Low Intracellular Zinc Impairs the Translocation of Activated NF-κB to the Nuclei in Human Neuroblastoma IMR-32 Cells

Abstract

In the current work, we studied how variations in extracellular zinc concentrations modulate different steps involved in nuclear factor B (NF-B) activation in human neuroblastoma IMR-32 cells. Cells were incubated in media containing varying concentrations of zinc (1.5, 5, 15, and 50 M). Within 3 h, the intracellular zinc content was lower in cells exposed to 1.5 and 5 M, compared with the other groups. Low intracellular zinc concentrations were associated with the activation of NF-B, based on high levels of IB␣ phosphorylation, low IB␣ concentrations, and high NF-B binding activity in total cell fractions. However, the active dimer accumulated in the cytosol, as shown by a low ratio of nuclear/cytosolic NF-B binding activity. This altered nuclear translocation was accompanied by a decreased transactivation of an endogenous NF-B-driven gene (ikba) and of a reporter gene (pNF-B-luc). In cells with low intracellular zinc concentrations, a low rate of in vitro tubulin polymerization was measured compared with the other groups. We conclude that low intracellular zinc concentrations induce tubulin depolymerization, which may be one signal for NF-B activation. However, NF-B nuclear translocation is impaired, which inhibits the transactivation of NF-B-driven genes. This could affect cell survival, and be an important factor in certain zinc deficiency-associated pathologies.

Low intracellular zinc induces oxidative DNA damage, disrupts p53, NFκB, and AP1 DNA binding, and affects DNA repair in a rat glioma cell line

“…These transcription factors play important roles in controlling oxidative stress response and cell proliferation (50,51), and their inactivation of binding impairs the ability of the cell to respond to oxidative stress and damage. Mackenzie et al (52) have also demonstrated recently alterations in NF B activation with low intracellular zinc in human neuroblastoma IMR32 cells. However, the precise mechanisms by which zinc affects transcription factor binding remain unclear.…”

Zinc and the cytoskeleton in the neuronal modulation of transcription factor NFAT

“…Nuclear and cytosolic fractions were isolated as previously described (Dignam et al, 1983;Osborn et al, 1989), with minor modifications (Mackenzie et al, 2002). Total cell fractions were prepared as previously described (Muller et al, 1997), with slight modifications (Mackenzie et al, 2006b).…”

“…We recently reported that a decrease in cellular zinc inhibits NF-kB-dependent gene expression. NF-kB nuclear translocation was impaired in association with a low rate of microtubule assembly in the zinc deficient cells (Mackenzie et al, 2002(Mackenzie et al, , 2006a. The activation of both, NF-kB and NFAT, involves the exposure of a NLS that targets the transcription factor to the nuclei.…”

Aldosterone Activates Transcription Factor Nrf2 in Kidney Cells both In Vitro and In Vivo

“…Nuclear fractions were isolated as previously described (35). For the EMSA, the oligonucleotides containing the consensus sequence of Nrf2 or SP-1 were end labeled with [c-32 P]-ATP using T4 polynucleotide kinase and purified using Chroma Spin-10 columns.…”