Elevated intracellular Na ⁺ and osmolarity stimulate catalytic activity of the ubiquitin ligase Nedd4-2

Abstract

Regulation of catalytic activity of E3 ubiquitin ligases is critical for their cellular functions. We identified an unexpected mode of regulation of E3 catalytic activity by ions and osmolarity; enzymatic activity of the HECT family E3 Nedd4-2/Nedd4L is enhanced by increased intracellular Na + ([Na + ] i ) and by hyperosmolarity. This stimulated activity is mediated by activation of p38-MAPK and is inhibited by WNKs. Moreover, protease (Furin)–mediated activation of the epithelial Na + channel ENaC (a bona fide Nedd4-2 substrate), which leads to increased [Na + ] i and osmolarity, results in enhanced Nedd4-2 catalytic activity. This enhancement is inhibited by a Furin inhibitor, by a protease-resistant ENaC mutant, or by treatment with the ENaC inhibitor amiloride. Moreover, WNK inhibition, which stimulates catalytic activity of Nedd4-2, leads to reduced levels of cell-surface ENaC and reduced channel activity. ENaC activity does not affect Nedd4-2:ENaC binding. Therefore, these results demonstrate activation of a ubiquitin ligase by Na + and osmotic changes. Importantly, they reveal a negative feedback loop in which active ENaC leads to stimulation of catalytic activity of its own suppressor, Nedd4-2, to protect cells from excessive Na + loading and hyperosmotic stress and to protect the animal from hypertension.

A pepper RING‐finger E3 ligase, CaFIRF1, negatively regulates the high‐salt stress response by modulating the stability of CaFAF1

“…Our data showed that CaFIRF1‐mediated ubiquitination of CaFAF1 decreased in response to salt, specifically sodium ions (Figure 6). Sodium ions affect cellular proteins through direct and indirect pathways (Maathuis, 2013; Mojtabavi et al, 2019; Pardo & Quintero, 2002; Persaud et al, 2022). In this context, sodium ions could directly or indirectly affect CaFIRF1 and/or CaFAF1.…”

Dendritic cell epithelial sodium channel induced inflammation and salt-sensitive hypertension

“…1). Moreover, elevated intracellular sodium and osmolarity trigger degradation of ENaC as a self-inhibitory mechanism [38]. These regulatory mechanisms are crucial for maintaining sodium levels according to the body's physiologic needs.…”

Aquaporin 9 is involved in CRC metastasis through DVL2-dependent Wnt/βcatenin signaling activation

“…Since AQP9 level is an important determinant of CRC metastasis, we sought to identify AQP9-interacting E3 ligases that could regulate its protein stability. The E3 ligase NEDD4L caught our attention as a candidate since it has been shown to target several membrane proteins for proteasome degradation, including ion channels, growth factor receptors and tight junction molecules [23][24][25][26]. The WW domains of NEDD4L mediate its binding to substrates containing L/PPXY (PY) motifs [27].…”