Cisplatin, carboplatin, and oxaliplatin are widely used anticancer drugs. Their efficacy is strongly reduced by development of cell resistance, a phenomenon not entirely understood, with contribution of drug detoxification, defective accumulation, and efflux from the cell. Down-regulation of CTR1, responsible for Cu uptake by the cell, and up-regulation of the Cu-ATPases, ATP7A and ATP7B, which accept Cu from the cytosolic chaperone Atox1 and transfer the metal ion into the secretory pathway where it is incorporated into cuproenzymes, have been associated to augmented drug resistance. To gain information on translocation of Pt drugs by human Cu-ATPases, we performed electrical measurements on COS-1 cell microsomal fraction, enriched with recombinant ATP7A, ATP7B, and selected mutants, adsorbed on a solid supported membrane (SSM). The experimental results demonstrate that Pt drugs activate Cu-ATPases and undergo ATP-dependent translocation with a mechanism identical to that of Cu. We then used NMR spectroscopy and ESI-MS to determine the binding mode of these drugs to the first N-terminal metal binding domain of ATP7A (Mnk1).

Based on UV-Vis, NMR, and EPR spectroscopies and DFT and molecular dynamics calculations, a model prebiotic [2Fe-2S] tripeptide was shown to accept and donate electrons. Duplications of the tripeptide sequence led to a protoferredoxin with increased stability. Duplications of primitive peptides may have contributed to the formation of contemporary ferredoxins.

Copper (Cu) transporters emerged as key factors at the basis of the biological response to antitumor platinum (Pt) drugs, which are among the most potent and broadly used chemotherapeutics. ATP7A and ATP7B (the Menkes and Wilson disease proteins, respectively) appear to be implicated in promoting tumor cell resistance to cisplatin. Cu-ATPases could bind the drug and, with the alleged involvement of the chaperone ATOX1, contribute to cell detoxification and survival. Here, we report the spectroscopic characterization of cisplatin binding to ATOX1 and MNK1, the first metal-binding domain of ATP7A, in the presence of the physiological reducing agent glutathione, a sulfur-containing molecule responsible for the majority of Pt detoxification in the cytosol. Under conditions mimicking the cellular environment, we show that cisplatin transfer from ATOX1 to MNK1 does not occur at a detectable rate. These results appear to contradict other literature data which, however, were obtained in the presence of exogenous reducing agents such as tris(2-carboxyethyl)phosphine (TCEP) having good coordinating ability for soft metal ions (such as Pt) and strong trans-labilizing effect. A better understanding of Pt drug processing by Cu trafficking proteins under physiological conditions may help to answer key issues, such as drug availability in tumor cells and resistance.

No abstract