Iron at the cell surface controls both DNA synthesis and plasma membrane redox system

Abstract

Addition of the impermeable iron II chelator bathophenanthroline disulfonate (BPS) to cultured Chinese hamster lung fibroblast (CCL 39 cells) inhibits DNA synthesis but not protein synthesis or cytoplasmic alkalinization, when cell growth is initiated with growth factors such as EGF plus insulin, thrombin, or ceruloplasmin. The BPS inhibition is reversed by addition of stoichiometric ferrous iron at stoichiometric concentration. BPS does not inhibit cell growth stimulated by fetal calf serum. The effect of the BPS differs from the inhibition of growth by hydroxyurea which acts on the ribonucleotide reductase. The BPS treatment leads to release of iron from the cells as determined by BPS iron II complex formation over 90 min. Cells treated with BPS just during starvation period cannot re-initiate DNA synthesis after mitogen stimulation even if BPS is removed from the medium and cells are previously washed. BPS treatment also inhibits transplasma membrane electron which is restored by incubation of cells with 10 μM ferric ammonium citrate. Growth factor stimulation of DNA synthesis is restored by addition of 1 μM ferrous ammonium sulfate or ferric ammonium citrate, or 0.1 μM diferric transferrin. Copper, cobalt, nickel, zinc, gallium, aluminum, or apotransferrin cannot restore the activity. The BPS effect is consistent with removal of iron from a site on the cell surface which controls electron transport and DNA synthesis.