RT Journal Article
SR Electronic
T1 Synthetic Metallochaperone ZMC1 Rescues Mutant p53 Conformation by Transporting Zinc into Cells as an Ionophore
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 825
OP 831
DO 10.1124/mol.114.097550
VO 87
IS 5
A1 Blanden, Adam R.
A1 Yu, Xin
A1 Wolfe, Aaron J.
A1 Gilleran, John A.
A1 Augeri, David J.
A1 O’Dell, Ryan S.
A1 Olson, Eric C.
A1 Kimball, S. David
A1 Emge, Thomas J.
A1 Movileanu, Liviu
A1 Carpizo, Darren R.
A1 Loh, Stewart N.
YR 2015
UL http://molpharm.aspetjournals.org/content/87/5/825.abstract
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 zinc metallochaperone-1 (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. In this study, we demonstrated that ZMC1 increases intracellular [Zn2+]free by functioning as a Zn2+ ionophore, binding Zn2+ in the extracellular environment, diffusing across the plasma membrane, and releasing it intracellularly. It raises intracellular [Zn2+]free in cancer (TOV112D) and noncancer human embryonic kidney cell line 293 to 15.8 and 18.1 nM, respectively, with half-times of 2–3 minutes. These [Zn2+]free levels 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 zinc metallochaperone-1 in both in vitro and in vivo activities and define the remaining critical parameter necessary for developing synthetic metallochaperones for clinical use.