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Simonson BT, Jegla M, Ryan JF, Jegla T. Functional analysis of ctenophore Shaker K + channels: N-type inactivation in the animal roots. Biophys J 2024; 123:2038-2049. [PMID: 38291751 PMCID: PMC11309979 DOI: 10.1016/j.bpj.2024.01.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/16/2023] [Accepted: 01/24/2024] [Indexed: 02/01/2024] Open
Abstract
Here we explore the evolutionary origins of fast N-type ball-and-chain inactivation in Shaker (Kv1) K+ channels by functionally characterizing Shaker channels from the ctenophore (comb jelly) Mnemiopsis leidyi. Ctenophores are the sister lineage to other animals and Mnemiopsis has >40 Shaker-like K+ channels, but they have not been functionally characterized. We identified three Mnemiopsis channels (MlShak3-5) with N-type inactivation ball-like sequences at their N termini and functionally expressed them in Xenopus oocytes. Two of the channels, MlShak4 and MlShak5, showed rapid inactivation similar to cnidarian and bilaterian Shakers with rapid N-type inactivation, whereas MlShak3 inactivated ∼100-fold more slowly. Fast inactivation in MlShak4 and MlShak5 required the putative N-terminal inactivation ball sequences. Furthermore, the rate of fast inactivation in these channels depended on the number of inactivation balls/channel, but the rate of recovery from inactivation did not. These findings closely match the mechanism of N-type inactivation first described for Drosophila Shaker in which 1) inactivation balls on the N termini of each subunit can independently block the pore, and 2) only one inactivation ball occupies the pore binding site at a time. These findings suggest classical N-type activation evolved in Shaker channels at the very base of the animal phylogeny in a common ancestor of ctenophores, cnidarians, and bilaterians and that fast-inactivating Shakers are therefore a fundamental type of animal K+ channel. Interestingly, we find evidence from functional co-expression experiments and molecular dynamics that MlShak4 and MlShak5 do not co-assemble, suggesting that Mnemiopsis has at least two functionally independent N-type Shaker channels.
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Affiliation(s)
- Benjamin T Simonson
- Department of Biology and Huck Institutes of the Life Sciences, Penn State University, University Park, Pennsylvania
| | - Max Jegla
- Department of Biology and Huck Institutes of the Life Sciences, Penn State University, University Park, Pennsylvania
| | - Joseph F Ryan
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL; Department of Biology, University of Florida, Gainesville, FL
| | - Timothy Jegla
- Department of Biology and Huck Institutes of the Life Sciences, Penn State University, University Park, Pennsylvania.
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2
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Tolstenkov O, Chatzigeorgiou M, Gorbushin A. Neuronal gene expression in two generations of the marine parasitic worm, Cryptocotyle lingua. Commun Biol 2023; 6:1279. [PMID: 38110640 PMCID: PMC10728431 DOI: 10.1038/s42003-023-05675-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Accepted: 12/04/2023] [Indexed: 12/20/2023] Open
Abstract
Trematodes, or flukes, undergo intricate anatomical and behavioral transformations during their life cycle, yet the functional changes in their nervous system remain poorly understood. We investigated the molecular basis of nervous system function in Cryptocotyle lingua, a species of relevance for fisheries. Transcriptomic analysis revealed a streamlined molecular toolkit with the absence of key signaling pathways and ion channels. Notably, we observed the loss of nitric oxide synthase across the Platyhelminthes. Furthermore, we identified upregulated neuronal genes in dispersal larvae, including those involved in aminergic pathways, synaptic vesicle trafficking, TRPA channels, and surprisingly nitric oxide receptors. Using neuronal markers and in situ hybridization, we hypothesized their functional relevance to larval adaptations and host-finding strategies. Additionally, employing a behavior quantification toolkit, we assessed cercaria motility, facilitating further investigations into the behavior and physiology of parasitic flatworms. This study enhances our understanding of trematode neurobiology and provides insights for targeted antiparasitic strategies.
