Disease-associated point mutants in the central region of PrP induce spontaneous inward currents. A, whole-cell patch clamp recordings at a holding potential of −80 mV were made from HEK cells expressing WT, M128V, P101L, G113V, or G130V PrP. PrP molecules did not carry a 3F4 tag. B, quantitation of the currents recorded in panel A, plotted as the percentage of total time the cells exhibited inward current ≥450 pA (mean ± S.E., n = 5 cells). C, Western blot showing relative PrP expression levels of each construct. D, surface immunofluorescence staining of PrP on HEK cells expressing the indicated constructs. Scale bar = 50 μm.