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AMP-activated kinase inhibits the epithelial Na+ channel through functional regulation of the ubiquitin ligase Nedd4-2.

We recently found that the metabolic sensor AMP-activated kinase (AMPK) inhibits the epithelial Na+ channel (ENaC) through decreased plasma membrane ENaC expression, an effect requiring the presence of a binding motif in the cytoplasmic tail of the beta-ENaC subunit for the ubiquitin ligase Nedd4-2. To further 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 co-expressing ENaC and wild-type (WT) or mutant forms of Nedd4-2. ENaC inhibition by AMPK was preserved in oocytes expressing WT Nedd4-2 but blocked in oocytes expressing either a dominant-negative (DN) or constitutively active (CA) Nedd4-2 mutant, suggesting that AMPK-dependent modulation of Nedd4-2 function is involved. Similar experiments utilizing WT or mutant forms of the serum- and glucocorticoid-regulated kinase (SGK1), modulators of protein kinase A (PKA), or extracellular-regulated kinase (ERK) did not affect ENaC inhibition by AMPK, suggesting that these pathways known to modulate the Nedd4-2-ENaC interaction are not responsible. AMPK-dependent phosphorylation of Nedd4-2 expressed in HEK-293 cells occurred both in vitro and in vivo, suggesting a potential mechanism for modulation of Nedd4-2 and thus cellular ENaC activity. Moreover, cellular AMPK activation significantly enhanced the interaction of the beta-ENaC subunit with Nedd4-2, as measured by co-immunoprecipitation assays in HEK-293 cells. In summary, these results suggest a novel mechanism for ENaC regulation in which AMPK promotes ENaC-Nedd4-2 interaction, thereby inhibiting ENaC by increasing Nedd4-2-dependent ENaC retrieval from the plasma membrane. AMPK-dependent ENaC inhibition may limit cellular Na+ loading under conditions of metabolic stress when AMPK becomes activated.

Pubmed ID: 16844684

Authors

  • Bhalla V
  • Oyster NM
  • Fitch AC
  • Wijngaarden MA
  • Neumann D
  • Schlattner U
  • Pearce D
  • Hallows KR

Journal

The Journal of biological chemistry

Publication Data

September 8, 2006

Associated Grants

  • Agency: NIDDK NIH HHS, Id: K08 DK059477
  • Agency: NIDDK NIH HHS, Id: K08 DK071648
  • Agency: NIDDK NIH HHS, Id: R01 DK056695
  • Agency: NIDDK NIH HHS, Id: R01 DK075048
  • Agency: NIDDK NIH HHS, Id: R01 DK075048-01A1
  • Agency: NIDDK NIH HHS, Id: R03 DK068390
  • Agency: NIDDK NIH HHS, Id: R03 DK068390
  • Agency: NIDDK NIH HHS, Id: R03 DK068390-01
  • Agency: NIDDK NIH HHS, Id: R03 DK068390-02

Mesh Terms

  • Animals
  • Cell Line
  • Cell Membrane
  • Cyclic AMP-Dependent Protein Kinases
  • Endosomal Sorting Complexes Required for Transport
  • Enzyme Activation
  • Epithelial Sodium Channel Blockers
  • Epithelial Sodium Channels
  • Extracellular Signal-Regulated MAP Kinases
  • Humans
  • Immediate-Early Proteins
  • Oocytes
  • Patch-Clamp Techniques
  • Phosphorylation
  • Protein Subunits
  • Protein-Serine-Threonine Kinases
  • Ubiquitin-Protein Ligases
  • Xenopus Proteins
  • Xenopus laevis