ABCC4 p.Lys1081Asn
| Predicted by SNAP2: | A: D (91%), C: D (91%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (91%), I: D (91%), L: D (91%), M: D (91%), N: D (91%), P: D (95%), Q: D (91%), R: D (85%), S: D (91%), T: D (91%), V: D (91%), W: D (95%), Y: D (95%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: D, L: D, M: D, N: D, P: D, Q: D, R: N, S: D, T: D, V: D, W: D, Y: D, |
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[hide] 6-mercaptopurine and 9-(2-phosphonyl-methoxyethyl)... Hum Mutat. 2008 May;29(5):659-69. Janke D, Mehralivand S, Strand D, Godtel-Armbrust U, Habermeier A, Gradhand U, Fischer C, Toliat MR, Fritz P, Zanger UM, Schwab M, Fromm MF, Nurnberg P, Wojnowski L, Closs EI, Lang T
6-mercaptopurine and 9-(2-phosphonyl-methoxyethyl) adenine (PMEA) transport altered by two missense mutations in the drug transporter gene ABCC4.
Hum Mutat. 2008 May;29(5):659-69., [PMID:18300232]
Abstract [show]
Multiple drug resistance protein 4 (MRP4, ABCC4) belongs to the C subfamily of the ATP-binding cassette (ABC) transporter superfamily and participates in the transport of diverse antiviral and chemotherapeutic agents such as 6-mercaptopurine (6-MP) and 9-(2-phosphonyl methoxyethyl) adenine (PMEA). We have undertaken a comprehensive functional characterization of protein variants of MRP4 found in Caucasians and other ethnicities. A total of 11 MRP4 missense genetic variants (nonsynonymous SNPs), fused to green fluorescent protein (GFP), were examined in Xenopus laevis oocytes for their effect on expression, localization, and function of the transporter. Radiolabeled 6-MP and PMEA were chosen as transport substrates. All MRP4 protein variants were found to be expressed predominantly in the oocyte membrane. A total of four variants (Y556C, E757 K, V776I, and T1142 M) exhibited a 20% to 40% reduced expression level compared to the wild type. Efflux studies showed that 6-MP is transported by MRP4 in unmodified form. Compared to wild-type MRP4, the transmembrane variant V776I, revealed a significant lower activity in 6-MP transport, while the amino acid exchange Y556C in the Walker(B) motif displayed significantly higher transport of PMEA. The transport properties of the other variants were comparable to wild-type MRP4. Our study shows that Xenopus oocytes are well suited to characterize MRP4 and its protein variants. Carriers of the rare MRP4 variants Y556C and V776I may have altered disposition of MRP4 substrates.
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No. Sentence Comment
165 Moreover, a mutation was introduced into the critical WalkerA motif of MRP4 ATP-binding site 2 (K1081N) to provide an additional, negative control for the efflux experiments.
X
ABCC4 p.Lys1081Asn 18300232:165:96
status: NEW167 In fact, substrate efflux in the absence or presence (Supplementary Fig. S4) of extracellular added unlabeled 500 mM 6-MP or 5 mM PMEA from oocytes expressing the MRP4(K1081N) mutant was not different from efflux of control oocytes, verifying that a functional WalkerA motif is necessary for MRP4, and providing a nonfunctional MRP4 control.
X
ABCC4 p.Lys1081Asn 18300232:167:168
status: NEW183 All other variants including MRP4 (K1081N) had a fluorescence intensity similar to wild-type MRP4.
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ABCC4 p.Lys1081Asn 18300232:183:35
status: NEW