Magnesium depletion causes growth inhibition, reduced expression of cyclin D1, and increased expression of P27KIP1 in normal but not in transformed mammary epithelial cells

Abstract

In this study, we have evaluated the effects of extracellular magnesium restriction on the growth and cell cycle parameters of normal (HC11) and transformed (MCF-7) breast epithelial cell lines. Cells were incubated in medium with different concentrations of Mg2+ (from 0.5 to 0 mM) and the growth rates were determined by [3H]-thymidine incorporation and cell counting. The growth of the HC11 cells was drastically inhibited by Mg2+ depletion whereas the MCF-7 cells were only slightly inhibited (about 50% and 15%, respectively, after incubation in 0.05 mM Mg for 48 h). Cell cycle analyses showed a decrease in the percentage of cells in the S phase when both cell lines were incubated at low Mg2+ concentration. However, while the percentage of cells in both the G0/G1 and G2/M phases was increased in the HC11 cells, only the percentage of cells in the G2/M phase was increased in the MCF-7 cell line. Extracellular magnesium depletion was associated with increased expression of the cyclin-dependent kinase inhibitor p27Kip1 and decreased expression of cyclin D1 in the HC11 but not in the MCF-7 cells. We also demonstrated that Mg2+ depletion does not inhibit kinase activities in the normal HC11 cells and that Mg2+-restricted HC11 cells are still responsive to the epidermal growth factor (EGF)- and insulin-mediated stimulation of cell growth. These data suggest that normal but not transformed mammary epithelial cells are inhibited by extracellular Mg2+ restriction and that this effect might be mediated by changes in the levels of expression of both cyclin D1 and p27Kip1.

Cell cycle-dependent regulation of store-operated ICRAC and Mg2+-nucleotide-regulated MagNuM (TRPM7) currents

“…Specifically, the Cip/Kip family protein p27 kip1 inhibits CDKs responsible to push progression from G1 to S phase. Indeed, p27 kip1 is distinctively up-regulated in HL-60 and HC11 mammary epithelial cells grown in Mg 2+ -deficient media [42,43] supporting the notion that the availability of extracellular Mg 2+ during cell cycle progression is most important during G1.…”

“…Furthermore, reports by Hazelton et al [41] and work from Cittadini's group [42,43] emphasize the importance of extracellular Mg 2+ specifically during G1 phase progression. Based on these and our data it is tempting to speculate that MagNuM, as a Ca 2+ -and Mg 2+ -permeable influx pathway, indeed provides these ions in a homeostatic fashion throughout G1, rendering the progression through this cell cycle stage largely independent of store-operated Ca 2+ influx mediated by I CRAC .…”

Magnesium deficiency accelerates cellular senescence in cultured human fibroblasts

“…Several studies on the effects of acute and severe magnesium deficiency on cells in culture have demonstrated reduced oxidative stress defense, cell cycle progression, culture growth, and cellular viability (13,(19)(20)(21)(22)(23)(24)60), whereas the expression of protooncogenes (e.g., c-fos, c-jun) and activation of transcription factors (e.g., NF-B) were increased (25). Few studies have investigated the cellular consequences of long-term and moderate magnesium deficiency in normal human cells.…”

Magnesium in the Central Nervous System

“…Cell cycle (Maguire, 1988;Sgambato et al, 1999;Touyz et Yao, 2003), cell proliferation (Wolf et al, 2009b) and cell differentiation (Covacci et al, 1998;Wolf et al, 1998;Di Francesco et al, 1998) have all been associated with the maintenance of an optimal cellular Mg 2+ level. Under conditions in which cellular Mg 2+ accessibility is restricted or reduced, cell proliferation and cell cycle progression are markedly impaired.…”

“…A decrease in extracellular Mg 2+ content also affects cell differentiation (Covacci et al, 1998;Wolf et al, 1998;Di Francesco et al, 1998). The mechanisms by which a decrease in cellular Mg 2+ content affects these cellular processes have been attributed to defective MAPKs (Touyz and Yao, 2003) and p27 (Sgambato et al, 1999) signalling, increased oxidative stress level (Wolf et al, 2009b), and decreased MgATP levels (Di Francesco et al, 1998;Rubin, 2005). Because cellular MgATP level is at a level optimal for protein synthesis (Rubin, 2005), any alteration in this metabolic parameter will have major repercussion on the proper functioning of the cell.…”