Ressurreicao, Margarida de Azevedo Gomes de Curvalho (2009) Cell signalling in 'Schistosoma mansoni': a role for p38 MAPK. (MSc(R) thesis), Kingston University, .

Abstract

“Schistosoma mansoni” is a parasitic trematode that can cause intestinal schistosomiasis in humans. This study focused on mitogen-activated protein kinases (MAPKs), particularly p38 MAPK signalling in different “S. mansoni” life stages, and the functional role of p38 MAPK in miracidia, cercariae and during transformation of miracidia into mother sporocysts. Using anti-phospho-p38 MAPK monoclonal antibodies and western blotting, a phosphorylated (activated) p38 MAPK-like protein was detected at approximately 43 kDa in miracidia, transforming miracidia, and adult worms. Immunoprecipitation and kinase assays incorporating ATF-2 substrate, a downstream target of p38 MAPK, revealed that the identified kinase possessed p38 MAPK activity which was inhibited by the p38 MAPK inhibitor, SB203580. Phosphorylation of p38 MAPK was low in intact miracidia; however, phosphorylation increased significantly when miracidia were exposed to the p38 MAPK activator, anisomycin. During in vitro transformation of miracidia into mother sporocysts, p38 MAPK phosphorylation levels increased to 3.7 times that of 4 h larvae after 28 h transformation. Transformation experiments carried out with anisomycin revealed that shedding of ciliated plates from miracidia occurred significantly faster than in control samples. Fluorescence confocal microscopy of miracidia challenged with this compound for 30 min showed that phosphorylated p38 MAPK was predominately associated with the cilliary plates. Moreover, video analysis of freshly-hatched miracidia incubated in anisomycin showed that this compound reduced swimming speed significantly, with total stoppage after 45 min exposure; in the presence of SB203580 the swimming speed of miracidia increased slightly. In addition, the phosphorylation status of p38 MAPK was observed in freshly-emerged cercariae by confocal microscopy; high levels of phosphorylation were seen associated with the head region and anisomycin did not seem to increase p38 MAPK phosphorylation. Video analysis of cercariae swimming in anisomycin revealed that this compound reduced swimming speed, with little swimming evident after 15 min. This study significantly enhances knowledge of p38 MAPK signalling in “S. mansoni” and supports a functional role of this kinase in motility and transformation of the parasite.

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