Figure 4. Lysosomal impairment promotes recovery of the rate of Ca²⁺ re-uptake in the endoplasmic reticulum, without affecting SOCE protein expression.

(A and B) Measurement of the Ca²⁺ re-uptake rate in the ER after depletion with an agonist (histamine 100 μM) using the ER-targeted chameleon (D1ER) probe in HeLa cells co-transfected with pcDNA3 (control) or TFEB3xflag (TFEB) for 48 h. As previously described for the aequorin experiments, cells were pretreated with 200 μM GPN (A) for 30 min or 10 μM Vac-1 (B) for 1 h, or with DMSO as a control. In both experiments, the rate of Ca²⁺ re-uptake into the ER was significantly recovered in HeLa cells overexpressing TFEB (for GPN experiments: pcDNA3 + Vehicle n = 10, TFEB + Vehicle n = 11, pcDNA3 + GPN n = 9, TFEB + GPN n = 9; for Vac-1 experiments: pcDNA3 + Vehicle n = 10, TFEB + Vehicle n = 11, pcDNA3 + Vac-1 n = 9, TFEB + Vac-1 n = 13). Data are presented as the means ± SEM; *p < 0.05, **p < 0.01.