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

• Published in: Archives of biochemistry and biophysics 2012-01, Vol.517 (1), p.43-52
• Main Authors: Sueyoshi, Noriyuki, Nimura, Takaki, Onouchi, Takashi, Baba, Hiromi, Takenaka, Shinobu, Ishida, Atsuhiko, Kameshita, Isamu
• Format: Article
• Language: English
• Subjects: Animals; brain; Brain - metabolism; CaMKP-N; catalytic activity; Catalytic Domain; Cell Line; cytosol; Danio rerio; Functional processing; Mice; Phosphoprotein Phosphatases - analysis; Phosphoprotein Phosphatases - metabolism; Proteasome; proteasome endopeptidase complex; Proteasome Endopeptidase Complex - metabolism; Proteasome Inhibitors; protein kinases; Proteolysis; Rats; Ubiquitin; Zebrafish - metabolism; Zebrafish Proteins - analysis; Zebrafish Proteins - metabolism
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2011.10.017

► In this study, we found that CaMKP-N bound to ubiquitinated proteins and underwent proteolytic processing. ► The proteolysis was effectively inhibited by the proteasome inhibitors. ► The proteolytic processing changed the subcellular localization and cellular targets of CaMKP-N. ► CaMKP-N was activated when the C-terminal domain was removed by the processing. ► The processing of CaMKP-N regulates its activity, localization and substrate targeting. Ca2+/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.