Figure 2. GrB-induced neurotoxicity is perforin and M6P receptor independent but mediated by Gi receptors and caspase dependent pathways. A) Human neuronal cultures were treated with GrB (1 nM), human perforin (50 ng/ml) or with the combination of the two. B) Human fetal neurons were treated with GrB in Locke’s buffer for 48 h. Mannose-6-phosphate (M6P, 1 mM), pertussis toxin (PTX, 100 ng/ml), or caspase inhibitor Z-VAD-FMK (Z-VAD, 10 µM) were added 1 h before GrB treatment. Neurotoxicity was determined with trypan blue uptake assay. C) cAMP levels were measured in neuronal cultures after GrB treatment. GrB treatment results in a significant decreases (P<0.01) in cAMP concentration at 5 min. Data represent the mean ± SEM of 3 replicates from 3 experiments.