Vitamin E isoforms directly bind PKCα and differentially regulate activation of PKCα

Christine McCary, Youngdae Yoon, Candace Panagabko, Wonhwa Cho, Jeffrey Atkinson, Joan M Cook-Mills*

*Corresponding author for this work

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

Vitamin E isoforms have opposing regulatory effects on leucocyte recruitment during inflammation. Furthermore, in vitro, vitamin E isoforms have opposing effects on leucocyte migration across endothelial cells by regulating VCAM (vascular cell-adhesion molecule)-1 activation of endothelial cell PKCα (protein kinase Cα). However, it is not known whether tocopherols directly regulate cofactor-dependent or oxidative activation of PKCα. We report in the present paper that cofactor-dependent activation of recombinant PKCα was increased by γ-tocopherol and was inhibited by α-tocopherol. Oxidative activation of PKCα was inhibited by α-tocopherol at a 10-fold lower concentration than γ -tocopherol. In binding studies, NBD (7-nitrobenz-2- oxa-1,3-diazole)-tagged α-tocopherol directly bound to fulllength PKCα or the PKCα-C1a domain, but not PKCζ. NBD-tagged α-tocopherol binding to PKCα or the PKCα-C1a domain was blocked by diacylglycerol, α-tocopherol, γ-tocopherol and retinol, but not by cholesterol or PS (phosphatidylserine). Tocopherols enhanced PKCα-C2 domain binding to PS-containing lipid vesicles. In contrast, the PKCα-C2 domain did not bind to lipid vesicles containing tocopherol without PS. The PKCα-C1b domain did not bind to vesicles containing tocopherol and PS. In summary, α-tocopherol and γ -tocopherol bind the diacylglycerol-binding site on PKCα-C1a and can enhance PKCα-C2 binding to PS-containing vesicles. Thus the tocopherols can function as agonists or antagonists for differential regulation of PKCα.

Original languageEnglish (US)
Pages (from-to)189-198
Number of pages10
JournalBiochemical Journal
Volume441
Issue number1
DOIs
StatePublished - Jan 1 2012

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Keywords

  • Cofactor
  • Oxidation
  • Protein kinase Cα
  • Vitamin E
  • α-tocopherol
  • γ-tocopherol

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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