Recent Abstracts

 

 

Siddiqui, Salma, Forrester, Sean (2009)

Isolation and electrophysiological characterization of two GABA receptor subunits from the parasitic nematode Haemonchus contortus

World Association for the Advancement of Veterinary Parasitology, Calgary AB

 

Haemonchus contortus is a gastrointestinal parasitic nematode, which infects cattle and sheep worldwide. This parasite is controlled by nematocides; many which target receptors of the inhibitory nervous system called ligand-gated chloride channels (LGCCs). Research on the model free-living nematode Caenorhabditis elegans has identified several different types of LGCCs. One example is a set of GABA receptors called UNC-49 that play a role in locomotion (Bamber et al 1999). Our aim was to determine whether there is structural and functional similarity between UNC-49 receptors in H. contortus compared to what has been reported for C. elegans. We have identified two H. contortus genes HcUNC-49B and C that, like C. elegans, appear to be generated from alternative splicing of the same UNC-49 gene. Electrophysiological analysis show HcUNC-49B is able to form a functional homomeric channel in Xenopus laevis oocytes that produces a robust dose dependant response to GABA and is highly sensitive to picrotoxin. In contrast, HcUNC-49C alone did not form a functional channel. When both HcUNC-49B and C are expressed in combination, the HcUNC-49B/C heteromer appears to be preferentially formed, evident by its increased sensitivity to GABA and lower sensitivity to picrotoxin. While the EC50 of GABA for the HcUNC-49B channel is similar to that reported for the same channel in C. elegans, the HcUNC-49B/C channel is 3x more sensitive to GABA compared to the C. elegans heteromeric channel. These results suggest that there may be differences in the function of the UNC-49 GABA receptors between the two nematode species.

 

Vijayaraghava TS Rao, Salma Z Siddiqui, Roger K Prichard, and Sean G Forrester (2009)

HcGGR3: Characterisation of a novel ligand-gated chloride channel (LGCC) subunit in Haemonchus contortus

Annual Meeting of the British Society for Parasitology. Edinburgh, UK

 

HcGGR3 is a gene which encodes a novel LGCC subunit. Protein sequence analysis indicates that this channel is anion selective and possesses all the signature motifs of a chloride channel subunit. Analysis of the cDNA sequence shows putative microRNA interaction site which could be important in relation to developmental expression of this subunit. qRT-PCR analysis of HcGGR3 shows that it is differentially expressed among the various life-stages and the rank order of expression was eggs > adult female > larvae > adult male. In addition, HcGGR3 is significantly down regulated in macrocyclic lactone (ML) selected laboratory strains of H. contortus. We also found a single nucleotide polymorphism in the 3’UTR that appears to be associated with ML selection. Immunolocalization of this subunit in adult worms has revealed that in females, the localization is distinctly punctate around the cervical papillae and in males, expression was observed around the cervical papillae and possibly some sheath cells. Electrophysiological analysis of this protein expressed in Xenopus laevis oocytes revealed that it forms a homomeric channel that responds primarily to dopamine. This subunit could have a possible role in mechanosensation.

 

Rao V, Siddiqui S, Prichard RK and Forrester SG (2009)

HcGGR3: A dopamine-gated ion channel subunit in Haemonchus contortus.

World Association for the Advancement of Veterinary Parasitology. Calgary AB, Canada

 

Vijayaraghava TS Rao, Salma Z Siddiqui, Roger K Prichard, and Sean G Forrester (2009)

Dopamine as a neurotransmitter in Haemonchus contortus

9th Annual Quebec Molecular Parasitology Symposium, Montreal Quebec

 

Vijayaraghava TS Rao, Roger K Prichard, Salma Z Siddiqui and Sean G Forrester (2009)

Characterisation of a novel dopamine-gated chloride channel (DGCC) subunit in Haemonchus contortus: Possible involvement in ivermectin resistance

Australian Society for Parasitology (ASP), Sydney Australia

 

Rao V, Prichard RK and Forrester SG (2008)

Cloning and characterization of a novel ligand-gated chloride channel in Haemonchus contortus

8th Annual Quebec Molecular Parasitology Symposium, Montreal Quebec

 

Siddiqui S, Brown D and Forrester SG (2008)

Identification of RDL-like GABA receptor subunit genes in Haemonchus contortus

8th Annual Quebec Molecular Parasitology Symposium, Montreal Quebec

 

Rao V, Prichard RK and Forrester SG (2007)

Cloning and characterization of a novel ligand-gated chloride channel gene in Haemonchus contortus.

Canadian Society of Zoologists, Montreal, Quebec

 

Siddiqui S, Dosani N and Forrester SG (2007)

Identification of GABA receptor subunit genes in Haemonchus contortus

Canadian Society of Zoologists, Montreal, Quebec