INSULIN UPREGULATED ALVEOLAR EPITHELIAL NA,K-ATPASE Α1/Β1 EXPRESSION VIA NDRG2

Xiao Yu¹, Xueting Huang², Jing Liu², Qiquan Wan^{2, *}

¹Department of Nursing, the Third Xiangya Hospital of Central South University, Changsha, Hunan 410013, China - ²Department of Transplant Surgery, the Third Xiangya Hospital of Central South University, Changsha, Hunan 410013, China

Objective: The N-myc downstream-regulated gene 2 (NDRG2) is involved in stabilizing Na,K-adenosine triphosphatase (Na,K-ATPase) β1 and increasing the holoenzyme activity of Na,K-ATPase. Here, we investigated whether insulin up-regulated the expression of Na,K-ATPase α1/β1 via up-regulating NDRG2 phosphorylation, and further explored the potential molecular mechanism. 

Methods: A549 cells were treated with insulin (100 nM) for 4 h. Western blot was used to detect the expression of p-AKT, p-NDRG2 and Na,K-ATPase α1/β1subunit. PI3K, mTOR and AKT inhibitors were used to suppress the expression of p-AKT and p-NDRG2. To further ascertain the role of NDRG2, NDRG2-shRNA was applied to knockdown the expression of NDRG2, and the effects of insulin were observed. 

Results: Insulin up-regulated the expressions of p-AKT, p-NDRG2, and Na,K-ATPase α1/β1 subunits protein, which could be blocked by PI3K, mTOR and AKT inhibitors. NDRG2 shRNA decreased NDRG2 expression effectively, and significantly reversed the effect of insulin. At the same time, NDRG2 and Na,K-ATPase β1 were co-localized in the cytoplasm region, which was observed via an immunofluorescent assay. 

Conclusion: The study is the first to identify that insulin upregulated alveolar epithelial Na,K-ATPase α1/β1 expression via NDRG2 and suggest a novel role of PI3K/mTOR/ AKT/NDRG2 signaling pathway in this process, providing some clues for further experimental research and clinical therapy for ARDS