Enterochromaffin cells act as intestinal signal integration hubs for microbial metabolites

The intestinal epithelium senses and responds to the myriad of signals from gut microbiota, but it remains unclear how these signals are integrated to drive physiological responses. In this work, we found that enterochromaffin (EC) cells in the gut serve as signal integration hubs for microbial metabolites. EC cells coordinate responses to combinations of microbial metabolites, resulting in complex alterations in serotonin signaling that drive changes in GI physiology. We found that microbial metabolites either directly trigger responses or alter the expression of receptors for other microbial metabolites in EC cells. The microbiota-derived purine derivative hypoxanthine triggers a signaling pathway by activating G-protein coupled receptor A1R, which in turn activates the calcium channel TRPC4, resulting in increased serotonin release and accelerated GI transit. On the other hand, bacteria-derived butyrate does not evoke EC cell calcium influx by itself, but drives epigenetic changes that upregulate TRPC4 expression, thereby enhancing response to metabolites like hypoxanthine and norepinephrine that act via TRPC4. Since the expression TRPC4 is limited to EC cells, these cells function as specialized epithelial sensors that integrate signals from regulatory (butyrate) and effector metabolites like hypoxanthine and norepinephrine. These findings offer new microbiota-driven therapeutic avenues for conditions associated with altered GI function.