The Drosophila Toll receptor and its ligand Spatzle (Spz) are used to transduce a signal from an extracellular space to an intracellular environment in two independent systems. These are the specification of the dorsal-ventral axis during embryogenesis and the expression of antimicrobial peptides during innate immune responses to Gram-positive bacterial and fungal infection. Each time binding to the receptor occurs following the proteolytic activation of Spz via a cascade of serine proteases. Easter (Ea) is the terminal protease responsible for Spz cleavage in embryos while the Spatzle Processing Enzyme (SPE) is the terminal protease triggering Spz activation in immunity. We have taken advantage of a Spz construct tagged at both the N- and C-termini to further understand the processing of Spz during signalling in vivo. To this end we have developed a strategy to investigate the processing of Spz during development using the hemolymph as a model for the perivitelline fluid (PVF). We have transformed the spiag construct downstream of UAS sites into Drosophila and demonstrated that it is expressed under the control ofa Gal4 driver. The expressed spztag can be detected in the hemolymph and appears to be processed upon immune challenge. We have attempted to detect proteolytic processing of Spztag by expressing constitutively active proteases known to result in expression of drosomycin via Spz-Toll signalling. We have also identified that an active form ofSPE is able to process the Necrotic (Nec) serpin. Psh has previously been shown to cleave Nec in response to immune challenge. We also see up regulation of both Serpin27A and Nec in the hemolymph in the presence of active SPE and Easter proteases (282 words).
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:491758 |
| Date | January 2007 |
| Creators | Thompson, Gavin |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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