title: Functional processing of nuclear Ca2+/calmodulin-dependent protein kinase phosphatase (CaMKP-N): evidence for a critical role of proteolytic processing in the regulation of its catalytic activity, subcellular localization and substrate targeting in vivo.
abstract: Ca(2+)/calmodulin-dependent protein kinase phosphatase (CaMKP) and its nuclear homolog CaMKP-N are Ser/Thr protein phosphatases that belong to the PPM family. These phosphatases are highly specific for multifunctional CaM kinases and negatively regulate their activities. CaMKP-N is only expressed in the brain and specifically localized in the nucleus. In this study, we found that zebrafish CaMKP-N (zCaMKP-N) underwent proteolytic processing in both the zebrafish brain and Neuro2a cells. In Neuro2a cells, the proteolytic processing was effectively inhibited by the proteasome inhibitors MG-132, Epoxomicin, and Lactacystin, suggesting that the ubiquitin-proteasome pathway was involved in this processing. Using MG-132, we found that the proteolytic processing changed the subcellular localization of zCaMKP-N from the nucleus to the cytosol. Accompanying this change, the cellular targets of zCaMKP-N in Neuro2a cells were significantly altered. Furthermore, we obtained evidence that the zCaMKP-N activity was markedly activated when the C-terminal domain was removed by the processing. Thus, the proteolytic processing of zCaMKP-N at the C-terminal region regulates its catalytic activity, subcellular localization and substrate targeting in vivo.
authors.affiliation: Department of Life Sciences, Kagawa University, Kagawa, Japan. sueyoshi@ag.kagawa-u.ac.jp
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Sueyoshi
authors.forename: Takaki
authors.initials: T
authors.lastname: Nimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Onouchi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Baba
authors.forename: Shinobu
authors.initials: S
authors.lastname: Takenaka
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Ishida
authors.forename: Isamu
authors.initials: I
authors.lastname: Kameshita
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D020134:Catalytic Domain; D002460:Cell Line; D051379:Mice; D010749:Phosphoprotein Phosphatases / Q000032:analysis* / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D059748:Proteolysis; D051381:Rats; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000032:analysis* / Q000378:metabolism*
chemical_list: D061988:Proteasome Inhibitors; D029961:Zebrafish Proteins; D010749:Phosphoprotein Phosphatases; C517871:ppm1e protein, zebrafish; D046988:Proteasome Endopeptidase Complex