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Familial Hyperkalemic Hypertension (FHHt) KLHL3 Mutations Disrupt Binding of ROMK Endocytic Regulatory Protein ARH
Author(s) -
Woodward Owen,
Kim Boyoung,
Fang Liang,
Welling Paul
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.666.8
Subject(s) - microbiology and biotechnology , intraflagellar transport , endocytic cycle , cilium , biology , pseudohypoaldosteronism , ubiquitin ligase , mutant , ubiquitin , endocytosis , chemistry , biochemistry , hyperkalemia , receptor , endocrinology , gene
Fammilial Hyperkalemic Hypertension (FHHt) is caused by mutations in CUL3 and KLHL3, components of an E3 ligase complex, and is characterized by a marked reduction in distal potassium secretion and reduction in ROMK (KCNJ1) expression, but the mechanism is not well understood. Here, we explore the possibility that CUL3/ KLHL3 regulate ROMK through direct targeting and ubiquitination of ARH, the key ROMK endocystic regulatory protein, independent of Na+ delivery to the distal nephron. We found endogenous KLHL3 can co‐immunoprecipitate ARH from mouse kidney cortex and that GST‐KLHL3 can directly bind HIS‐ARH, an interaction requiring the propeller domain of KLHL3 and the N‐terminal portion of ARH, and results in increased ARH ubiquitination and degradation. Significantly, we found FHHt mutations in KLHL3 are disrupting. Many of FHHt mutants in the KLHL3 propeller are not efficiently expressed and the loss‐of–function leads to increased ARH abundance when co‐expressed in COS7 cells. One KLHL3 mutant, S433G, had no significant expression defect but blocked the ARH interaction. We conclude that FHHt KLHL3 mutants either through defects in expression or binding result in increased ARH abundance and ROMK endocytosis, contributing to the hyperkalemia of FHHt patients.