Abstract
The mechanism of enhanced presentation of ovalbumin (OVA) internalized as immunoglobulin A (IgA)-OVA via the IgA Fc receptor (FcalphaR) was analyzed by focusing on the role of the FcalphaR-associated gamma chain. Comparison of B-cell transfectants expressing FcalphaR plus wild-type (WT) gamma chain or gamma chain in which the immunoreceptor tyrosine-based activation motif (ITAM) was altered by tyrosine mutation or substitution with the ITAM of FcgammaRIIA showed that signaling-competent ITAM was not required for endocytosis of IgA-OVA. However, antigen presentation was impaired by ITAM changes. Signaling-competent gamma-chain ITAM appeared necessary for transport of ligated FcalphaR to a lamp-1(+) late endocytic compartment for remodeling and/or activation of that compartment and also for efficient degradation of IgA complexes. Moreover, FcalphaR ligation also activated efficient processing of nonreceptor-targeted antigen. The results suggest that gamma-chain signaling activates the antigen processing compartment.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Motifs / genetics
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Amino Acid Motifs / immunology
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Amino Acid Motifs / physiology
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Amino Acid Substitution
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Antigen Presentation / immunology*
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Antigens, CD / immunology
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Antigens, CD / metabolism*
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B-Lymphocytes / immunology
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Endocytosis / immunology
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Humans
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Immunoglobulin A / metabolism
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Mutagenesis, Site-Directed
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Ovalbumin / immunology
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Ovalbumin / metabolism*
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Protein Subunits
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Receptors, Antigen, B-Cell / immunology
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Receptors, Antigen, B-Cell / metabolism
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Receptors, Fc / immunology
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Receptors, Fc / metabolism*
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Receptors, IgG / chemistry
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Receptors, IgG / immunology
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Receptors, IgG / metabolism
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Receptors, Immunologic / genetics
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Receptors, Immunologic / immunology
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Receptors, Immunologic / physiology
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Signal Transduction / immunology*
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Transfection
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Tyrosine
Substances
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Antigens, CD
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Fc(alpha) receptor
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Immunoglobulin A
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Protein Subunits
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Receptors, Antigen, B-Cell
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Receptors, Fc
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Receptors, IgG
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Receptors, Immunologic
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Tyrosine
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Ovalbumin