Skip to Content
Merck
  • Insulin-like modulation of Akt/FoxO signaling by copper ions is independent of insulin receptor.

Insulin-like modulation of Akt/FoxO signaling by copper ions is independent of insulin receptor.

Archives of biochemistry and biophysics (2014-06-17)
Ingrit Hamann, Kerstin Petroll, Larson Grimm, Andrea Hartwig, Lars-Oliver Klotz
ABSTRACT

Copper ions are known to induce insulin-like effects in various cell lines, stimulating the phosphoinositide 3'-kinase (PI3K)/Akt signaling cascade and leading to the phosphorylation of downstream targets, including FoxO transcription factors. The aim of this work was to study the role of insulin- and IGF1-receptors (IR and IGF1R) in insulin-like signaling induced by copper in HepG2 human hepatoma cells. Cells were exposed to Cu(II) at various concentrations for up to 60 min. While Akt and FoxO1a/FoxO3a were strongly phosphorylated in copper- and insulin-treated cells at all time points studied, only faint tyrosine phosphorylation of IR/IGF1R was detected in cells exposed to Cu(II) by either immunoprecipitation/immunoblot or by immunoblotting using phospho-specific antibodies, whereas insulin triggered strong phosphorylation at these sites. Pharmacological inhibition of IR/IGF1R modestly attenuated Cu-induced Akt and FoxO phosphorylation, whereas no attenuation of Cu-induced Akt activation was achieved by siRNA-mediated IR depletion. Cu(II)-induced FoxO1a nuclear exclusion was only slightly impaired by pharmacological inhibition of IR/IGF1R, whereas insulin-induced effects were blunted. In contrast, genistein, a broad-spectrum tyrosine kinase inhibitor, at concentrations not affecting IR/IGF1R, attenuated Cu(II)-induced Akt phosphorylation, pointing to the requirement of tyrosine kinases other than IR/IGF1R for Cu(II)-induced signaling.

MATERIALS
Product Number
Brand
Product Description

Supelco
Genistein, analytical standard
Sigma-Aldrich
MISSION® esiRNA, targeting human INSR
Sigma-Aldrich
Genistein, synthetic, ≥98% (HPLC), powder
Sigma-Aldrich
Genistein, from Glycine max (soybean), ~98% (HPLC)
Sigma-Aldrich
MISSION® esiRNA, targeting mouse Insr
Sigma-Aldrich
DL-Tyrosine, 99%
Sigma-Aldrich
β-D-Allose, rare aldohexose sugar
Tyrosine, European Pharmacopoeia (EP) Reference Standard