Effects of cations on ceramide-activated protein phosphatase 2A

Sehamuddin Galadari, Abdulkadir Hago, Mahendra Patel

Research output: Contribution to journalArticlepeer-review


Characterization of ceramide-effector(s), which includes protein phosphatase 2A (PP2A) is an important prelude to understanding the molecular basis of sphingolipid-mediated biological effects such as cell growth, differentiation and apoptosis. Recently, the existence of a metal-dependent form of PP2A has been reported (Cai et al., 1995). In this study, we investigated the effects of metal ions and chelators on ceramide-activated PP2A (CAPP). Our study demonstrates that at 0.5 mM concentration, Mg2+ appears to have no significant effect on either basal or ceramide-stimulated phosphatase activities, whereas Ca2+ stimulated the basal phosphatase activity, but was inhibitory towards CAPP. Moreover, the divalent cations Cr2+, Mn2+, Fe2+, Ni2+, Cu2+ and Zn2+ were tested and all were found to be inhibitory towards both CAPP and basal phosphatase activities. By contrast, Cs+ and Li+ had almost no effect on CAPP, although both stimulated basal phosphatase activity. The effects of EDTA and EGTA were tested and it was observed that EDTA decreased CAPP activity in a dose-dependent fashion, but had no effect upon basal phosphatase activity. These results suggest that CAPP is a metal-dependent protein, but, because Ca2+ inhibitied CAPP and EGTA was much less potent than EDTA in inhibiting CAPP, Ca2+ is unlikely to be its metal cofactor.

Original languageEnglish (US)
Pages (from-to)240-244
Number of pages5
JournalExperimental and Molecular Medicine
Issue number4
StatePublished - Dec 31 2001


  • Cations
  • Ceramide
  • Phosphatases

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Clinical Biochemistry


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