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The High‐Affinity Immunoglobulin‐E Receptor (FceRI) is Endocytosed by an AP‐2/Clathrin‐Independent, Dynamin‐Dependent Mechanism
Author(s) -
Fattakhova Gul'nar,
Masilamani Madhan,
Borrego Francisco,
Gilfillan Alasdair M.,
Metcalfe Dean D.,
Coligan John E.
Publication year - 2006
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2006.00423.x
Subject(s) - internalization , dynamin , endocytosis , clathrin , lipid raft , microbiology and biotechnology , receptor mediated endocytosis , caveolae , biology , transferrin receptor , clathrin adaptor proteins , caveolin , receptor , transferrin , ldl receptor , fc receptor , biochemistry , signal transduction , lipoprotein , cholesterol
Aggregation of the high‐affinity immunoglobulin E (IgE) receptor (FcɛRI), expressed on mast cells and basophils, initiates the immediate hypersensitivity reaction. Aggregated FcɛRI has been reported to rapidly migrate to lipid rafts in RBL‐2H3 cells. We confirmed that aggregated FcɛRI is found in the lipid raft fractions of cellular lysates. Furthermore, we show that the cross‐linked FcɛRI remains associated with detergent‐resistant structures upon internalization. Previous morphological studies have reported that aggregated FcɛRI is endocytosed via clathrin‐coated pits, which in general are not lipid raft associated. To address this apparent discrepancy, we employed siRNA to suppress expression of components of the clathrin‐mediated internalization machinery, namely, clathrin heavy chain, and the AP‐2 (α‐adaptin or µ2‐subunit). Transferrin receptor (TfR) is endocytosed by a clathrin‐mediated process and, as expected, each transfected siRNA caused a two to threefold elevation of TfR surface expression and almost completely inhibited its endocytosis. In contrast, there was no effect on surface expression levels of FcɛRI nor on the endocytosis of the dinitrophenyl‐human serum albumin (DNP‐HSA)/IgE/FcɛRI complex. On the contrary, internalization of DNP‐HSA/IgE/FcɛRI was inhibited by overexpression of a dominant‐negative dynamin mutant. We conclude that internalization of cross‐linked FcɛRI does not require the AP‐2/clathrin complex but is dynamin‐dependent and may be lipid raft mediated.