Molecular Basis of the Differential Sensitivity of Nematode and Mammalian Muscle to the Anthelmintic Agent Levamisole

Rayes, Diego; Rosa, Maria Jose de; Bartos, Mariana; Bouzat, Cecilia

doi:10.1074/jbc.m403096200

Cited by 33 publications

(32 citation statements)

References 40 publications

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“…We demonstrated that key residues of the principal face, Y190 located in loop C and G153 located in loop B, are also required for GABA activation of muscle nAChR. The effects of aY190F and aG153S mutations on muscle nAChR activation have been well characterized Salamone et al, 1999;Grutter et al, 2003;Rayes et al, 2004;Mukhtasimova et al, 2009;Auerbach, 2011, 2013;Jadey et al, 2013). In parallel with the changes observed for ACh, GABA responses are increased in aG153S mutant and are negligible in aY190F mutant.…”

Section: Discussionmentioning

confidence: 52%

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Neurotransmitter GABA Activates Muscle but Notα7 Nicotinic Receptors

et al. 2014

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Cys-loop receptors are neurotransmitter-activated ion channels involved in synaptic and extrasynaptic transmission in the brain and are also present in non-neuronal cells. As GABA A and nicotinic receptors (nAChR) belong to this family, we explored by macroscopic and single-channel recordings whether the inhibitory neurotransmitter GABA has the ability to activate excitatory nAChRs. GABA differentially activates nAChR subtypes. It activates muscle nAChRs, with maximal peak currents of about 10% of those elicited by acetylcholine (ACh) and 15-fold higher EC 50 with respect to ACh. At the single-channel level, the weak agonism is revealed by the requirement of 20-fold higher concentration of GABA for detectable channel openings, a major population of brief openings, and absence of clusters of openings when compared with ACh. Mutations at key residues of the principal binding-site face of muscle nAChRs (aY190 and aG153) affect GABA activation similarly as ACh activation, whereas a mutation at the complementary face («G57) shows a selective effect for GABA. Studies with subunit-lacking receptors show that GABA can activate muscle nAChRs through the a/d interface. Interestingly, single-channel activity elicited by GABA is similar to that elicited by ACh in gain-of-function nAChR mutants associated to congenital myasthenic syndromes, which could be important in the progression of the disorders due to steady exposure to serum GABA. In contrast, GABA cannot elicit singlechannel or macroscopic currents of a7 or the chimeric a7-serotonin-type 3 receptor, a feature important for preserving an adequate excitatory/inhibitory balance in the brain as well as for avoiding activation of non-neuronal receptors by serum GABA.

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Section: Discussionmentioning

confidence: 52%

“…Single-channel kinetic analysis of aG153S nAChR revealed a markedly decreased rate of ACh dissociation, which causes the mutant nAChR to open repeatedly forming bursts Rayes et al, 2004) (Fig. 2).…”

Section: Resultsmentioning

confidence: 99%

Neurotransmitter GABA Activates Muscle but Notα7 Nicotinic Receptors

et al. 2014

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“…6). At this positive potential, openchannel block is almost undetected (Neher and Steinbach, 1978;Rayes et al, 2004). This observation together with the fact that a reduction in peak current by channel block is not observed in the control chimera at 500 M pyrantel (see above) indicate that the reduction in the maximum response is originated from a reduced efficacy and not from channel block.…”

