Figure 9. PrP is not involved in the export of iron from cells.

(A) Cells expressing PrP^C, PrP^Δ51–89, PrP^Δ23–89, and PrP^102L were radiolabeled with ⁵⁹FeCl₃, washed with PBS supplemented with DFO, and chased in complete medium for 30, 60, 90, 120 min, and 16 hours. At the indicated time points equal aliquots of medium samples were quantified in a γ-counter. Estimation of released ⁵⁹Fe does not show a significant difference between the indicated cell lines at any time point. n = 6 experiments in triplicate. (B) Cell associated ⁵⁹Fe after 16 h of chase reflects the ferritin iron content of each cell line noted in Figure 1 above, though the difference between cell lines is significantly less. (C) Possible ferroxidase activity of recombinant PrP was measured using the established colorimetric method [44] with modifications. Negative controls included water and albumin supplemented with copper, and positive controls included plasma in the absence or presence of copper. Recombinant PrP does not show detectable ferroxidase activity either in the absence or presence of copper, whereas plasma shows a robust reaction under similar conditions.