Genetic p23 knockdown in DAergic N27 cells protects against MPP+-mediated neurotoxicity. Cell viability in p23 versus scrambled siRNA or untransfected controls in MPP+-treated (dark grey bars; 500 μM, 24 hrs) versus untreated cells (light grey bars);* p<0.05 versus untreated. B. Representative western blot analyses of HSP70 in N27 cells transfected with p23 siRNA (80 nM), 24 hrs. Top panel, HSP70; middle panel, p23; lower panel, actin as a loading control. C, Densitometric quantitation of HSP70 and p23 steady-state protein levels normalized to actin.