title: D1 dopamine receptor mediates dopamine-induced cytotoxicity via the ERK signal cascade.
abstract: Postsynaptic striatal neurodegeneration occurs through unknown mechanisms, but it is linked to high extracellular levels of synaptic dopamine. Dopamine-mediated cytotoxicity of striatal neurons occurs through two distinct pathways: autoxidation and the D1 dopamine receptor-linked signaling pathway. Here we investigated the mitogen-activated protein kinase (MAPK) signaling pathways activated upon the acute stimulation of D1 dopamine receptors. In SK-N-MC neuroblastoma cells, endogenously expressing D1 dopamine receptors, dopamine caused activation of phosphorylated (p-)ERK1/2 and of the stress-signaling kinases, p-JNK and p-p38 MAPK, in a time- and dose-dependent manner. Selective stimulation of D1 receptors with the agonist SKF R-38393 caused p-ERK1/2, but not p-JNK or p-p38 MAPK activation, in a manner sensitive to the receptor-selective antagonist SCH 23390, protein kinase A inhibition (KT5720), and MEK1/2 inhibition (U0126 or PD98059). Activation of ERK by D1 dopamine receptors resulted in oxidative stress and cytotoxicity. In cells transfected with a catalytically defective mutant of MEK1, the upstream ERK-specific kinase, both dopamine- and SKF R-38393-mediated cytotoxicity was markedly attenuated, confirming the participation of the ERK signaling pathway. Cell fractionation studies showed that only a small amount of p-ERK1/2 was translocated to the nucleus, with the majority retained in the cytoplasm. From coimmunoprecipitation studies, p-ERK was found to form stable heterotrimeric complexes with the D1 dopamine receptor and beta-arrestin2. In cells transfected with the dominant negative mutant of beta-arrestin2, the formation of such complexes was substantially inhibited. These data provide novel mechanistic insights into the role of ERK in the cytotoxicity mediated upon activation of the D1 dopamine receptor.
authors.affiliation: Department of Pediatrics, Georgetown University, Washington, DC 20007, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.forename: Milan
authors.initials: M
authors.lastname: Rusnak
authors.forename: Robert R
authors.initials: RR
authors.lastname: Luedtke
authors.forename: Anita
authors.initials: A
authors.lastname: Sidhu
mesh_terms: D045744:Cell Line, Tumor / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology; D004298:Dopamine / Q000633:toxicity*; D006801:Humans; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009447:Neuroblastoma; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D017447:Receptors, Dopamine D1 / Q000378:metabolism*
chemical_list: D017447:Receptors, Dopamine D1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D004298:Dopamine