2. Academic Validation
  3. Structural mechanisms of calmodulin activation of Shigella effector OspC3 to ADP-riboxanate caspase-4/11 and block pyroptosis

Structural mechanisms of calmodulin activation of Shigella effector OspC3 to ADP-riboxanate caspase-4/11 and block pyroptosis

  • Nat Struct Mol Biol. 2023 Jan 9. doi: 10.1038/s41594-022-00888-3.
Yanjie Hou # 1,  Huan Zeng # 1 2 3,  Zilin Li 3 4,  Na Feng 1,  Fanyi Meng 1 2,  Yue Xu 3 5,  Lin Li 3,  Feng Shao 6 7 8 9,  Jingjin Ding 10 11 12
Affiliations

Affiliations

  • 1 National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
  • 2 University of Chinese Academy of Sciences, Beijing, China.
  • 3 National Institute of Biological Sciences, Beijing, Beijing, China.
  • 4 Research Unit of Pyroptosis and Immunity, Chinese Academy of Medical Sciences and National Institute of Biological Sciences, Beijing, China.
  • 5 Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
  • 6 National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China. shaofeng@nibs.ac.cn.
  • 7 National Institute of Biological Sciences, Beijing, Beijing, China. shaofeng@nibs.ac.cn.
  • 8 Research Unit of Pyroptosis and Immunity, Chinese Academy of Medical Sciences and National Institute of Biological Sciences, Beijing, China. shaofeng@nibs.ac.cn.
  • 9 Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing, China. shaofeng@nibs.ac.cn.
  • 10 National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China. jding@ibp.ac.cn.
  • 11 University of Chinese Academy of Sciences, Beijing, China. jding@ibp.ac.cn.
  • 12 National Institute of Biological Sciences, Beijing, Beijing, China. jding@ibp.ac.cn.
  • # Contributed equally.
PMID: 36624349 DOI: 10.1038/s41594-022-00888-3
Abstract

The caspase-4/11-GSDMD Pyroptosis axis recognizes cytosolic lipopolysaccharide for Antibacterial defenses. Shigella flexneri employs an OspC3 effector to block Pyroptosis by catalyzing NAD+-dependent arginine ADP-riboxanation of caspase-4/11. Here, we identify CA2+-free Calmodulin (CaM) that binds and stimulates OspC3 ADP-riboxanase activity. Crystal structures of OspC3-CaM and OspC3-caspase-4 binary complexes reveal unique CaM binding to an OspC3 N-terminal domain featuring an ADP-ribosyltransferase-like fold and specific recognition of caspase-4 by an OspC3 ankryin repeat domain, respectively. CaM-OspC3-caspase-4 ternary complex structures show that NAD+ binding reorganizes the catalytic pocket, in which D231 and D177 activate the substrate arginine for initial ADP-ribosylation and ribosyl 2'-OH in the ADP-ribosylated arginine, respectively, for subsequent deamination. We also determine structures of unmodified and OspC3-ADP-riboxanated caspase-4. Mechanisms derived from this series of structures covering the entire process of OspC3 action are supported by biochemical analyses in vitro and functional validation in S. flexneri-infected mice.

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