랫트신장에서의 organic anion transporter 3와 caveolin-1 및 -2와의 공분포

초록

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/-2. The rOAT3 mRNA and protein expression were observed in the rat kidney, and the expressions of Cav-1/-2 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/-2 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 of Xenopus Cav-1/-2 were co-injected into Xenopus oocytes, the [3H] estrone sulfate uptake was significantly decreased. These findings suggest that rOAT3 and caveolin-1/-2 share a cellular expression in the plasma membrane and Cav-1/-2 up-regulates the organic anionic compound uptake via rOAT3 under normal physiological conditions.