Glutaredoxin 1 is a major player in copper metabolism in neuroblastoma cells

BACKGROUND: Glutaredoxin 1 (Grx1), a small protein belonging to the thioredoxin family, is involved in redox-regulation since it catalyzes the reduction of protein disulfides and that of mixed disulfides. It was reported to modulate active copper extrusion from cells, by affecting the function of the pumps ATP7A and B. These are components of the network of protein chaperones involved in the control of the homeostasis of copper, an essential, though harmful, metal. However, the effect of Grx1 on copper levels, copper chaperones and copper-elicited cell toxicity was never investigated. METHODS: In order to investigate the effect of Grx1 on copper metabolism, we constitutively overexpressed Grx1 in human neuroblastoma SH-SY5Y cells (SH-Grx1 cells) and assessed a number of copper-related parameters. RESULTS: SH-Grx1 cells show a basal intracellular copper level higher than control cells, accumulate more copper upon CuSO4 treatment, but are more resistant to copper-induced toxicity. Grx1 shows copper-binding properties and copper overload produces a decrease of Grx1 enzyme activity in SH-Grx1 cells. Finally, Grx1 overexpression decreases copper accumulation in mitochondria upon copper overload and modulates the expression of copper transporter 1 (Ctr1). CONCLUSION: Altogether, these data demonstrate that Grx1 is a major player in copper metabolism in neuronal cells.