SHIP negatively regulates IgE + antigen-induced IL-6 production in mast cells by inhibiting NF-kappa B activity.
We demonstrate in this study that IgE + Ag-induced proinflammatory cytokine production is substantially higher in Src homology-2-containing inositol 5'-phosphatase (SHIP)(-/-) than in SHIP(+/+) bone marrow-derived mast cells (BMMCs). Focusing on IL-6, we found that the repression of IL-6 mRNA and protein production in SHIP(+/+) BMMCs requires the enzymatic activity of SHIP, because SHIP(-/-) BMMCs expressing wild-type, but not phosphatase-deficient (D675G), SHIP revert the IgE + Ag-induced increase in IL-6 mRNA and protein down to levels seen in SHIP(+/+) BMMCs. Comparing the activation of various signaling pathways to determine which ones might be responsible for the elevated IL-6 production in SHIP(-/-) BMMCs, we found the phosphatidylinositol 3-kinase/protein kinase B (PKB), extracellular signal-related kinase (Erk), p38, c-Jun N-terminal kinase, and protein kinase C (PKC) pathways are all elevated in IgE + Ag-induced SHIP(-/-) cells. Moreover, inhibitor studies suggested that all these pathways play an essential role in IL-6 production. Looking downstream, we found that IgE + Ag-induced IL-6 production is dependent on the activity of NF-kappa B and that I kappa B phosphorylation/degradation and NF-kappa B translocation, DNA binding and transactivation are much higher in SHIP(-/-) BMMCs. Interestingly, using various pathway inhibitors, it appears that the phosphatidylinositol 3-kinase/PKB and PKC pathways elevate IL-6 mRNA synthesis, at least in part, by enhancing the phosphorylation of I kappa B and NF-kappa B DNA binding while the Erk and p38 pathways enhance IL-6 mRNA synthesis by increasing the transactivation potential of NF-kappa B. Taken together, our data are consistent with a model in which SHIP negatively regulates NF-kappa B activity and IL-6 synthesis by reducing IgE + Ag-induced phosphatidylinositol-3,4,5-trisphosphate levels and thus PKB, PKC, Erk, and p38 activation.
Kalesnikoff
Janet
J
Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada.
Baur
Nicole
N
Leitges
Michael
M
Hughes
Michael R
MR
Damen
Jacqueline E
JE
Huber
Michael
M
Krystal
Gerald
G
D000818:Animals; D000941:Antigens / Q000276:immunology; D001854:Bone Marrow Cells / Q000276:immunology; D002478:Cells, Cultured; D020868:Gene Silencing; D051550:I-kappa B Kinase; D007073:Immunoglobulin E / Q000276:immunology*; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D007700:Kinetics; D008407:Mast Cells / Q000201:enzymology / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D018448:Models, Immunological; D009154:Mutation; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
D000941:Antigens; D051550:I-kappa B Kinase; D007073:Immunoglobulin E; D015850:Interleukin-6; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; C496564:Chuk protein, mouse; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; C098706:INPPL1 protein, human