Synthetic metallochaperone ZMC1 rescues mutant p53 conformation by transporting zinc into cells as an ionophore

Adam R. Blanden, Xin Yu, Aaron J. Wolfe, John A. Gilleran, David J. Augeri, Ryan S. O'Dell, Eric C. Olson, S. David Kimball, Thomas J. Emge, Liviu Movileanu, Darren R. Carpizo, Stewart N. Loh

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34 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)825-831
Number of pages7
JournalMolecular Pharmacology
Volume87
Issue number5
DOIs
StatePublished - May 1 2015

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ASJC Scopus subject areas

  • Pharmacology
  • Molecular Medicine

Cite this

Blanden, A. R., Yu, X., Wolfe, A. J., Gilleran, J. A., Augeri, D. J., O'Dell, R. S., Olson, E. C., Kimball, S. D., Emge, T. J., Movileanu, L., Carpizo, D. R., & Loh, S. N. (2015). Synthetic metallochaperone ZMC1 rescues mutant p53 conformation by transporting zinc into cells as an ionophore. Molecular Pharmacology, 87(5), 825-831. https://doi.org/10.1124/mol.114.097550