The inhibitory IgG receptor, FcγRIIB, blocks signalling by co-aggregated antigen receptors on mature and activated B-cells. FcγRIIB is also expressed by immature B-cells; however, its function on these cells has not been defined. In the present paper, we demonstrate that immature B-cells are highly sensitive to inhibitory signalling mediated by FcγRIIB. Co-aggregation of FcγRIIB with the B-cell antigen receptor (BCR) on immature B-cells leads to near ablation of late phase calcium mobilization. Concomitant with enhanced inhibitory signalling, we found that Src-homology-2-domain-containing inositol 5′-phosphatase (SHIP) is expressed at much higher levels in immature B-cells than in mature B-cells. Perhaps most importantly, we report that SHIP activated by BCR–FcγRIIB co-aggregation inhibits independently ligated receptors whose signalling requires PtdIns(3,4,5)P3. We found that stromal-derived factor 1 (SDF-1)-induced cell migration is impaired by prior activation of FcγRIIB. This inhibition is reduced in SHIP-deficient B-cells. Therefore receptor-mediated signalling responses that are dependent on PtdIns(3,4,5)P3 are subject to both direct and indirect inhibition by FcγRIIB-activated SHIP.
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February 2003
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Conference Article|
February 01 2003
FcγRIIB activation leads to inhibition of signalling by independently ligated receptors
A.M. Brauweiler;
A.M. Brauweiler
Integrated Department of Immunology, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, U.S.A., and University of Colorado Health Sciences Center, 1400 Jackson Street, Denver, CO 80206, U.S.A.
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J.C. Cambier
J.C. Cambier
1
Integrated Department of Immunology, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, U.S.A., and University of Colorado Health Sciences Center, 1400 Jackson Street, Denver, CO 80206, U.S.A.
1To whom correspondence should be addressed (e-mail cambierj@njc.org).
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Publisher: Portland Press Ltd
Received:
September 10 2002
Online ISSN: 1470-8752
Print ISSN: 0300-5127
Copyright 2003 Biochemical Society
2003
Biochem Soc Trans (2003) 31 (1): 281–285.
Article history
Received:
September 10 2002
Citation
A.M. Brauweiler, J.C. Cambier; FcγRIIB activation leads to inhibition of signalling by independently ligated receptors. Biochem Soc Trans 1 February 2003; 31 (1): 281–285. doi: https://doi.org/10.1042/bst0310281
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