TY - JOUR
T1 - Mechanism of NAIP—NLRC4 inflammasome activation revealed by cryo-EM structure of unliganded NAIP5
AU - Paidimuddala, Bhaskar
AU - Cao, Jianhao
AU - Nash, Grady
AU - Xie, Qing
AU - Wu, Hao
AU - Zhang, Liman
N1 - Funding Information:
We thank C. Lopez at the Multiscale Microscopy Core of OHSU, S. Mulligan, N. Meyer and C. Yoshioka at the Pacific Northwest Center for Cryo-EM (PNCC) for their help in cryo-EM data collection. A portion of this research was supported by National Institutes of Health grant no. U24GM129547 and performed at the PNCC at OHSU and accessed through the Environmental Molecular Sciences Laboratory (grid.436923.9), a Department of Energy Office of Science User Facility sponsored by the Office of Biological and Environmental Research. We thank I. Rauch at OHSU for discussion and X. Xiao at OHSU for sharing the HEK293T cell line. This work was supported by the National Institutes of Health grant nos. R00AI137300 and R01AI165580 (L.Z.), and the Medical Research Foundation New Investigator grant no. 1019214 (L.Z.). We apologize to authors whose work could not be cited because of space limitation.
Publisher Copyright:
© 2023, The Author(s), under exclusive licence to Springer Nature America, Inc.
PY - 2023/2
Y1 - 2023/2
N2 - The nucleotide-binding domain (NBD), leucine rich repeat (LRR) domain containing protein family (NLR family) apoptosis inhibitory proteins (NAIPs) are cytosolic receptors that play critical roles in the host defense against bacterial infection. NAIPs interact with conserved bacterial ligands and activate the NLR family caspase recruitment domain containing protein 4 (NLRC4) to initiate the NAIP—NLRC4 inflammasome pathway. Here we found the process of NAIP activation is completely different from NLRC4. Our cryo-EM structure of unliganded mouse NAIP5 adopts an unprecedented wide-open conformation, with the nucleating surface fully exposed and accessible to recruit inactive NLRC4. Upon ligand binding, the winged helix domain (WHD) of NAIP5 undergoes roughly 20° rotation to form a steric clash with the inactive NLRC4, which triggers the conformational change of NLRC4 from inactive to active state. We also show the rotation of WHD places the 17–18 loop at a position that directly bind the active NLRC4 and stabilize the NAIP5–NLRC4 complex. Overall, these data provide structural mechanisms of inactive NAIP5, the process of NAIP5 activation and NAIP-dependent NLRC4 activation.
AB - The nucleotide-binding domain (NBD), leucine rich repeat (LRR) domain containing protein family (NLR family) apoptosis inhibitory proteins (NAIPs) are cytosolic receptors that play critical roles in the host defense against bacterial infection. NAIPs interact with conserved bacterial ligands and activate the NLR family caspase recruitment domain containing protein 4 (NLRC4) to initiate the NAIP—NLRC4 inflammasome pathway. Here we found the process of NAIP activation is completely different from NLRC4. Our cryo-EM structure of unliganded mouse NAIP5 adopts an unprecedented wide-open conformation, with the nucleating surface fully exposed and accessible to recruit inactive NLRC4. Upon ligand binding, the winged helix domain (WHD) of NAIP5 undergoes roughly 20° rotation to form a steric clash with the inactive NLRC4, which triggers the conformational change of NLRC4 from inactive to active state. We also show the rotation of WHD places the 17–18 loop at a position that directly bind the active NLRC4 and stabilize the NAIP5–NLRC4 complex. Overall, these data provide structural mechanisms of inactive NAIP5, the process of NAIP5 activation and NAIP-dependent NLRC4 activation.
UR - http://www.scopus.com/inward/record.url?scp=85145750028&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85145750028&partnerID=8YFLogxK
U2 - 10.1038/s41594-022-00889-2
DO - 10.1038/s41594-022-00889-2
M3 - Article
C2 - 36604500
AN - SCOPUS:85145750028
SN - 1545-9993
VL - 30
SP - 159
EP - 166
JO - Nature Structural Biology
JF - Nature Structural Biology
IS - 2
ER -