Notch-Jagged signaling complex defined by an interaction mosaic

The Notch signaling system links cellular fate to that of its neighbors, driving proliferation, apoptosis, and cell differentiation in metazoan organisms, whereas dysfunction leads to debilitating developmental disorders and cancers. Here we probe the molecular architecture of mammalian Notch1 full ectodomain in complex with the canonical ligand Jagged1 using cross-linking mass spectrometry (XL-MS). Our data reveals that three Jagged1 sites, C2-epidermal growth factor (EGF) 1, EGF10 and cysteine-rich domain (CRD), are in proximity to the Notch1 negative regulatory region (NRR) in the Notch1-Jagged1 full ectodomain complex. We verified direct interactions and identified additional interacting regions by quantitative-binding experiments. In addition, XL-MS and structural analysis reveal Notch1 and Jagged1 ectodomain intramolecular interactions and structural flexibility that support the formation of backfolded architectures. Together the data suggest a direct and intricate role for the different extracellular regions of Notch1 and Jagged1 in the activation and regulation of Notch1 signaling.