Functional Characterization of a Novel Family of Acetylcholine-Gated Chloride Channels in Schistosoma mansoni
Figure 2
Phylogenetic analysis of cys-loop ion channel subunits.
A bootstrapped, neighbor-joining tree was constructed in PHYLIP from a CLUSTALX alignment of vertebrate and invertebrate Cys-loop superfamily receptor subunits. The tree is midpoint-rooted and was visualized using FigTree 3.0. Only nodes supported by bootstrap values of 70% or higher are shown. Two distinct groups of receptors can be seen, the γ-aminobutyric acid (GABA)/glycine-like anion channels and the nicotinic acetylcholine receptors (nAChRs). The C. elegans acetylcholine-gated chloride channels (ACC) form a distinct clade within the larger group of GABA/glycine anion channels (green inset). In contrast the predicted Schistosoma acetylcholine-gated chloride channels (SmACCs) align with cholinergic nicotinic nAChRs, suggesting divergent evolutionary paths. The SmACCs described here are indicated by arrows and they constitute a separate clade in the nAChR tree along with putative homologs from flatworms Dugesia (Dtig), Clonorchis (Cs) and S. haematobium, as well as the snail Lymnaea (Lym). Accession numbers for sequences used in the alignment are listed in Table S1.