Enterococcus-derived tyramine hijacks a2A-adrenergic receptor in intestinal stem cells to exacerbate colitis
Inflammatory bowel disease (IBD) is characterized by dysbiosis of the gut microbiota and dysfunction of in testinal stem cells (ISCs). However, the direct interactions between IBD microbial factors and ISCs are unde scribed. Here, we identify a2A-adrenergic receptor (ADRA2A) as a highly expressed GPCR in ISCs. Through PRESTO-Tango screening, we demonstrate that tyramine, primarily produced by Enterococcus via tyrosine decarboxylase (tyrDC), serves as a microbial ligand for ADRA2A. Using an engineered tyrDC deficient  Enterococcus faecalis strain and intestinal epithelial cell-specific Adra2a knockout mice, we show that Enterococcus-derived tyramine suppresses ISC proliferation, thereby impairing epithelial regeneration and  exacerbating DSS-induced colitis through ADRA2A. Importantly, blocking the axis with an ADRA2A antagonist, yohimbine, disrupts tyramine-mediated suppression on ISCs and alleviates colitis.Our findings highlight  a microbial ligand-GPCR pair in ISCs, revealing a causal link between microbial regulation of ISCs and colitis exacerbation and yielding a targeted therapeutic approach to restore ISC function in colitis. Overall design: After dissociated into single cell with TripLE for 10min,intestine organoids were treated with 100uM tyramine for 16h (n=3) or with control medium(n=3).