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

Arch Biochem Biophys. 2012 Jan 1;517(1):43-52. doi: 10.1016/j.abb.2011.10.017. Epub 2011 Nov 11.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / metabolism
  • Catalytic Domain
  • Cell Line
  • Mice
  • Phosphoprotein Phosphatases / analysis*
  • Phosphoprotein Phosphatases / metabolism*
  • Proteasome Endopeptidase Complex / metabolism
  • Proteasome Inhibitors
  • Proteolysis
  • Rats
  • Zebrafish / metabolism*
  • Zebrafish Proteins / analysis*
  • Zebrafish Proteins / metabolism*

Substances

  • Proteasome Inhibitors
  • Zebrafish Proteins
  • Phosphoprotein Phosphatases
  • ppm1e protein, Zebrafish
  • Proteasome Endopeptidase Complex