| Research Abstract |
We investigated multiplicity of the transporters involved in vectorial transport of amino acids and drugs in epithelial cells as well as the regulatory mechanism of their membrane trafficking. The region of BCRP necessary for its apical sorting was identified. Contribution of transporters to the drug-transport was investigated in kidney and choroid plexus (OAT1 and OAT3, and PEPT2 andOAT3, respectively). Functional characterization of MRP3 and BCRP was performed, and their involvement in drug-transport in the small intestine has been suggested. Uptake (OATP2) and efflux (MRP2) transporters were co-expressed in a polarized cell line (MDCK II) as an in vitro model of hepatobiliary transport of organic anions. In vitro. transcellular transport across P-gp-expressing monolayers can be used to predict the extent to which intestinal absorption and brain uptake is affected by Pigp. Furthermore, using a double transfectant (Oatp4/Mrp2), in vitro transcellular transport can be used to predict h
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epatobiliary clearance of organic anions. Double-transfectants expressing Ntcp and Bsep was established as model of hepatobiliary transport of bile acids.
Seven amino acid transporters (Asc-2, AGT1, TAT1, LAT3, LAT4, CAT5 and B^0AT1) were newly cloned, and their functional characterization was performed. As luminal transporter for organic anions in the kidney, OATv1, URAT1 and OAT7 were cloned, and their functional characterization was performed. Mutations in B0AT1 and URAT1 cause Hartnup disorder and renal hypouricemia, respectively. Transmembrane domain of rBAT and 4F2hc is necessary for its interaction with their partner molecules. The "VVPP" sequence at C-terminus of BAT1 is essential for its membrane sorting. RACK1 was isolated by yeast-two-hybrid using the sequence as bait. RACK1 is a scaffold-protein contains multiple PDZ motifs, and we confirmed that it interacts with "VVPP" sequence of BAT1. The PDZ interacting motif at the C-terminus of URAT1 interacts with PDZK1. PDZ interactions may play an important role in clustering transporters. Less
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