title: Formation of a mast cell synapse: Fc epsilon RI membrane dynamics upon binding mobile or immobilized ligands on surfaces.
abstract: Fc epsilonRI on mast cells form a synapse when presented with mobile, bilayer-incorporated Ag. In this study, we show that receptor reorganization within the contacting mast cell membrane is markedly different upon binding of mobile and immobilized ligands. Rat basophilic leukemia mast cells primed with fluorescent anti-DNP IgE were engaged by surfaces presenting either bilayer-incorporated, monovalent DNP-lipid (mobile ligand), or chemically cross-linked, multivalent DNP (immobilized ligand). Total internal reflection fluorescence imaging and electron microscopy methods were used to visualize receptor reorganization at the contact site. The spatial relationships of Fc epsilonRI to other cellular components at the synapse, such as actin, cholesterol, and linker for activation of T cells, were also analyzed. Stimulation of mast cells with immobilized polyvalent ligand resulted in typical levels of degranulation. Remarkably, degranulation also followed interaction of mast cells, with bilayers presenting mobile, monovalent ligand. Receptors engaged with mobile ligand coalesce into large, cholesterol-rich clusters that occupy the central portion of the contacting membrane. These data indicate that Fc epsilonRI cross-linking is not an obligatory step in triggering mast cell signaling and suggest that dense populations of mobile receptors are capable of initiating low-level degranulation upon ligand recognition.
authors.affiliation: Department of Pathology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Carroll-Portillo
authors.forename: Kathrin
authors.initials: K
authors.lastname: Spendier
authors.forename: Janet
authors.initials: J
authors.lastname: Pfeiffer
authors.forename: Gary
authors.initials: G
authors.lastname: Griffiths
authors.forename: Haitao
authors.initials: H
authors.lastname: Li
authors.forename: Keith A
authors.initials: KA
authors.lastname: Lidke
authors.forename: Janet M
authors.initials: JM
authors.lastname: Oliver
authors.forename: Diane S
authors.initials: DS
authors.lastname: Lidke
authors.forename: James L
authors.initials: JL
authors.lastname: Thomas
authors.forename: Bridget S
authors.initials: BS
authors.lastname: Wilson
authors.forename: Jerilyn A
authors.initials: JA
authors.lastname: Timlin
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D002450:Cell Communication / Q000276:immunology*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000276:immunology* / Q000378:metabolism* / Q000648:ultrastructure; D002784:Cholesterol / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000378:metabolism; D007073:Immunoglobulin E / Q000378:metabolism; D054992:Immunological Synapses / Q000378:metabolism* / Q000648:ultrastructure; D008024:Ligands; D008051:Lipid Bilayers / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D008407:Mast Cells / Q000276:immunology* / Q000378:metabolism / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D051381:Rats; D017455:Receptors, IgE / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D013499:Surface Properties
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D003432:Cross-Linking Reagents; C491733:Lat protein, rat; D008024:Ligands; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010750:Phosphoproteins; D017455:Receptors, IgE; D007073:Immunoglobulin E; D002784:Cholesterol