Novel mechanism of Notch regulation revealed
Signaling by Notch receptors is a key cell-cell communication mechanism essential for developmental patterning throughout evolution, controlling cell fate decision, cellular differentiation, as well as morphogenesis and growth of multiple organ systems. In the vascular system, Notch signaling coordinates critical steps of angiogenic blood vessel growth during development and tumor formation. Even subtle differences in endothelial Notch activity have profound consequences for the vascular morphogenesis – yet the mechanisms that balance endothelial Notch responses are poorly understood.
In the present study, we identified the deubiquitinating enzyme USP10 as a novel cell-intrinsic regulator of endothelial Notch signaling. We showed that USP10 interacts with the NOTCH1 intracellular domain (NICD1) – the single-activated NOTCH1 receptor – to remove ubiquitin molecules that mark NICD1 for proteasomal degradation. Combining genetic, biochemical and transcriptome analyses, we further demonstrated that USP10 is a regulator of Notch signaling dynamics, whose inactivation reduces the amplitude and duration of endothelial Notch responses. Our data thus reveal USP10 as a NICD1 deubiquitinase and uncover reversible ubiquitination of NICD1 as a molecular mechanism for modulating the kinetics of Notch signaling.
We further illustrated that this mechanism is relevant for angiogenic blood vessel growth during which dynamic changes in Notch activity determine the specification and position shuffling of endothelial cells. Using genetic models, we show that endothelial-specific deletion of USP10 mimics aspects of Notch loss-of-function phenotypes, and that USP10 inactivation can restore, in part, vascular patterning defects caused by ectopic Notch activation. Our study thereby identifies USP10 as a regulatory component of the Notch pathway, which fine-tunes Notch-dependent vessel branching morphogenesis. USP10, itself regulated by metabolic and cellular stress signals, might allow endothelial cells to adjust Notch responses to changing tissue environments.