Serum- and glucocorticoid-inducible kinase SGK2 regulates human organic anion transporters 4 via ubiquitin ligase Nedd4-2

Biochem Pharmacol. 2016 Feb 15:102:120-129. doi: 10.1016/j.bcp.2015.11.024. Epub 2015 Dec 29.

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.

Keywords: Drug transport; Organic anion transporter; Regulation; Serum and glucocorticoid-inducible kinase; Ubiquitin ligase; Ubiquitination.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Endosomal Sorting Complexes Required for Transport / metabolism*
  • Humans
  • Immediate-Early Proteins / physiology*
  • Nedd4 Ubiquitin Protein Ligases
  • Organic Anion Transporters, Sodium-Independent / metabolism*
  • Protein Serine-Threonine Kinases / physiology*
  • Protein Transport / physiology
  • Ubiquitin-Protein Ligases / metabolism*

Substances

  • Endosomal Sorting Complexes Required for Transport
  • Immediate-Early Proteins
  • Organic Anion Transporters, Sodium-Independent
  • SLC22A11 protein, human
  • Nedd4 Ubiquitin Protein Ligases
  • Nedd4 protein, human
  • Nedd4L protein, human
  • Ubiquitin-Protein Ligases
  • Protein Serine-Threonine Kinases
  • serum-glucocorticoid regulated kinase