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Title: The function of heat shock protein 27 in interleukin-1 signalling
Author: Brennan, Bryony Rachel
ISNI:       0000 0004 2694 0025
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
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The p38 mitogen activated protein kinase (MAPK) pathway enhances the expression of proinflammatory response genes, including cyclooxgenase (COX)-2 and interleukin (IL)-6 in response to stimuli including IL-1. Heat shock protein 27 (HSP27) is a major protein phosphorylated by MAPK activated protein kinase 2 (MK2), a downstream kinase of p38 MAPK. However, the role of HSP27 in inflammation is unclear. Previous work has shown the requirement of HSP27 for stabilisation of COX-2 and IL-6 mRNAs following IL-1 treatment of HeLa cells. To examine the role of HSP27 in IL-1 signalling I depleted the protein from HeLa cells, human alveolar epithelial (A549) cells and human dermal fibroblasts (HDFs) by RNA interference (RNAi) using multiple short interfering RNAs (siRNAs). HSP27 suppression in HeLa cells inhibited IL-1 induced activation of MK2, p38 MAPK and c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase (ERK). Upstream MAPK kinase (MKK) 3, 4, 6 and 7 and TGF-beta-activated kinase 1 (TAK1) were also inhibited. HSP27 depletion did not disrupt the constitutive interaction found between TAK1 and its binding protein TAB1. HSP27 appeared to impinge on signalling at a point lying between cell surface receptors and TAK1 or at TAK1 itself as activation of JNK and p38 MAPK by tumour necrosis factor (TNF) was inhibited by HSP27 knockdown. A transfection procedure was developed for transfection of siRNA into HDF cells. In HDFs and A549 cell types HSP27 was required for COX-2 protein expression and the full activation of p38 MAPK. However, while TAK1 was shown to be responsible for sustained activation of p38 MAPK, TAK1 activity was not affected by HSP27 depletion in HDFs. MKK3 (rather than MKK6) appeared to be the major HDF activator of p38 MAPK in response to IL-1. My results demonstrate that HSP27 has a novel role in augmenting IL-1 signalling in epithelial cell lines and fibroblasts.
Supervisor: Dean, Jon ; Saklatvala, Jerry Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral