HIF and HOIL-1L-mediated PKCζ degradation stabilizes plasma membrane Na,K-ATPase to protect against hypoxia-induced lung injury

Proc Natl Acad Sci U S A. 2017 Nov 21;114(47):E10178-E10186. doi: 10.1073/pnas.1713563114. Epub 2017 Nov 6.


Organisms have evolved adaptive mechanisms in response to stress for cellular survival. During acute hypoxic stress, cells down-regulate energy-consuming enzymes such as Na,K-ATPase. Within minutes of alveolar epithelial cell (AEC) exposure to hypoxia, protein kinase C zeta (PKCζ) phosphorylates the α1-Na,K-ATPase subunit and triggers it for endocytosis, independently of the hypoxia-inducible factor (HIF). However, the Na,K-ATPase activity is essential for cell homeostasis. HIF induces the heme-oxidized IRP2 ubiquitin ligase 1L (HOIL-1L), which leads to PKCζ degradation. Here we report a mechanism of prosurvival adaptation of AECs to prolonged hypoxia where PKCζ degradation allows plasma membrane Na,K-ATPase stabilization at ∼50% of normoxic levels, preventing its excessive down-regulation and cell death. Mice lacking HOIL-1L in lung epithelial cells (CreSPC/HOIL-1Lfl/fl ) were sensitized to hypoxia because they express higher levels of PKCζ and, consequently, lower plasma membrane Na,K-ATPase levels, which increased cell death and worsened lung injury. In AECs, expression of an α1-Na,K-ATPase construct bearing an S18A (α1-S18A) mutation, which precludes PKCζ phosphorylation, stabilized the Na,K-ATPase at the plasma membrane and prevented hypoxia-induced cell death even in the absence of HOIL-1L. Adenoviral overexpression of the α1-S18A mutant Na,K-ATPase in vivo rescued the enhanced sensitivity of CreSPC/HOIL-1Lfl/fl mice to hypoxic lung injury. These data suggest that stabilization of Na,K-ATPase during severe hypoxia is a HIF-dependent process involving PKCζ degradation. Accordingly, we provide evidence of an important adaptive mechanism to severe hypoxia, whereby halting the exaggerated down-regulation of plasma membrane Na,K-ATPase prevents cell death and lung injury.

Keywords: HOIL-1L; Na,K-ATPase; PKCζ; alveolar epithelial cells; hypoxia.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Animals
  • Apoptosis
  • COS Cells
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Hypoxia
  • Cell Membrane / metabolism
  • Chlorocebus aethiops
  • Down-Regulation
  • Endocytosis
  • Epithelial Cells / pathology
  • Humans
  • Hypoxia / complications
  • Hypoxia / pathology*
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Lung Injury / etiology
  • Lung Injury / pathology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred ICR
  • Mice, Knockout
  • Mutation
  • Phosphorylation
  • Primary Cell Culture
  • Protein Kinase C / metabolism*
  • Proteolysis
  • Pulmonary Alveoli / cytology
  • Pulmonary Alveoli / pathology
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Sodium-Potassium-Exchanging ATPase / genetics
  • Sodium-Potassium-Exchanging ATPase / metabolism*


  • Carrier Proteins
  • HIF1A protein, human
  • HOIL-1L protein, mouse
  • Hif1a protein, mouse
  • Hif1a protein, rat
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • RNA, Small Interfering
  • protein kinase C zeta
  • Protein Kinase C
  • Sodium-Potassium-Exchanging ATPase