[Pt(dien)(N7-G)] transport by the mitochondrial deoxynucleotide carrier: possible role in the cytotoxicity of platinated purines

In a previous work we were able to demonstrate that platinated DNA can be formed in vitro by Taq DNA polymerase promoted incorporation of a model platinated purine, i.e. complex [Pt(dien)(N7-G)], dien = diethylenetriamine, G = 5’-dGTP. This has led to hypothesize the formation of platinated purines, for the interaction of platinum drugs with free nucleic bases, in the cytoplasmatic environment. As the cell death resulting from treatment with platinum drugs seems to be caused also by mitochondrial DNA damage we have examined if platinated purines are transported in these organelles. For this reason, we have studied their import into proteoliposomes reconstituted with the fruit fly DmTpc1p, the ortholog of the human mitochondrial deoxynucleotide carrier SLC25A19. 1H NMR and ICP Pt data have shown that the E. coli over-expressed recombinant DmTpc1p, reconstituted into phospholipid vesicles, transports [Pt(dien)(N7-G)] across liposomal membranes with high affinity. Furthermore, our results present a strong evidence for a specific import of [Pt(dien)(N7-G)] from the cytosol to respiring mitochondria isolated from rat liver.