title: Dopamine D(2) receptor activation causes mitogenesis via p44/42 mitogen-activated protein kinase in opossum kidney cells.
abstract: This study was conducted to determine the expression of dopamine D(2)-like receptors in opossum kidney (OK) cells and to examine the potential role of these receptors in mitogenesis. First, the presence of D(2)-like receptor binding sites in OK cell membranes was demonstrated by radioligand binding, using [(3)H]spiperone. The D(2)-like receptor subtypes expressed in OK cells were subsequently demonstrated, by Western blotting, to be D(2), D(3), and D(4) receptors. OK cells were stimulated with bromocriptine, (+/-)-2-(N-phenylethyl-N-propyl)amino-5-hydroxytetralin hydrochloride, (R)-(+)-2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide, or PD 168,077 maleate (D(2)-like, D(2), D(3), and D(4) receptor agonists, respectively), and mitogenesis was measured as a function of [(3)H]thymidine incorporation. It was observed that, whereas bromocriptine and (+/-)-2-(N-phenylethyl-N-propyl)amino-5-hydroxytetralin hydrochloride produced increases in [(3)H]thymidine incorporation, (R)-(+)-2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide and PD 168,077 maleate did not produce such an effect, indicating the involvement of D(2) receptors in the mitogenic response. Pertussis toxin and PD 98059 blocked the mitogenesis caused by bromocriptine, suggesting a role for G(i) or G(o) proteins and p44/42 mitogen-activated protein kinase (MAPK), respectively. Furthermore, it was observed that bromocriptine produced a time-dependent increase in the phosphorylation (activation) of p44/42 MAPK, which was blocked by domperidone, pertussis toxin, or PD 98059. Therefore, this study demonstrates that, although OK cells express D(2), D(3), and D(4) receptors, activation of only D(2) receptors causes mitogenesis via phosphorylation of p44/42 MAPK. Furthermore, the cellular mechanisms contributing to D(2) receptor-mediated phosphorylation of p44/42 MAPK seem to involve the tyrosine kinase, phosphatidylinositol-3-kinase, and protein kinase C pathways. It is likely that bromocriptine and other preferential D(2) receptor agonists might provide protection against ischemic reperfusion injury in renal proximal tubular cells, by increasing the survival rates for ischemic cells.
authors.affiliation: Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas.
authors.forename: Vihang A
authors.initials: VA
authors.lastname: Narkar
authors.affiliation: Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas.
authors.forename: Tahir
authors.initials: T
authors.lastname: Hussain
authors.affiliation: Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas.
authors.forename: Carlos
authors.initials: C
authors.lastname: Pedemonte
authors.affiliation: Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas.
authors.forename: Mustafa F
authors.initials: MF
authors.lastname: Lokhandwala
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D007668:Kidney / Q000166:cytology / Q000502:physiology*; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D008938:Mitosis / Q000502:physiology*; D009893:Opossums; D010766:Phosphorylation / Q000187:drug effects; D020033:Protein Isoforms / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D013936:Thymidine / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D020033:Protein Isoforms; D017448:Receptors, Dopamine D2; D000242:Cyclic AMP; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases; D019204:GTP-Binding Proteins; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D013936:Thymidine