The influence of PrP expression on cellular iron status was evaluated in M17 cells expressing endogenous PrPC or stably transfected to express 6–7 fold higher levels of PrPC or the following mutant PrP forms: 1) PrP231stop that lacks the glycosylphosphatidyl inositol (GPI) anchor and is secreted into the medium, 2) PrPΔ51–89 that lacks the copper binding octa-peptide repeat region, 3) PrPΔ23–89 that lacks the N-terminal 90 amino acids, and 4) PrP102L associated with Gerstmann-Straussler-Scheinker disease (GSS), a familial prion disorder (Fig. 1A). This evidence concerns the gene PRNP and Gerstmann-Straussler-Scheinker syndrome.