Signaling assemblies formed in mast cells activated via Fcepsilon receptor I dimers.
Although aggregation of the Fcepsilon receptor I (FcepsilonRI) is necessary for Ag-mediated mast cell triggering, the relationship between the extent of the FcepsilonRI aggregation and subsequent biochemical and topographical events is incompletely understood. In this study, we analyzed the activation events induced by FcepsilonRI dimers, elicited by binding of anti-FcepsilonRI mAb to rat basophilic leukemia cells. We found that, in contrast to extensively aggregated FcepsilonRI, receptor dimers (1) induced a less extensive association of FcepsilonRI with detergent-resistant membranes, (2) delayed the tyrosine phosphorylation and membrane recruitment of several signaling molecules, (3) triggered a slower but more sustained increase in concentration of free cytoplasmic calcium, (4) induced degranulation which was not inhibited at higher concentrations of the cross-linking mAb, and (5) failed to produce clusters of FcepsilonRI, Syk kinase and Grb2 adapter in osmiophilic membranes, as detected by immunogold electron microscopy on membrane sheets. Despite striking differences in the topography of FcepsilonRI dimers and multimers, biochemical differences were less pronounced. The combined data suggest that FcepsilonRI-activated mast cells propagate signals from small signaling domains formed around dimerized/oligomerized FcepsilonRI; formation of large FcepsilonRI aggregates in osmiophilic membranes seems to promote both strong receptor triggering and rapid termination of the signaling responses.
Dráberová
Lubica
L
Department of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnská 1083, CZ 142-20 Prague 4, Czech Republic.
Lebduska
Pavel
P
Hálová
Ivana
I
Tolar
Pavel
P
Stokrová
Jitka
J
Tolarová
Helena
H
Korb
Jan
J
Dráber
Petr
P
D000199:Actins / Q000096:biosynthesis; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015549:Basophil Degranulation Test; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000276:immunology / Q000648:ultrastructure; D019281:Dimerization; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008407:Mast Cells / Q000276:immunology* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017455:Receptors, IgE / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; C110810:LAT protein, human; D008565:Membrane Proteins; D010750:Phosphoproteins; D017455:Receptors, IgE; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606898:Syk protein, rat