Ludtmann, Marthe Helene Regina (2008) Protein kinase C signalling in 'Schistosoma mansoni' and its role in larval development. (MSc(R) thesis), Kingston University, .

Abstract

Schistosoma mansoni is an important trematode parasite that causes human intestinal schistosomiasis. Little is known about cell signalling in S. mansoni and how signal transduction is regulated during its development. This study focused on Protein Kinase C (PKC) signalling in S. mensont miracidia and modulation of PKC phosphorylation (activation) during transformation of miracidia into mother sporocysts. Using anti-phospho PKC antibodies and western blotting, a PKC-like protein was detected at approximately 76 kDa in miracidia protein extracts. Phosphorylation of this protein was significantly increased after 10 min when intact miracidia were exposed to the classical PKC activator, phorbol-myristate-acetate (PMA). Moreover, PKC pathway inhibitors (U73122 and GF 109203X) reduced the phosphorylation status of this enzyme after 90 min incubation. Phosphorylated PKC was also detected in adult worms and a phosphorylated MARCKS-like protein was identified in miracidia. During in vitro transformation of S. mansoni, PKC phosphorylation levels fluctuated. In freshly hatched miracidia, phosphorylation was approximately 1.5 times that observed in miracidia cultured for 24 h (transforming into mother sporocysts), whereas after 48 h PKC phosphorylation was only weakly detectable in fully transformed parasites. Transformation experiments carried out in the presence of GF 109203X revealed that development from miracidia to mother sporocysts occurred significantly faster than in controls; miracidial plates were also shed much earlier during transformation. These findings suggest that PKC plays an important role in the development of S. mansoni miracidia to sporocysts. Finally, fluorescence confocal microscopy of miracidia showed that phosphorylated PKC is predominately associated with the tegument and the terebratorium; immunoreactivity was also seen in the neuronal mass, the excretory vesicle and the germinal cells. The phosphorylation of PKC in these regions vanished during transformation of S. mansoni into mother sporocysts. This study significantly enhances knowledge of PKC signalling in S. mansoni and for the first time, defines a role for this kinase in development of the parasite.

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