Figure 3.

Schematic of the ASC speck formation. (A) The PYDs in sensors (e.g., NLRP3) oligomerize as a seed to recruit the PYDs of ASC. (B) This homotypic PYD-PYD interaction creates a unidirectional (A-end to B-end), right-handed, three-start helix as a linear ASC filamentous backbone structure with CARDs exposed and self-interacting outside the filaments, resembling buds on the stem surface. (C) CARD-CARD interaction between ASC and caspase-1 allows caspase-1 recruitment as a left-handed one-start helix, thus increasing the local concentration and promoting activation.