title: An active C-terminally truncated form of Ca (2+) /calmodulin-dependent protein kinase phosphatase-N (CaMKP-N/PPM1E).
abstract: Ca(2+)/calmodulin-dependent protein kinase phosphatase (CaMKP/PPM1F) and its nuclear homolog CaMKP-N (PPM1E) are Ser/Thr protein phosphatases that belong to the PPM family. CaMKP-N is expressed in the brain and undergoes proteolytic processing to yield a C-terminally truncated form. The physiological significance of this processing, however, is not fully understood. Using a wheat-embryo cell-free protein expression system, we prepared human CaMKP-N (hCaMKP-N(WT)) and the truncated form, hCaMKP-N(1-559), to compare their enzymatic properties using a phosphopeptide substrate. The hCaMKP-N(1-559) exhibited a much higher V(max) value than the hCaMKP-N(WT) did, suggesting that the processing may be a regulatory mechanism to generate a more active species. The active form, hCaMKP-N(1-559), showed Mn(2+) or Mg(2+)-dependent phosphatase activity with a strong preference for phospho-Thr residues and was severely inhibited by NaF, but not by okadaic acid, calyculin A, or 1-amino-8-naphthol-2,4-disulfonic acid, a specific inhibitor of CaMKP. It could bind to postsynaptic density and dephosphorylate the autophosphorylated Ca(2+)/calmodulin-dependent protein kinase II. Furthermore, it was inactivated by H2O2 treatment, and the inactivation was completely reversed by treatment with DTT, implying that this process is reversibly regulated by oxidation/reduction. The truncated CaMKP-N may play an important physiological role in neuronal cells.
authors.affiliation: Laboratory of Molecular Brain Science, Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan. aishida@hiroshima-u.ac.jp
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Ishida
authors.forename: Kumiko
authors.initials: K
authors.lastname: Tsumura
authors.forename: Megu
authors.initials: M
authors.lastname: Oue
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takenaka
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shigeri
authors.forename: Naoki
authors.initials: N
authors.lastname: Goshima
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishihara
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hirano
authors.forename: Hiromi
authors.initials: H
authors.lastname: Baba
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Sueyoshi
authors.forename: Isamu
authors.initials: I
authors.lastname: Kameshita
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamazaki
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000737:chemistry*; D004789:Enzyme Activation; D004795:Enzyme Stability; D010748:Phosphopeptides / Q000737:chemistry*; D010749:Phosphoprotein Phosphatases / Q000737:chemistry*; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D010748:Phosphopeptides; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C459194:PPM1F protein, human; D010749:Phosphoprotein Phosphatases