<p><b>a.</b> Neurons with the R1628P mutation display a higher sensitivity to MPP+. Primary-cultured cortical neurons from wild-type mice were transfected with GFP-tagged wild-type (WT) or R1628P mutant LRRK2 plasmids for 24 h, and then exposed to MPP+ (30 μM) for 24 h. The dead cells were labeled with EthD-1 in red, and 200 GFP-positive neurons were counted to calculate the percentage of cell death. <b>b.</b> Cdk5 deletion protects the neurons with the R1628P mutation from MPP+ toxicity. The above procedures were performed in primary-cultured cortical neurons from the neuronal Cdk5 conditional knockout mice. Single cell survival assay was conducted as above. The results represent at least three independent experiments as the mean ± SD, **P<0.01 (ANOVA). <b>c.</b> The higher sensitivity of R1628P to MPP+ requires the phosphorylation of S1627 on LRRK2. Primary-cultured cortical neurons from wild-type mice were transfected with GFP vector, GFP-tagged wild-type (WT) LRRK2 or R1628P, S1627A:R1628P, S1627D:R1628P mutant for 24 h, and then exposed to MPP+ (30 μM) for 24 h. The dead cells were labeled with EthD-1 in red, and 200 GFP-positive neurons were counted to calculate the percentage of cell death. The results represent at least three independent experiments as the mean ± SD, *P<0.05, (ANOVA)</p
