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| The EMBO Journal
(1997) 16, 1921–1933, doi:10.1093/emboj/16.8.1921 |
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| MNK1, a new MAP kinase-activated protein kinase, isolated by a novel expression screening method for identifying protein kinase substrates |
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| Rikiro Fukunaga2 and Tony Hunter1 |
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1 Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA 2 Present address: Department of Genetics, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565, Japan To whom correspondence should be addressed Tony Hunter, hunter@salk.edu Received 6 September 1996; Revised 9 January 1997. |
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| Abstract |
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We have developed a novel expression screening method for identifying protein kinase substrates. In this method, a  phage cDNA expression library is screened by in situ, solid-phase phosphorylation using purified protein kinase and [ -32P]ATP. Screening a HeLa cDNA library with ERK1 MAP kinase yielded cDNAs of previously characterized ERK substrates, c-Myc and p90RSK, demonstrating the utility of this method for identifying physiological protein kinase substrates. A novel clone isolated in this screen, designated MNK1, encodes a protein-serine/threonine kinase, which is most similar to MAP kinase-activated protein kinase 2 (MAPKAP-K2), 3pK/MAPKAP-K3 and p90RSK. Bacterially expressed MNK1 was phosphorylated and activated in vitro by ERK1 and p38 MAP kinases but not by JNK/SAPK. Further, MNK1 was activated upon stimulation of HeLa cells with 12-O-tetradecanoylphorbol-13-acetate, fetal calf serum, anisomycin, UV irradiation, tumor necrosis factor- , interleukin-1 or osmotic shock, and the activation by these stimuli was differentially inhibited by the MEK inhibitor PD098059 or the p38 MAP kinase inhibitor SB202190. Together, these results indicate that MNK1 is a novel class of protein kinase that is activated through both the ERK and p38 MAP kinase signaling pathways. |
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| Keywords: expression cloning, MAP kinase, phosphorylation, protein kinase, signal transduction |
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