Suppression of protein kinase Cepsilon mediates 17beta-estradiol-induced neuroprotection in an immortalized hippocampal cell line

J Neurochem. 2005 Nov;95(3):745-55. doi: 10.1111/j.1471-4159.2005.03424.x. Epub 2005 Sep 2.

Abstract

Although estrogens are neuroprotective in a variety of neuroprotection models, the precise underlying mechanisms are currently not well understood. Here, we examined the role of protein kinase C (PKC) in mediating estrogen-induced neuroprotection in the HT-22 immortalized hippocampal cell line. The neuroprotection model utilized calcein fluorescence to quantitate cell viability following glutamate insults. 17beta-Estradiol (betaE2) protected HT-22 cells when treatment was initiated before or after the glutamate insult. The inhibition of PKC by bis-indolylmaleimide mimicked and enhanced betaE2-induced neuroprotection. In contrast, the inhibition of specific PKC isozymes (alpha and beta) by Go6976, inhibition of 1-phosphatidylinositol 3 kinase by wortmannin, or inhibition of protein kinase A by H-89, did not alter cell viability, suggesting a specific involvement of PKC in an isozyme-dependent manner. We further examined whether estrogen interacts with PKC in a PKC isozyme-specific manner. Protein levels and activity of PKC isozymes (alpha, delta, epsilon, and zeta) were assessed by western blot analysis and radiolabeled phosphorylation assays respectively. Among the isozymes tested, betaE2 altered only PKCepsilon; it reduced the activity and membrane translocation of PKCepsilon in a manner that correlated with its protection against glutamate toxicity. Furthermore, betaE2 reversed the increased activity of membrane PKCepsilon induced by glutamate. These data suggest that the neuroprotective effects of estrogens are mediated in part by inhibition of PKCepsilon activity and membrane translocation.

Publication types

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

MeSH terms

  • Animals
  • Carbazoles / pharmacology
  • Cell Line, Transformed
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Enzyme Inhibitors / pharmacology
  • Estradiol / pharmacology*
  • Glutamic Acid / toxicity
  • Hippocampus / cytology
  • Indoles / pharmacology
  • Maleimides / pharmacology
  • Mice
  • Neurons / cytology
  • Neurons / drug effects*
  • Neurons / enzymology*
  • Neuroprotective Agents / pharmacology*
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase C-epsilon / antagonists & inhibitors
  • Protein Kinase C-epsilon / metabolism*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology

Substances

  • Carbazoles
  • Enzyme Inhibitors
  • Indoles
  • Maleimides
  • Neuroprotective Agents
  • Phosphoinositide-3 Kinase Inhibitors
  • Go 6976
  • Glutamic Acid
  • Estradiol
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C-epsilon
  • bisindolylmaleimide