Additionally, we employed the human neuroblastoma SH-SY5Y cell line as an in vitro model of dopaminergic neurons with which to investigate the interaction between endogenous GRK2 and D2R upon the stimulation of the β-arrestin signaling pathway after pretreatment with the Src kinase inhibitor PP2 (Figure S4). This evidence concerns the gene GRK2 and neuroblastoma.