Investigating the non-genomic actions of the glucocorticoid receptor

UoM administered thesis: Phd

  • Authors:
  • Stephen Kershaw

Abstract

Glucocorticoids (GCs) are a class of steroid hormone that play essential roles in development, glucose homeostasis, and reducing inflammation. Clinically, GCs are potent anti-inflammatory and immunosuppressive agents used to treat a variety of diseases. However, the therapeutic benefit of GCs is negatively impacted by the induction of severe side effects. In this thesis, I present two studies that have contributed to the understanding of the non-genomic actions of GCs. GCs inhibit cell migration by a non-transcriptional pathway involving HDAC6: A negative side effect of GC therapy is impaired wound healing which is ascribed to inhibited cell migration. Using live-cell microscopy, I show that GCs inhibit cell migration within 30 minutes of administration. GCs alter the dynamics of the microtubule network through rapid induction of tubulin acetylation (by inhibition of HDAC6) which increases microtubule stability and slows cell movement. The inhibitory effect of GCs on cell migration is reversed by overexpressing HDAC6. Using quantitative imaging, I identified a rapid ligand-dependent association of the GR and HDAC6 within the cytoplasm that is absent in the nucleus. However, a very small proportion of HDAC6 enters the nucleus post-GC treatment, suggesting that HDAC6 accompanies the GR during nuclear translocation. This study demonstrates that GCs rapidly inhibit cell migration by a non-transcriptional mechanism involving HDAC6. Investigating the rapid effects of GCs on the phosphoproteome: Non-steroidal GCs are useful tool compounds to dissect glucocorticoid receptor (GR) activity. Here, I investigated the early, rapid effect of GCs on the phosphoproteome of A549 cells using SILAC-based phosphoproteomics. A consistent spectrum of phosphoproteins was differentially regulated by GC within 10 minutes of administration, notably including regulators of RNA polymerase II, chromatin remodifying proteins, transcription factors, cytoskeletal modifiers, regulators of intracellular calcium signalling and endocytosis. These phosphoproteins were validated by western blotting. This study shows a clear early effect of GCs on the phosphoproteome with implications for non-specific, non-transcriptional activity of GCs.

Details

Original languageEnglish
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Award date31 Dec 2018