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Protein kinase C activation downregulates human organic anion transporter 1-mediated transport through carrier

Natascha A Wolff1, Karen Thies, Nicola Kuhnke

  • 1Center for Physiology and Pathophysiology, Georg August University, Göttingen, Germany. nwolff@veg-physiol.med.uni-goettengen.de

Journal of the American Society of Nephrology : JASN
|July 23, 2003
PubMed

Insights

Protein kinase C (PKC) activation downregulates organic anion transport by causing human organic anion transporter 1 (hOAT1) to move from the cell membrane. This mechanism of hOAT1 internalization is key to understanding renal transporter regulation.

Area of Science:

  • Renal physiology
  • Molecular biology
  • Cellular transport mechanisms

Background:

  • Organic anion transport is crucial for renal function, involving transporters like human organic anion transporter 1 (hOAT1).
  • Protein kinase C (PKC) activation is known to downregulate organic anion transport in renal proximal tubules.
  • The precise mechanism by which PKC mediates this downregulation remains unclear.

Purpose of the Study:

  • To elucidate the mechanism underlying PKC-induced downregulation of hOAT1-mediated organic anion transport.
  • To investigate the role of hOAT1 internalization and phosphorylation in response to PKC stimulation.

Main Methods:

  • Stimulation of PKC using sn-1,2-dioctanoylglycerol in Xenopus oocytes and HEK293 cells expressing hOAT1.
  • Measurement of p-aminohippurate transport activity.
  • Assessment of hOAT1 internalization using microscopy.
  • Evaluation of the effect of staurosporine and cytoskeletal destabilizing agents.

Main Results:

  • PKC stimulation strongly inhibited hOAT1-mediated p-aminohippurate transport and induced hOAT1 internalization.
  • Inhibition was partially reversed by staurosporine, indicating a role for PKC.
  • Downregulation was independent of canonical PKC phosphorylation sites on hOAT1 and cytoskeletal interactions.

Conclusions:

  • PKC-induced downregulation of hOAT1 is primarily mediated by carrier retrieval (internalization) from the cell membrane.
  • This process does not involve the phosphorylation of predicted classic PKC consensus sites within the hOAT1 protein.
  • The findings reveal a novel mechanism for regulating renal organic anion transport.

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