Trematode flatworms of the genus Schistosoma are the causative agents of schistosomiasis, a tropical parasitic disease with over 200 million people infected worldwide. Praziquantel (PZQ) is the current drug of choice against schistosomiasis, but the mechanism by which PZQ acts remains poorly defined, even several decades following its discovery. Our laboratory has shown that PZQ is likely interacting with a molecular component of schistosome voltage-gated Ca2+ (Cav) channels, specifically a structurally and functionally atypical Cav channel b subunit. This b subunit subtype has been found to date only in platyhelminths;PZQ is not effective against nematodes, and nematode genomes do not contain this variant Cav channel b subunit. This exploratory R21 proposal describes a high-risk/high-potential payoff project to transfer PZQ sensitivity to nematodes by transforming C. elegans with this variant schistosome Cav channel b subunit. We hypothesize that expression of the variant schistosome b subunit in appropriate C. elegans cell types will result in the formation of nematode Cav channels that are sensitive to PZQ. As such, we will place the schistosome b subunit under the control of several different tissue- and cell-specific C. elegans promoters. We will also use conditional promoters to control expression of the gene. If successful, these experiments will offer further compelling evidence that the schistosome variant b subunit is indeed targeted by PZQ, and will also provide the opportunity to acquire important information about the physiological role played by this unique b subunit. Additionally, development of this transgenic model could pave the way for further experiments (as an R01 project) to obtain details of the mode of action of PZQ, including the identification of interacting factors, by exploiting the far more tractable and powerful C. elegans model system.
The specific aims of the project are to: 1. Produce transgenic C. elegans lines expressing the schistosome SmCavbvar Cav channel subunit under the control of various promoters. 2. Test transgenic C. elegans lines expressing bvar for sensitivity to PZQ, either in whole worms or in specific tissues.

Public Health Relevance

Schistosomiasis is a major tropical disease caused by parasitic flatworms called schistosomes. Although there is an effective drug against schistosomiasis, the mechanism by which it works is unclear. By understanding that mechanism, it may be possible to obtain drugs that affect the same molecular target, or molecules that interact with that target. In this project, we are using an innovative approach to define the molecular target of this drug with a future goal of identifying other factors that might interact with this drug target.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21AI082390-02
Application #
7843485
Study Section
Drug Discovery and Mechanisms of Antimicrobial Resistance Study Section (DDR)
Program Officer
Rogers, Martin J
Project Start
2009-05-15
Project End
2011-04-30
Budget Start
2010-05-01
Budget End
2011-04-30
Support Year
2
Fiscal Year
2010
Total Cost
$233,888
Indirect Cost
Name
University of Pennsylvania
Department
Pathology
Type
Schools of Veterinary Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Greenberg, Robert M (2013) New approaches for understanding mechanisms of drug resistance in schistosomes. Parasitology 140:1534-46
Stoltzfus, Jonathan D; Massey Jr, Holman C; Nolan, Thomas J et al. (2012) Strongyloides stercoralis age-1: a potential regulator of infective larval development in a parasitic nematode. PLoS One 7:e38587
Yin, Jiangmei; Dai, Anlan; Arango, Tatiana et al. (2012) IL-4 and IFN-? induced by human immunodeficiency virus vaccine in a schistosome infection model. Hum Vaccin Immunother 8:1555-63
Salvador-Recatalà, Vicenta; Greenberg, Robert M (2012) Calcium channels of schistosomes: unresolved questions and unexpected answers. Wiley Interdiscip Rev Membr Transp Signal 1:85-93
Kasinathan, Ravi S; Greenberg, Robert M (2012) Pharmacology and potential physiological significance of schistosome multidrug resistance transporters. Exp Parasitol 132:2-6
Kasinathan, Ravi S; Morgan, William M; Greenberg, Robert M (2011) Genetic knockdown and pharmacological inhibition of parasite multidrug resistance transporters disrupts egg production in Schistosoma mansoni. PLoS Negl Trop Dis 5:e1425
Kasinathan, Ravi S; Goronga, Tinopiwa; Messerli, Shanta M et al. (2010) Modulation of a Schistosoma mansoni multidrug transporter by the antischistosomal drug praziquantel. FASEB J 24:128-35
Kasinathan, Ravi S; Greenberg, Robert M (2010) Schistosoma mansoni soluble egg antigens trigger erythrocyte cell death. Cell Physiol Biochem 26:767-74
Salvador-Recatalà, Vicenta; Greenberg, Robert M (2010) The N terminus of a schistosome beta subunit regulates inactivation and current density of a Cav2 channel. J Biol Chem 285:35878-88
Kasinathan, Ravi S; Morgan, William M; Greenberg, Robert M (2010) Schistosoma mansoni express higher levels of multidrug resistance-associated protein 1 (SmMRP1) in juvenile worms and in response to praziquantel. Mol Biochem Parasitol 173:25-31