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. 2020 Jul 10;11:1210. doi: 10.3389/fimmu.2020.01210

Figure 1.

Figure 1

LPS signaling. Extracellular gram-negative bacteria release LPS in the form of micelles or OMVs. OMVs and micelles containing LPS can be delivered intracellularly where LPS activates caspase-dependent responses (right). Soluble LPS-binding protein (LBP) allows CD14 to capture LPS monomers. CD14 increases the sensitivity of TLR4-MD2 for LPS and favors the re-location of the complex formed by LPS, CD14, and TLR4-MD2 in the plasma membrane lipids rafts. Once in the lipid rafts, TLR4-MD2 starts TIRAP-MyD88-dependent responses. CD14 also induces the endocytosis of LPS and TLR4-MD2. From endosomes TLR4-MD2 triggers the TRAM-TRIF pathway and thereby sustains the activation of NF-κB and the production of type I IFNs (5–8).