a) Lysates from untransfected SH-SY5Y cells (Un) or cells expressing PrP C were incubated with phosphopeptide for 45 min at 37 °C to measure tyrosine phosphatase activity. Data shown as mean (±s.e.m.) ( n=3). Independent Student's t-test, ** P<0.01. ( b) Tyrosine phosphatase activity was measured in whole-brain homogenate from wild-type 129/P2 (WT) or 129/P2 PrP −/− mice. Data shown as mean (±s.e.m.; n=8). Independent Student's t-test, * P<0.05. ( c) SH-SY5Y cells expressing the various disease-associated mutants of PrP C were exposed to 100 μM Zn 2+ and stained using 10 μM Zinpyr-1. Data shown as mean (±s.e.m.). Zinpyr-1 fluorescence corrected against DNA content ( n=8). Kruskal–Wallis, ** P<0.01. Insert shows expression of the various disease-associated mutants of PrP C. Lane 1, wild-type PrP C; lane 2, PG14; lane 3, A116V; lane 4, P101L; lane 5, D177N/M128; and lane 6, D117N/V128. Molecular weight marker in kDa. ( d) Co-immunoprecipitation from P101 L, D177N (M128), D177N (V128) mouse brain or SH-SY5Y cell lysates expressing PG14 or A116V using antibodies against PrP C (6H4), control rabbit anti-mouse IgG or no antibody for the bead-only control, and then probed with antibodies against PrP C (SAF32), GluA1 or GluA2 as indicated. Zinc uptake measured using Newport Green in ( e) uninfected N2a cells and ( f) scrapie-infected ScN2a cells, either not supplemented with Zn 2+ (light blue symbols) or supplemented with 32 μM Zn 2+ (dark blue symbols). Data shown as the relative Newport Green fluorescence corrected against DNA content and plotted as mean±s.e.m. ( n=3). Kruskal–Wallis, P<0.05 in the uninfected cells.