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Affiliation(s)
| | | | - Alexander Gorbushin
- Sechenov Institute of Evolutionary Physiology and Biochemistry, St Petersburg, Russia
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3
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Nor B, Young ND, Korhonen PK, Hall RS, Tan P, Lonie A, Gasser RB. Pipeline for the identification and classification of ion channels in parasitic flatworms. Parasit Vectors 2016; 9:155. [PMID: 26983991 PMCID: PMC4794918 DOI: 10.1186/s13071-016-1428-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 03/05/2016] [Indexed: 01/05/2023] Open
Abstract
Background Ion channels are well characterised in model organisms, principally because of the availability of functional genomic tools and datasets for these species. This contrasts the situation, for example, for parasites of humans and animals, whose genomic and biological uniqueness means that many genes and their products cannot be annotated. As ion channels are recognised as important drug targets in mammals, the accurate identification and classification of parasite channels could provide major prospects for defining unique targets for designing novel and specific anti-parasite therapies. Here, we established a reliable bioinformatic pipeline for the identification and classification of ion channels encoded in the genome of the cancer-causing liver fluke Opisthorchis viverrini, and extended its application to related flatworms affecting humans. Methods We built an ion channel identification + classification pipeline (called MuSICC), employing an optimised support vector machine (SVM) model and using the Kyoto Encyclopaedia of Genes and Genomes (KEGG) classification system. Ion channel proteins were first identified and grouped according to amino acid sequence similarity to classified ion channels and the presence and number of ion channel-like conserved and transmembrane domains. Predicted ion channels were then classified to sub-family using a SVM model, trained using ion channel features. Results Following an evaluation of this pipeline (MuSICC), which demonstrated a classification sensitivity of 95.2 % and accuracy of 70.5 % for known ion channels, we applied it to effectively identify and classify ion channels in selected parasitic flatworms. Conclusions MuSICC provides a practical and effective tool for the identification and classification of ion channels of parasitic flatworms, and should be applicable to a broad range of organisms that are evolutionarily distant from taxa whose ion channels are functionally characterised. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1428-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Bahiyah Nor
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Neil D Young
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia.
| | - Pasi K Korhonen
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Ross S Hall
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Patrick Tan
- Genome Institute of Singapore, 60 Biopolis Street, Singapore, 138672, Republic of Singapore.,Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, Singapore, 138672, Republic of Singapore
| | - Andrew Lonie
- Victorian Life Sciences Computation Initiative (VLSCI), The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Robin B Gasser
- Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia.
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4
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Parker-Manuel SJ, Hahnel S, Grevelding CG. Inhibition of Schistosoma mansoni ether-a-go-go related gene-encoded potassium channels leads to hypermotility and impaired egg production. Exp Parasitol 2015; 158:48-54. [PMID: 26188142 DOI: 10.1016/j.exppara.2015.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Revised: 06/26/2015] [Accepted: 07/01/2015] [Indexed: 11/19/2022]
Abstract
The purpose of this work was to investigate the effect of ether-a-go-go related gene (ERG) potassium channel inhibition on Schistosoma mansoni. Use of dofetilide to block the schistosome ERGs resulted in a striking 'corkscrew' effect. The worms were unable to control their motility; they were hypermotile. The treated worms produced abnormal eggs, some of which consisted of little more than a spine. One of the S. mansoni ERGs (SmERGs), Smp_161140, was chosen for further study by RNAi. The transcript was knocked down to 50% compared to the controls. These RNAi-treated worms demonstrated seizure-like movements. In S. mansoni, as in other organisms, ERG channels seem to play a role in regulating muscle excitability. This work shows that egg production can be greatly reduced by effectively targeting muscle coordination in these important parasites.
