siRNA-mediated depletion of endogenous protein phosphatase 2Acalpha markedly attenuates ceramide-activated protein phosphatase activity in insulin-secreting INS-832/13 cells

Biochem Biophys Res Commun. 2006 Sep 22;348(2):649-52. doi: 10.1016/j.bbrc.2006.07.100. Epub 2006 Jul 28.

Abstract

The sphingolipid ceramide (CER) and its metabolites have been recognized as important mediators of signal transduction processes leading to a variety of cellular responses, including survival and demise via apoptosis. Accumulating evidence implicates key regulatory roles for intracellularly generated CER in metabolic dysfunction of the islet beta cell. We have previously reported localization of an okadaic (OKA)-sensitive CER-activated protein phosphatase (CAPP) in the islet beta cell. We have also reported immunological identification of the structural A subunit, the regulatory B56alpha subunit, and the catalytic C subunit for CAPP holoenzyme complex in insulin-secreting INS-1 cells. Herein, we provide the first evidence to suggest that siRNA-mediated knockdown of the alpha isoform of the catalytic subunit of PP2Ac (PP2Acalpha) markedly reduces the CAPP activity in INS 832/13 cells. Potential significance of the functional activation of CAPP holoenzyme in the context of lipid-and glucose-induced metabolic dysfunction of the islet beta cell is discussed.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Ceramides / pharmacology
  • Insulinoma
  • Okadaic Acid / pharmacology
  • Pancreatic Neoplasms
  • Phosphoprotein Phosphatases / genetics*
  • Protein Phosphatase 2
  • RNA, Small Interfering / pharmacology*
  • Rats

Substances

  • Ceramides
  • RNA, Small Interfering
  • Okadaic Acid
  • Phosphoprotein Phosphatases
  • Ppp2ca protein, rat
  • Protein Phosphatase 2