Section: Pyrantel Activation Of Nicotinic Receptors 1313mentioning

confidence: 57%

Molecular Determinants of Pyrantel Selectivity in Nicotinic Receptors

Bartos¹,

Rayes²,

Bouzat³

2006

Mol Pharmacol

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Nicotinic receptors (acetylcholine receptors, AChRs) play key roles in synaptic transmission throughout the nervous system. AChRs mediate neuromuscular transmission in nematodes, and they are targets for antiparasitic drugs. The anthelmintic agents levamisole and pyrantel, which are potent agonists of nematode muscle AChRs, are partial agonists of mammalian muscle AChRs. To further explore the structural basis of the differential activation of AChR subtypes by anthelmintics, we studied the activation of ␣7 AChRs using the high-conductance form of the ␣7-5-hydroxytryptamine-3A receptor, which is a good model for pharmacological studies involving the extracellular region of ␣7. Macroscopic and single-channel current recordings show that levamisole is a weak agonist of ␣7. It is interesting that pyrantel is a more potent agonist of ␣7 than acetylcholine (ACh). To identify determinants of this differential activation, we replaced residues of the complementary face of the binding site by the homologous residues in the muscle subunit and evaluated changes in activation. The mutation Q57G does not affect the activation by either ACh or levamisole. However, it increases EC 50 values and decreases the maximal response to pyrantel. Kinetic analysis shows that gating of the mutant channel activated by pyrantel is profoundly impaired. The decreased sensitivity of ␣7-Q57G to pyrantel agrees with its weak action at muscle AChRs, indicating that when glycine occupies position 57, as in the mammalian muscle AChR, pyrantel behaves as a partial agonist. Thus, position 57 located at the complementary face of the binding site plays a key role in the selective activation of AChRs by pyrantel.Cysteine-loop receptors are pentameric ligand-gated ion channels that play key roles in chemical synapses throughout the nervous system. In vertebrates, the cysteine-loop receptor superfamily consists of two families of cation-selective channels: the nicotinic acetylcholine (AChR) and the 5-hydroxytryptamine type 3 receptors (5HT 3 Rs); and two families of anionic channels: the ␥-aminobutyric acid and the glycine receptors (Le Novére and Changeux, 2001;Lester et al., 2004). In invertebrates, this superfamily also includes ␥-aminobutyric acid-gated cationic channels and ACh-, serotonin-, glutamate-, and histamine-gated chloride channels (Jones and Sattelle, 2003;Putrenko et al., 2005).AChR subunits are classified as ␣, which contain a disulfide bridge involved in the recognition and binding of agonists, and non-␣ subunits, which lack this motif. To date, several ␣ and non-␣ subunits have been identified. Receptors can be either heteromeric, composed of ␣ and non-␣ subunits, or homomeric, composed of five identical ␣ subunits. Each subunit is divided into an N-terminal or ligand-binding domain and a transmembrane region. The binding sites are located at the interface between two subunits (Brejc et al., 2001;Sine, 2002). Results from affinity labeling and sitedirected mutagenesis studies on AChR, which were later supported by the structural...

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“…By acting as potent agonists of nematode AChRs, without being rapidly degraded, these drugs produce body-wall muscle hypercontraction, paralysis, and ultimately death of C. elegans and parasitic nematodes. These anthelmintics are highly selective for nematode AChRs, whereas they are very low-efficacy agonists of vertebrate muscle AChRs (Rayes et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Contribution of Subunits toCaenorhabditis elegansLevamisole-Sensitive Nicotinic Receptor Function

et al. 2012

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Caenorhabditis elegans muscle contains seven different nicotinic receptor (AChR) subunits, five of which have been shown to be components of adult levamisole-sensitive AChRs (LAChRs). To elucidate the reason for such subunit diversity, we explore their functional roles in larva 1 (L1) muscle cells. Singlechannel and macroscopic current recordings reveal that the ␣-type LEV-8 subunit is a component of native L1 L-AChRs but behaves as a nonessential subunit. It plays a key role in maintaining a low rate and extent of desensitization of L-AChRs. In the absence of the ␣-type ACR-8 subunit, L-AChR channel properties are not modified, thus indicating that ACR-8 is not a component of L1 L-AChRs. Together with our previous findings, this study reveals that L1 muscle cells express a main L-AChR type composed of five different subunits: UNC-38, UNC-63, UNC-29, LEV-1, and LEV-8. Analysis of a double lev-8; acr-8-null mutant, which shows an uncoordinated and levamisole-resistant phenotype, reveals that ACR-8 can replace LEV-8 in its absence, thus attributing a functional role to this subunit. Docking into homology modeled L-AChRs proposes that ACh forms the typical cation-interaction, suggests why levamisole is less efficacious than ACh, and shows that ACR-8 can form activatable binding-sites, thus opening doors for elucidating subunit arrangement and anthelmintic selectivity.

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Molecular Basis of the Differential Sensitivity of Nematode and Mammalian Muscle to the Anthelmintic Agent Levamisole

Cited by 33 publications

References 40 publications

Neurotransmitter GABA Activates Muscle but Notα7 Nicotinic Receptors

Neurotransmitter GABA Activates Muscle but Notα7 Nicotinic Receptors

Molecular Determinants of Pyrantel Selectivity in Nicotinic Receptors

Contribution of Subunits toCaenorhabditis elegansLevamisole-Sensitive Nicotinic Receptor Function

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