Allantopyrone A interferes with multiple components of the TNF receptor 1 complex and blocks RIP1 modifications in the TNF-α-induced signaling pathway.

Allantopyrone A is a fungal metabolite that uniquely possesses two α,β-unsaturated carbonyl moieties. We recently reported that allantopyrone A inhibited the nuclear factor-κB (NF-κB) signaling pathway induced by tumor necrosis factor (TNF)-α in human lung carcinoma A549 cells. In the present study, the mechanism by which allantopyrone A inhibits the TNF-α-induced signaling pathway was investigated in more detail. Allantopyrone A blocked extensive modifications to receptor-interacting protein 1 (RIP1) in the TNF receptor 1 (TNF-R1) complex. Allantopyrone A augmented the high-MW bands of TNF-R1, TNF receptor-associated factor 2, RIP1, the NF-κB subunit RelA and inhibitor of NF-κB kinase β in A549 cells, suggesting that it binds to and promotes the crosslinking of these proteins. The extracellular cysteine-rich domains of TNF-R1 were crosslinked by allantopyrone A more preferentially than its intracellular portion. The present results demonstrate that allantopyrone A interferes with multiple components of the TNF-R1 complex and blocks RIP1 modifications in the TNF-α-induced NF-κB signaling pathway.