Integrative structural biology to decipher the receptor binding mechanism of the adhesin FadA from Fusobacterium nucleatum

• Applicants: Professor Dr. Adam Lange; Dr. Daniel Roderer
• Subject Area: Structural Biology ; Biochemistry ; Biophysics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 575240064

Dysbiosis of the human colon microbiome can promote the progression of colorectal cancer (CRC). The gram-negative Fusobacterium nucleatum (Fn) is often overrepresented in the colon of CRC patients, and its presence is correlated with metastasis and poor therapeutic prognosis. In addition, Fn is often found in conjunction with breast cancer, periodontal disease, and preterm birth. The bacterium is highly involved in biofilm formation; thus, its surface is covered with adhesins. Of these adhesins, FadA is crucial for the association of Fn to human CRC cells using epithelial cadherin (E-cadherin) as a receptor, and this binding stimulates tumor cell growth through activation of the β-catenin pathway. Whereas the structure of monomeric FadA and its leucine zipper oligomerization motif is known, no high-resolution structural information is available on filament assembly, the interplay of two FadA components (mFadA and preFadA) within the filaments, and the interaction with E-cadherin. This limits the understanding of molecular mechanisms of CRC cell binding of Fn and is a hurdle for structure-based drug design against fusobacterial cell binding. We propose an integrative structural biology approach that includes solid-state nuclear magnetic resonance (ssNMR) spectroscopy, cryogenic electron microscopy and -tomography (cryo-EM and cryo-ET, respectively) to unravel molecular details of FadA filament assembly and receptor binding at hitherto unachieved resolution and completeness. In work package (WP) 1, we will elucidate the FadA filament architecture by combining NMR restraints with cryo-EM data, and validate the structure with site-directed mutagenesis. In WP 2, we will reveal the molecular interaction of E-cadherin and FadA using ssNMR, cryo-ET and sub-tomogram averaging (STA) of FadA/E-cadherin complexes. For this, we propose a comparative analysis of NMR data of FadA in the presence and absence of attached E-cadherin and correlate these results with a medium-resolution STA map. In WP3, we will transfer the in vitro structural data from WPs 1 and 2 to a cancer cell model using super-resolution microscopy, correlative cryo-microscopy, cryo focused ion beam milling and cryo-ET. The proposal is grounded on strong preliminary work in which the applicants have demonstrated the ability to assess the structure of FadA filaments by cryo-EM and ssNMR, create and stabilize a complex of FadA with E-cadherin, analyzing this in cryo-ET, and establish CRC cell growth and FadA binding on cryo-EM grids. Moreover, the Lange lab has demonstrated its proficiency in integrative structural biology of filaments using ssNMR and cryo-EM. Our project will provide groundbreaking molecular insights in the tumor adhesion mechanisms of Fn, paving the way for the development of therapeutics to target the underlying protein-protein interactions.

• DFG Programme: Research Grants
• Co-Investigators: Dr. Christoph Andreas Diebolder; Dr. Martin Lehmann; Professorin Dr. Han Sun