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Affiliation(s)
- S J Parker-Manuel
- Institute of Parasitology, Justus-Liebig-University Giessen, Germany.
| | - S Hahnel
- Institute of Parasitology, Justus-Liebig-University Giessen, Germany
| | - C G Grevelding
- Institute of Parasitology, Justus-Liebig-University Giessen, Germany
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Muñoz FJ, Godoy JA, Cerpa W, Poblete IM, Huidobro-Toro JP, Inestrosa NC. Wnt-5a increases NO and modulates NMDA receptor in rat hippocampal neurons. Biochem Biophys Res Commun 2014; 444:189-94. [PMID: 24440698 DOI: 10.1016/j.bbrc.2014.01.031] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 01/10/2014] [Indexed: 10/25/2022]
Abstract
Wnt signaling has a crucial role in synaptic function at the central nervous system. Here we evaluate whether Wnts affect nitric oxide (NO) generation in hippocampal neurons. We found that non-canonical Wnt-5a triggers NO production; however, Wnt-3a a canonical ligand did not exert the same effect. Co-administration of Wnt-5a with the soluble Frizzled related protein-2 (sFRP-2) a Wnt antagonist blocked the NO production. Wnt-5a activates the non-canonical Wnt/Ca(2+) signaling through a mechanism that depends on Ca(2+) release from Ryanodine-sensitive internal stores. The increase in NO levels evoked by Wnt-5a promotes the insertion of the GluN2B subunit of the NMDA receptor (NMDAR) into the neuronal cell surface. To the best of our knowledge, this is the first time that Wnt-5a signaling is related to NO production, which in turn increases NMDARs trafficking to the cell surface.
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Affiliation(s)
- Francisco J Muñoz
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile; Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Parc de Recerca Biomédica de Barcelona, Spain
| | - Juan A Godoy
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile
| | - Waldo Cerpa
- Laboratorio de Función y Patología Neuronal, Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile
| | - Inés M Poblete
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile; Departamento de Fisiología, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile
| | - Juan Pablo Huidobro-Toro
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile; Departamento de Fisiología, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile; Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago, Santiago de Chile, Chile
| | - Nibaldo C Inestrosa
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago de Chile, Chile; Centre for Healthy Brain Ageing, School of Psychiatry, UNSW, Faculty of Medicine, University of New South Wales, Sydney, Australia.
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Copeland CS, Marz M, Rose D, Hertel J, Brindley PJ, Santana CB, Kehr S, Attolini CSO, Stadler PF. Homology-based annotation of non-coding RNAs in the genomes of Schistosoma mansoni and Schistosoma japonicum. BMC Genomics 2009; 10:464. [PMID: 19814823 PMCID: PMC2770079 DOI: 10.1186/1471-2164-10-464] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 10/08/2009] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Schistosomes are trematode parasites of the phylum Platyhelminthes. They are considered the most important of the human helminth parasites in terms of morbidity and mortality. Draft genome sequences are now available for Schistosoma mansoni and Schistosoma japonicum. Non-coding RNA (ncRNA) plays a crucial role in gene expression regulation, cellular function and defense, homeostasis, and pathogenesis. The genome-wide annotation of ncRNAs is a non-trivial task unless well-annotated genomes of closely related species are already available. RESULTS A homology search for structured ncRNA in the genome of S. mansoni resulted in 23 types of ncRNAs with conserved primary and secondary structure. Among these, we identified rRNA, snRNA, SL RNA, SRP, tRNAs and RNase P, and also possibly MRP and 7SK RNAs. In addition, we confirmed five miRNAs that have recently been reported in S. japonicum and found two additional homologs of known miRNAs. The tRNA complement of S. mansoni is comparable to that of the free-living planarian Schmidtea mediterranea, although for some amino acids differences of more than a factor of two are observed: Leu, Ser, and His are overrepresented, while Cys, Meth, and Ile are underrepresented in S. mansoni. On the other hand, the number of tRNAs in the genome of S. japonicum is reduced by more than a factor of four. Both schistosomes have a complete set of minor spliceosomal snRNAs. Several ncRNAs that are expected to exist in the S. mansoni genome were not found, among them the telomerase RNA, vault RNAs, and Y RNAs. CONCLUSION The ncRNA sequences and structures presented here represent the most complete dataset of ncRNA from any lophotrochozoan reported so far. This data set provides an important reference for further analysis of the genomes of schistosomes and indeed eukaryotic genomes at large.
