The Abelson kinase and the Nedd4 family E3 ligases co-regulate Notch trafficking to limit signaling

Precise output from the conserved Notch signaling pathway governs a plethora of cellular processes and developmental transitions. Unlike other pathways that use a cytoplasmic relay, the Notch cell surface receptor transduces signaling directly to the nucleus, with endocytic trafficking providing critical regulatory nodes. Here we report that the cytoplasmic tyrosine kinase Abelson (Abl) facilitates Notch internalization into late endosomes/multivesicular bodies (LEs), thereby limiting signaling output in both ligand-dependent and -independent contexts. Abl phosphorylates the PPxY motif within Notch, a molecular target for its degradation via Nedd4 family ubiquitin ligases. We show that Su(dx), a family member, mediates the Abl-directed LE regulation of Notch via the PPxY, while another family member, Nedd4Lo, contributes to Notch internalization into LEs through both PPxY-dependent and -independent mechanisms. Our findings demonstrate how a network of posttranslational modifiers converging at LEs cooperatively modulates Notch signaling to ensure the precision and robustness of its cellular and developmental functions.