Kidney Week

Abstract: SA-PO1058

The Different Modulations of NCC by ERK 1 and ERK 2 Signaling Pathway

Session Information

• Na+, K+, Cl-
  November 04, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

Category: Fluid, Electrolytes, and Acid-Base

• 703 Na+, K+, Cl- Basic

Authors

• Feng, Xiuyan, Emory University School of Medicine, Atlanta, Georgia, United States

Xiuyan Feng,

• Chen, Shan, Emory University School of Medicine, Atlanta, Georgia, United States

Shan Chen,

• Xiao, Jia, Emory University School of Medicine, Atlanta, Georgia, United States

Jia Xiao,

• Chen, Xinxin, Emory University School of Medicine, Atlanta, Georgia, United States

Xinxin Chen,

• Cai, Hui, Emory University School of Medicine, Atlanta, Georgia, United States

Hui Cai,

Background

In our previous studies we found that ERK 1/2 knock-down increased NCC expression in cell experiments. Staub group previously reported that total NCC abundance was siginificantly decreased in the nephron-specific Nedd4L knockout (KO) mice. ERK1 and ERK2 are presumed to be functionally redundant given their 84% sequence homology, shared upstream activators, and similar substrate specificity. Our preliminary data indicated that ERK 1 and ERK 2 have different roles in NCC modulation in vivo. However, the relationship between ERK 1/2 and Nedd4-2 as well as the effects of unique ERK 1 and ERK 2 on NCC remain not entirely clear. In this study, we investigated the different roles of ERK 1 and ERK 2 in NCC modulation in cells and in both ERK1 KO mice and Pax8+cre+ERK2^flox/flox mice.

Methods

Cell culture, western blot analysis, siRNA knock-down experiments, ERK 1 global KO and Pax8+cre+ERK2^flox/flox mice were used in this study.

Results

Firstly, we knocked down ERK1 or ERK2 expression separately in Cos-7 cells cotransfected with NCC. We found that ERK1 knock down increased NCC expression while ERK 2 knock down decreased NCC expression. To further explored the different roles of ERK 1 and ERK 2 on NCC. We generated the inducible nephron-specific ERK 2 KO (ERK 2 KO) mice by feeding Pax8+cre+ERK2^flox/flox mice with doxycycline 1g/L for 14 days. Western blot results showed that the NCC expression in ERK1 global KO mice increased by 27.7%, whereas in ERK 2 KO mice NCC decreased to 62.1% compared to those in WT mice. We also found that total Nedd4-2, phospho-S448-Nedd4-2 and phospho-S328-Nedd4-2 were decreased to 50.4%, 52.5% and 76.8% respectively in ERK1 KO mice, while they were increased by 1.46, 1.5 and 3.11 folds in ERK 2 KO mice. We further tested the effects of low salt diet (LSD) on NCC abundance in ERK 2 KO mice fed with LSD for 14 days. We found that NCC abundance decreased to 68.8% while 14-3-3 gamma expression increased by 2.07 folds and total NEDD4-2 increased by 2.47 folds compared with that in WT mice.

Conclusion

All data suggested that ERK 1 and ERK 2 signalings have different role in regulationg NCC likely through modulating Nedd4-2 and 14-3-3 gamma. However, the interactions among MAPK- ERK1/2 signaling pathway, Nedd4-2 and 14-3-3 gamma need to be further investigated in the future studies.

Funding

• Veterans Affairs Support