| NEDD4‑L (also termed NEDD4‑2) is a HECT‑type E3 ubiquitin ligase of the NEDD4 family that uses a C2–WW–HECT domain architecture to recognize and ubiquitinate a broad set of membrane and signaling proteins, thereby coupling surface receptor and channel turnover to ion homeostasis, growth‑factor signaling, and stress responses. The N‑terminal C2 domain targets NEDD4‑L to membranes in a calcium‑ and phospholipid‑dependent manner, central WW domains bind PY motifs and related degrons in substrates or adaptors, and the C‑terminal HECT domain accepts ubiquitin from E2 enzymes and forms a transient thioester intermediate before transferring ubiquitin to lysines on selected cargos or associated signaling factors. Through this modular organization, NEDD4‑L regulates multiple ion channels and transporters, including the epithelial sodium channel ENaC, the Na⁺–Cl⁻ cotransporter NCC, and several voltage‑gated Na⁺ channels, by promoting their ubiquitination, endocytosis, and lysosomal or proteasomal degradation, which limits apical Na⁺ reabsorption in kidney and airway epithelia and contributes to blood pressure and fluid homeostasis. NEDD4‑L also targets growth and survival signaling components; it ubiquitinates activated receptors such as NTRK1 and elements of the TGF‑β and Wnt pathways, and together with the closely related NEDD4, it ubiquitinates the Wnt co‑receptor LGR5 in intestinal crypts, thereby dampening Wnt signaling and controlling intestinal stem‑cell priming and gut homeostasis. Upstream regulatory circuits tune NEDD4‑L activity through phosphorylation and adaptor binding: kinases such as SGK1 and AKT phosphorylate specific sites on NEDD4‑L, creating docking sites for 14‑3‑3 proteins that inhibit binding to substrates like ENaC and reduce ubiquitination, while NDFIP1/2 adaptor proteins recruit NEDD4‑L to particular cargos and cellular compartments and deubiquitinases such as USP2‑45 modulate NEDD4‑L stability through removal of autoubiquitin chains. In cancer biology, NEDD4‑L controls substrates involved in autophagy, growth‑factor signaling, and epithelial–mesenchymal transition, including ULK1, components of the Notch, EGFR, and Wnt cascades, and various transporters; altered NEDD4‑L expression or function associates with either tumor‑suppressive or pro‑tumor roles depending on whether its predominant substrates in a given context are oncogenic drivers or negative regulators of proliferation and survival. Genetic and association data link NEDD4L variants with human hypertension and renal salt handling, and mouse models show that NEDD4‑L loss or reduced function elevates ENaC and NCC abundance at the plasma membrane, increasing Na⁺ uptake and contributing to salt‑sensitive hypertension, while selective modulation of NEDD4‑L activity in epithelia and tumors is under investigation as a strategy to adjust ion transport, dampen aberrant Wnt or TGF‑β signaling, or influence gasdermin‑dependent cell‑death pathways. |
