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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.


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The congruent helical symmetry between filaments assembled by AIM2PYD and ASCPYD.(a) The ns-EM average power spectra of the AIM2PYD filament (left) and the ASCPYD filament (right; personal communication; Dr Hao Wu, Harvard). The coloured arrows indicate corresponding helical symmetry lines observed from both filaments. (b,c) A homology of model of the AIM2PYD filament based on the cryo-EM structure of the ASCPYD filament (PDB ID: 3J63). The AIM2 side chains important for dsDNA binding and auto-oligomerization are highlighted.
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f7: The congruent helical symmetry between filaments assembled by AIM2PYD and ASCPYD.(a) The ns-EM average power spectra of the AIM2PYD filament (left) and the ASCPYD filament (right; personal communication; Dr Hao Wu, Harvard). The coloured arrows indicate corresponding helical symmetry lines observed from both filaments. (b,c) A homology of model of the AIM2PYD filament based on the cryo-EM structure of the ASCPYD filament (PDB ID: 3J63). The AIM2 side chains important for dsDNA binding and auto-oligomerization are highlighted.

Mentions: Several previous studies reported the direct interaction between AIM2PYD and ASCPYD (refs 7, 19, 20). The helical architecture of the ASCPYD filament is known7; however, whether or not the upstream AIM2 oligomer provides a ‘polymerization template ' via a congruent oligomeric architecture as seen from the Rig-I·MAVS interaction9 is an open question. Thus, we determined the helical symmetry of the core stem of the AIM2FL filaments. The average power spectrum of the AIM2FL filaments obtained from ns-EM is remarkably similar to that of the ASCPYD filament (Fig. 7a, see also ref. 7), which is an ∼90-Å wide, six-start helix with three-fold symmetry7. These parameters also agree with our proposition in which the AIM2PYD filament constitutes the core stem (Fig. 6). On the basis of the consistent helical symmetry, we generated a homology model of the AIM2PYD filament using the cryo-EM structure of the ASCPYD filament as a template7, where we found that all the side chains we have identified to be important for dsDNA binding and auto-oligomerization are located at the subunit interfaces (Fig. 7b,c). Overall, our EM analysis suggests that the upstream AIM2PYD filament provides a structural template for the polymerization of downstream ASCPYD (Fig. 1a).


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)

The congruent helical symmetry between filaments assembled by AIM2PYD and ASCPYD.(a) The ns-EM average power spectra of the AIM2PYD filament (left) and the ASCPYD filament (right; personal communication; Dr Hao Wu, Harvard). The coloured arrows indicate corresponding helical symmetry lines observed from both filaments. (b,c) A homology of model of the AIM2PYD filament based on the cryo-EM structure of the ASCPYD filament (PDB ID: 3J63). The AIM2 side chains important for dsDNA binding and auto-oligomerization are highlighted.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f7: The congruent helical symmetry between filaments assembled by AIM2PYD and ASCPYD.(a) The ns-EM average power spectra of the AIM2PYD filament (left) and the ASCPYD filament (right; personal communication; Dr Hao Wu, Harvard). The coloured arrows indicate corresponding helical symmetry lines observed from both filaments. (b,c) A homology of model of the AIM2PYD filament based on the cryo-EM structure of the ASCPYD filament (PDB ID: 3J63). The AIM2 side chains important for dsDNA binding and auto-oligomerization are highlighted.
Mentions: Several previous studies reported the direct interaction between AIM2PYD and ASCPYD (refs 7, 19, 20). The helical architecture of the ASCPYD filament is known7; however, whether or not the upstream AIM2 oligomer provides a ‘polymerization template ' via a congruent oligomeric architecture as seen from the Rig-I·MAVS interaction9 is an open question. Thus, we determined the helical symmetry of the core stem of the AIM2FL filaments. The average power spectrum of the AIM2FL filaments obtained from ns-EM is remarkably similar to that of the ASCPYD filament (Fig. 7a, see also ref. 7), which is an ∼90-Å wide, six-start helix with three-fold symmetry7. These parameters also agree with our proposition in which the AIM2PYD filament constitutes the core stem (Fig. 6). On the basis of the consistent helical symmetry, we generated a homology model of the AIM2PYD filament using the cryo-EM structure of the ASCPYD filament as a template7, where we found that all the side chains we have identified to be important for dsDNA binding and auto-oligomerization are located at the subunit interfaces (Fig. 7b,c). Overall, our EM analysis suggests that the upstream AIM2PYD filament provides a structural template for the polymerization of downstream ASCPYD (Fig. 1a).

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