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Transport activity of human MRP3 expressed in Sf9 cells: comparative studies with rat MRP3
Hidetaka Akita1, Hiroshi Suzuki, Tomoko Hirohashi
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan.
Purpose:
Multidrug resistance-associated protein 3 (MRP3) was initially cloned as a hepatic transporter induced under cholestatic/ hyperbilirubinemic conditions. In the present study, transport property of human MRP3 (hMRP3) was compared with that of rat MRP3 (rMRP3).
Methods:
Adenosine 5' triphosphate (ATP)-dependent uptake of several organic anions into the membrane vesicles isolated from the Sf9 cells expressing hMRP3 and rMRP3 was measured by rapid filtration technique.
Results:
ATP-dependent uptake of glucuronide conjugates, glutathione conjugates. and [3H]methotrexate (MTX) was stimulated by infection of cDNAs for hMRP3 and rMRP3. The mean (+/- SE) Km values for the uptake of 17beta estradiol 17beta-D-glucuronide ([3H]E(2)17 betaG) by hMRP3 and rMRP3 were 42.9 +/- 4.3 microM and 33.4 +/- 2.2 microM, respectively. Although the Ki values of glucuronides on the uptake of E217betaG were similar in humans and rats, hMRP3 exhibited higher Ki values toward MTX. In addition, although glycocholate and taurolithocholate 3-sulfate (TLC-S) were transported by both hMRP3 and rMRP3, taurocholate was only transported to a significant degree by rMRP3. Moreover, the inhibitory effect of taurocholate and glycocholate on the transport of E(2)17beta3G was much more potent in rMRP3 compared to hMRP3.
Conclusion:
Collectively, the substrate specificity of hMRP3 resembles that of rMRP3 although differences were observed, particularly in bile acid transport.
Insights
Human and rat multidrug resistance-associated protein 3 (MRP3) transporters show similar substrate specificities, with notable differences in bile acid transport, impacting drug resistance and cholestasis.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Multidrug resistance-associated protein 3 (MRP3) is a hepatic transporter.
- MRP3 expression is induced under cholestatic and hyperbilirubinemic conditions.
Purpose of the Study:
- To compare the transport properties of human MRP3 (hMRP3) and rat MRP3 (rMRP3).
Main Methods:
- Adenosine 5' triphosphate (ATP)-dependent uptake of organic anions was measured.
- Membrane vesicles from Sf9 cells expressing hMRP3 and rMRP3 were used.
- Rapid filtration technique was employed for uptake measurements.
Main Results:
- Both hMRP3 and rMRP3 transported glucuronide conjugates, glutathione conjugates, and methotrexate (MTX).
- Km values for 17beta-estradiol 17beta-D-glucuronide uptake differed slightly between hMRP3 (42.9 microM) and rMRP3 (33.4 microM).
- Differences were observed in bile acid transport, with rMRP3 showing significant taurocholate transport and stronger inhibition by taurocholate and glycocholate.
Conclusions:
- The substrate specificity of hMRP3 is similar to rMRP3.
- Key differences in bile acid transport exist between human and rat MRP3.