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Assembly-driven activation of the AIM2 foreign-dsDNA sensor provides a polymerization template for downstream ASC.

Morrone SR, Matyszewski M, Yu X, Delannoy M, Egelman EH, Sohn J - Nat Commun (2015)

Bottom Line: The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers.The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC.Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine Baltimore, Maryland 21205, USA.

ABSTRACT
AIM2 recognizes foreign dsDNA and assembles into the inflammasome, a filamentous supramolecular signalling platform required to launch innate immune responses. We show here that the pyrin domain of AIM2 (AIM2(PYD)) drives both filament formation and dsDNA binding. In addition, the dsDNA-binding domain of AIM2 also oligomerizes and assists in filament formation. The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers. The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC. Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

No MeSH data available.


Related in: MedlinePlus

Oligomerization is integral to dsDNA binding by AIM2.(a) A model for the assembly of the AIM2 inflammasome on foreign dsDNA. AIM2 is comprised of one PYD that oligomerizes and one dsDNA-binding HIN200 domain, flanked by an unstructured 50 amino acid-linker region. ASC is a bipartite protein containing one PYD and one CARD. Procaspase-1 contains one CARD followed by the protease domain. Only a few protease domains are shown for simplicity. (b) Binding of AIM2 variants to FAM-dsDNA72 (2.5 nM) was monitored by changes in fluorescence anisotropy. The lines are fits to a Hill form of binding isotherm. The apparent binding constants (KD) are determined by the Hill equation (bound=1/(1+(KD/(AIM2))Hill constant)) and the values are listed in Supplementary Table 1. All presented experiments were performed at least three times. (c,d) Competition EMSAs in which increasing concentrations of dsDNA60 (190, 95, 45, 23, 12, 6, 3 and 1.5 μg ml−1) were added to AIM2 (variants) FAM-dsDNA72 (200 nM and 0.2 μg ml−1, respectively).
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f1: Oligomerization is integral to dsDNA binding by AIM2.(a) A model for the assembly of the AIM2 inflammasome on foreign dsDNA. AIM2 is comprised of one PYD that oligomerizes and one dsDNA-binding HIN200 domain, flanked by an unstructured 50 amino acid-linker region. ASC is a bipartite protein containing one PYD and one CARD. Procaspase-1 contains one CARD followed by the protease domain. Only a few protease domains are shown for simplicity. (b) Binding of AIM2 variants to FAM-dsDNA72 (2.5 nM) was monitored by changes in fluorescence anisotropy. The lines are fits to a Hill form of binding isotherm. The apparent binding constants (KD) are determined by the Hill equation (bound=1/(1+(KD/(AIM2))Hill constant)) and the values are listed in Supplementary Table 1. All presented experiments were performed at least three times. (c,d) Competition EMSAs in which increasing concentrations of dsDNA60 (190, 95, 45, 23, 12, 6, 3 and 1.5 μg ml−1) were added to AIM2 (variants) FAM-dsDNA72 (200 nM and 0.2 μg ml−1, respectively).

Mentions: AIM2 is a prototypical member of the AIM2-like receptor (ALR) family, which also includes other major foreign-dsDNA sensors such as interferon-inducible protein 16 (IFI16) (refs 17, 18, 19, 20, 21). ALRs directly assemble filamentous signalling platforms termed the inflammasomes on foreign dsDNA71819202122232425. For instance, AIM2 oligomerizes on cytosolic dsDNA and nucleates the polymerization of the ASC (apoptosis-associated speck-forming protein containing CARD (caspase-recruiting domain)) adaptor filament, which then nucleates the polymerization of the procaspase-1 filament; this final polymerization step activates caspase-1 via auto-proteolysis, triggering inflammatory responses including cytokine maturation and pyroptosis (Fig. 1a)7818192021.


Assembly-driven activation of the AIM2 foreign-dsDNA sensor provides a polymerization template for downstream ASC.

Morrone SR, Matyszewski M, Yu X, Delannoy M, Egelman EH, Sohn J - Nat Commun (2015)

Oligomerization is integral to dsDNA binding by AIM2.(a) A model for the assembly of the AIM2 inflammasome on foreign dsDNA. AIM2 is comprised of one PYD that oligomerizes and one dsDNA-binding HIN200 domain, flanked by an unstructured 50 amino acid-linker region. ASC is a bipartite protein containing one PYD and one CARD. Procaspase-1 contains one CARD followed by the protease domain. Only a few protease domains are shown for simplicity. (b) Binding of AIM2 variants to FAM-dsDNA72 (2.5 nM) was monitored by changes in fluorescence anisotropy. The lines are fits to a Hill form of binding isotherm. The apparent binding constants (KD) are determined by the Hill equation (bound=1/(1+(KD/(AIM2))Hill constant)) and the values are listed in Supplementary Table 1. All presented experiments were performed at least three times. (c,d) Competition EMSAs in which increasing concentrations of dsDNA60 (190, 95, 45, 23, 12, 6, 3 and 1.5 μg ml−1) were added to AIM2 (variants) FAM-dsDNA72 (200 nM and 0.2 μg ml−1, respectively).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525163&req=5

f1: Oligomerization is integral to dsDNA binding by AIM2.(a) A model for the assembly of the AIM2 inflammasome on foreign dsDNA. AIM2 is comprised of one PYD that oligomerizes and one dsDNA-binding HIN200 domain, flanked by an unstructured 50 amino acid-linker region. ASC is a bipartite protein containing one PYD and one CARD. Procaspase-1 contains one CARD followed by the protease domain. Only a few protease domains are shown for simplicity. (b) Binding of AIM2 variants to FAM-dsDNA72 (2.5 nM) was monitored by changes in fluorescence anisotropy. The lines are fits to a Hill form of binding isotherm. The apparent binding constants (KD) are determined by the Hill equation (bound=1/(1+(KD/(AIM2))Hill constant)) and the values are listed in Supplementary Table 1. All presented experiments were performed at least three times. (c,d) Competition EMSAs in which increasing concentrations of dsDNA60 (190, 95, 45, 23, 12, 6, 3 and 1.5 μg ml−1) were added to AIM2 (variants) FAM-dsDNA72 (200 nM and 0.2 μg ml−1, respectively).
Mentions: AIM2 is a prototypical member of the AIM2-like receptor (ALR) family, which also includes other major foreign-dsDNA sensors such as interferon-inducible protein 16 (IFI16) (refs 17, 18, 19, 20, 21). ALRs directly assemble filamentous signalling platforms termed the inflammasomes on foreign dsDNA71819202122232425. For instance, AIM2 oligomerizes on cytosolic dsDNA and nucleates the polymerization of the ASC (apoptosis-associated speck-forming protein containing CARD (caspase-recruiting domain)) adaptor filament, which then nucleates the polymerization of the procaspase-1 filament; this final polymerization step activates caspase-1 via auto-proteolysis, triggering inflammatory responses including cytokine maturation and pyroptosis (Fig. 1a)7818192021.

Bottom Line: The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers.The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC.Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine Baltimore, Maryland 21205, USA.

ABSTRACT
AIM2 recognizes foreign dsDNA and assembles into the inflammasome, a filamentous supramolecular signalling platform required to launch innate immune responses. We show here that the pyrin domain of AIM2 (AIM2(PYD)) drives both filament formation and dsDNA binding. In addition, the dsDNA-binding domain of AIM2 also oligomerizes and assists in filament formation. The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers. The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC. Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

No MeSH data available.


Related in: MedlinePlus