PKA signalling in cercariae and somules of 'Schistosoma mansoni'

Schistosoma mansoni is a parasitic trematode that is the causative agent of human intestinal schistosomiasis, a neglected tropical disease that is considered secondonly to malaria in terms of importance. There is relatively little known about cell signalling within schistosomes and how signalling pathways in the parasite may be invdlved in host parasite interactions. This study focuses on protein kinase A (PKA) in the cercariae and schistosomule larval stages of the parasite. Using 'smart' anti-phospho PKA antibodies and western blotting, a phosphorylated (activated) PKA protein was detected at approximately 40 kDa in both cercariae and somules. Using laser scanning confocal microscopy, activated PKA was localised in the somule tegument, nervous system, cephalic ganglia, ventral sucker and the rudimentary oesophagus. Activated PKA was also localised in anteriorsensory structures and the junction between the head and tail in cercariae.Staining of somules or cercariae with anti-phospho PKA substrate antibodies revealed similar regions of PKA activation. Exposure of somules to serotonin or dopamine resulted in increased phosphorylation (activation) of PKA. However, in contrast, exposure of somules to neuropeptide Y (NPY) resulted in decreased PKA phosphorylation (activation). Finally exposure of somules to the PKA activator forskolin resulted in increased phosphorylation of PKA, and video analysis showed forskolin to significantly increase the number of somule contractions. in summary, these results increase our understanding of PKA signalling in schistosomes and its potential role in host parasite interactions.