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Affiliation(s)
- Claudia S Copeland
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, University of Leipzig, Härtelstrasse 16-18, D-04107 Leipzig, Germany.
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7
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Berriman M, Haas BJ, LoVerde PT, Wilson RA, Dillon GP, Cerqueira GC, Mashiyama ST, Al-Lazikani B, Andrade LF, Ashton PD, Aslett MA, Bartholomeu DC, Blandin G, Caffrey CR, Coghlan A, Coulson R, Day TA, Delcher A, DeMarco R, Djikeng A, Eyre T, Gamble JA, Ghedin E, Gu Y, Hertz-Fowler C, Hirai H, Hirai Y, Houston R, Ivens A, Johnston DA, Lacerda D, Macedo CD, McVeigh P, Ning Z, Oliveira G, Overington JP, Parkhill J, Pertea M, Pierce RJ, Protasio AV, Quail MA, Rajandream MA, Rogers J, Sajid M, Salzberg SL, Stanke M, Tivey AR, White O, Williams DL, Wortman J, Wu W, Zamanian M, Zerlotini A, Fraser-Liggett CM, Barrell BG, El-Sayed NM. The genome of the blood fluke Schistosoma mansoni. Nature 2009; 460:352-8. [PMID: 19606141 PMCID: PMC2756445 DOI: 10.1038/nature08160] [Citation(s) in RCA: 807] [Impact Index Per Article: 53.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Accepted: 05/22/2009] [Indexed: 11/24/2022]
Abstract
Schistosoma mansoni is responsible for the neglected tropical disease schistosomiasis that affects 210 million people in 76 countries. We report here analysis of the 363 megabase nuclear genome of the blood fluke. It encodes at least 11,809 genes, with an unusual intron size distribution, and novel families of micro-exon genes that undergo frequent alternate splicing. As the first sequenced flatworm, and a representative of the lophotrochozoa, it offers insights into early events in the evolution of the animals, including the development of a body pattern with bilateral symmetry, and the development of tissues into organs. Our analysis has been informed by the need to find new drug targets. The deficits in lipid metabolism that make schistosomes dependent on the host are revealed, while the identification of membrane receptors, ion channels and more than 300 proteases, provide new insights into the biology of the life cycle and novel targets. Bioinformatics approaches have identified metabolic chokepoints while a chemogenomic screen has pinpointed schistosome proteins for which existing drugs may be active. The information generated provides an invaluable resource for the research community to develop much needed new control tools for the treatment and eradication of this important and neglected disease.
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8
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Klassen TL, Buckingham SD, Atherton DM, Dacks JB, Gallin WJ, Spencer AN. Atypical Phenotypes From Flatworm Kv3 Channels. J Neurophysiol 2006; 95:3035-46. [PMID: 16452260 DOI: 10.1152/jn.00858.2005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Divergence of the Shaker superfamily of voltage-gated (Kv) ion channels early in metazoan evolution created numerous electrical phenotypes that were presumably selected to produce a wide range of excitability characteristics in neurons, myocytes, and other cells. A comparative approach that emphasizes this early radiation provides a comprehensive sampling of sequence space that is necessary to develop generally applicable models of the structure–function relationship in the Kv potassium channel family. We have cloned and characterized two Shaw-type potassium channels from a flatworm ( Notoplana atomata) that is arguably a representative of early diverging bilaterians. When expressed in Xenopus oocytes, one of these cloned channels, N.at-Kv3.1, exhibits a noninactivating, outward current with slow opening kinetics that are dependent on both the holding potential and the activating potential. A second Shaw-type channel, N.at-Kv3.2, has very different properties, showing weak inward rectification. These results demonstrate that broad phylogenetic sampling of proteins of a single family will reveal unexpected properties that lead to new interpretations of structure–function relationships.
