The CXXC motifs in the metal binding domains are required for ATP7B to mediate resistance to cisplatin

The copper (Cu) exporter ATP7B mediates resistance to cisplatin (cDDP) but details of the mechanism are unknown. We explored the role of the CXXC motifs in the metal binding domains (MBDs) of ATP7B by investigating binding of cDDP to the sixth metal binding domain (MBD6) or a variant in which the CXXC motif was converted to SXXS. Platinum measurement showed that cDDP bound to wild type MBD6 but not to the SXXS variant. Wild type ATP7B rendered ovarian 2008 cells resistant to cDDP. In 2008 and in HEK293T cells, wild type ATP7B trafficked from TGN to peripheral locations in response to Cu or cDDP. A variant in which the CXXC motifs in all 6 MBDs were converted to SXXS localized correctly to the TGN but failed to traffic when exposed to either Cu or cDDP. Deletion of either the first 5 MBDs or all 6 MBDs resulted in failure to localize to the TGN. Neither the SXXS variant nor the deletion variant was able to mediate resistance to cDDP. We conclude that cDDP binds to the CXXC motifs of ATP7B and that this interaction is essential to the trafficking of ATP7B and to its ability to mediate resistance to cDDP.

The CXXC motif in the sixth metal binding domain of the Cu exporter ATP7B reacts with cisplatin; the ability of ATP7B to mediate resistance to cisplatin, and to traffic from the trans-Golgi to peripheral vesicles in response to cisplatin exposure, requires the CXXC motifs in the six metal binding domains.Figure optionsDownload as PowerPoint slideHighlights
► Cisplatin binds to the sixth metal binding domain of ATP7B.
► Binding occurs via the CXXC motif.
► CXXC motifs are required for ATP7B to mediate cisplatin resistance.
► CXXC are required for the trafficking of ATP7B in response to cisplatin.