Nakagawa Rinako, Hara Yoshikazu, Arakawa Hiroharu, Nishimura Susumu, Komatani Hideya
Banyu Tsukuba Research Institute in Collaboration with Merck Research Laboratories, 3 Okubo, Ibaraki 300-2611, Japan.
Biochem Biophys Res Commun. 2002 Dec 13;299(4):669-75. doi: 10.1016/s0006-291x(02)02712-2.
The ABC half-transporter, ABCG2, is known to confer resistance to chemotherapeutic agents including indolocarbazole derivatives. MCF7 cells were introduced by either wild type ABCG2 (ABCG2-482R) or mutant ABCG2 (-482T), whose amino acid at position 482 is substituted to threonine from arginine, and their cross-resistance pattern was analyzed. Although this amino acid substitution seems to affect cross-resistance patterns, both 482T- and 482R-transfectants showed strong resistance to indolocarbazoles, confirming that ABCG2 confers resistance to them. For further characterization of ABCG2-mediated transport, we investigated indolocarbazole compound A (Fig. 1) excretion in cell-free system. Compound A was actively transported in membrane vesicles prepared from one of the 482T- transfectants and its uptake was supported by hydrolysis of various nucleoside triphosphates. This transport was inhibited completely by the other indolocarbazole compound, but not by mitoxantrone, implying that the binding site of mitoxantrone or the transport mechanisms for mitoxantrone is different from those of indolocarbazoles. These results showed that ABCG2 confers resistance to indolocarbazoles by transporting them in an energy-dependent manner.
ABC半转运蛋白ABCG2已知可赋予对包括吲哚咔唑衍生物在内的化疗药物的抗性。通过野生型ABCG2（ABCG2 - 482R）或突变型ABCG2（-482T）转染MCF7细胞，其中482位的氨基酸由精氨酸替换为苏氨酸，并分析它们的交叉抗性模式。尽管这种氨基酸替换似乎影响交叉抗性模式，但482T和482R转染子均对吲哚咔唑表现出强抗性，证实ABCG2赋予对它们的抗性。为了进一步表征ABCG2介导的转运，我们在无细胞系统中研究了吲哚咔唑化合物A（图1）的排泄。化合物A在从一种482T转染子制备的膜囊泡中被主动转运，并且其摄取受到各种核苷三磷酸水解的支持。这种转运被另一种吲哚咔唑化合物完全抑制，但不受米托蒽醌抑制，这意味着米托蒽醌的结合位点或米托蒽醌的转运机制与吲哚咔唑不同。这些结果表明，ABCG2通过以能量依赖的方式转运吲哚咔唑来赋予对其的抗性。
