Impact of overexpression of metallothionein-1 on cell cycle progression and zinc toxicity

Paul J. Smith, Marie Wiltshire, Emeline Furon, John Hamilton Beattie, Rachel J. Errington

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    8 Citations (Scopus)

    Abstract

    Metallothioneins (MTs) have an important role in zinc homeostasis and may counteract the impact of oversupply. Both intracellular zinc and MT expression have been implicated in proliferation control and resistance to cellular stress, although the interdependency is unclear. The study addresses the consequences of a steady-state overexpression of MT-1 for intracellular zinc levels, cell cycle progression, and protection from zinc toxicity using a panel of cell lines with differential expression of MT-1. The panel comprised parental Chinese hamster ovary-K1 cells with low endogenous expression of MT and transfectants with enhanced expression of mouse MT-1 on an autonomously replicating expression vector with a noninducible promoter. Cell cycle progression, determined by flow cytometry and time-lapse microscopy, revealed that enhanced cytoplasmic expression of MT-1 does not impact on normal cell cycle operation, suggesting that basal levels of MT-1 expression are not limiting for background levels of oxidative stress. MT-1 overexpression correlated with a steady-state increase in cytoplasmic free Zn2+, assessed using the fluorescent zinc-sensor Zinquin, particularly at high levels of overexpression, further suggesting that zinc availability is normally not limiting for cell cycle progression. Enhanced MT-1 expression, over a 10-fold range, had a clear impact on resistance to Cd2+ and Zn2+ toxicity. In the case of Zn2+, the degree of protection afforded was less, indicating that MT-1 has a limited range and saturable capacity for effecting resistance. The results have implications for the use of cellular stress responses to exogenously supplied zinc and zinc-based systemic therapies.

    Original languageEnglish
    Pages (from-to)C1399-C1408
    Number of pages10
    JournalAmerican Journal of Physiology: Cell Physiology
    Volume295
    Issue number5
    Early online date24 Sep 2008
    DOIs
    Publication statusPublished - Nov 2008

    Keywords

    • cadmium
    • metallothioneins
    • flow cytometry
    • two-photon laser scanning microscopy
    • zinquin
    • hamster ovary cells
    • I/II knockout mice
    • DNA-damage
    • fluorescent probe
    • mammalian-cells
    • nuclear-localization
    • intracellular zinc
    • epithelial-cells
    • gene-expression
    • flow-cytometry
    • Zinquin

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