Role of Melanotransferrin (p97) in Non-transferrin Iron Uptake by HeLa and K562 Cells

We tested whether melanotransferrin (p97), an iron-binding protein of the plasma membrane, is involved in the transport of non-transferrin iron into human HeLa and K562 cells. The expression of melanotransferrin was detected in HeLa but not in K562 cells. PI-PLC treatment dramatically decreased (to 20% of the original value) p97 expression by HeLa cells. However, the rate of iron uptake from 55Fe-ferric citrate by PI-PLC-treated HeLa cells was comparable or only slightly lower (80-100%) than the rate of iron uptake by untreated cells. PI-PLC treatment had no effect on iron uptake by K562 cells. These findings strongly support the suggestion that melanotransferrin does not play a substantial role in non-transferrin iron uptake by either HeLa or K562 cells.