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Ro31‐8220 inhibits protein kinase C to block the phorbol ester‐stimulated release of choline‐ and ethanolamine‐metabolites from C6 glioma cells: p70 S6 kinase and MAPKAP kinase‐1β do not function downstream of PKC in activating PLD
Author(s) -
Morreale Angela,
Mallon Barbara,
Beale Gary,
Watson John,
Rumsby Martin
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)01252-0
Subject(s) - protein kinase c , p70 s6 kinase 1 , cyclin dependent kinase 2 , chemistry , map kinase kinase kinase , kinase , mitogen activated protein kinase kinase , protein kinase a , ask1 , biochemistry , microbiology and biotechnology , phosphorylation , biology , protein kinase b
The use of bisindolylmaleimide derivatives of staurosporine as selective inhibitors of protein kinase C (PKC) is in doubt following the report by Alessi [FEBS Lett. 402 (1997) 121–123] that Ro31‐8220 and GF109203X are potent in vitro inhibitors of p70 S6 kinase and mitogen‐activated protein kinase‐activated protein kinase‐1β, as well as of PKC. Here we show that the phorbol ester‐stimulated release of choline‐ and ethanolamine‐metabolites from C6 glioma cells due to phospholipid hydrolysis by phospholipase D (PLD) is not inhibited by rapamycin or PD98059, specific inhibitors respectively of p70 S6 kinase and MAPKK (MEK) and thus of MAPKAP kinase‐1β but is still completely blocked by Ro31‐8220. We conclude therefore that p70 S6k and MAPKAP kinase‐1β as well as MAPK are not involved in signalling pathways downstream of PKC that regulate phorbol ester‐stimulated phospholipid turnover and that the inhibitory action of Ro31‐8220 occurs by blocking PKC which regulates at least one pathway to PLD activation. The PI‐3 kinase inhibitor, wortmannin, inhibits the phorbol ester‐stimulated release of ethanolamine‐ but not choline‐metabolites from C6 cells suggesting that different PLD isoforms regulate the turnover of PtdEth and PtdCho in C6 cells. Both PLD isoforms are activated via PKC but the PtdEth‐PLD is also regulated via a wortmannin‐sensitive pathway.