A proteomic view of cellular responses to copper ion in two different modes

Copper is both an essential metal for life, but is also toxic at high concentrations. In mammalian cells, two copper transporters are known, one localized at the plasma membrane (CTR1) and one localized in late endosomes-lysosomes (CTR2). In order to gain insights on the possible influence of the importing pathway on cellular responses to copper, two copper challenges were compared, one with copper ion, which is likely to use preferentially CTR1, and one with a copper-polyacrylate complex, which will likely to be internalized via the endosomal pathway and therefore use preferentially CTR2. A model system consisting in the J774A1 mouse macrophage system, with a strong endosomal/lysosomal pathway, was used. In order to gain wide insights into the cellular responses to copper, a two-dimensional gel-based proteomic approach was used. The proteomic results were validated by targeted experiments, and showed differential effects of the import mode on general cellular physiology parameters such as the reduced glutathione content, the actin cytoskeleton or the mitochondrial potential, but also on more specialized macrophage functions such as phagocytosis or inflammatory responses.