title: Scaffold Function of Ca2+-Dependent Protein Kinase: Tobacco Ca2+-DEPENDENT PROTEIN KINASE1 Transfers 14-3-3 to the Substrate REPRESSION OF SHOOT GROWTH after Phosphorylation.
abstract: A molecular mechanism to ensure signaling specificity is a scaffold. REPRESSION OF SHOOT GROWTH (RSG) is a tobacco (Nicotiana tabacum) transcription factor that is involved in gibberellin feedback regulation. The 14-3-3 proteins negatively regulate RSG by sequestering it in the cytoplasm in response to gibberellins. The N. tabacum Ca2+-dependent protein kinase NtCDPK1 was identified as an RSG kinase that promotes 14-3-3 binding of RSG by phosphorylation of RSG. CDPKs are unique sensor responders of Ca2+that are only found in plants and some protozoans. Here, we report a scaffolding function of CDPK. 14-3-3 proteins bound to NtCDPK1 by a new mode. Autophosphorylation of NtCDPK1 was necessary for the formation of the binding between NtCDPK1 and 14-3-3 but not for its maintenance. NtCDPK1 formed a heterotrimer with RSG and 14-3-3. Furthermore, we found that NtCDPK1 transfers 14-3-3 to RSG after phosphorylation of RSG and that RSG dissociates from NtCDPK1 as a complex with 14-3-3. These results suggest that NtCDPK1 is an interesting scaffolding kinase that increases the specificity and efficiency of signaling by coupling catalysis with scaffolding on the same protein.
authors.affiliation: Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan (T.I., M.N., J.F., Y.T.); andDepartment of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan (S.I.).
authors.forename: Takeshi
authors.identifier: http://orcid.org/0000-0002-5648-1371
authors.initials: T
authors.lastname: Ito
authors.affiliation: Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan (T.I., M.N., J.F., Y.T.); andDepartment of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan (S.I.).
authors.forename: Masaru
authors.initials: M
authors.lastname: Nakata
authors.affiliation: Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan (T.I., M.N., J.F., Y.T.); andDepartment of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan (S.I.).
authors.forename: Jutarou
authors.initials: J
authors.lastname: Fukazawa
authors.affiliation: Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan (T.I., M.N., J.F., Y.T.); andDepartment of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan (S.I.).
authors.forename: Sarahmi
authors.initials: S
authors.lastname: Ishida
authors.affiliation: Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan (T.I., M.N., J.F., Y.T.); andDepartment of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan (S.I.) ytakahas@hiroshima-u.ac.jp.
authors.forename: Yohsuke
authors.initials: Y
authors.lastname: Takahashi