Prediction of structural properties of cisplatin/protein adducts from QM/MM methods
Final Report Abstract
Cisplatin (c/s-diamminedichloridoplatinum(II)) is one of the most widely used anticancer drugs. Unfortunately, the clinical efficacy of cisplatin is severely limited by the emergence of resistance upon repeated administrations of the drug. The resistance is characterized by a decrease of drug uptake and an increase of drug efflux and sequestration, which is related, among other factors, to the altered activity of some proteins involved in the maintenance of copper homeostasis and able to bind cisplatin. These include the copper transporter Ctrl, involved in the cellular uptake of cisplatin; the copper pumps ATP7A (Menkes disease protein) and ATP7B (Wilson's disease protein) that have been reported to be responsible for sequestration and efflux of cisplatin; and the copper chaperone Atoxl, which has been found to be involved in the regulation of cisplatin uptake as well as in the delivery of cisplatin to the copper pumps ATP7A/ATP7B. A detailed knowledge of the Pt coordination chemistry to these proteins represents a key step to set up a pharmacological strategy to counter-act cisplatin resistance. Because of the lack of experimental structural information, here we have quantitatively characterized the overall structural determinants of the cisplatin binding to Ctrl, ATP7A and Atox1 in solution, using a multistep in silico-in vitro approach. In particular we modelled the platinated adducts based on the qualitative binding modes inferred from a variety of spectroscopic approaches, such as 1H, 13C, 15N and 195Pt chemical shifts, and EXAFS combined with Electro-Spray Ionization Mass Spectra, provided by our collaborators. The latter showed that 1) cisplatin binds to the eight-residue long peptide Mets7 (MTGMKGMS) that mimicks one of the extracellular methionine (Met)-rich motifs of yeast Ctrl. The complex loses all of its ligands and binds to the sulfur atoms of the three Met residues. A fourth ligand (a chloride or a water/hydroxyl oxygen) completes the coordination shell. 2) The first N-terminal domain of human ATP7A (Mnk1), differently from Mets7, reacts with cisplatin leaving unaltered the two cis ammines and donating the sulfur atoms of Cys19 and Cys22 of the highly conserved CxxC sequence. 3) Atox1, like the structurally similar Mnk1, binds to cisplatin through the Cys12 and Cy15 residues of the CxxC metal binding domain, leaving unaltered the two cis ammines; moreover, the adduct is monomeric. The in silico models have been subjected to hybrid Car-Parrinello QM/MM simulations. The comparison between experimental and theoretical spectroscopy data has proved the accuracy of the predicted models and has provided the first quantitative molecular view of the 3D structure of these adducts in solution. The project (study of structure and energetics) was then extended to the complex between chromosomal High Mobility Group Box proteins (HMGB) and Pt-DNA, which may prevent Pt-DNA to be repaired by repair enzymes. This allowed the identification of the molecular basis of the recognition process as well as of the decreased affinity of oxidized HMGB1A for platinated DNA.
Publications
- Journal of Chemical Theory and Computation, 2012, 8, 2912-2920
T. H. Nguyen, F. Arnesano, S. Scintilla, G. Rossetti, E. Ippoliti, P. Carloni and G. Natile
- Chemistry A European Journal, 2014, 20 (37) 2014, 11719–11725
V. Calandrini, T.H. Nguyen, F. Arnesano, A. Galliani, E. Ippoliti, P. Carloni, G. Natile
(See online at https://doi.org/10.1002/chem.201402834) - Dalton Transactions, 2014, 43, 12085-12094
V. Calandrini, F. Arnesano, A. Galliani, T. H. Nguyen, E. Ippoliti, P. Carloni, G. Natile
(See online at https://doi.org/10.1039/c4dt01339e) - Journal of Chemical Theory and Computation, 2014, 2014, 10 (8), pp 3578–3584
T. H. Nguyen, G. Rossetti, F. Arnesano, E. Ippoliti, G. Natile and P. Carloni
(See online at https://doi.org/10.1021/ct500402e)
