TNFR1 links TNF exocytosis to TNF production in allergen-activated RBL-2H3 cells.

We previously reported that the maximal production of Tumor Necrosis Factor (TNF or TNFα) in antigen-activated RBL-2H3 cells (a tumor analog of mucosal mast cells) requires Munc13-4, a regulator of exocytic fusion. In this study, we investigated the involvement of various fusion catalysts in TNF production. We observed a strong correlation between the total TNF level and TNF exocytosis in RBL-2H3 cells. RT-qPCR shows that TNFR1 (TNF receptor 1) is the sole TNFR expressed in these cells, and that its transcription is upregulated upon allergen-mediated activation. Importantly, the addition of soluble TNFR1 inhibits antigen-elicited TNF production in a dosage-dependent fashion. Likewise, TNF production is diminished in the presence of TACE (TNFα Converting Enzyme) inhibitor KP-457, which prevents the generation of soluble TNF (sTNF). Together, these findings indicate that sTNF and TNFR1 function as autocrine agent and receptor respectively at the mast cell surface to boost TNF proliferation during allergic inflammation.