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

Natalia D. Magnani, Laura A. Dada, Markus A. Queisser, Patricia L. Brazee, Lynn C. Welch, Kishore R. Anekalla, Guofei Zhou, Olga Vagin, Alexander V. Misharin, G. R. Scott Budinger, Kazuhiro Iwai, Aaron J. Ciechanover*, Jacob I. Sznajder

*Corresponding author for this work

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)E10178-E10186
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number47
DOIs
StatePublished - Nov 21 2017

Keywords

  • Alveolar epithelial cells
  • HOIL-1L
  • Hypoxia
  • Na,K-ATPase
  • PKCζ

ASJC Scopus subject areas

  • General

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