Zinc inhibits the nuclear translocation of the tumor suppressor protein p53 and protects cultured human neurons from copper-induced neurotoxicity

Abstract

High concentrations of the trace metal zinc (Zn) have previously been shown to provide transient protection of cells from apoptotic death. The molecular mechanisms responsible for this protection are not known. Thus, this work explored the ability of Zn to protect human neurons in culture (NT2-N) from Cu-mediated death and tested the hypotheses that the tumor-suppressor protein p53 plays a role in Cu-induced neuronal death and is part of the mechanism of Zn protection. Copper toxicity (100 µM) resulted in significant apoptotic neuronal death by 12 h. Addition of 100 µM Zn to Cu-treated cells increased neuronal death. However, the addition of 700 µM Zn to Cu-treated cells resulted in neuronal viability that was not different from untreated controls through 24 h. p53 mRNA abundance, while increased by the addition of Cu and 100 µM Zn, was decreased to 50% of control with the addition of 500 µM Zn in Cu-treated cells, and to 10% of control with 700 µM Zn. Consistent with its role as a transcription factor, both Western analysis and immunocytochemistry showed significant increases in nuclear p53 protein levels in Cu toxicity. The role of p53 in Cu-mediated apoptosis was further confirmed by elimination of apoptosis in Cu-treated cells that had been transfected with a dominant-negative p53 construct to prevent p53 expression. Furthermore, the addition of 500–700 µM Zn prevented the movement of p53 into the nucleus suggesting that Zn not only protects neurons from Cu toxicity by regulating p53 mRNA abundance but also by preventing the translocation of p53 to the nucleus.