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The AMPK-related kinase SIK2 is regulated by cAMP via phosphorylation at Ser(358) in adipocytes

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Author

  • Emma Henriksson
  • Helena Jones
  • Kashyap Patel
  • Mark Peggie
  • Nicholas Morrice
  • Kei Sakamoto
  • Olga Göransson

Summary, in English

SIK2 (salt-inducible kinase 2) is a member of the AMPK (AMP-activated protein kinase) family of kinases and is highly expressed in adipocytes. We investigated the regulation of SIK2 in adipocytes in response to cellular stimuli with relevance for adipocyte function and/or AMPK signalling. None of the treatments, including insulin, cAMP inducers or AICAR (5-amino-4-imidazolecarboxamide riboside), affected SIK2 activity towards peptide or protein substrates in vitro. However, stimulation with the cAMP-elevating agent forskolin and the beta-adrenergic receptor agonist CL 316,243 resulted in a PKA (protein kinase A)-dependent phosphorylation and 14-3-3 binding of SIK2. Phosphopeptide mapping of SIK2 revealed several sites phosphorylated in response to cAMP induction, including Ser(358). Site-directed mutagenesis demonstrated that phosphorylation of See(358), but not the previously reported PKA site See(587), was required for 14-3-3 binding. Immunocytochemistry illustrated that the localization of exogenously expressed SIK2 in HEK (human embryonic kidney)-293 cells was exclusively cytosolic and remained unchanged after cAMP elevation. Fractionation of adipocytes, however, revealed a significant increase of wild-type, but not Ser358Ala, HA (haemagglutinin) SIK2 in the cytosol and a concomitant decrease in a particulate fraction after CL 316,243 treatment. This supports a phosphorylation-dependent relocalization in adipocytes. We hypothesize that regulation of SIK2 by cAMP could play a role for the critical effects of this second messenger on lipid metabolism in adipocytes.

Publishing year

2012

Language

English

Pages

503-514

Publication/Series

Biochemical Journal

Volume

444

Document type

Journal article

Publisher

Portland Press

Topic

  • Biochemistry and Molecular Biology

Keywords

  • 14-3-3
  • cAMP
  • insulin
  • phosphorylation
  • salt-induced kinase (SIK)
  • 3T3-L1 adipocyte

Status

Published

Research group

  • Protein Phosphorylation
  • Insulin Signal Transduction

ISBN/ISSN/Other

  • ISSN: 0264-6021