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


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 (PKC?) phosphorylates the ?1-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 PKC? degradation. Here we report a mechanism of prosurvival adaptation of AECs to prolonged hypoxia where PKC? 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 PKC? and, consequently, lower plasma membrane Na,K-ATPase levels, which increased cell death and worsened lung injury. In AECs, expression of an ?1-Na,K-ATPase construct bearing an S18A (?1-S18A) mutation, which precludes PKC? 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 ?1-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 PKC? 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.

SUBMITTER: Magnani ND 

PROVIDER: S-EPMC5703319 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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

Magnani Natalia D ND   Dada Laura A LA   Queisser Markus A MA   Brazee Patricia L PL   Welch Lynn C LC   Anekalla Kishore R KR   Zhou Guofei G   Vagin Olga O   Misharin Alexander V AV   Budinger G R Scott GRS   Iwai Kazuhiro K   Ciechanover Aaron J AJ   Sznajder Jacob I JI  

Proceedings of the National Academy of Sciences of the United States of America 20171106 47


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 α<sub>1</sub>-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 induce  ...[more]

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