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

Exposure to hypoxia requires adaptive mechanisms for survival. During acute hypoxia, Na,K-ATPase endocytosis in alveolar epithelial cells (AEC) occurs via protein kinase C zeta (PKCζ) phosphorylation of α1- Na,K-ATPase independently of the hypoxia inducible factor (HIF). However, exaggerated Na,K-ATPase down-regulation leads to cell death. Here we report that during prolonged hypoxia plasma membrane Na,K-ATPase levels were maintained at ~50% of normoxic values due to HIF mediated regulation of HOIL-1L which targets PKCζ for degradation. Silencing HOIL-1L in the lung epithelium prevented PKCζ degradation causing Na,K-ATPase downregulation. Accordingly, HIF regulation of HOIL-1L targets the phosphorylated PKCζ for degradation and serves as an hypoxia-adaptive mechanism to stabilize the Na,K-ATPase avoiding significant lung injury. ATII mRNA profiles of 8-10 weeks old wild-type (WT) and CreSPC/HOIL-1Lfl/fl mice were generated and sequenced by NextSeq 500 High Output reagent kit (Illumina Inc).