The role of p90 ribosomal S6 kinases (RSKs) in Steroid signalling 
                       
                       
                   Ryan Cronin 
                       
                       
       A thesis submitted for the title of Master of Science (by Dissertation) 
                       
                       
               School of Biological Sciences  
                       
                       
                  University of Essex  
                       
                       
                Examination March 2019 
                       
                       
       
       Abstract 
       The p90 ribosomal S6 kinases (RSKs) are a family of serine/threonine kinases consisting of 
       four isoforms (RSK1-4), which regulate key cellular processes including cell cycle, 
       proliferation, motility and survival. Among the several transcription factors targeted by RSKs, 
       several studies have identified the Steroid Receptors (SRs) as substrates of the RSKs. SRs 
       are a subfamily of the nuclear receptor superfamily consisting of five proteins (androgen, 
       glucocorticoid, estrogen, progesterone and mineralocorticoid receptors). These proteins 
       regulate gene expression thus are involved in crucial biological processes, including organ 
       development and maintenance, the immune system, neuroprotection and metabolic 
       homeostasis. Importantly, SRs are the main drivers of hormone driven cancers. Therefore, 
       we hypothesised that the RSKs could play an important part in SR signalling within hormone 
       driven cancer development and progression.  
       This was investigated using recombinant DNA techniques to incorporate the RSKs genes 
       into the mammalian expression vector PCDNA 3.1(+) and to produce phospho-mimetic 
       mutants. Luciferase assays were used to determine optimal hormone and DNA 
       concentrations, the role of RSKs on SR activity, the activity of the endogenous MAPK 
       pathway and the significance of phosphorylation state. The PMA experiments indicated that 
       in most cases PMA does not induce a significant change to RSK activity, thus the 
       endogenous MAPK pathway is sufficiently active. The mutant experiments suggested that 
       the phospho-mimetic mutation used does not cause constitutive activation of the RSKs. 
       Together considering all experiments it was illustrated that the RSKs have differential effects 
       on SR signalling. All the RSKs increased AR and GR activity despite some contradictions 
       within the data. RSK4 significantly decreased ERα activity and RSK3 significantly increased 
       PR activity. 
                     
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                Statement of Originality 
                I declare that the work within this document is of my own unless stated within the text.                                 
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       Acknowledgements  
       Firstly, I would like to thank my primary supervisor Dr. Filippo Prischi for his support from my 
       undergraduate degree all the way through to the end of my MSD and in securing me a PhD 
       position under his supervision for the next three years. He has helped me further my 
       laboratory skills and broaden my knowledge within biochemistry whilst simultaneously 
       enriching my passion for science. I would also like to thank my secondary supervisor Dr. 
       Greg Brooke for his support throughout my MSD where he has helped me broaden my 
       scientific field, deepen my understanding and develop my laboratory techniques within 
       cancer biology. I would also like to thank the members of the Prischi lab group for their moral 
       and scientific support throughout day to day life in the lab. I would also like to thank the 
       Brooke group members for their support in the day to day life in the lab. Lastly, I would like to 
       thank my family and friends for their continued support in my pursuit of a scientific career 
       and encouraging me to keep motivated throughout.  
        
                     
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