Premium
Inhibition of the Epithelial Sodium Channel by AMP‐Activated Kinase Involves Modulation of Nedd4‐2 Activity
Author(s) -
Hallows Kenneth R,
Oyster Nicholas M,
Bhalla Vivek,
Pearce David
Publication year - 2006
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.20.4.a795-c
Subject(s) - epithelial sodium channel , sgk1 , nedd4 , ampk , chemistry , microbiology and biotechnology , protein kinase a , phosphorylation , ubiquitin ligase , biology , ubiquitin , biochemistry , sodium , gene , organic chemistry
The metabolic sensor AMP‐activated kinase (AMPK) inhibits the epithelial Na + channel (ENaC), suggesting a potential mechanism for the inhibition of cellular Na + influx under conditions of metabolic stress. AMPK inhibits ENaC by decreasing its plasma membrane expression, and the inhibition requires an intact PY motif in the ENaC tail, suggesting that the ubiquitin ligase Nedd4‐2 is involved in the regulation. To more directly examine the role of Nedd4‐2 in the regulation of ENaC by AMPK, we studied the effects of AMPK activation on ENaC currents in Xenopus oocytes expressing ENaC along with wild‐type or mutant forms of Nedd4‐2 or the serum and glucocorticoid‐regulated kinase 1 (SGK1). Co‐expression of a dominant‐negative (DN) Nedd4‐2 mutant (C938S) greatly enhanced ENaC currents, while co‐expression of either wild‐type (WT) Nedd4‐2 or a constitutively active (CA) Nedd4‐2 mutant (S338A, S444A) greatly reduced ENaC currents. ENaC inhibition by the AMPK activator ZMP was preserved in oocytes expressing WT Nedd4‐2 but blocked in oocytes expressing either of the two Nedd4‐2 mutants, suggesting that AMPK‐dependent modulation of Nedd4‐2 is required for ENaC inhibition. Co‐expression of WT, DN, or CA mutants of SGK1 modulated ENaC currents, but AMPK‐dependent ENaC inhibition was preserved in each case, suggesting that AMPK inhibition does not occur through modulation of SGK1 activity. AMPK directly phosphorylated Nedd4‐2 in vitro , suggesting a possible mechanism for modulation of Nedd4‐2 and thus ENaC activity in cells. Further studies to define the site(s) and functional consequences of AMPK‐dependent phosphorylation of Nedd4‐2 are underway.