Fig. 3

DX2 reduced neuronal apoptosis A SH-SY5Y cells were transfected with EV, AIMP2, and DX2 expression plasmids, incubated with 200 μM H₂O₂ for 24 h, and cell viability was measured with trpyphan blue-based cell counting device. B SH-SY5Y were transfected with EV, AIMP2, and DX2 expression plasmids and incubated with or without and treated with 100 μM 6-OHDA for 24 h. The cell death was analyzed by Propidium Iodide (PI) staining. C and D SH-SY5Y cells are co-transfected with EV, AIMP2, and DX2 expression plasmids, incubated with 200 μM H₂O₂ for 24 h, and cell viability was measured with cell counting device. The number shows the amounts of transfected DNA. E Representative images of the vGlut-pH response at synapses in Control, AIMP2-overexpressing, and DX2-overexpressing neurons. Neurons transfected with vG-pH or vG-pH with AIMP2 or vG-pH with DX2 were stimulated with 100 Action Potentials (APs) at 10 Hz in the presence of 6-OHDA (600 μM) for 0, 30, and 60 min. The scale bar: 5 μm. F Average traces of vGlut-pH in the response of 100 APs in Control (black), AIMP2- (red), and DX2-overexpressing neurons (green) in the time course of 6-OHDA incubation as described. The traces were normalized to the peak of trace at 0 min. G The mean values of the peak of synaptic transmission in Control (black), AIMP2- (red), and DX2-expressing (green) neurons in the time course of 6-OHDA incubation. [Control]_30 min = 0.99 ± 0.06 (n = 83 boutons), [AIMP2]_30 min = 0.68 ± 0.05 (n = 46 boutons), [DX2]_30 min = 1.47 ± 0.12 (n = 55 boutons); [Control]_60 min = 0.81 ± 0.06 (n = 83 boutons), [AIMP2]_60 min = − 0.04 ± 0.03 (n = 46 boutons), [DX2]_60 min = 1.63 ± 0.19 (n = 55 boutons) (***p < 0.001, **p < 0.01, *p < 0.05). Data were expressed as mean ± SEM. H Average traces of vG-pH endocytosis after stimulation of 100 APs in Control (left), AIMP2- (middle), and DX2-overexpressing (right) neurons in the presence of 6-OHDA for 0, 30, and 60 min. I The normalized mean values of post-stimulus endocytic time constants in Control, AIMP2-, and DX2-overexpressing neurons in the course of 6-OHDA incubation for 0, 30, and 60 min. [Con]τ_endo30min = 1.67 ± 0.14 (n = 14 boutons), [AIMP2]τ_endo30min = 2.50 ± 0.20 (n = 32 boutons), [DX2]τ_endo30min = 1.04 ± 0.15 (n = 12 boutons); [Con]τ_endo60min = 2.17 ± 0.17 (n = 14 boutons), [AIMP2]τ_endo60min = 3.22 ± 0.29 (n = 32 boutons), [DX2]τ_endo60min = 1.68 ± 0.15 (n = 12 boutons). (***p < 0.001, **p < 0.01, *p < 0.05). Data were expressed as means ± SEM. Each endocytosis was normalized to 0 min endocytosis time constant