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

• Published in: The Journal of biological chemistry 2014-08, Vol.289 (31), p.21401-21412
• Main Authors: Alidousty, Christina, Rauen, Thomas, Hanssen, Lydia, Wang, Qiang, Alampour-Rajabi, Setareh, Mertens, Peter R., Bernhagen, Jürgen, Floege, Jürgen, Ostendorf, Tammo, Raffetseder, Ute
• Format: Article
• Language: English
• Subjects: Base Sequence; Calcineurin; Calcineurin - physiology; CCL5; Cell Differentiation - drug effects; Cell Line; Chemokine; Chemokine CCL5 - genetics; DNA Primers; Gene Expression; Gene Regulation; Humans; Immunology; Monocyte Differentiation; Monocytes - cytology; Monocytes - metabolism; Phosphatase; Phosphorylation; Polymerase Chain Reaction; Promoter Regions, Genetic; Tetradecanoylphorbol Acetate - pharmacology; Y-box Protein-1; Y-Box-Binding Protein 1 - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.562991

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. Background: Transcription factor YB-1 constitutes a key regulator in immune cell homeostasis. It has been demonstrated to be involved in monocyte/macrophage differentiation. However, the underlying mechanisms are poorly understood. Results: Protein phosphatase calcineurin (CN) regulates YB-1 activities on the CCL5 promoter during macrophage differentiation. Conclusion: Dephosphorylation of YB-1 by CN is crucial to counteract the overwhelming pro-inflammatory propensities of YB-1. Significance: Overshooting inflammation may be counteracted by dephosphorylation of YB-1.