Saponin treatment extracts cytosolic SOD1 immunostaining. HEK293FT cells were transfected with vectors for WT (A, B) or A4V SOD1 (C, D) and after 24 hours treated with saponin for 30 minutes at a concentration of 0.01% in 1× PBS. The cells were then fixed and immunostained as explained in Methods. Images were captured on a standard fluorescence microscope with an immersion oil 100× objective. All bars represent 20 μm. The images shown are representative of at least 3 independent transfection experiments.