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L‐WNK1 Stimulates ROMK Endocytosis By Phosphorylation‐Dependent Stabilization Of ARH
Author(s) -
Fang Liang,
Welling Paul A
Publication year - 2011
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.25.1_supplement.1041.33
Subject(s) - endocytosis , phosphorylation , chemistry , microbiology and biotechnology , immunoprecipitation , potassium channel , clathrin , signal transducing adaptor protein , signal transduction , endocrinology , biochemistry , biology , cell , gene
The clathrin adaptor protein, ARH, interacts with the ROMK renal potassium channel to mark channels for endocytosis in states of dietary potassium deprivation (Fang et al, Journal of Clinical Investigation ’09). In the present study, we explore the mechanism by which WNK1, a kinase mutated in a familial disease of hyperkalemia and hypertension, stimulates ROMK endocytosis through this pathway. In the absence of L‐WNK1, ARH is polyubiquitinated and highly liable, decaying in with a half‐life of less than 2 hours by the proteasome. Co‐expression of L‐WNK1 rendered ARH insensitive to degradation, and increased ARH abundance. As measured by immunoprecipitation with anti‐phospho antibodies, L‐WNK1 also dramatically increased ARH phosphorylation. In vitro studies with purified proteins revealed ARH is substrate of L‐WNK1 phosphorylation, but a signaling intermediate was found to be required for maximal activity. In conclusion, L‐WNK1 enhances phosphorylation and blocks proteasomal degradation of ARH, stimulating ROMK endocytosis. The signaling pathway provides a likely explanation for how ARH protein abundance is augmented in states of dietary potassium deficiency.