FIG. 2.

Cellular PRRs. TLRs are membrane-bound receptors localized at the cellular or endosomal membranes, recognizing PAMPs via the LRR domain and transducing signals to the intracellular environment through the TIR domain. RLRs with a C-terminal helicase domain bind RNA and become activated to transduce CARD-dependent signaling. The dsRNA-activated kinase PKR is an intracellular PRR that senses RNA through binding to two N-terminal dsRNA-binding domains. DAI and AIM2 are intracellular DNA sensors. NLRs are a class of intracellular proteins characterized by a central NOD domain and a C-terminal LRR domain, the latter of which serves as a pattern recognition domain. Signals are transduced through N-terminal domains, including CARD and pyrin (PYD) domains.