Targeting mannosylation of nicastrin N-glycans attenuates γ-secretase activity and notch-dependent leukemia progression.

γ-Secretase is a transmembrane protease complex that cleaves multiple type I transmembrane proteins, including amyloid precursor protein and neurogenic locus notch homolog protein (NOTCH). Although numerous γ-secretase inhibitors and modulators targeting Notch-dependent cancers have been developed in recent decades, their clinical translation has been hampered by low substrate specificity and on-target gut toxicity. Using a proteomics-based screening approach, we identified dedicator of cytokinesis protein 2 (DOCK2) as an interactor of the γ-secretase subunit nicastrin (NCSTN). We further demonstrate that DOCK2 regulates mannosylation of NCSTN N-glycans, which in turn modulates γ-secretase activity toward NOTCH receptors. Both genetic depletion of DOCK2 and pharmacological inhibition of NCSTN mannosylation with kifunensine attenuated Notch-dependent leukemia progression in vivo. Collectively, these findings uncover a regulatory mechanism underlying substrate-specific activation of γ-secretase and suggest a promising therapeutic strategy for Notch-related diseases.