Modulation of lysophosphatidic acid-induced Cl- currents by protein kinases A and C in the Xenopus oocyte.
The roles of protein kinase C (PKC) and protein kinase A (PKA) in the regulation of lysophosphatidic acid (LPA)-induced Cl- currents in Xenopus oocytes were examined. PKC activation by phorbol 12-myristate 13-acetate (PMA) treatment completely blocked LPA-induced Cl- currents by inhibiting inositol 1,4,5-trisphosphate (IP3) elevation. This inhibitory effect of PMA on the LPA response was blocked by pretreatment of oocytes with staurosporine and 3-[N-(dimethylamino)propyl-3-indiolyll-4-[3-indolyl]maleimide (GF109203X), PKC inhibitors. In addition, treatment of oocytes with GF109203X enhanced the LPA response by increasing IP3 production. Elevation of the intracellular adenosine 3',5'-cyclic monophosphate (cAMP) concentration by treating oocytes with either forskolin (FK) plus isobutylmethylxanthine (IBMX) or 2'-O-dibutyryl-cAMP (dB-cAMP) reduced LPA-induced Cl- currents. The effect of activation of the cAMP pathway appears to be mediated by PKA, since treatment of oocytes with FK plus IBMX or dB-cAMP enhanced PKA activity. Furthermore, the inhibitory effect of dB-cAMP on the LPA response was blocked by treatment of oocytes with N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulframide-2 HCl (H-89), a selective inhibitor of PKA. Both FK plus IBMX and dB-cAMP treatment reduced IP3 generation in response to LPA stimulation. Inhibition of PKA activity with H-89 or Rp-cyclic 3',5'-hydrogen phosphorothioate adenosine triethylammonium had no effect on LPA-induced Cl- currents. Finally, inhibition of the LPA response by activation of PKA was independent of extracellular Ca2+. These results demonstrate that both PKC and PKA play active roles in modulating the LPA-induced signaling pathway.
Kim
M J
MJ
Department of Life Science, Pohang University of Science and Technology, Kyungbuk, South Korea.
Lee
Y S
YS
Han
J K
JK
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004594:Electrophysiology; D004789:Enzyme Activation; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D014982:Xenopus laevis
D018118:Chloride Channels; D002712:Chlorides; D008246:Lysophospholipids; D015544:Inositol 1,4,5-Trisphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002118:Calcium