title: Serum- and glucocorticoid-inducible kinase SGK2 regulates human organic anion transporters 4 via ubiquitin ligase Nedd4-2.
abstract: Human organic anion transporter 4 (hOAT4) belongs to a family of organic anion transporters that play critical roles in the body disposition of clinically important drugs, including anti-viral therapeutics, anti-cancer drugs, antibiotics, antihypertensives, and anti-inflammatories. hOAT4 is abundantly expressed in the kidney and placenta. In the current study, we examined the regulation of hOAT4 by serum- and glucocorticoid-inducible kinase 2 (sgk2) in the kidney COS-7 cells. We showed that sgk2 stimulated hOAT4 transport activity. Such stimulation mainly resulted from an increased cell surface expression of the transporter, kinetically revealed as an increased maximal transport velocity Vmax without significant change in substrate-binding affinity Km. We further showed that regulation of hOAT4 activity by sgk2 was mediated by ubiquitin ligase Nedd4-2. Overexpression of Nedd4-2 enhanced hOAT4 ubiquitination, and inhibited hOAT4 transport activity, whereas overexpression of ubiquitin ligase-dead mutant Nedd4-2/C821A or siRNA knockdown of endogenous Nedd4-2 had opposite effects on hOAT4. Our co-immunoprecipitation experiment revealed that sgk2 weakened the association between hOAT4 and Nedd4-2. In conclusion, our study demonstrated for the first time that sgk2 stimulated hOAT4 transport activity by abrogating the inhibitory effect of Nedd4-2 on the transporter.
authors.affiliation: Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA.
authors.forename: Haoxun
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA.
authors.forename: Da
authors.initials: D
authors.lastname: Xu
authors.affiliation: Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA.
authors.forename: May Fern
authors.initials: MF
authors.lastname: Toh
authors.affiliation: Department of Medicine, Stanford University, Palo Alto, CA 94304, USA.
authors.forename: Alan C
authors.initials: AC
authors.lastname: Pao
authors.affiliation: Department of Pharmaceutics, Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA. Electronic address: gyou@rci.rutgers.edu.
authors.forename: Guofeng
authors.initials: G
authors.lastname: You
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins / Q000502:physiology*; D000075702:Nedd4 Ubiquitin Protein Ligases; D029362:Organic Anion Transporters, Sodium-Independent / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D017874:Immediate-Early Proteins; D000075702:Nedd4 Ubiquitin Protein Ligases; D029362:Organic Anion Transporters, Sodium-Independent; D017346:Protein Serine-Threonine Kinases; D044767:Ubiquitin-Protein Ligases; D000099184:Serum-Glucocorticoid Regulated Kinases; C427207:SLC22A11 protein, human; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human
keywords: Drug transport; Organic anion transporter; Regulation; Serum and glucocorticoid-inducible kinase; Ubiquitin ligase; Ubiquitination