Kidney collecting duct cell type composition is regulated by Notch signaling via modulation of mTORC1

The plasticity and diversity of cell types with specialized functions likely defines the capacity of multicellular organisms to adapt to physiologic stressors. The kidney collecting ducts contribute to water, electrolyte, and pH homeostasis and are composed of mature intermingled epithelial cell types that are susceptible to transdifferentiate. The conversion of kidney collecting duct principal cells to intercalated cells is actively inhibited by Notch signaling to ensure urine concentrating capability. Here we identify Hes1, a target of Notch signaling, allows for maintenance of functionally distinct epithelial cell types within the same microenvironment by regulating mechanistic target of rapamycin complex 1 (mTORC1) activity. Hes1 directly represses the expression of insulin receptor substrate 1 ( Irs1 ), an upstream component of mTOR pathway and suppresses mTORC1 activity in principal cells. Genetic inactivation of tuberous sclerosis complex 2 ( Tsc2 ) to increase mTORC1 activity in mature principal cells is sufficient to promote acquisition of intercalated cell properties, while inhibition of mTORC1 in adult kidney epithelia suppresses intercalated cell properties. Considering that mTORC1 integrates environmental cues, the linkage of functionally distinct epithelial cell types to mTORC1 activity levels likely allows for cell plasticity to be regulated by physiologic and metabolic signals and the ability to sense/transduce these signals.