Cryo-EM structures of ASC and NLRC4 CARD filaments reveal a unified mechanism of nucleation and activation of caspase-1

Li, Yang; Fu, Tian‐Min; Lu, Alvin; Witt, Kristen C; Ruan, Jianbin; Shen, Chen; Wu, Hao

doi:10.1073/pnas.1810524115

Cited by 118 publications

(169 citation statements)

References 48 publications

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“…1c, d). These observations are in agreement with previously characterized CARDs from cytosolic signaling molecules 29,30 . Interestingly, we also observed features of mAire CARD filament distinct from those of previously studied CARDs 29, 30 .…”

supporting

confidence: 93%

“…Such heterogeneity in mAire CARD filaments differ from previously characterized CARD filaments (e.g. MAVS and ASC CARDs), which form highly cooperative filaments of homogeneous thicknesses 29,30 . Our efforts to determine higher resolution structure of Aire CARD filaments were unsuccessful because of aggregation and distortion of the filaments on cryo-EM grids.While cytosolic CARDs can form filaments with divergent helical symmetries, they utilize common surface areas in the conserved CARD fold 3 .…”

contrasting

confidence: 78%

“…CARD domains are generally known to form helical assemblies, either in the form of small oligomers 28 or filamentous polymer 29,30 . In our effort to dissect the functions and structures of Aire CARD (Fig.…”

Section: Aire Card Forms Filaments In Vitromentioning

confidence: 99%

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Dual functions of Aire CARD multimerization in the transcriptional regulation of T cell tolerance

Huoh¹,

Wu²,

Park

et al. 2020

Preprint

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ABSTRACTAggregate-like biomolecular assemblies are emerging as new conformational states with functionality. Aire, a transcription factor essential for central T cell tolerance, is known to form large aggregate-like assemblies visualized as nuclear foci. We demonstrate that Aire utilizes Caspase Activation Recruitment Domain (CARD) to form filamentous homo-multimers in vitro, and this assembly mediates foci formation and transcriptional activity. However, CARD-mediated multimerization is a double-edged sword as it also makes Aire susceptible to interaction with PML bodies, sites of many nuclear processes including protein quality control of nuclear aggregates. Several loss-of-function Aire mutants, including those causing autoimmune polyendocrine syndrome type-1, form foci with increased PML body association. Directing Aire to PML bodies impairs Aire’s transcriptional activity, while dispersing PML bodies with a viral antagonist restores it. Thus, our study reveals a new regulatory role of PML bodies in Aire function and highlights the interplay between nuclear aggregate-like assemblies and PML-mediated quality control.

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supporting

confidence: 93%

contrasting

confidence: 78%

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Dual functions of Aire CARD multimerization in the transcriptional regulation of T cell tolerance

Huoh¹,

Wu²,

Park

et al. 2020

Preprint

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“…To the best of our knowledge, this is the 6 first time such a 'two-layer' architecture has been observed for a FIIND-containing inflammasome sensor. It is remarkably reminiscent of activated NLRC4 and NLRP6 20,21 , where the nucleotide-binding domain (NBD) pre-oligomerizes to bring the CARD or PYRIN domains into close proximity. Furthermore, the observed dimensions of the inner core filament is consistent with those of the recombinant filaments composed of CARD alone ( Fig.S1b, 8 nm in diameter, see below).…”

Section: Nlrp1-card Oligomerization and Dramatically Lowers Its Thresmentioning

confidence: 99%

Structural basis for distinct inflammasome complex assembly by human NLRP1 and CARD8

Gong

Robinson²,

et al. 2020

Preprint

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Nod-like receptor (NLR) proteins activate pyroptotic cell death and IL-1 driven inflammation by assembling and activating the inflammasome complex. Closely related NLR proteins, NLRP1 and CARD8 undergo unique auto-proteolysis-dependent activation and are implicated in auto-inflammatory diseases; however, the molecular mechanisms of activation are not understood. Here we report the structural basis of how the activating domains (FIIND UPA -CARD) of NLRP1 and CARD8 self-oligomerize to trigger the assembly of distinct inflammasome complexes. Recombinant FIIND UPA -CARD of NLRP1 forms a two-layered filament, with an inner core composed of oligomerized CARD domains and the outer layer consisting of FIIND UPA rings.Biochemically, oligomerized NLRP1-CARD is sufficient to drive ASC speck formation in cultured human cells via filament formation-a process that is greatly enhanced by NLRP1-FIIND UPA , which forms ring-like oligomers in vitro. In addition, we report the cryo-EM structures of NLRP1-CARD and CARD8-CARD filaments at 3.7 Å, which uncovers unique structural features that enable NLRP1 and CARD8 to discriminate between ASC and pro-caspase-1. In summary, our findings provide unique structural insight into the mechanisms of activation for human NLRP1 and CARD8, uncovering an unexpected level of specificity in inflammasome signaling mediated by heterotypic CARD domain interactions.

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“…), ASC CARD (Li et al . ) and caspase‐1 CARD (Lu et al . ) have also been solved using purified protein complexes and have defined quaternary structures and polymerization interfaces.…”

Section: Inflammasomesmentioning

confidence: 99%

From atoms to physiology: what it takes to really understand inflammasomes

Schmidt

2019

The Journal of Physiology

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Rapid inflammatory responses to cytosolic threats are mediated by inflammasomes – large macromolecular signalling complexes that control the activation of the pro‐inflammatory cytokines interleukin (IL)‐1β and IL‐18, as well as cell death by pyroptosis. Different inflammasome sensors are activated by diverse direct and indirect signals, and subsequently nucleate the polymerization of the adaptor molecule ASC to form signalling platforms macroscopically observed as ASC specks. Caspase‐1 is autocatalytically activated at these sites and subsequently matures pro‐inflammatory cytokines and the pore‐forming effector molecule gasdermin D. While most molecules and basic assembly principles have been deduced from reductionist experimental systems, we still lack fundamental information on the structure and regulation of these complexes in their physiological environment and in the interplay with other signalling pathways. In this review, novel experimental approaches are proposed, including some that rely on nanobodies and single domain antibodies, to understand inflammasome assembly and regulation in the context of the relevant tissues or cells.

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Cryo-EM structures of ASC and NLRC4 CARD filaments reveal a unified mechanism of nucleation and activation of caspase-1

Cited by 118 publications

References 48 publications

Dual functions of Aire CARD multimerization in the transcriptional regulation of T cell tolerance

Dual functions of Aire CARD multimerization in the transcriptional regulation of T cell tolerance

Structural basis for distinct inflammasome complex assembly by human NLRP1 and CARD8

From atoms to physiology: what it takes to really understand inflammasomes

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