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Heat shock protein (HSP) 27 has long been known to be a component of the p38 mitogen-activated protein kinase (MAPK) signaling pathway. p38 MAPK has important functions in the inflammatory response, but the role of HSP27 in inflammation has remained unknown. We have used small interfering RNAs to suppress HSP27 expression in HeLa cells and fibroblasts and found that it is required for pro-inflammatory cell signaling and the expression of pro-inflammatory genes. HSP27 is needed for the activation by interleukin (IL)-1 of TAK1 and downstream signaling by p38 MAPK, JNK, and their activators (MKK-3, -4, -6, -7) and IKKbeta. IL-1-induced ERK activation appears to be independent of HSP27. HSP27 is required for both IL-1 and TNF-induced signaling pathways for which the most upstream common signaling protein is TAK1. HSP27 is also required for IL-1-induced expression of the pro-inflammatory mediators, cyclooxygenase-2, IL-6, and IL-8. HSP27 functions to drive cyclooxygenase-2 and IL-6 expression by augmenting the activation of the kinase downstream of p38 MAPK, MK2, resulting in stabilization of cyclooxygenase-2 and IL-6 mRNAs. The mechanism may not occur in cells of myeloid lineage because HSP27 protein was undetectable in human monocytes and murine macrophages.

Original publication

DOI

10.1074/jbc.m610987200

Type

Journal article

Journal

The Journal of biological chemistry

Publication Date

03/2007

Volume

282

Pages

6232 - 6241

Addresses

Kennedy Institute of Rheumatology Division, Faculty of Medicine, Imperial College London, London W6 8LH, United Kingdom.

Keywords

Cells, Cultured, Hela Cells, Fibroblasts, Humans, Inflammation, MAP Kinase Kinase Kinases, Mitogen-Activated Protein Kinases, Tumor Necrosis Factor-alpha, Heat-Shock Proteins, Neoplasm Proteins, Interleukin-1, Interleukin-6, Signal Transduction, Gene Expression Regulation, RNA Stability, Cyclooxygenase 2, HSP27 Heat-Shock Proteins