Acute Regulation of OAT3-Mediated Estrone Sulfate

Mahidol University, Krung Thep, Bangkok, Thailand
American journal of physiology. Renal physiology (Impact Factor: 3.25). 12/2004; 287(5):F1021-9. DOI: 10.1152/ajprenal.00080.2004
Source: PubMed


We investigated the regulation of organic anion transport driven by the organic anion transporter 3 (OAT3), a multispecific OAT localized at the basolateral membrane of the renal proximal tubule. PMA, a PKC activator, inhibited uptake of estrone sulfate (ES), a prototypic substrate for OAT3, in a dose- and time-dependent manner. This inhibition was reduced by 100 nM bisindoylmaleimide I (BIM), a specific PKC inhibitor. The alpha(1)-adrenergic receptor agonist phenylephrine also inhibited ES uptake, and this effect was reduced by BIM. These results suggest that PKC activation downregulates OAT3-mediated organic anion transport. In contrast, epidermal growth factor (EGF) increased ES uptake following activation of MAPK. Exposure to PGE(2) or dibutyryl (db)-cAMP also enhanced ES uptake. Stimulation produced by PGE(2) and db-cAMP was prevented by the PKA inhibitor H-89, indicating that this stimulation required PKA activation. In addition, inhibition of cyclooxygenase 1 (COX1) (but not COX2) inhibited ES uptake. Furthermore, the stimulatory effect of EGF was eliminated by inhibition of either COX1 or PKA. These data suggest that EGF stimulates ES uptake by a process in which MAPK activation results in increased PGE(2) production that, in turn, activates PKA and subsequently stimulates ES uptake. Interestingly, EGF did not induce upregulation immediately following phenylephrine-induced downregulation; and phenylephrine did not induce downregulation immediately after EGF-induced upregulation. These data are the first to show the regulatory response of organic anion transport driven by OAT3 in intact renal proximal tubules.

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Available from: Stephen H Wright, Oct 04, 2015
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    • "Also like the OAT1 results, EGF stimulates ES uptake in isolated rabbit renal proximal tubules. The signalling process for this effect is identical to that described above for OAT1 up-regulation (Soodvilai et al. 2004). In our laboratory, we have recently shown that both insulin and EGF are able to stimulate ES transport in rat renal cortical slices through the activation of PKCζ, an atypical PKC that is not activated by phorbol esters, calcium, or DOG (Hirai and Chida 2003; Jenny et al. 2005). "
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    ABSTRACT: 1. The transport of negatively charged drugs, xenobiotics, and metabolites by epithelial tissues, particularly the kidney, plays critical roles in controlling their distribution, concentration, and retention in the body. Thus, organic anion transporters (OATs) impact both their therapeutic efficacy and potential toxicity. 2. This review summarizes current knowledge of the properties and functional roles of the cloned OATs, the relationships between transporter structure and function, and those factors that determine the efficacy of transport. Such factors include plasma protein binding of substrates, genetic polymorphisms among the transporters, and regulation of transporter expression. 3. Clearly, much progress has been made in the decade since the first OAT was cloned. However, unresolved questions remain. Several of these issues--drug-drug interactions, functional characterization of newly cloned OATs, tissue differences in expression and function, and details of the nature and consequences of transporter regulation at genomic and intracellular sites--are discussed in the concluding Perspectives section.
    Xenobiotica 08/2008; 38(7-8):889-935. DOI:10.1080/00498250801927435 · 2.20 Impact Factor
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    • "In addition to PKC, PKA has been shown to play a role in modulating several membrane transport activities [32] [33]. To further determine this possible regulatory action of PKA on NaDC-3-mediated succinate uptake in Hep G2 cells, a potent activator of adenylate cyclase (AC), forskolin that has been extensively used to increase intracellular cAMP level and to elicit cAMP-dependent PKA activation [34], was tested. "
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    ABSTRACT: The rat organic anion transporter 3 (rOAT3) has recently been identified as the third isoform of the OAT family. The mechanisms that regulate rOAT3's functions remain to be elucidated. rOAT3 contributes for moving a number of negatively charged organic compounds between cells and their extracellular milieu. Caveolin (Cav) also plays a role as a membrane transporter. To address the relationship of these two proteins, we investigated the protein-protein interaction between rOAT3 and Cav-1. The rOAT3 mRNA and protein expression were observed in the rat kidney, and the expressions of Cav-1 mRNA and protein were also detected in the kidney. Confocal microscopy of the immuno-cytochemistry experiments using primary cultured renal proximal tubular cells showed that rOAT3 and Cav-1 were co-localized at the plasma membrane. This finding was confirmed by Western blot analysis using isolated caveolae-enriched membrane fractions from the rat kidney and immuno-precipitation experimentation. When rOAT3's synthesized cRNA of rOAT3 along with the antisense oligo deoxynucleotide ofXenopusCav-1 were co-injected intoXenopusoocytes, the [(3)H] estrone sulfate uptake was significantly decreased. These findings suggest that rOAT3 and caveolin-1 share a cellular expression in the plasma membrane and Cav-1 up-regulates the organic anionic compound uptake via rOAT3 under normal physiological conditions.
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