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. 2007 Nov 1;117(11):3403–3411. doi: 10.1172/JCI32033

Figure 4. WNK3 and WNK4 compete to regulate NCC.

Figure 4

(A) Increasing WNK4 445–1,222 cRNA reverses WNK3 421–1,743–mediated NCC stimulation, whereas WNK3 overcame WNK4-mediated NCC inhibition. Note that the amplitude of NCC activity, when regulated by both WNK3 and WNK4, was considerably greater than when regulated by either WNK3 or WNK4 alone. Injected amounts were: 3 ng NCC, 0–9 ng WNK3, 0–9 ng WNK4; n = 6. (B) WNK4, but not FHHt mutant WNK4 (WNK4 Q562E), attenuated stimulation of NCC activity by WNK3. KS-WNK1, full-length WNK1, and kinase-dead WNK1 had no effect on WNK3-mediated NCC stimulation. n = 4. (C) FHHt-mutant WNK4 Q562E, but not kinase-dead WNK4 D318A, inhibited wild-type WNK4 inhibition of WNK3 effects on NCC. Amounts of injected WNK4 are shown. n = 3. (D) The current results show that NCC abundance at the plasma membrane (step 1) is determined by WNK3 and WNK4 directly and by interaction between WNK3 and WNK4. FHHt-mutant WNK4 Q562E acts as a dominant-negative regulator of WNK4 actions on WNK3. WNK1 also interacts with WNK4 to regulate NCC and in turn is regulated by KS-WNK1. KS-WNK1 also inhibits WNK3 kinase activity, although it is not clear whether this affects WNK3 actions on NCC. As noted in the text, NCC is also activated by phosphorylation by unknown kinases (step 2). WNK kinases may be involved in this process. +, positive regulation; –, negative regulation.