Distinct aggregation of beta- and gamma-chains of the high-affinity IgE receptor on cross-linking.
The high-affinity IgE receptor (FcepsilonRI) on mast cells and basophils consists of a ligand-binding alpha-chain and two kinds of signaling chains, a beta-chain and disulfide-linked homodimeric gamma-chains. Crosslinking by multivalent antigen results in the aggregation of the bound IgE/alpha-chain complexes at the cell surface, triggering cell activation, and subsequent internalization through coated pits. However, the precise topographical alterations of the signaling beta- and gamma-chains during stimulation remain unclarified despite their importance in ligand binding/signaling coupling. Here we describe the dynamics of FcepsilonRI subunit distribution in rat basophilic leukemia cells during stimulation as revealed by immunofluorescence and immunogold electron microscopy. Immunolocalization of beta- and gamma-chains was homogeneously distributed on the cell surfaces before stimulation, while crosslinking with multivalent antigen, which elicited optimal degranulation, caused a distinct aggregation of these signaling chains on the cell membrane. Moreover, only gamma- but not beta-chains were aggregated during the stimulation that evoked suboptimal secretion. These findings suggest that high-affinity IgE receptor beta- and gamma-chains do not co-aggregate but for the most part form homogenous aggregates of beta-chains or gamma-chains after crosslinking.
Asai
K
K
Department of Pediatrics and Developmental Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Fujimoto
K
K
Harazaki
M
M
Kusunoki
T
T
Korematsu
S
S
Ide
C
C
Ra
C
C
Hosoi
S
S
D000818:Animals; D005614:Freeze Fracturing; D008566:Membranes; D008854:Microscopy, Electron / Q000379:methods; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D051381:Rats; D017455:Receptors, IgE / Q000737:chemistry / Q000502:physiology*; D014407:Tumor Cells, Cultured
D017455:Receptors, IgE