Nicotinic Receptors and Anthelmintic Resistance

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Nicotinic Receptors and Anthelmintic Resistance

• Richard J. Martin, Adrian J. Wolstenholme, S. M.
  Williamson Alan P. Robertson
• Department of Biomedical Sciences, Iowa State
  University, Ames, Iowa USA Dept of Infectious
  Diseases, University of Georgia, Athens, Georgia

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Nicotinic Anthelmintics

• Imidazothiazoles levamisole, agonist
• Tetrahydropyrimidines pyrantel , agonist
• Quaternary Amines bephenium , agonist
• AADs monepantel , agonist
• Macfortines paraherquamide derquantel,
  antagonist

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A
B
C
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C. elegans nicotinic receptor subunits Jones et
al., 2007 29 subunits, 5 core structures
levamisole
AADs
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Muscle nAChRs in C. elegans
G 30 pS (Qian et al, 2008)
C. elegans levamisole sensitive receptor
C. elegans nicotine sensitive receptor
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Pharmacological Diversity in Ascaris
3 receptor types in Ascaris suum N-type (low
sensitivity to paraherquaminde) L-type (sensitive
to paraherquamide and 2 desoxo-paraherquamide
derquantel) B-type (most sensitive to
2-desoxo-paraherquamide derquantel)
N-type
L-type
B-type
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3 channel currents 3 nAChR subtypes
B
A
C
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Asu-UNC38
Asu-UNC29
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Kopp et al. 2008 IJP qtPCR A. caninum
pyrantel-sensitive vs -resistant. Expression of
aar-38, aar-63 and aar-29 reduced
Ref gene Isolate aar-38 aar-38 aar-63 aar-63 aar-29 aar-29 aar-19 aar-19 aar-15 aar-15 aar-8 PR/NT aar-8 PR/NT

60S PR 0.11  0.013 0.29 0.66  0.0090 0.55 0.94  0.046 0.62 0.54  0.021 0.99 0.31  0.018 0.89 0.41  0.037 0.92
NT 0.37  0.022a 1.2  0.070a 1.5  0.035a 0.55  0.0082 0.35  0.091 0.45  0.018

• Also no changes in E153 and Q57
  pyrantel-specific sites Rayes et al. (2006)
• aar-29 -I50L, S206T,I309L (adults and larvae),
  I422L in both isolates and L466M in the NT
  isolate,
• aar-63-L393I(adults and larvae)
• No 38 amino-acid changes
• 15-46 nucleotide changes

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nAChR subtypes and resistance
levamisole resistance
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Monepantel resistance Hco-mptl-1 Hco-des -2H
Hco-deg-3H Rufener et al.,
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Monepantel resistance Hco-mptl-1, some lack
splice acceptor (TTTCAG)
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Molecular detection of resistance levamisole
monepantel

• Kopp et al., Did not find specific SNPs
  associated with resistance
• E153 Q57 not associated with pyrantel
  resistance
• Expression levels of UNC-38, UNC-29 and UNC-63
  are reduced in pyrantel resistance
• Rufener et al., Hco-mptl-1 Hco-des-2H,
• 1. a panel of mutations (null mutants)
  including deletions at intron-exon boundaries
  giving mis-spliced transients premature stop
  codons
• 2. Altered expression levels of Hco-mptl-1
  Hco-des-2H and Hco-deg-3H

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C. elegans proteins involved in levamisole
resistance
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Resistance may be due to a panel of functional
null mutant genes with deletions and insertions
and reduced expression of the target receptor
genes other sites!
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Acknowledgments

• Alan Robertson
• Sally Williamson
• Sreekanth Puttachary
• Sam Buxton
• Cheryl Clark
• Adrian Wolstenholme
• Steve Koppe
• Andrew Kotze
• Supported by NIH R01 R 01 AI 047194

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