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Disease-causing mutations in KLHL3 impair its effect on WNK4 degradation.

ABSTRACT: Mutations in with-no-lysine (K) kinase 4 (WNK4) and a ubiquitin E3 ligase complex component kelch-like 3 (KLHL3) both cause pseudohypoaldosteronism II (PHAII), a hereditary form of hypertension. We determined whether WNK4 or its effector is regulated by KLHL3 in Xenopus oocytes. KLHL3 inhibited the positive effect of WNK4 on Na(+)-Cl(-) cotransporter (NCC) by decreasing WNK4 protein abundance without decreasing that of NCC and the downstream kinase OSR1 directly. Ubiquitination and degradation of WNK4 were induced by KLHL3. The effect of KLHL3 on WNK4 degradation was blocked by a dominant negative form of cullin 3. All five PHAII mutations of KLHL3 tested disrupted the regulation on WNK4. We conclude that KLHL3 is a substrate adaptor for WNK4 in a ubiquitin E3 ligase complex.

SUBMITTER: Wu G

PROVIDER: S-EPMC3697765 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Disease-causing mutations in KLHL3 impair its effect on WNK4 degradation.

Wu Guojin G Peng Ji-Bin JB

FEBS letters 20130509 12

Mutations in with-no-lysine (K) kinase 4 (WNK4) and a ubiquitin E3 ligase complex component kelch-like 3 (KLHL3) both cause pseudohypoaldosteronism II (PHAII), a hereditary form of hypertension. We determined whether WNK4 or its effector is regulated by KLHL3 in Xenopus oocytes. KLHL3 inhibited the positive effect of WNK4 on Na(+)-Cl(-) cotransporter (NCC) by decreasing WNK4 protein abundance without decreasing that of NCC and the downstream kinase OSR1 directly. Ubiquitination and degradation o ...[more]

PMID: 23665031

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Project description:The WNK (with no lysine kinase)-SPAK (SPS1-related proline/alanine-rich kinase)/OSR1 (oxidative stress-responsive kinase 1) signalling pathway plays an important role in controlling mammalian blood pressure by modulating the activity of ion co-transporters in the kidney. Recent studies have identified Gordon's hypertension syndrome patients with mutations in either CUL3 (Cullin-3) or the BTB protein KLHL3 (Kelch-like 3). CUL3 assembles with BTB proteins to form Cullin-RING E3 ubiquitin ligase complexes. To explore how a CUL3-KLHL3 complex might operate, we immunoprecipitated KLHL3 and found that it associated strongly with WNK isoforms and CUL3, but not with other components of the pathway [SPAK/OSR1 or NCC (Na(+)/Cl(-) co-transporter)/NKCC1 (Na(+)/K(+)/2Cl(-) co-transporter 1)]. Strikingly, 13 out of the 15 dominant KLHL3 disease mutations analysed inhibited binding to WNK1 or CUL3. The recombinant wild-type CUL3-KLHL3 E3 ligase complex, but not a disease-causing CUL3-KLHL3[R528H] mutant complex, ubiquitylated WNK1 in vitro. Moreover, siRNA (small interfering RNA)-mediated knockdown of CUL3 increased WNK1 protein levels and kinase activity in HeLa cells. We mapped the KLHL3 interaction site in WNK1 to a non-catalytic region (residues 479-667). Interestingly, the equivalent region in WNK4 encompasses residues that are mutated in Gordon's syndrome patients. Strikingly, we found that the Gordon's disease-causing WNK4[E562K] and WNK4[Q565E] mutations, as well as the equivalent mutation in the WNK1[479-667] fragment, abolished the ability to interact with KLHL3. These results suggest that the CUL3-KLHL3 E3 ligase complex regulates blood pressure via its ability to interact with and ubiquitylate WNK isoforms. The findings of the present study also emphasize that the missense mutations in WNK4 that cause Gordon's syndrome strongly inhibit interaction with KLHL3. This could elevate blood pressure by increasing the expression of WNK4 thereby stimulating inappropriate salt retention in the kidney by promoting activation of the NCC/NKCC2 ion co-transporters. The present study reveals how mutations that disrupt the ability of an E3 ligase to interact with and ubiquitylate a critical cellular substrate such as WNK isoforms can trigger a chronic disease such as hypertension.

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Disease-causing mutations in KLHL3 impair its effect on WNK4 degradation.

Publications

Disease-causing mutations in KLHL3 impair its effect on WNK4 degradation.

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