Figure 7.

Cartoon depicting events in flagellin-triggered host cell signaling. Although Toll is able to activate NF-κB in the absence of extracellular ATP, Toll-signaling requires ATP to activate Erk1/2. Flagellin causes an increased association between ASGM1 and TLR5 to mediate the autocrine release of ATP. Once released from the cell, ATP binds and activates a G protein–coupled nucleotide receptor on the cell surface, leading to Ca²⁺ mobilization and Erk1/2 phosphorylation.