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Affiliation(s)
- Tara L Klassen
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E1
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9
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Jang JH, Kim SD, Park JB, Hong SJ, Ryu PD. Ion channels of Fasciola hepatica incorporated into planar lipid bilayers. Parasitology 2004; 128:83-9. [PMID: 15002907 DOI: 10.1017/s0031182003004232] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ion channels are important target sites of anthelmintics, but little is known about those in Fasciola hepatica. In this work, we applied a planar lipid bilayer technique to characterize the properties of single ion channels in F. hepatica. Under a 200/40 mM KCl gradient, a large conductance channel of 251 pS was observed in 18% of the membranes studied. The channel was selective to K(+) over Cl(-) with a permeability ratio of K(+) to Cl(-) (PK/PCl) of 4.9. Open state probability (Po) of the channel was less than 0.5 and dependent on voltage (-60 to approximately +40 mV) and Ca(2+) (approximately 100 microM). The other two types of single channels observed in 11 and 5% of membranes, respectively, were a K(+)-permeable channel of 80 pS (PK/PCl=4.6) and a Cl(-)-permeable channel of 64 pS (PK/PCl=0.058). Open state probability of both channels showed little voltage dependence. The results indicate that distinct single channels of 60 to approximately 251 pS are present in relative abundance and, in addition, that the planar lipid bilayer technique can be a useful tool for the study of single ion channels in F. hepatica.
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Affiliation(s)
- J H Jang
- Laboratory of Pharmacology, College of Veterinary Medicine and School of Agricultural Biotechnology, Seoul National University, San 56-1 Sillim-dong, Kwanak-gu, Seoul 151-742, Republic of Korea
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Cobbett P, Day TA. Functional voltage-gated Ca2+ channels in muscle fibers of the platyhelminth Dugesia tigrina. Comp Biochem Physiol A Mol Integr Physiol 2003; 134:593-605. [PMID: 12600668 DOI: 10.1016/s1095-6433(02)00350-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The presence and function of voltage-gated Ca(2+) channels were examined in individual muscle fibers freshly dispersed from the triclad turbellarian Dugesia tigrina. Individual muscle fibers contracted in response to elevated extracellular K(+) in a concentration-dependent fashion. These depolarization-induced contractions were blocked by extracellular Co(2+) (2.5 mM), suggesting that they were dependent on depolarization-induced Ca(2+) influx across the sarcolemma. A voltage-gated inward current was apparent in whole cell recordings when the outward K(+) current was abolished by replacement of intracellular K(+) by Cs(+). This inward current was amplified with increasing concentration (</=10 mM) of extracellular Ba(2+) and was independent of extracellular Na(+) concentration suggesting the current was mediated by voltage-gated Ca(2+) channels. Further, and supporting the hypothesis that the inward current was mediated by these Ca(2+) channels, the Ba(2+) current was blocked by extracellular Co(2+) (2.5 mM) but not by tetrodotoxin (5 microM). Action potentials were generated by the muscle fibers in the presence of, but not in the absence of, extracellular Ba(2+) (5 mM). These data are the first clear demonstration of a voltage-gated Ca(2+) channel current in platyhelminth muscle, and they demonstrate a role for Ca(2+) influx in depolarization-induced contractions of muscle in these organisms.
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Affiliation(s)
- Peter Cobbett
- Department of Pharmacology and Toxicology, and the Neuroscience Program, Michigan State University, East Lansing, MI 48824-1317, USA.
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11
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Buckingham SD, Spencer AN. Role of high-voltage activated potassium currents in high-frequency neuronal firing: evidence from a basal metazoan. J Neurophysiol 2002; 88:861-8. [PMID: 12163537 DOI: 10.1152/jn.2002.88.2.861] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Certain neurons of vertebrates are specialized for high-frequency firing. Interestingly, high-frequency firing is also seen in central neurons in basal bilateral metazoans. Recently, the role of potassium currents with rightward-shifted activation curves in producing high-frequency firing has come under scrutiny. We apply intracellular recording, patch-clamp techniques, and compartmental modeling to examine the roles of rightward-shifted potassium currents in repetitive firing and shaping of action potentials in central neurons of the flatworm, Notoplana atomata (Phylum Platyhelminthes). The kinetic properties of potassium and sodium currents were determined from patch-clamp experiments on dissociated brain cells. To predict the effects of changing the steady-state and kinetic properties of these potassium currents, these data were incorporated into a computer model of a 30-microm spherical cell with the levels of current adjusted to approximate the values recorded in voltage-clamp experiments. The model was able to support regenerative spikes at high frequencies in response to injected current. Current-clamp recordings of cultured cells and of neurons in situ also showed evidence of very-high-frequency firing. Adjusting the ratio of inactivating to non-inactivating potassium currents had little effect upon the firing pattern of the cell or its ability to fire at high frequencies, whereas the presence of the non-inactivating current was necessary for repetitive firing. Computer simulations suggested that the rightward shift in voltage sensitivity confers a raised firing threshold, while rapid channel kinetics underlie high frequency firing, and the large activation range enhances the coding range of the cell.
