Activation of protein kinase Czeta increases OAT1 (SLC22A6)- and OAT3 (SLC22A8)-mediated transport.
Organic anion transporters (OATs) play a pivotal role in the clearance of small organic anions by the kidney, yet little is known about how their activity is regulated. A yeast two-hybrid assay was used to identify putative OAT3-associated proteins in the kidney. Atypical protein kinase Czeta (PKCzeta) was shown to bind to OAT3. Binding was confirmed in immunoprecipitation assays. The OAT3/PKCzeta interaction was investigated in rodent renal cortical slices from fasted animals. Insulin, an upstream activator of PKCzeta, increased both OAT3-mediated uptake of estrone sulfate (ES) and PKCzeta activity. Both effects were abolished by a PKCzeta-specific pseudosubstrate inhibitor. Increased ES transport was not observed in renal slices from OAT3-null mice. Transport of the shared OAT1/OAT3 substrate, rho-aminohippurate, behaved similarly, except that stimulation was reduced, not abolished, in the OAT3-null mice. This suggested that OAT1 activity was also modified by PKCzeta, subsequently confirmed using an OAT1-specific substrate, adefovir. Inhibition of PKCzeta also blocked the increase in ES uptake seen in response to epidermal growth factor and to activation of protein kinase A. Thus, PKCzeta acted downstream of the epidermal growth factor to protein kinase A signaling pathway. Activation of transport was accompanied by an increase in V(max) and was blocked by microtubule disruption, indicating that activation may result from trafficking of OAT3 into the plasma membrane. These data demonstrate that PKCzeta activation up-regulates OAT1 and OAT3 function, and that protein-protein interactions play a central role controlling these two important renal drug transporters.
Barros
Scott A
SA
Laboratory of Pharmacology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709.
Srimaroeng
Chutima
C
Laboratory of Pharmacology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709.
Perry
Jennifer L
JL
Laboratory of Pharmacology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709.
Walden
Ramsey
R
Laboratory of Pharmacology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709.
Dembla-Rajpal
Neetu
N
Laboratory of Pharmacology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709.
Sweet
Douglas H
DH
Department of Pharmaceutical Sciences, Medical University of South Carolina, Charleston, South Carolina 29425.
Pritchard
John B
JB
Laboratory of Pharmacology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709. Electronic address: pritcha3@niehs.nih.gov.
D000818:Animals; D001692:Biological Transport; D004789:Enzyme Activation; D066298:In Vitro Techniques; D051379:Mice; D018345:Mice, Knockout; D027362:Organic Anion Transport Protein 1 / Q000235:genetics / Q000502:physiology*; D029362:Organic Anion Transporters, Sodium-Independent / Q000235:genetics / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000099221:Protein Kinase C zeta
D027362:Organic Anion Transport Protein 1; D029362:Organic Anion Transporters, Sodium-Independent; D011493:Protein Kinase C; D000099221:Protein Kinase C zeta; C105033:Slc22a6 protein, mouse; C421043:Slc22a6 protein, rat; C114338:organic anion transport protein 3