Plasticity in PYD assembly revealed by cryo-EM structure of the PYD filament of AIM2.Lu, A., Li, Y., Yin, Q., Ruan, J., Yu, X., Egelman, E., Wu, H.
(2015) Cell Discov 1
- PubMed: 26583071
- DOI: 10.1038/celldisc.2015.13
- Primary Citation of Related Structures:
- PubMed Abstract:
Absent in melanoma 2 (AIM2) is an essential cytosolic double-stranded DNA receptor that assembles with the adaptor, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1 to form the AIM2 inflammasome, wh ...
Absent in melanoma 2 (AIM2) is an essential cytosolic double-stranded DNA receptor that assembles with the adaptor, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1 to form the AIM2 inflammasome, which leads to proteolytic maturation of cytokines and pyroptotic cell death. AIM2 contains an N-terminal Pyrin domain (PYD) that interacts with ASC through PYD/PYD interactions and nucleates ASC PYD filament formation. To elucidate the molecular basis of AIM2-induced ASC PYD polymerization, we generated AIM2 PYD filaments fused to green fluorescent protein (GFP) and determined its cryo-electron microscopic (cryo-EM) structure. The map showed distinct definition of helices, allowing fitting of the crystal structure. Surprisingly, the GFP-AIM2 PYD filament is a 1-start helix with helical parameters distinct from those of the 3-start ASC PYD filament. However, despite the apparent symmetry difference, helical net and detailed interface analyses reveal minimal changes in subunit packing. GFP-AIM2 PYD nucleated ASC PYD filament formation in comparable efficiency as untagged AIM2 PYD , suggesting assembly plasticity in both AIM2 PYD and ASC PYD . The DNA-binding domain of AIM2 is able to form AIM2/DNA filaments, within which the AIM2 PYD is brought into proximity to template ASC PYD filament assembly. Because ASC is able to interact with many PYD-containing receptors for the formation of inflammasomes, the observed structural plasticity may be critically important for this versatility in the PYD/PYD interactions.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA ; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.