Schistosoma mansoni:l-Glutamate-Induced Contractions in Isolated Muscle Fibers; Evidence for a Glutamate Transporter

Miller, Crystal; Day, Tim A.; Bennett, J.L.; Pax, Ralph A.

doi:10.1006/expr.1996.0129

Cited by 22 publications

(14 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…L-glutamate has been implicated in the regulation of neuromuscular activity in schistosomes, but the mechanisms mediating these effects are unclear. Direct application of L-glutamate did not affect basal motor activity in intact worms [81], but a subsequent study provided evidence of glutamate-induced, concentration-dependent contractions mediated by a glutamate/Na + co-transporter in isolated S. mansoni muscles fibers [82]. Kainate, an iGluR agonist, was subsequently shown to produce tonic muscle contraction and paralysis in whole worms [83].…”

Section: Resultsmentioning

confidence: 97%

Molecular Cloning and Characterization of Novel Glutamate-Gated Chloride Channel Subunits from Schistosoma mansoni

et al. 2013

View full text Add to dashboard Cite

Cys-loop ligand-gated ion channels (LGICs) mediate fast ionotropic neurotransmission. They are proven drug targets in nematodes and arthropods, but are poorly characterized in flatworms. In this study, we characterized the anion-selective, non-acetylcholine-gated Cys-loop LGICs from Schistosoma mansoni. Full-length cDNAs were obtained for SmGluCl-1 (Smp_096480), SmGluCl-2 (Smp_015630) and SmGluCl-3 (Smp_104890). A partial cDNA was retrieved for SmGluCl-4 (Smp_099500/Smp_176730). Phylogenetic analyses suggest that SmGluCl-1, SmGluCl-2, SmGluCl-3 and SmGluCl-4 belong to a novel clade of flatworm glutamate-gated chloride channels (GluCl) that includes putative genes from trematodes and cestodes. The flatworm GluCl clade was distinct from the nematode-arthropod and mollusc GluCl clades, and from all GABA receptors. We found no evidence of GABA receptors in S. mansoni. SmGluCl-1, SmGluCl-2 and SmGluCl-3 subunits were characterized by two-electrode voltage clamp (TEVC) in Xenopus oocytes, and shown to encode Cl−-permeable channels gated by glutamate. SmGluCl-2 and SmGluCl-3 produced functional homomers, while SmGluCl-1 formed heteromers with SmGluCl-2. Concentration-response relationships revealed that the sensitivity of SmGluCl receptors to L-glutamate is among the highest reported for GluCl receptors, with EC50 values of 7–26 µM. Chloride selectivity was confirmed by current-voltage (I/V) relationships. SmGluCl receptors are insensitive to 1 µM ivermectin (IVM), indicating that they do not belong to the highly IVM-sensitive GluClα subtype group. SmGluCl receptors are also insensitive to 10 µM meclonazepam, a schistosomicidal benzodiazepine. These results provide the first molecular evidence showing the contribution of GluCl receptors to L-glutamate signaling in S. mansoni, an unprecedented finding in parasitic flatworms. Further work is needed to elucidate the roles of GluCl receptors in schistosomes and to explore their potential as drug targets.

show abstract

Section: Resultsmentioning

confidence: 97%

Molecular Cloning and Characterization of Novel Glutamate-Gated Chloride Channel Subunits from Schistosoma mansoni

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Other GPCRs such as SmGPR-3 [39] and SmD2 [40] which are activated by dopamine and are expressed in the central/peripheral nervous systems and body wall musculature, respectively, might influence S. mansoni movement in a complex fashion given that dopamine suppresses S. mansoni motor activity [39], [41] but induces cAMP production via SmD2 [40]. Furthermore, l -glutamate induces muscle contraction in isolated S. mansoni muscle fibres [42] likely via l -glutamate receptors [43] and kainic acid, an agonist that mimics the effect of glutamate, causes hyperkinesias and coiling in adult worms [44] similar to that observed with forskolin in the present study. Motor activity in S. mansoni thus appears to be under complex regulatory control from neuromodulators and classical neurotransmitters some of which will likely signal to PKA.…”

Section: Discussionmentioning

confidence: 99%

Functional Mapping of Protein Kinase A Reveals Its Importance in Adult Schistosoma mansoni Motor Activity

et al. 2013

View full text Add to dashboard Cite

Cyclic AMP (cAMP)-dependent protein kinase/protein kinase A (PKA) is the major transducer of cAMP signalling in eukaryotic cells. Here, using laser scanning confocal microscopy and ‘smart’ anti-phospho PKA antibodies that exclusively detect activated PKA, we provide a detailed in situ analysis of PKA signalling in intact adult Schistosoma mansoni, a causative agent of debilitating human intestinal schistosomiasis. In both adult male and female worms, activated PKA was consistently found associated with the tegument, oral and ventral suckers, oesophagus and somatic musculature. In addition, the seminal vesicle and gynaecophoric canal muscles of the male displayed activated PKA whereas in female worms activated PKA localized to the ootype wall, the ovary, and the uterus particularly around eggs during expulsion. Exposure of live worms to the PKA activator forskolin (50 µM) resulted in striking PKA activation in the central and peripheral nervous system including at nerve endings at/near the tegument surface. Such neuronal PKA activation was also observed without forskolin treatment, but only in a single batch of worms. In addition, PKA activation within the central and peripheral nervous systems visibly increased within 15 min of worm-pair separation when compared to that observed in closely coupled worm pairs. Finally, exposure of adult worms to forskolin induced hyperkinesias in a time and dose dependent manner with 100 µM forskolin significantly increasing the frequency of gross worm movements to 5.3 times that of control worms (P≤0.001). Collectively these data are consistent with PKA playing a central part in motor activity and neuronal communication, and possibly interplay between these two systems in S. mansoni. This study, the first to localize a protein kinase when exclusively in an activated state in adult S. mansoni, provides valuable insight into the intricacies of functional protein kinase signalling in the context of whole schistosome physiology.

show abstract

“…In fact, pharmacological and immunohistochemical evidence has strong suggested that L-glutamate and L-aspartate are neurotransmitters in platyhelminths (Keenan and Koopowitz, 1982;Mendonça-Silva et al, 2002;Miller et al, 1996;Webb, 1987). The precise identity of EgAT1 inside the DAACS family could not be defined by bioinformatic analysis.…”

Section: Discussionmentioning

confidence: 92%

Sequencing, bioinformatic characterization and expression pattern of a putative amino acid transporter from the parasitic cestode Echinococcus granulosus

Camicia¹,

Paredes²,

Chalar

et al. 2008

Gene

View full text Add to dashboard Cite

Schistosoma mansoni:l-Glutamate-Induced Contractions in Isolated Muscle Fibers; Evidence for a Glutamate Transporter

Cited by 22 publications

References 0 publications

Molecular Cloning and Characterization of Novel Glutamate-Gated Chloride Channel Subunits from Schistosoma mansoni

Molecular Cloning and Characterization of Novel Glutamate-Gated Chloride Channel Subunits from Schistosoma mansoni

Functional Mapping of Protein Kinase A Reveals Its Importance in Adult Schistosoma mansoni Motor Activity

Sequencing, bioinformatic characterization and expression pattern of a putative amino acid transporter from the parasitic cestode Echinococcus granulosus

Contact Info

Product

Resources

About