CD24, a signal transducer modulating B cell activation responses, is a very short peptide with a glycosyl phosphatidylinositol membrane anchor.
CD24 is a signal-transducing molecule on the surfaces of most human B cells that can modulate their response to activation signals by antagonizing IL-induced differentiation into antibody-forming cells and inducing proliferation in combination with signals generated by Ag receptors. A cDNA that directs the expression of CD24 on the surfaces of transfected COS cells was cloned by its homology to a cDNA encoding the murine M1/69-J11d heat stable Ag. The CD24 cDNA encodes a mature peptide of only 31 to 35 amino acids that is extensively glycosylated and is attached to the outer surface of the plasma membrane by a glycosyl phosphatidylinositol lipid anchor. Although CD24 is structurally similar to M1/69-J11d, and the two Ag appear to have a common genetic ancestry, the homology of CD24 to the M1/69-J11d Ag is confined to a small cluster of amino acids comprising potential N-linked glycosylation sites. Combined with the differences in expression patterns of the human and murine Ag, this indicates that CD24 and M1/69-J11d may not have equivalent functional roles in lymphoid development. The novel structure of CD24 suggests that signaling could be triggered by the binding of a lectin-like ligand to the carbohydrates projecting from the CD24 peptide, and transduced through the release of second messengers derived from the glycosyl phosphatidylinositol membrane anchor of CD24.
Kay
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Terry Fox Laboratory, British Columbia Cancer Research Centre, Vancouver, Canada.
Rosten
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Humphries
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D015703:Antigens, CD / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D051927:CD24 Antigen; D016827:CD8 Antigens; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D006017:Glycolipids / Q000502:physiology*; D017261:Glycosylphosphatidylinositols; D006801:Humans; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D010716:Phosphatidylinositols / Q000502:physiology*; D015398:Signal Transduction
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D051927:CD24 Antigen; C497889:CD24 protein, human; D016827:CD8 Antigens; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; D010716:Phosphatidylinositols; D004247:DNA