| First Author | Ito K | Year | 1998 |
| Journal | J Biol Chem | Volume | 273 |
| Issue | 3 | Pages | 1684-8 |
| PubMed ID | 9430713 | Mgi Jnum | J:45296 |
| Mgi Id | MGI:1194982 | Doi | 10.1074/jbc.273.3.1684 |
| Citation | Ito K, et al. (1998) Functional analysis of a canalicular multispecific organic anion transporter cloned from rat liver. J Biol Chem 273(3):1684-8 |
| abstractText | Transport of many organic anions across the bile canalicular membrane is mediated by the canalicular multispecific organic anion transporter (cMOAT). Previously, we cloned cDNA that may encode cMOAT from Sprague-Dawley rat liver (Ito, K., Suzuki, H., Hirohashi, T., Kume, K., Shimizu, T., and Sugiyama, Y. (1997) Am. J. Physiol. 272, G16-G22). In the present study, the function of this cloned cDNA was investigated by examining the ATP-dependent uptake of S-(2,4-dinitrophenyl)-glutathione (DNP-SG) into membrane vesicles isolated from an NIH/3T3 cell line transfected with an expression vector containing the cloned cDNA. Although the membrane vesicles from the control NIH/3T3 cells exhibited endogenous activity in transporting DNP-SG and leukotriene C4 in an ATP-dependent manner, the transfection of cMOAT cDNA resulted in a significant increase in the transport activity for these ligands. The uptake of DNP-SG into membrane vesicles was osmotically sensitive and was stimulated to some extent by other nucleotide triphos-phates (GTP, UTP, and CTP) but not by AMP or ADP. The K(m) and Vmax values for the uptake of DNP-SG by the membrane vesicles were 0.175 +/- 0.031 microM and 11.0 +/- 0.73 pmol/min/mg protein, respectively, for the transfected rat cMOAT and 0.141 +/- 0.036 microM and 3.51 +/- 0.39 pmol/min/mg protein, respectively, for the endogenous transporter expressed on control NIH/3T3 cells. These results suggest that the product of the previously cloned cDNA has cMOAT activity being able to transport organic anions in an ATP-dependent manner. Alternatively, it is possible that the cDNA product encodes an activator of endogenous transporter since the K(m) value for DNP-SG was comparable between the vector- and cMOAT-transfected cells. The transport activity found in the control NIH/3T3 cells may be ascribed to mouse cMOAT since Northern blot analysis indicated the presence of a transcript that hybridyzed to the carboxyl-terminal ATP-binding cassette sequence of the murine protein. |
