Transport of platinum bonded nucleotides into proteoliposomes, mediated by Drosophila melanogaster thiamine pyrophosphate carrier protein (DmTpc1)

• DmTpc1 is involved in the uptake of free cytoplasmic Pt bonded nucleotides.
• Mitochondrial nucleotide carriers can be involved in the transport of Pt drugs.
• Mitochondrial carriers are directly involved in the transport of metalated purines.
• Sterical hindrance of platinated nucleotides can affect the membrane transport rate.
• We measured by ICP-AES the transport of metalated nucleobases in proteoliposomes.

The results of the present study suggest that DmTpc1 is actively implicated in the specific uptake of free cytoplasmic Pt bonded nucleotides, and therefore could be linked to the mechanism of action of some platinum-based antitumor drugs. Although DmTpc1 has a low affinity for model [Pt(dien)(N7-5′-dGTP)] and cis-[Pt(NH3)2(py)(N7-5′-dGTP)] compared to dATP it's well known that DNA platination level of few metal atoms per double-stranded molecule may account for the pharmacological activity of platinum based antitumor drugs. This is the first investigation where it has been demonstrated that a mitochondrial carrier is directly involved in the transport of metalated purines related with the cisplatin mechanism of action. Moreover it is shown as a lower hindrance of nucleotide bonded platinum complexes could strongly enhance mitochondrial uptake. Furthermore, a new application of ICP-AES addressed to measure the transport of metalated nucleobases, by using a recombinant protein reconstituted into liposomes, has been here, for the first time, developed and compared with a standard technique such as the liquid scintillation counting.

This is the first investigation where it has been demonstrated that a mitochondrial thiamine pyrophosphate carrier protein (DmTpc1, orthologous of the human Tpc), is directly involved in the transport of metalated purines (model [Pt(dien)(N7-5’-dGTP)], dien = diethylenetriamine, and cis-[Pt(NH3)2(py)(N7-5’-dGTP)], py = pyridine, were used) related with the cisplatin mechanism of action.Figure optionsDownload as PowerPoint slide