Authors
E SHAKIR1; R Kirk1; G Rinaldi2; A J Walker1; 1 Kingston University, UK; 2 Wellcome Trust Sanger Institute, UK Discussion
Eukaryotic protein kinases have been well conserved through evolution and the genome of Schistosoma mansoni encodes over 250 of these regulatory proteins. To further understand protein kinase signal transduction and function during male-female interactions of S. mansoni, we investigated the temporal effects of excreted-secretory molecules produced by adult male worms over 20 h culture on protein kinase activities in female worms, and vice versa. Western blotting with anti-phospho tyrosine/serine/threonine antibodies revealed that the phosphorylation status of multiple proteins changed over 60 min in response to exposure to secretory molecules released from worms of the opposite sex. This finding encouraged us to test for activation of specific pathways in worms in response to these secretory molecules using antibodies that react specifically with activated protein kinase C (PKC), extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (p38 MAPK) or protein kinase A (PKA). Exchange of male/female culture media between groups of single sex worms resulted in the rapid activation of protein kinase pathways, particularly the ERK and p38 MAPK pathways where activation was seen as early as 5 min. Immunofluorescence and confocal laser scanning microscopy revealed that activation occurred in different structures including the parasite tegument. The motility of the parasites was also enhanced in response to the opposite-sex media. The secreted molecules were next biotinylated and fluorescence confocal laser scanning microscopy revealed that the secreted adult male molecules bound the surface of females and vice versa. This study is the first to report that male-female secretory molecules influence signal transduction mechanisms in worms of the opposite sex. Future studies aim to further characterise the importance of the excretory-secretory molecules in S. mansoni male-female interactions. 
