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Effects of bisindolylmaleimide PKC inhibitors on p90 RSK activity in vitro and in adult ventricular myocytes
Author(s) -
Roberts Neil A,
Haworth Robert S,
Avkiran Metin
Publication year - 2005
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0706210
Subject(s) - bisindolylmaleimide , protein kinase c , phorbol , kinase , chemistry , protein kinase a , microbiology and biotechnology , biology , biochemistry
1 Bisindolylmaleimide inhibitors of protein kinase C (PKC), such as GF109203X and Ro31‐8220, have been used to investigate the roles of PKC isoforms in many cellular processes in cardiac myocytes, but these agents may also inhibit p90 RSK activity. 2 In in vitro kinase assays utilising 50 μ M [ATP], GF109203X and Ro31‐8220 inhibited p90 RSK isoforms (IC 50 values for inhibition of RSK1, RSK2 and RSK3, respectively, were 610, 310 and 120 n M for GF109203X, and 200, 36 and 5 n M for Ro31‐8220) as well as classical and novel PKC isoforms (IC 50 values for inhibition of PKC α and PKC ɛ , respectively, were 8 and 12 n M for GF109203X, and 4 and 8 n M for Ro31‐8220). 3 At physiological [ATP] (5 m M ), both GF109203X and Ro31‐8220 exhibited reduced potency as inhibitors of RSK2, PKC α and PKC ɛ (IC 50 values of 7400, 310 and 170 n M , respectively, for GF109203X, and 930, 150 and 140 n M , respectively, for Ro31‐8220), with the latter agent retaining its relatively greater potency. 4 To determine the effects of GF109203X and Ro31‐8220 on p90 RSK activity in cultured adult rat ventricular myocytes (ARVM), phosphorylation of the eukaryotic elongation factor 2 kinase (eEF2K) at Ser366, a known p90 RSK target, was used as the index of such activity. Adenoviral expression of a constitutively active form of mitogen‐activated protein kinase (MAPK) or extracellular signal‐regulated kinase (ERK) kinase 1 (MEK1) was used to induce PKC‐independent p90 RSK activation and downstream phosphorylation of eEF2K. 5 eEF2K phosphorylation was abolished by U0126 (1 μ M ), a selective inhibitor of MEK1, and was significantly reduced by GF109203X at 3 μ M and by Ro31‐8220 at 1 μ M . At 1 μ M , both agents inhibited PMA‐induced PKC activity in ARVM. 6 These data show that GF109203X and Ro31‐8220 inhibit various isoforms of PKC and p90 RSK in vitro and in intact ARVM, with the former agent exhibiting relatively greater selectivity for PKC.British Journal of Pharmacology (2005) 145 , 477–489. doi: 10.1038/sj.bjp.0706210