CD23 (the low-affinity IgE receptor) as a C-type lectin: a multidomain and multifunctional molecule.
This review, regards the low-affinity receptor CD23 as a C-type lectin and compares it with other C-type lectins and C-type lectin-like receptors. C-type lectins such as the asialoglycoprotein receptor, as well as the dendritic cell immunoreceptor and the dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin on dendritic cell lectin, possess amino acid sequences which interact with Ca++ and sugar, and many of them possess an endocytosis signal sequence that includes tyrosine or serine in the cytoplasmic region. In contrast, natural killer receptors lack the Ca++ and sugar-binding amino acids but conserve homologous cysteines in the form of C-type lectin, and possess an immunoreceptor tyrosine-based inhibitory motif in the cytoplasmic region which inhibits killer activity when they recognize the self major histocompatibility (MHC) class I molecule. Since human CD23a form has a similar amino acid sequence, the possibility that this sequence is an endocytosis signal or an ITIM is discussed. The function of the reverse RGD and RGD-binding inhibitory peptide in human CD23 from the point of view of the relation between a C-type lectin and MHC class II molecules is also considered.
Kijimoto-Ochiai
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Institute of Immunology, Hokkaido University, Sapporo, Japan. chk30950@hkg.odn.ne.jp
D000595:Amino Acid Sequence; D000818:Animals; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D037102:Lectins / Q000737:chemistry* / Q000502:physiology*; D037181:Lectins, C-Type; D016350:Leucine Zippers; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011961:Receptors, Fc / Q000737:chemistry; D017455:Receptors, IgE / Q000737:chemistry* / Q000502:physiology*; D016415:Sequence Alignment
D037102:Lectins; D037181:Lectins, C-Type; D008024:Ligands; D009842:Oligopeptides; D011961:Receptors, Fc; D017455:Receptors, IgE; D007073:Immunoglobulin E; C047981:arginyl-glycyl-aspartic acid