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Rodrigues NB, Coura Filho P, de Souza CP, Jannoti Passos LK, Dias-Neto E, Romanha AJ. Populational structure of Schistosoma mansoni assessed by DNA microsatellites. Int J Parasitol 2002; 32:843-51. [PMID: 12062555 DOI: 10.1016/s0020-7519(02)00031-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
DNA microsatellites were used as molecular markers to analyse the population structure of the laboratory LE strain and of 10 field isolates of Schistosoma mansoni, the aetiologic agent of schistosomiasis. Out of 16,000 DNA sequences analysed in databases, 622 microsatellite loci were identified in 481 sequences (3.0%). The AT repetitions were the most frequent, followed by AAT and AC. Six loci showing perfect repetitions were selected and used in the polymerase chain reaction to evaluate polymorphisms in the number of repeats. Two groups of worms were studied. The first group consisted of 78 individuals, 39 of each sex, of the LE strain. The second group of worms consisted of 10 field isolates: seven from humans and three from snails. Four of the six loci were polymorphic, containing 11-17 alleles per locus. No linkage disequilibrium was observed among loci and none of the loci was sex linked. In both groups of worms, a significant deviation from Hardy-Weinberg equilibrium was observed. The observed heterozygosity was always lower than the expected one. The polymerase chain reaction primers were S. mansoni specific. The LE strain showed a lower total number of alleles or a lower average number of alleles/polymorphic locus than the field isolates, suggesting that 41 years of laboratory maintenance exerted selective pressure on the LE strain. The S. mansoni populations from the field were most genetically undifferentiated (R(ST)<0.027), suggesting a high gene flow among them. Our results showed the usefulness of microsatellites for population analysis of S. mansoni, offering a new alternative for a better understanding of schistosomiasis epidemiology.
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Affiliation(s)
- N B Rodrigues
- Lab. de Parasitologia Celular e Molecular, Centro de Pesquisas René Rachou-FIOCRUZ, Ministério da Saúde-Fundação, Oswaldo Cruz, Caixa Postal 1743, Av. Augusto de Lima, 1715-Barro Preto, CEP 30190-002, Belo Horizonte, MG, Brazil
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Weiss JL, Yang J, Jie C, Walker DL, Ahmed S, Zhu Y, Huang Y, Johansen KM, Johansen J. Molecular cloning and characterization of LKv1, a novel voltage-gated potassium channel in leech. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1097-4695(19990205)38:2<287::aid-neu10>3.0.co;2-u] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
The musculature of parasitic platyhelminths (monogeneans, digeneans and cestodes) presents an attractive target for chemotherapeutic intervention in that it is central to locomotory movement and attachment and serves an essential role in alimentation (feeding, translocation of food and digestive waste) and reproduction (insemination, egg formation and oviposition). Here, Gunnar Mair, Aaron Maule, Chris Shaw and David Halton review muscle organization in flatworm parasites, and outline some of the recent physiological and molecular advances that have been made in flatworm muscle research.
