, single quantum dot (QD) tracking and hyperspectral microscopy methods were used for defining the relationship between receptor mobility and signaling. QD-IgE-FcepsilonRI aggregates of at least three receptors remained highly mobile over extended times at low concentrations of antigen that induced Syk kinase activation and near-maximal secretion. Multivalent antigen, presented as DNP-QD, also remained mobile at low doses that supported secretion. FcepsilonRI immobilization was marked at intermediate and high antigen concentrations, correlating with increases in cluster size and rates of receptor internalization. The kinase inhibitor PP2 blocked secretion without affecting immobilization or internalization. We propose that immobility is a feature of highly crosslinked immunoreceptor aggregates and a trigger for receptor internalization, but is not required for tyrosine kinase activation leading to secretion.
authors.affiliation: Department of Pathology and Cancer Research and Treatment Center, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Andrews
authors.forename: Janet R
authors.initials: JR
authors.lastname: Pfeiffer
authors.forename: A Marina
authors.initials: AM
authors.lastname: Martinez
authors.forename: David M
authors.initials: DM
authors.lastname: Haaland
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Davis
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kawakami
authors.forename: Janet M
authors.initials: JM
authors.lastname: Oliver
authors.forename: Bridget S
authors.initials: BS
authors.lastname: Wilson
authors.forename: Diane S
authors.initials: DS
authors.lastname: Lidke
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D045744:Cell Line, Tumor; D007073:Immunoglobulin E / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D010766:Phosphorylation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000276:immunology / Q000378:metabolism; D021381:Protein Transport; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D045663:Quantum Dots; D051381:Rats; D017455:Receptors, IgE / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction; D000072377:Syk Kinase
chemical_list: D000941:Antigens; D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D017455:Receptors, IgE; D007073:Immunoglobulin E; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606898:Syk protein, rat