Reducing Ca ²⁺ permeability of TPC2 corrects deviant LRRK2-mediated Ca ²⁺ entry. (a) Effect of TPC2-A1-P (30 µM) and riluzole (50 µM) on depolarization-evoked Ca²⁺ signals in the indicated cell type (mean ± SEM, n = 3–4 independent biological replicates). (b) Summary data (mean ± SEM, n = 3–4 independent biological replicates) quantifying the peak change in the Ca²⁺ signals from the indicated line and treatment. Each point represents the mean response from a cell population. *P < 0.05, **P < 0.01 (one-way ANOVA, Tukey’s test). (c) Schematic of protocol used to generate iPSC-derived midbrain DANs from 3 PD patients carrying the G2019S mutation and two healthy controls (HC). (d) Epifluorescence images of live DANs loaded with Fura-2. Scale bar: 100 µm. (e) Exemplar Ca²⁺ signals recorded from PD DANs loaded with Fura-2. Cells were stimulated with TPC2-A1-N (30 µM), TPC2-A1-P (30 µM), and a combination of the two. Gray lines are responses from individual cells. The thick lines are the population average. (f) Summary data quantifying the peak change in the Ca²⁺ signals from the indicated stimulation. Each point represents the mean response from two to three independent PD lines. (g) Exemplar Ca²⁺ signals recorded from healthy and PD DANs loaded with Fura-2. Cells were stimulated K⁺ (50 mM). PD DANs were treated with TPC2-A1-P (30 µM) or vehicle (DMSO) prior to stimulation. Gray lines are responses from individual cells. The thick lines are the population average. (h) Summary data (mean ± SEM) quantifying the peak change in the Ca²⁺ signals from the indicated line and stimulation. Each point represents the mean response from 2 independent healthy control lines and three independent PD lines. DANs, dopaminergic neurons.