Auxilin in enteroendocrine cells controls intestinal homeostasis through inter-cell signaling relays

Adult stem cells are critical for the homeostasis of residential tissue and organism fitness. Residential stem cells must constantly perceive external and internal signals and adjust their proliferation rate accordingly to avoid unlimited proliferation or premature differentiation. However, how differentiated cells affect stem cell proliferation and tissue homeostasis through cell-cell communication still remains poorly understood. Here, we unveil an unprecedented function of Auxilin (Aux) in enteroendocrine cells (EEs) by restricting intestinal stem cell (ISC) proliferation. aux depletion in all EEs leads to intestinal homeostasis disruption. The levels of Slit are dramatically reduced in aux-depleted EEs and cytokine Upd3 expression is significantly increased in some aux-depleted EEs and neighboring wild type enterocytes (ECs). Ectopic expression of slit could effectively rescue the defects observed in prosts > auxRNAi intestines. Interestingly, EGFR signaling is ectopically activated due to EGFR accumulation in aux-depleted EEs. Further inhibiting EGFR signaling completely suppresses the defects in prosts > auxRNAi intestines. Finally, EGFR signaling suppresses slit transcription by Pointed binding to slit regulatory regions. Together, these data show that Aux in EEs restrains ISCs from excessive proliferation and aberrant progeny differentiation to maintain intestinal homeostasis through inter-cell communications. Thus our study uncovers the underlying mechanism of how stem cell proliferation is properly controlled by differentiated cells through inter-cell signaling relays during tissue homeostasis and tumorigenesis.