Cross-linking of Fc gamma receptor to surface immunoglobulin on B cells provides an inhibitory signal that closes the plasma membrane calcium channel.
Stimulation of B lymphocytes by the cross-linking of surface Ig (sIg) with an F(ab')2 antibody fragment leads to the rapid activation of several tyrosine kinases. This gives rise to the activation of phospholipase C gamma (PLC gamma) and the generation of inositol phosphates. These, in turn, lead to a prolonged elevation of intracellular Ca2+ ([Ca2+]i) consisting of a rapid release of Ca2+ from intracellular stores and a sustained influx of extracellular Ca2+. In contrast, co-cross-linking sIg to Fc gamma receptor (Fc gamma RII) with intact anti-sIg induces a much more transient increase in [Ca2+]i. Stimulation of the murine B cell lymphoma, A20, with F(ab')2 anti-sIgG leads to the production of high levels of IL-2, while co-cross-linking of sIgG with Fc gamma RII blocks this response. In studies reported here, we show that co-cross-linking of Fc gamma RII with sIg prevents the influx of extracellular Ca2+ without significantly affecting the tyrosine phosphorylation of substrates including PLC gamma 1, PLC gamma 2, and Syk or the mobilization of Ca2+ from intracellular stores. In cells that had been previously activated with F(ab')2 anti-IgG, co-cross-linking of sIg to Fc gamma RII rapidly abrogated the influx of extracellular Ca2+ by closing the plasma membrane Ca2+ channel. Additionally, even 2-3 h after stimulation of the cells with F(ab')2 fragment, addition of intact anti-IgG to the cells, or removal of extracellular Ca2+, markedly inhibited (> 90%) IL-2 production. These results indicate that co-cross-linking sIg with Fc gamma RII both prevented the opening of and actively closed the Ca2+ channel, and, through this mechanism, Fc gamma RII was able to control production of IL-2. Overall, since influx of extracellular Ca2+ has been found to be necessary for the proliferation and differentiation of B cells, Fc gamma RII may play a critical role in controlling these responses by regulating the opening of the Ca2+ channel.
Diegel
M L
ML
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121.
Rankin
B M
BM
Bolen
J B
JB
Dubois
P M
PM
Kiener
P A
PA
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005456:Fluorescent Dyes; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D007074:Immunoglobulin G / Q000276:immunology; D007211:Indoles; D007376:Interleukin-2 / Q000096:biosynthesis; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D010750:Phosphoproteins / Q000378:metabolism; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D017452:Receptors, IgG / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D003432:Cross-Linking Reagents; D005456:Fluorescent Dyes; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D007211:Indoles; D007376:Interleukin-2; D007527:Isoenzymes; D010750:Phosphoproteins; D011947:Receptors, Antigen, B-Cell; D017452:Receptors, IgG; D019000:Phosphotyrosine; D014443:Tyrosine; D004533:Egtazic Acid; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; C048960:indo-1; D002118:Calcium