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Abstract
Shal (Kv4) potassium channel genes encode classical subthreshold A-currents, and their regulation may be a key factor in determining neuronal firing frequency. The inactivation rate of Shal channels is increased by a presently unidentified class of proteins in both Drosophila and mammals. We have cloned a novel Shal channel subunit (jShalgamma1) from the jellyfish Polyorchis penicillatus that alters Shal currents from both invertebrates and vertebrates. When co-expressed with the conserved jellyfish Shal homolog jShal1, jShalgamma1 dramatically changes both the rate of inactivation and voltage range of activation and steady-state inactivation. jShalgamma1 provides fast inactivation by a classic N-type mechanism, which is independent of its effects on voltage dependence. jShalgamma1 forms functional channels only as a heteromultimer, and jShalgamma1 + jShal1 heteromultimers are functional only in a 2:2 subunit stoichiometry.
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Wei A, Jegla T, Salkoff L. Eight potassium channel families revealed by the C. elegans genome project. Neuropharmacology 1996; 35:805-29. [PMID: 8938713 DOI: 10.1016/0028-3908(96)00126-8] [Citation(s) in RCA: 189] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The wealth of accumulating data from the Caenorhabditis elegans genome sequencing project has rapidly accelerated the discovery of novel potassium channel genes and now places within reach the possibility of describing the total complement of potassium channels used by an individual species. Using annotated GenBank sequences, BLAST searches of unfinished sequences and degenerate oligonucleotide polymerase chain reaction (PCR) screens, we have identified and compiled genes for 38 C. elegans potassium channel and two cyclic nucleotide-gated cation channel subunits, representing eight conserved multigene families. Novel families of potassium channel genes were revealed, as well as conserved homologues of all known vertebrate families. Two separate families represent C. elegans homologues for human potassium channels recently implicated in hereditary long QT arrhythmias. Of particular note is an exceptionally large class of at least 23 genes with a novel subunit structure having two tandem 'P' domains; these channels may form as dimers in contrast to all other potassium channel types which form as tetramers. The 40 potassium channel genes are evenly distributed on all six C. elegans chromosomes, with the exception of the instances of gene clustering on the fifth and X chromosomes.
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Affiliation(s)
- A Wei
- Department of Anatomy and Neurobiology, Washington University, School of Medicine, Saint Louis, MO 63110, USA
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Pax RA, Day TA, Miller CL, Bennett JL. Neuromuscular physiology and pharmacology of parasitic flatworms. Parasitology 1996; 113 Suppl:S83-96. [PMID: 9051929 DOI: 10.1017/s003118200007791x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The trematode and cestode flatworms include numerous parasitic forms of major medical and economic importance. A better knowledge of the neuromuscular physiology of these animals could lead to development of new control measures against these parasites. Since these animals are near the stem from which all other animals have evolved, better knowledge of these animals could also yield valuable information about the early evolution of nerve and muscle systems in the animal kingdom. This review focuses on what is known about the characteristics of the somatic muscle in these animals. The anatomy of the muscles is described along with a review of current information about their electrophysiology, including descriptions of the ion channels present. Also included is a summary of recently acquired data concerning the nature of serotonin, peptide, acetylcholine and glutamate receptors on the membranes of the muscles.
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Affiliation(s)
- R A Pax
- Department of Zoology, Michigan State University, East Lansing 48824, USA
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Thompson DP, Klein RD, Geary TG. Prospects for rational approaches to anthelmintic discovery. Parasitology 1996; 113 Suppl:S217-38. [PMID: 9051937 DOI: 10.1017/s0031182000077994] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Rational approaches to anthelmintic discovery include the design of screens for compounds directed at specific proteins in helminths that are pharmacologically distinguishable from their vertebrate homologues. The existence of several anthelmintics that selectively target the neuromusculature of helminths (e.g. levamisole, ivermectin, praziquantel, metrifonate), together with recent basic research in helminth physiology, have contributed to the recognition that neurobiology distinguishes these organisms from their vertebrate hosts. In this survey, we focus on mechanism-based screening and its application to anthelmintic discovery, with particular emphasis on targets in the neuromusculature of helminths. Few of these proteins have been exploited in chemotherapy. However, recent studies in comparative pharmacology and molecular biology, including the C. elegans genome project, have provided insights on potential new targets and, in some cases, molecular probes useful for their incorporation in mechanism-based screens.
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