The stimulative effect of glucocorticoids on the maintenance of fluid and electrolyte balance has been known for more than two decades. Pharmacological doses of methylprednisolone stimulated Na+ absorption in small animals. However, molecular mechanisms underlying this activation remain elusive. Na+/H+ exchanger NHE3 in the brush border membrane of intestine and kidney plays a major role in transepithelial Na+ absorption. We previously demonstrated that methylprednisolone in rabbits specifically stimulated NHE3 mRNA in ileum without affecting NHE1 mRNA levels. Others have shown that glucocorticoids specifically activated NHE3 mRNA in ileum, proximal colon and renal proximal tubules. These results suggest that glucocorticoids activate NHE3 activity by gene expression of NHE3. However, we recently found using Caco-2 cells that dexamethasone activates NHE3 transport without affecting NHE3 mRNA expression. This non-transcriptional activation of NHE3 by dexamethasone was demonstrated in OK cells, suggesting that transcriptional activation of NHE3 may not be the only determining factor in glucocorticoid-stimulation of NHE3. We found that dexamethasone enhanced NHE3 activity only in the presence of a NHE3 regulatory protein, NHERF2. We identified serum- and glucocorticoids-induced protein kinase 1, SGK1, as a protein interacting with PDZ domains of NHERF2. We demonstrated that SGK1 activated NHE3 activity and expression of """"""""kinase-dead"""""""" SGK1 in OK cells markedly blocked the dexamethasone effect, demonstrating the importance of SGKI. We also showed that SGK1 directly phosphorylated NHE3 in vitro suggesting phosphorylation-dependent regulation of NHE3. In this application, we propose to investigate: (1) the roles of SGK1 and NHERF2 in activation of NHE3 by glucocorticoids; (2) molecular mechanisms underlying the activation of NHE3 by SGK1 and NHERF2 in response to glucocorticoid; and (3) the interaction between SGK1, NHERF2 and NHE3. This proposal will resolve complexity in NHE3 regulation by glucocorticoids, and enhance our understanding of protein-protein interaction in regulation of membrane transport proteins. ? ?

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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General Medicine A Subcommittee 2 (GMA)
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May, Michael K
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Emory University
Internal Medicine/Medicine
Schools of Medicine
United States
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Ritter-Makinson, Stefanie L; Paquet, Maryse; Bogenpohl, James W et al. (2017) Group II metabotropic glutamate receptor interactions with NHERF scaffold proteins: Implications for receptor localization in brain. Neuroscience 353:58-75
He, Peijian; Zhao, Luqing; No, Yi Ran et al. (2016) The NHERF1 PDZ1 domain and IRBIT interact and mediate the activation of Na+/H+ exchanger 3 by ANG II. Am J Physiol Renal Physiol 311:F343-51
No, Yi Ran; He, Peijian; Yoo, Byong Kwon et al. (2015) Regulation of NHE3 by lysophosphatidic acid is mediated by phosphorylation of NHE3 by RSK2. Am J Physiol Cell Physiol 309:C14-21
Yun, C Chris; Kumar, Ajay (2015) Diverse roles of LPA signaling in the intestinal epithelium. Exp Cell Res 333:201-7
Yeruva, Sunil; Chodisetti, Giriprakash; Luo, Min et al. (2015) Evidence for a causal link between adaptor protein PDZK1 downregulation and Na?/H? exchanger NHE3 dysfunction in human and murine colitis. Pflugers Arch 467:1795-807
He, Peijian; Zhao, Luqing; Zhu, Lixin et al. (2015) Restoration of Na+/H+ exchanger NHE3-containing macrocomplexes ameliorates diabetes-associated fluid loss. J Clin Invest 125:3519-31
No, Yi Ran; He, Peijian; Yoo, Byong Kwon et al. (2014) Unique regulation of human Na+/H+ exchanger 3 (NHE3) by Nedd4-2 ligase that differs from non-primate NHE3s. J Biol Chem 289:18360-72
Lee, Hye Jeong; Kwon, Min Hyung; Lee, Soojung et al. (2014) Systematic family-wide analysis of sodium bicarbonate cotransporter NBCn1/SLC4A7 interactions with PDZ scaffold proteins. Physiol Rep 2:
Sultan, Ayesha; Luo, Min; Yu, Qin et al. (2013) Differential association of the Na+/H+ Exchanger Regulatory Factor (NHERF) family of adaptor proteins with the raft- and the non-raft brush border membrane fractions of NHE3. Cell Physiol Biochem 32:1386-402
Hu, Zhigang; Hu, Jie; Zhang, Zhonghua et al. (2013) Regulation of expression and function of scavenger receptor class B, type I (SR-BI) by Na+/H+ exchanger regulatory factors (NHERFs). J Biol Chem 288:11416-35

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