Structural basis of Fusobacterium nucleatum adhesin Fap2 interaction with receptors on cancer and immune cells

Autor/innen

  • F. Schöpf
  • G.L. Marongiu
  • K. Milaj
  • T. Sprink
  • J. Kikhney
  • A. Moter
  • D. Roderer

Journal

  • bioRxiv

Quellenangabe

  • bioRxiv

Zusammenfassung

  • The intestinal microbiome (IM) is decisive for the human host’s health. Numerous microbiota drive the progression of colorectal cancer (CRC), the third-most common cancer worldwide. The Gramnegative Fusobacterium nucleatum (Fn) is overrepresented in the IM of CRC patients and has been correlated with the emergence, progression, and metastasis of tumors. A key pathogenic factor of Fn is the adhesin Fap2, an autotransporter protein that facilitates association to cancer and immune cells via two receptors, the glycan Gal-GalNAc and the T-cell protein TIGIT, respectively. The latter interaction leads to deactivation of immune cells. Mechanistic details of the Fap2/TIGIT interaction remain elusive due to the lack of high-resolution structural data. Here, we report a system to recombinantly express functional Fap2 on the Escherichia coli surface, which interacts with Gal-GalNAc on cancer cells and with purified TIGIT with submicromolar affinity. Cryo-EM structures of Fap2, alone and in complex with TIGIT, show that the ~50 nm long rod-shaped Fap2 extracellular region binds to TIGIT on its membrane-distal tip via an extension of a β-helix domain. Moreover, by combining structure predictions, cryo-EM, docking and MD simulations, we identified a binding pit for Gal-GalNAc on the tip of Fap2. Our data represent the first purification and high-resolution structural analysis of a Fn autotransporter adhesin and its receptor association.


DOI

doi:10.1101/2024.02.28.582045