title: Downregulation of urea transporter UT-A1 activity by 14-3-3 protein.
abstract: Urea transporter (UT)-A1 in the kidney inner medulla plays a critical role in the urinary concentrating mechanism and thereby in the regulation of water balance. The 14-3-3 proteins are a family of seven isoforms. They are multifunctional regulatory proteins that mainly bind to phosphorylated serine/threonine residues in target proteins. In the present study, we found that all seven 14-3-3 isoforms were detected in the kidney inner medulla. However, only the 14-3-3 γ-isoform was specifically and highly associated with UT-A1, as demonstrated by a glutathione-S-transferase-14-3-3 pulldown assay. The cAMP/adenylyl cyclase stimulator forskolin significantly enhanced their binding. Coinjection of 14-3-3γ cRNA into oocytes resulted in a decrease of UT-A1 function. In addition, 14-3-3γ increased UT-A1 ubiquitination and protein degradation. 14-3-3γ can interact with both UT-A1 and mouse double minute 2, the E3 ubiquitin ligase for UT-A1. Thus, activation of cAMP/PKA increases 14-3-3γ interactions with UT-A1 and stimulates mouse double minute 2-mediated UT-A1 ubiquitination and degradation, thereby forming a novel regulatory mechanism of urea transport activity.
authors.affiliation: Renal Division, Department of Medicine, Emory University, School of Medicine, Atlanta, Georgia; Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia.
authors.forename: Xiuyan
authors.initials: X
authors.lastname: Feng
authors.affiliation: Department of Pharmacology, Emory University, School of Medicine, Atlanta, Georgia;
authors.forename: Zenggang
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Pharmacology, Emory University, School of Medicine, Atlanta, Georgia;
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Du
authors.affiliation: Department of Pharmacology, Emory University, School of Medicine, Atlanta, Georgia;
authors.forename: Haian
authors.initials: H
authors.lastname: Fu
authors.affiliation: Renal Division, Department of Medicine, Emory University, School of Medicine, Atlanta, Georgia; Department of Physiology, Emory University, School of Medicine, Atlanta, Georgia; and.
authors.forename: Janet D
authors.initials: JD
authors.lastname: Klein
authors.affiliation: Renal Division, Department of Medicine, Emory University, School of Medicine, Atlanta, Georgia; Department of Physiology, Emory University, School of Medicine, Atlanta, Georgia; and Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia.
authors.forename: Hui
authors.initials: H
authors.lastname: Cai
authors.affiliation: Renal Division, Department of Medicine, Emory University, School of Medicine, Atlanta, Georgia; Department of Physiology, Emory University, School of Medicine, Atlanta, Georgia; and.
authors.forename: Jeff M
authors.identifier: http://orcid.org/0000-0001-9822-0607
authors.initials: JM
authors.lastname: Sands
authors.affiliation: Renal Division, Department of Medicine, Emory University, School of Medicine, Atlanta, Georgia; Department of Physiology, Emory University, School of Medicine, Atlanta, Georgia; and gchen3@emory.edu.
authors.forename: Guangping
authors.initials: G
authors.lastname: Chen
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D007679:Kidney Medulla / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D054875:Ubiquitination; D000096982:Urea Transporters
chemical_list: D048948:14-3-3 Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D026901:Membrane Transport Proteins; D020033:Protein Isoforms; D051736:Proto-Oncogene Proteins c-mdm2; D000096982:Urea Transporters
keywords: accessory protein; protein kinase A; protein turnover; urea transporter