Coupling Far-Western Blotting with Peptide Microarrays Reveals Novel E-Cadherin Spore-Surface Ligands in...

Clostridioides difficile is an anaerobic spore-forming bacterium and the leading cause of nosocomial diarrhea. A major clinical challenge is C. difficile infection recurrence, affecting 20-30% of patients, mainly driven by spore persistence. The mechanisms underlying spore persistence in the gut remain poorly understood. Recently, our group showed that E-cadherin acts as a spore receptor mediating adherence to intestinal epithelial cells (PMID: 36448839), but the identity of the E-cadherin-binding proteins remains unknown. Here, far-Western blotting coupled with MS/MS-identified E-cadherin-binding spore ligands. The spore surface proteins CotE (CDIF27147_01458) and CdeM (CDIF27147_01682), along with two uncharacterized proteins, CDIF27147_03838 and CDIF27147_02282, interact with E-cadherin. Peptide microarray analysis mapped discrete E-cadherin-binding regions within these proteins, corresponding to 9-20 residue motifs, predicted to be surface-exposed by AlphaFold. However, competitive E-cadherin pull-down assays using synthetic peptides of these motifs did not reduce E-cadherin binding to C. difficile spores. Comparative genomics showed that these ligands and motifs are conserved across all five classical C. difficile clades (C1-C5). Similar levels of E-cadherin binding were observed in spores from all five classical clades. Collectively, this work identifies CDIF27147_03838 and CDIF27147_02282 as novel E-cadherin ligands and suggests additional roles for CotE and CdeM, expanding insights into spore-host interactions.