UBR5 is a novel regulator of WNK1 stability

Abstract

The with no lysine (K) 1 (WNK1) protein kinase maintains cellular ion homeostasis in many tissues through actions on ion cotransporters and channels. Increased accumulation of WNK1 protein leads to pseudohypoaldosteronism type II (PHAII), a form of familial hypertension. WNK1 can be degraded via its adaptor-dependent recruitment to the Cullin3-RBX1 E3 ligase complex by the ubiquitin-proteasome system. Disruption of this process also leads to disease. To determine if this is the primary mechanism of WNK1 turnover, we examined WNK1 protein stability and degradation by measuring its rate of decay after blockade of translation. Here, we show that WNK1 protein degradation exhibits atypical kinetics in Hela cells. Consistent with this apparent complexity, we found that multiple degradative pathways can modulate cellular WNK1 protein amount. WNK1 protein is degraded not only by the proteasome, but also by the lysosome. Non-lysosomal cysteine proteases calpain and caspases also influence WNK1 degradation, as inhibitors of these proteases modestly increased WNK1 protein expression. Importantly, we discovered that the E3 ubiquitin ligase UBR5 interacts with WNK1 and its deficiency results in increased WNK1 protein. Our results further demonstrate that increased WNK1 in UBR5-depleted cells is attributable to reduced lysosomal degradation of WNK1 protein. Taken together, our findings provide insights into the multiplicity of degradative pathways involved in WNK1 turnover and uncover UBR5 as a previously unknown regulator of WNK1 protein stability that leads to lysosomal degradation of WNK1 protein.

WNK1 in Malignant Behaviors: A Potential Target for Cancer?

“…This is supported by the finding that WNK1 abundance was increased and OSR1/SPAK activation were observed in mice lacking NEDD4-2 ( Roy et al, 2015 ; Al-Qusairi et al, 2017 ). We recently showed that WNK1 is degraded not only by the ubiquitin-proteasome pathway, but also by the lysosomal pathway ( Jung et al, 2022 ). Non-lysosomal cysteine proteases calpain and caspase-3 were also able to influence WNK1 abundance.…”

“…Non-lysosomal cysteine proteases calpain and caspase-3 were also able to influence WNK1 abundance. This study identified UBR5 (ubiquitin protein ligase E3 component N-recognin 5) as a previously unknown regulator of WNK1 turnover that mediates lysosomal degradation of WNK1 protein ( Jung et al, 2022 ). Though UBR5 inhibition only modestly elevated WNK1 protein, that change caused a significant increase in phosphorylation of OSR1/SPAK, indicating that even small changes in WNK1 protein will have a significant impact on cellular processes.…”