The identification of ATP-citrate lyase as a protein kinase B (Akt) substrate in primary adipocytes

J Biol Chem. 2002 Sep 13;277(37):33895-900. doi: 10.1074/jbc.M204681200. Epub 2002 Jul 9.

Abstract

Protein kinase B (Akt) plays a central role in cellular regulation, although many of the physiologically relevant substrates for the kinase remain to be identified. In this study, we have isolated a protein from primary epididymal adipocytes with an apparent molecular weight of 125,000. This protein exhibited immunoreactivity, in an insulin-dependent manner, with a phosphospecific antibody raised against the protein kinase B substrate consensus sequence RXRXX(pS/pT) as well as a phosphospecific antibody that recognizes serine 21/9 of GSK-3alpha/beta. MALDI-TOF mass spectrometry revealed the protein to be ATP-citrate lyase, suggesting that the two phosphospecific antibodies recognize phosphoserine 454, a previously reported insulin- and isoproterenol-stimulated ATP-citrate lyase phosphorylation site. Indeed, both insulin and isoproterenol stimulated the phosphorylation of this protein on the site recognized by the phosphospecific antibodies in a wortmannin-sensitive and -insensitive manner, respectively. In addition, transient expression of a constitutively active protein kinase B in primary adipocytes mimicked the effect of insulin on ATP-citrate lyase phosphorylation. Furthermore, ATP-citrate lyase was phosphorylated in vitro by recombinant protein kinase B on the same site. Taken together, these results demonstrate that serine 454 of ATP-citrate lyase is a novel and major in vivo substrate for protein kinase B.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Citrate (pro-S)-Lyase / metabolism*
  • Adipocytes / metabolism*
  • Amino Acid Sequence
  • Animals
  • Insulin / pharmacology
  • Molecular Sequence Data
  • Molecular Weight
  • Phosphatidylinositol 3-Kinases / physiology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Rats
  • Rats, Wistar
  • Transfection

Substances

  • Insulin
  • Proto-Oncogene Proteins
  • ATP Citrate (pro-S)-Lyase
  • Phosphatidylinositol 3-Kinases
  • Akt1 protein, rat
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt