Oak J N, Lavine N, Van Tol H H
Laboratory of Molecular Neurobiology, Centre for Addiction and Mental Health, Toronto, Ontario, Canada.
Mol Pharmacol. 2001 Jul;60(1):92-103. doi: 10.1124/mol.60.1.92.
The ability of dopamine D(4) and D(2) receptors to activate extracellular signal-regulated kinases (ERKs) 1 and 2 was compared using Chinese hamster ovary (CHO-K1) cells transfected with D(4.2), D(4.4), D(4.7), and D(2L) receptors. Dopamine stimulation of D(4) or D(2L) receptors produced a transient, dose-dependent increase in ERK1/2 activity. Receptor-specific activation of the ERK mitogen-activated protein kinase (MAPK) pathway was confirmed using the D(2)-like receptor-selective agonist quinpirole, whereas the specific antagonist haloperidol blocked activation. MAPK stimulation was dependent on a pertussis-toxin-sensitive G protein (G(i/o)). trans-Activation of the platelet-derived growth factor (PDGF) receptor was an essential step in D(4) and D(2L) receptor-induced MAPK activation. PDGF receptor-selective tyrosine kinase inhibitors tyrphostin A9 and AG1295 abolished or significantly inhibited ERK1/2 activation by D(4) and D(2L) receptors. Dopamine stimulation of the D(4) receptor also produced a rapid increase in tyrosine phosphorylation of the PDGF receptor-beta. The Src-family tyrosine kinase inhibitor PP2 blocked MAPK activation by dopamine; however, this drug was also found to inhibit PDGF-BB-stimulated ERK activity and autophosphorylation of the PDGF receptor-beta. Downstream signaling pathways support the involvement of a receptor tyrosine kinase. The phosphoinositide 3-kinase inhibitors wortmannin and LY294002, protein kinase C inhibitors GF109203X and Calphostin C, dominant-negative RasN17, and the MEK inhibitor PD98059 significantly attenuated or abolished activation of MAPK by dopamine D(4) and D(2L) receptors. Our results indicate that D(4) and D(2L) receptors activate the ERK kinase cascade by first mobilizing signaling by the PDGF receptor, followed by the subsequent activation of ERK1/2 by pathways associated with this receptor tyrosine kinase.
使用转染了D(4.2)、D(4.4)、D(4.7)和D(2L)受体的中国仓鼠卵巢（CHO-K1）细胞，比较多巴胺D(4)和D(2)受体激活细胞外信号调节激酶（ERK）1和2的能力。多巴胺对D(4)或D(2L)受体的刺激导致ERK1/2活性出现短暂的、剂量依赖性增加。使用D(2)样受体选择性激动剂喹吡罗证实了ERK丝裂原活化蛋白激酶（MAPK）途径的受体特异性激活，而特异性拮抗剂氟哌啶醇则阻断了激活。MAPK刺激依赖于对百日咳毒素敏感的G蛋白（G(i/o)）。血小板衍生生长因子（PDGF）受体的反式激活是D(4)和D(2L)受体诱导的MAPK激活的关键步骤。PDGF受体选择性酪氨酸激酶抑制剂 tyrphostin A9和AG1295消除或显著抑制D(4)和D(2L)受体对ERK1/2的激活。多巴胺对D(4)受体的刺激也使PDGF受体-β的酪氨酸磷酸化迅速增加。Src家族酪氨酸激酶抑制剂PP2阻断了多巴胺对MAPK的激活；然而，还发现该药物抑制PDGF-BB刺激的ERK活性以及PDGF受体-β的自磷酸化。下游信号通路支持受体酪氨酸激酶的参与。磷脂酰肌醇3激酶抑制剂渥曼青霉素和LY294002、蛋白激酶C抑制剂GF109203X和钙泊三醇、显性负性RasN17以及MEK抑制剂PD98059显著减弱或消除了多巴胺D(4)和D(2L)受体对MAPK的激活。我们的结果表明，D(4)和D(2L)受体通过首先动员PDGF受体的信号传导，随后通过与该受体酪氨酸激酶相关的途径激活ERK1/2，从而激活ERK激酶级联反应。
