Calcineurin-mediated YB-1 Dephosphorylation Regulates CCL5 Expression During Monocyte Differentiation

J Biol Chem. 2014 Aug 1;289(31):21401-12. doi: 10.1074/jbc.M114.562991. Epub 2014 Jun 19.

Abstract

Y-box (YB) protein-1 serves as a master regulator in gene transcription and mRNA translation. YB-1 itself is regulated at various levels, e.g. through post-translational modifications. In our previous work, we identified RANTES/CCL5 as a transcriptional target of YB-1. We previously demonstrated that YB-1 protein is transiently up-regulated during monocyte/macrophage differentiation evidenced in monocytic cells (THP-1 cells) that were differentiated using phorbol myristate acetate (PMA). Here we provide evidence that YB-1 phosphorylation, specifically at its serine residue 102 (Ser-102), increases early on in THP-1 cells following PMA treatment as well as in differentiated primary human monocytes. This process is mediated through the Akt signaling pathway. Ser-102-phosphorylated YB-1 displays stronger binding affinity and trans-activating capacity at the CCL5 gene promoter. Notably, Ser-102-phosphorylated YB-1 disappears at later stages of the monocyte/macrophage differentiation process. We demonstrate that serine-threonine phosphatase calcineurin (CN) dephosphorylates YB-1 preventing it from binding to and trans-activating the CCL5 promoter. Co-immunoprecipitation assays prove a direct YB-1/CN interaction. Furthermore, analyses in kidney tissues from mice that were treated with the CN inhibitor cyclosporine A revealed an in vivo effect of CN on the YB-1 phosphorylation status. We conclude that YB-1 phosphorylation at Ser-102 is an important prerequisite for CCL5 promoter activation during macrophage differentiation. Our findings point to a critical role of YB-1 in the resolution of inflammatory processes which may largely be due to CN-mediated dephosphorylation.

Keywords: CCL5; Calcineurin; Chemokine; Gene Expression; Gene Regulation; Monocyte Differentiation; Phosphatase; Y-box Protein-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Calcineurin / physiology*
  • Cell Differentiation* / drug effects
  • Cell Line
  • Chemokine CCL5 / genetics*
  • DNA Primers
  • Humans
  • Monocytes / cytology
  • Monocytes / metabolism*
  • Phosphorylation
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic
  • Tetradecanoylphorbol Acetate / pharmacology
  • Y-Box-Binding Protein 1 / metabolism*

Substances

  • CCL5 protein, human
  • Chemokine CCL5
  • DNA Primers
  • Y-Box-Binding Protein 1
  • YBX1 protein, human
  • Calcineurin
  • Tetradecanoylphorbol Acetate