High potassium concentration regulates the WNK3‒SPAK‒NKCC1 phosphorylation cascade via kelch-like protein 2 in mouse vascular smooth muscle cells

We have previously demonstrated that kelch-like protein 2 (KLHL2) forms a complex with Cullin3 that functions as an E3 ligase in the degradation of with-no-lysine kinases (WNKs). KLHL2 physiologically mediates the WNK3‒SPAK‒NKCC1 phosphorylation cascade in vascular smooth cells, thereby regulating vascular tone. A high-potassium diet can attenuate hypertension by reducing peripheral vascular resistance. In addition, we have reported that extracellular potassium can negatively regulate the WNK‒OSR1/SPAK‒NCC phosphorylation cascade in COS7 cells. However, the effect of high-potassium concentrations on the role of WNKs in vascular tone regulation has not yet been clarified. In the present study, we investigated whether the WNK‒SPAK‒NKCC1 cascade in mouse vascular smooth muscle (MOVAS) cells could be regulated by high potassium concentrations. We confirmed that the WNK3‒SPAK‒NKCC1 phosphorylation cascade was significantly inhibited in high-potassium medium but that the protein level of WNK1 remained unchanged. Furthermore, KLHL2 levels increased when MOVAS cells were incubated in a high-potassium medium. KLHL2-knockdown experiments confirmed that the inhibition of the WNK3‒SPAK‒NKCC1 phosphorylation cascade induced by high potassium concentrations was attributable to KLHL2-mediated degradation of WNK3. Thus, the present study could explain one of the mechanisms underlying antihypertensive effects of high dietary potassium intake.