Stimulation by extracellular ATP and UTP of the mitogen-activated protein kinase cascade and proliferation of rat renal mesangial cells.
1. Extracellular ATP and UTP have been reported to activate a nucleotide receptor that mediates phosphoinositide and phosphatidylcholine hydrolysis by phospholipases C and D, respectively. Here we report that ATP and UTP potently stimulate mesangial cell proliferation. 2. Both nucleotides stimulate phosphorylation and activation of mitogen-activated protein kinase and a biphasic phosphorylation of the up-stream mitogen-activated protein kinase kinase. 3. When added at 100 microM, ATP gamma S, UTP and ATP were the most potent activators of mitogen-activated protein kinase. beta gamma-imido-ATP was somewhat less active and ADP and 2-methylthio-ATP caused a weak induction of enzyme activity. Activation of mitogen-activated protein kinase by both ATP and UTP is dose-dependently attenuated by the P2-receptor antagonist, suramin. 4. The protein kinase C activator 12-0-tetradecanoylphorbol 13-acetate, but not the biologically inactive 4 alpha-phorbol 12,13-didecanoate, increased mitogen-activated protein kinase activity in mesangial cells, suggesting that protein kinase C may mediate nucleotide-induced stimulation of mitogen-activated protein kinase. 5. Down-regulation of protein kinase C -alpha and -delta isoenzymes by 4 h or 8 h treatment with phorbol ester partially inhibited ATP- and UTP-triggered mitogen-activated protein kinase activation. Moreover, a 24 h treatment of mesangial cells with phorbol ester, a regimen that also causes depletion of protein kinase C-epsilon did not further reduce the level of mitogen-activated protein kinase stimulation. 6. The specific protein kinase C inhibitor, CGP 41251, which displayed a selectivity for the Ca2+-dependent isoenzymes, as compared to the Ca2+-independent isoenzymes did not inhibit nucleotide stimulated mitogen-activated protein kinase phosphorylation, thus implicating the involvement of a Ca2+-independent protein kinase C isoform.7. In summary, these results suggest that ATP and UTP trigger the activation of the mitogen-activated protein kinase signalling cascade in mesangial cells and this may be responsible for the potent mitogenic activity of both nucleotides.
Huwiler
A
A
Department of Pharmacology, University of Basel, Switzerland.
Pfeilschifter
J
J
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases; D008934:Mitogens / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D013268:Stimulation, Chemical; D013936:Thymidine / Q000378:metabolism; D014544:Uridine Triphosphate / Q000502:physiology*
D007527:Isoenzymes; D008934:Mitogens; D010455:Peptides; D047428:Protein Kinase Inhibitors; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D011494:Protein Kinases; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases; D014544:Uridine Triphosphate; D013936:Thymidine