PT  - JOURNAL ARTICLE
AU  - Adam R. Blanden
AU  - Xin Yu
AU  - Aaron J. Wolfe
AU  - John A. Gilleran
AU  - David J. Augeri
AU  - Ryan S. O'Dell
AU  - Eric C. Olson
AU  - S. David Kimball
AU  - Thomas J. Emge
AU  - Liviu Movileanu
AU  - Darren R. Carpizo
AU  - Stewart N. Loh
TI  - Synthetic Metallochaperone ZMC1 Rescues Mutant p53 Conformation by Transporting Zinc into Cells as an Ionophore
AID  - 10.1124/mol.114.097550
DP  - 2015 Feb 20
TA  - Molecular Pharmacology
PG  - mol.114.097550
4099  - http://molpharm.aspetjournals.org/content/early/2015/02/20/mol.114.097550.short
4100  - http://molpharm.aspetjournals.org/content/early/2015/02/20/mol.114.097550.full
AB  - p53 is a Zn2+-dependent tumor suppressor inactivated in >50% of human cancers. The most common mutation, R175H, inactivates p53 by reducing its affinity for the essential zinc ion, leaving the mutant protein unable to bind the metal in the low [Zn2+]free environment of the cell. The exploratory cancer drug ZMC1 was previously demonstrated to reactivate this and other Zn2+-binding mutants by binding Zn2+ and buffering it to a level such that Zn2+ can repopulate the defective binding site, but how it accomplishes this in the context of living cells and organisms is unclear. Here, we demonstrate that ZMC1 increases intracellular [Zn2+]free by functioning as a zinc ionophore. ZMC1 binds Zn2+ in the extracellular environment, diffuses across the plasma membrane as the neutral complex, and releases zinc into the cell once again as the Zn2+ ion. It raises intracellular [Zn2+]free in cancer (TOV112D) and non-cancer (HEK293) cell lines to 15.8 and 18.1 nM, respectively, with half times of 2-3 min. These [Zn2+]free are predicted to result in ~90% saturation of p53-R175H, thus accounting for its observed reactivation. This mechanism is supported by the x-ray crystal structure of the [Zn(ZMC1)2] complex, which demonstrates structural and chemical features consistent with those of known metal ionophores. These findings provide a physical mechanism linking ZMC1's in vitro and in vivo activities, and define the remaining critical parameter necessary for developing synthetic metallochaperones for clinical use.