Portal de Periódicos da CAPES

Loss of ATP-dependent Transport Activity in Pseudoxanthoma Elasticum-associated Mutants of Human ABCC6 (MRP6)

2002; Elsevier BV; Volume: 277; Issue: 19 Linguagem: Inglês

10.1074/jbc.m110918200

1083-351X

Attila Iliás, Zsolt Urbán, Thomas L. Seidl, Olivier Le Saux, Emese Sinkó, Charles D. Boyd, Balázs Sarkadi, András Váradi,

Amyloidosis: Diagnosis, Treatment, Outcomes

Mutations in the ABCC6 (MRP6) gene cause pseudoxanthoma elasticum (PXE), a rare heritable disorder resulting in the calcification of elastic fibers. In the present study a cDNA encoding a full-length normal variant of ABCC6 was amplified from a human kidney cDNA library, and the protein was expressed in Sf9 insect cells. In isolated membranes ATP binding as well as ATP-dependent active transport by ABCC6 was demonstrated. We found that glutathione conjugates, including leukotriene C 4 and N -ethylmaleimide S -glutathione (NEM-GS), were actively transported by human ABCC6. Organic anions (probenecid, benzbromarone, indomethacin), known to interfere with glutathione conjugate transport of human ABCC1 and ABCC2, inhibited the ABCC6-mediated NEM-GS transport in a specific manner, indicating that ABCC6 has a unique substrate specificity. We have also expressed three missense mutant forms of ABCC6, which have recently been shown to cause PXE. MgATP binding was normal in these proteins; ATP-dependent NEM-GS or leukotriene C 4 transport, however, was abolished. Our data indicate that human ABCC6 is a primary active transporter for organic anions. In the three ABCC6 mutant forms examined, the loss of transport activity suggests that these mutations result in a PXE phenotype through a direct influence on the transport activity of this ABC transporter.