Mitogenic signaling via endogenous kappa-opioid receptors in C6 glioma cells: evidence for the involvement of protein kinase C and the mitogen-activated protein kinase signaling cascade.
As reports on G protein-coupled receptor signal transduction mechanisms continue to emphasize potential differences in signaling due to relative receptor levels and cell type specificities, the need to study endogenously expressed receptors in appropriate model systems becomes increasingly important. Here we examine signal transduction mechanisms mediated by endogenous kappa-opioid receptors in C6 glioma cells, an astrocytic model system. We find that the kappa-opioid receptor-selective agonist U69,593 stimulates phospholipase C activity, extracellular signal-regulated kinase 1/2 phosphorylation, PYK2 phosphorylation, and DNA synthesis. U69,593-stimulated extracellular signal-regulated kinase 1/2 phosphorylation is shown to be upstream of DNA synthesis as inhibition of signaling components such as pertussis toxin-sensitive G proteins, L-type Ca2+ channels, phospholipase C, intracellular Ca2+ release, protein kinase C, and mitogen-activated protein or extracellular signal-regulated kinase kinase blocks both of these downstream events. In addition, by overexpressing dominant-negative or sequestering mutants, we provide evidence that extracellular signal-regulated kinase 1/2 phosphorylation is Ras-dependent and transduced by Gbetagamma subunits. In summary, we have delineated major features of the mechanism of the mitogenic action of an agonist of the endogenous kappa-opioid receptor in C6 glioma cells.
Bohn
L M
LM
E.A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, Missouri 63104, USA.
Belcheva
M M
MM
Coscia
C J
CJ
D000818:Animals; D044482:Benzeneacetamides; D004247:DNA / Q000096:biosynthesis; D051418:Focal Adhesion Kinase 2; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D019204:GTP-Binding Proteins / Q000502:physiology; D005910:Glioma / Q000473:pathology / Q000503:physiopathology; D020962:Heterotrimeric GTP-Binding Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology; D008938:Mitosis / Q000502:physiology*; D010716:Phosphatidylinositols / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000502:physiology
D044482:Benzeneacetamides; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D010716:Phosphatidylinositols; D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D004247:DNA; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; C496054:Ptk2b protein, rat; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins; D018631:ras Proteins; C045444:U 69593