Figure 4.

Acidic conditions favor polyamine removal of PrP^Sc. (A) ScN2a cells were treated, lane 1: Control media. Lane 2: 7.5 μg/ml PEI (average-MW ≈60,000). Lane 3: PEI plus 100 μM chloroquine. Lane 4: PEI plus 30 mM NH₄Cl. Chloroquine and NH₄Cl were added 1 h before addition of PEI. Cells were harvested 16 h after addition of PEI. All samples shown were subjected to limited proteolysis to measure PrP^Sc. Apparent molecular masses based on migration of protein standards are 38, 26, and 15 kDa. (B) In vitro mixture of crude mouse brain homogenates with SuperFect under a range of pH conditions was performed as described in Methods (measured pH of each sample before neutralization denoted above the lanes). Addition of 60 μg/ml SuperFect denoted as “+SF” and control with no addition as “-SF”. All samples shown were adjusted to pH 7.5 and then subjected to limited proteolysis to measure PrP^Sc. Apparent molecular masses based on migration of protein standards are 30 and 27 kDa.