Ion channel inhibition by targeted recruitment of NEDD4-2 with divalent nanobodies.

Targeted protein degradation/downregulation (TPD/TPDR) is a disruptive paradigm for developing therapeutics. <2% of ~600 E3 ligases have been exploited for this modality, and efficacy for multi-subunit ion channels has not been demonstrated. NEDD4-2 E3 ligase regulates myriad ion channels, but its utility for TPD/TPDR is uncertain due to complex regulatory mechanisms. Here, we identify a nanobody that binds NEDD4-2 HECT domain without disrupting catalysis sites as revealed by cryo-electron microscopy and in vitro ubiquitination assays. Recruiting NEDD4-2 to diverse ion channels (Ca(V)2.2; KCNQ1; and epithelial Na(+) channel, ENaC, with a Liddle syndrome mutation) using divalent nanobodies (DiVas) strongly suppresses their surface density and function. Global proteomics indicates DiVa recruitment of endogenous NEDD4-2 to KCNQ1-YFP yields dramatically lower off-target effects compared to NEDD4-2 overexpression. The results establish utility of NEDD4-2 recruitment for TPD/TPDR, validate ion channels as susceptible to this modality, and introduce a general method to generate ion channel inhibitors.