Abstract 1930 Iron-responsive element of Divalent metal transporter 1 (Dmt1) controls Notch-mediated cell fates

Notch receptor activation is regulated by the intramembrane protease γ-secretase, which cleaves and liberates the Notch intracellular domain (Nicd) that regulates gene transcription. Here, we identify Divalent metal transporter 1 (Dmt1, Slc11A2) as a novel and essential regulator of Notch signalling. Cells lacking Dmt1 exhibit defects in Notch signaling, accompanied by disruptions in autophagosomal and endolysosomal functions.Dmt1 deficiency leads to elevated Fe2+ levels, disturbed ferritin dynamics, heightened cytoplasmic and mitochondrial reactive oxygen species (ROS), increased lipid peroxidation, and altered autophagic flux. Consequently, these changes culminate in reduced lysosomal activity, impeding the degradation of Lamp1 and cleaved Notch1 (NICD1) proteins. Notably, Dmt1 exists in two isoforms, with and without an iron response element (ire). Our investigation reveals that silencing Dmt1-ire and Dmt1+ire through isoform-specific RNA interference yields opposite effects on Notch-dependent cell fates in both cell lines and primary murine intestinal organoids.Specifically, loss of Dmt1-ire suppresses Notch activation, promoting cellular differentiation. Conversely, loss of Dmt1+ire induces Notch activation, maintaining stem-progenitor cell fates. Dmt1 isoform expression aligns with Notch and Wnt signaling in Apc-deficient intestinal organoids and human colorectal cancers. Silencing Dmt1-ire prompts Notch-dependent differentiation in colorectal cancer cells, establishing Dmt1 isoforms as binary switches governing Notch cell fate decisions in normal and tumorous cellular contexts. Importantly, our findings underscore that while γ-secretase cleavage is a prerequisite for Notch activation, it is insufficient without vesicular trafficking. Netherlands Organisation of scientific research (NWO OCENW.M20.155).