Histamine signalling in Schistosoma mansoni: Immunolocalisation and characterisation of a new histamine-responsive receptor (SmGPR-2)

Biochemical Characterization and Differential Expression of a 16.5-Kilodalton Tegument-Associated Antigen from the Liver Fluke Fasciola hepatica

“…Immunohistochemistry studies demonstrated that in the adult fluke, FhTP16.5 is strongly expressed at the outer surface of the tegument as well as in parenchymal tissue associated with the tegument, which is a pattern similar to those of other proteins of trematodes, such as F. gigantica fatty acid binding protein (FgFABP) (59), S. mansoni alkaline phosphatase (SmAP) (11), superoxide dismutase (Sm-SOD) (53), and histamineresponsive receptor (SmGPR) (24). However, the observation that it is moderately expressed in the syncytium could indicate that FhTP16.5 is not actually part of the architecture of the tegument but is a protein that is produced in parenchymal cells, is delivered to the tegument, and accumulates there.…”

Biogenic amines and the control of neuromuscular signaling in schistosomes

“…Aside from these three, the remaining BAlike GPCRs of S. mansoni are novel sequences that cannot be categorized into any particular type of amine receptor. The most divergent of these sequences are the SmGPRs, which represent approximately half of all the aminergic receptors in S. mansoni and constitute a separate branch in the BA GPCR tree (El-Shehabi and Ribeiro 2010;El-Shehabi et al 2012). Included in this group are the histamine-and dopamine-activated SmGPRs described earlier, which are more closely related to each other (and to other SmGPRs) than they are to histamine or dopamine receptors.…”

“…At higher magnification, b SmGPR-3 expression in seen in large nerve fibers (solid arrows) and cell bodies (solid arrow heads) of the CNS. Expression is also seen in smaller nerve fibers that innervate the body wall musculature (open arrow heads) (El-Shehabi et al 2012) abundantly expressed in parasitic larval forms of S. mansoni than the adult worms El-Shehabi and Ribeiro 2010). At the RNA level, the expression levels of these receptors were &50-fold higher in young schistosomula than either cercaria or adult worms, and a significant difference was also observed at the protein level.…”

“…Some of this evidence comes for immunolocalization studies of BAcontaining neurons and the expression patterns of BA receptors in the worm. For example, virtually all of the BA receptors that have been characterized are abundantly expressed in the innervation of the suckers, both oral and ventral suckers El-Shehabi and Ribeiro 2010;Taman and Ribeiro 2009), suggesting a probable role for the activating amines in host attachment and feeding. In addition, dopaminergic receptors were found in the muscular lining of the cecum (Taman and Ribeiro 2009) and the innervation of the male testes (El-Shehabi et al 2012), whereas serotonin is believed to modulate egg production in females (Halton and Gustafsson 1996).…”

“…Other highthroughput GPCR assays are based on reporter genes expressed in either transfected mammalian cells or yeast (Dowell and Brown 2009;Durocher et al 2000;Shultz et al 2008;Wang et al 2006). The yeast expression system described by Wang and colleagues (Wang et al 2006) was shown to be effective in expression of both schistosome and ascarid GPCRs and was used to produce a first pharmacological profile of these receptors (El-Shehabi and Ribeiro 2010;El-Shehabi et al 2012;Kimber et al 2009;Taman and Ribeiro 2009). More recently, a variety of assays have been described that do not require interaction with a G protein and are therefore suitable to measure activity of a wider range of GPCRs, including those that do not signal through the canonical G-protein coupling mechanism.…”