Hamdan, F. F. et al. A novel Schistosoma mansoni G protein-coupled receptor is responsive to histamine. Mol. Biochem. Parasitol. 119, 75-86

Institute of Parasitology, McGill University, 21,111 Lakeshore Road, Que., H9X 3V9, Ste. Anne de Bellevue, Canada.
Molecular and Biochemical Parasitology (Impact Factor: 1.79). 02/2002; 119(1):75-86. DOI: 10.1016/S0166-6851(01)00400-5
Source: PubMed


A new cDNA was cloned from the bloodfluke, Schistosoma mansoni and shown to encode a protein with structural characteristics of a biogenic amine G protein-coupled receptor (GPCR). At the amino acid level, the parasite receptor (SmGPCR) shared about the same level of sequence homology (approximately 30%) with all major types of amine GPCRs and could not be identified on the basis of sequence. SmGPCR exhibited several nonconservative substitutions at key GPCR positions, including an unusual asparagine substitution (Asn(111)) for the highly conserved aspartate of transmembrane (TM) 3. The full-length SmGPCR cDNA was double-tagged with N-terminal FLAG and C-terminal hexahistidine epitopes, and was codon-optimized for expression in cultured HEK293 and COS7 cells. In situ immunofluorescence analyses targeting the two N- and C-terminal epitopes demonstrated that the modified SmGPCR was expressed at high level in mammalian cells and assumed a typical GPCR topology, the N-terminus being extracellular and the C-terminus intracellular. Functional activity assays revealed that SmGPCR was responsive to histamine, which caused a dose-dependent elevation in intracellular Ca2+ (EC50=0.54+/-0.05 microM). An Asn(111)-->Asp mutation had no effect on the responsiveness to histamine, suggesting that SmGPCR does not require the TM3 aspartate for agonist activation, in contrast to most amine GPCRs. None of the other monoamines tested had any significant effect on receptor activity, using assays that measured both Ca2+- and cAMP-mediated signaling. The results suggest that SmGPCR is a novel structural class of histamine receptor that may be unique to flatworms.

Download full-text


Available from: Aisha Mousa, Nov 18, 2014
17 Reads
  • Source
    • "To mention just two examples, Dictyostelium discoideum uses GPCR signaling for many cellular processes including development [36], and the parasitic helminth Schistosoma mansoni uses a GPCR to sense histamine and to trigger cell responses via calcium and cAMP [37]. Madeira et al. [38] identified four putative serpentine receptors in P. falciparum and their functions are under analysis. "
  • Source
    • "The tegument of trematodes is rich in excretory/secretory (ES) inclusions, bounded externally by a plasma membrane bearing a dense glycocalyx, and is composed of conserved proteins, suggesting similarities in the structure and function of the surface layer [19]. Proteomic and functional expression analyses [20-23] have identified various salient, molecular components of the tegumental matrix, including G protein-coupled receptors (GPCRs). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Schistosomiasis is a parasitic disease affecting ~200 million people worldwide. Schistosoma haematobium and S. mansoni are two relatively closely related schistosomes (blood flukes), and the causative agents of urogenital and hepatointestinal schistosomiasis, respectively. The availability of genomic, transcriptomic and proteomic data sets for these two schistosomes now provides unprecedented opportunities to explore their biology, host interactions and schistosomiasis at the molecular level. A particularly important group of molecules involved in a range of biological and developmental processes in schistosomes and other parasites are the G protein-coupled receptors (GPCRs). Although GPCRs have been studied in schistosomes, there has been no detailed comparison of these receptors between closely related species. Here, using a genomic-bioinformatic approach, we identified and characterised key GPCRs in S. haematobium and S. mansoni (two closely related species of schistosome). Methods Using a Hidden Markov Model (HMM) and Support Vector Machine (SVM)-based pipeline, we classified and sub-classified GPCRs of S. haematobium and S. mansoni, combined with phylogenetic and transcription analyses. Results We identified and classified classes A, B, C and F as well as an unclassified group of GPCRs encoded in the genomes of S. haematobium and S. mansoni. In addition, we characterised ligand-specific subclasses (i.e. amine, peptide, opsin and orphan) within class A (rhodopsin-like). Conclusions Most GPCRs shared a high degree of similarity and conservation, except for members of a particular clade (designated SmGPR), which appear to have diverged between S. haematobium and S. mansoni and might explain, to some extent, some of the underlying biological differences between these two schistosomes. The present set of annotated GPCRs provides a basis for future functional genomic studies of cellular GPCR-mediated signal transduction and a resource for future drug discovery efforts in schistosomes.
    Parasites & Vectors 05/2014; 7(1):242. DOI:10.1186/1756-3305-7-242 · 3.43 Impact Factor
  • Source
    • "The top grouping is comprised exclusively of amine (GAR and 5HT) and peptide GPCRs. Among them is a receptor pair orthologous to Gt-NPR1 [7], the only neuropeptide receptor deorphanized in this phylum. This degree of sequence conservation promotes the use of planaria as a convenient heterologous system to study parasite receptors. "
    [Show abstract] [Hide abstract]
    ABSTRACT: G protein-coupled receptors (GPCRs) constitute one of the largest groupings of eukaryotic proteins, and represent a particularly lucrative set of pharmaceutical targets. They play an important role in eukaryotic signal transduction and physiology, mediating cellular responses to a diverse range of extracellular stimuli. The phylum Platyhelminthes is of considerable medical and biological importance, housing major pathogens as well as established model organisms. The recent availability of genomic data for the human blood fluke Schistosoma mansoni and the model planarian Schmidtea mediterranea paves the way for the first comprehensive effort to identify and analyze GPCRs in this important phylum. Application of a novel transmembrane-oriented approach to receptor mining led to the discovery of 117 S. mansoni GPCRs, representing all of the major families; 105 Rhodopsin, 2 Glutamate, 3 Adhesion, 2 Secretin and 5 Frizzled. Similarly, 418 Rhodopsin, 9 Glutamate, 21 Adhesion, 1 Secretin and 11 Frizzled S. mediterranea receptors were identified. Among these, we report the identification of novel receptor groupings, including a large and highly-diverged Platyhelminth-specific Rhodopsin subfamily, a planarian-specific Adhesion-like family, and atypical Glutamate-like receptors. Phylogenetic analysis was carried out following extensive gene curation. Support vector machines (SVMs) were trained and used for ligand-based classification of full-length Rhodopsin GPCRs, complementing phylogenetic and homology-based classification. Genome-wide investigation of GPCRs in two platyhelminth genomes reveals an extensive and complex receptor signaling repertoire with many unique features. This work provides important sequence and functional leads for understanding basic flatworm receptor biology, and sheds light on a lucrative set of anthelmintic drug targets.
    BMC Genomics 12/2011; 12(1):596. DOI:10.1186/1471-2164-12-596 · 3.99 Impact Factor
Show more