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Title: The detection and evaluation of cathepsin S activity in nanoparticle-induced inflammation
Author: Hughes, Caroline Sarah
ISNI:       0000 0004 6060 0905
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2016
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This project aims to examine the utility of the proteolytic activity signatures of caspase 1 and cathepsin S (CTSS) as readouts of particle-induced inflammation and to elucidate the role and dynamic regulation of CTSS in response to cellular stress. Initially, a novel cell permeable probe, Z-PraVG-DMK was synthesised which permitted disclosure of CTSS activity in living cells, following cell lysis and rhodamine azide conjugation, by employing click chemistry protocols. Using such probes and also reporter substrates, it was demonstrated that extracellular CTSS levels and intracellular caspase 1 activity levels positively correlated with an increase in IL-1 beta levels, following lysosomal rupture and can act as surrogate biomarkers for nano particle-induced toxicity. In addition, a role for intracellular CTSS activity was found to lie upstream from caspase 1-dependent processing of IL-1 beta. Finally, the cellular regulatory mechanisms underlying CTSS activity, trafficiking and secretion were also explored; revealing that direct ubiquitination of CTSS may influence stabilisation of activity and export from the cell. In conclusion, the development, optimisation and implementation of assays to detect the proteolytic activity of CTSS have proved to be extremely valuable in unravelling the extralysosomal roles and regulation of CTSS. Results demonstrate the utility of intracellular caspase 1 and extracellular CTSS proteolytic activities in the as biomarkers of lysosomal rupture and acute inflammation and in the future, the activity-based detection of these enzymes may prove useful during the development of nanotherapeutics. Crucially, this study supports the emerging significance of CTSS as a regulator of the innate immune response, highlighting its role in maximal cytokine production and potentiating the IL-1 beta response.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available