TY - JOUR
T1 - Convergence of Fcγ receptor IIA and Fcγ receptor IIIB signaling pathways in human neutrophils
AU - Chuang, Frank
AU - Sassaroli, Massimo
AU - Unkeless, Jay C.
PY - 2000/1/1
Y1 - 2000/1/1
N2 - Human neutrophils (PMNs) express two receptors for the Fc domain of IgG: the transmembrane FcγRIIA, whose cytosolic sequence contains an immunoreceptor tyrosine-based activation motif, and the GPI-anchored FcγRIIIB. Cross-linking of FcγRIIIB induces cell activation, but the mechanism is still uncertain. We have used mAbs to cross-link selectively each of the two receptors and to assess their signaling phenotypes and functional relation. Cross-linking of FcγRIIIB induces intracellular Ca2+ release and receptor capping. The Ca2+ response is blocked by wortmannin and by N,N-dimethylsphingosine, inhibitors of phosphatidylinositol 3-kinase and sphingosine kinase, respectively. Identical dose-response curves are obtained for the Ca2+ release stimulated by Cross-linking FcγRIIA, implicating these two enzymes in a common signaling pathway. Wortmannin also inhibits capping of both receptors, but not receptor endocytosis. Fluorescence microscopy in double-labeled PMNs demonstrates that FcγRIIA colocalizes with cross-linked FcγRIIIB. The signaling phenotypes of the two receptors diverge only under frustrated phagocytosis conditions, where FcγRIIIB bound to substrate-immobilized Ab does not elicit cell spreading. We propose that FcγRIIIB signaling is conducted by molecules of FcγRIIA that are recruited to protein/lipid domains induced by clustered FcγRIIIB and, thus, are brought into juxtaposition for immunoreceptor tyrosine-based activation motif phosphorylation and activation of PMNs.
AB - Human neutrophils (PMNs) express two receptors for the Fc domain of IgG: the transmembrane FcγRIIA, whose cytosolic sequence contains an immunoreceptor tyrosine-based activation motif, and the GPI-anchored FcγRIIIB. Cross-linking of FcγRIIIB induces cell activation, but the mechanism is still uncertain. We have used mAbs to cross-link selectively each of the two receptors and to assess their signaling phenotypes and functional relation. Cross-linking of FcγRIIIB induces intracellular Ca2+ release and receptor capping. The Ca2+ response is blocked by wortmannin and by N,N-dimethylsphingosine, inhibitors of phosphatidylinositol 3-kinase and sphingosine kinase, respectively. Identical dose-response curves are obtained for the Ca2+ release stimulated by Cross-linking FcγRIIA, implicating these two enzymes in a common signaling pathway. Wortmannin also inhibits capping of both receptors, but not receptor endocytosis. Fluorescence microscopy in double-labeled PMNs demonstrates that FcγRIIA colocalizes with cross-linked FcγRIIIB. The signaling phenotypes of the two receptors diverge only under frustrated phagocytosis conditions, where FcγRIIIB bound to substrate-immobilized Ab does not elicit cell spreading. We propose that FcγRIIIB signaling is conducted by molecules of FcγRIIA that are recruited to protein/lipid domains induced by clustered FcγRIIIB and, thus, are brought into juxtaposition for immunoreceptor tyrosine-based activation motif phosphorylation and activation of PMNs.
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M3 - Article
C2 - 10605030
AN - SCOPUS:0033975859
VL - 164
SP - 350
EP - 360
JO - Journal of Immunology
JF - Journal of Immunology
SN - 0022-1767
IS - 1
ER -