Muscarinic toxins: novel pharmacological tools for the muscarinic cholinergic system

Jerusalinsky, Diana; Kornisiuk, Edgar; Alfaro, P.; Quillfeldt, Jorge Alberto; Ferreira, Amâncio Romanelli; Rial, Verde E.; Durán, Rosario; Červeñanský, Carlos

doi:10.1016/s0041-0101(99)00196-8

Cited by 53 publications

(40 citation statements)

References 42 publications

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“…It was found that, even at high concentration (40 M), sMT1 had no significant effect on the [ 3 H]NMS dissociation rate, suggesting that this toxin interacts not with the allosteric site but more probably with the orthosteric site. This result agrees well with previous reports on the pharmacological and functional properties of MT1 (Jerusalinsky and Harvey, 1994;Waelbroeck et al, 1996;Jerusalinsky et al, 2000), even if conflicting data on the MT1 binding site are reported (Jerusalinsky et al, 1995). Nevertheless, we cannot conclude definitively on the binding of MT1 to the orthosteric site, because a high degree of negative cooperativity is indistinguishable from a competition interaction.…”

Section: Discussionsupporting

confidence: 88%

“…Several neurotoxins have been purified from the venom of African mambas (Dendroaspis angusticeps and Dendroaspis polylepis) and characterized for their specific interaction with various muscarinic receptors (for review, see Bradley, 2000;Jerusalinsky et al, 2000;Karlsson et al, 2000;Potter, 2001). These muscarinic toxins are peptides of 63 to 66 residues with four disulfide bonds and a common three-finger fold structure (Segalas et al, 1995).…”

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confidence: 99%

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Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M₁ Muscarinic Receptor

et al. 2003

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Two muscarinic toxins, MT1 and MT7, were obtained by onestep solid-phase synthesis using the 9-fluorenylmethoxycarbonyl-based method. The synthetic and natural toxins, isolated from the snake venom or recombinantly expressed, display identical physicochemical properties and pharmacological profiles. High protein recovery allowed us to specify the selectivity of these toxins for various muscarinic receptor subtypes. Thus, sMT7 has a selectivity for the M 1 receptor that is at least 20,000 times that for the other subtypes. The stability of the toxinreceptor complexes indicates that sMT1 interacts reversibly with the M 1 receptor, unlike sMT7, which binds it quasi-irreversibly. The effect of the synthetic toxins on the atropineinduced [3 H]N-methylscopolamine (NMS) dissociation confirms that sMT7 targets the allosteric site on the M 1 receptor, whereas sMT1 seems interact on the orthosteric one. The great decreases in the binding potencies observed after the R34A modification in sMT1 and sMT7 toxins highlight the functional role of this conserved residue in their interactions with the M 1 receptor. Interestingly, after the R34A modification, the sMT7 toxin binds reversibly on the M 1 receptor. Furthermore, the potency of sMT7-R34A for the NMS-occupied receptor is lower compared with unmodified toxin, supporting the role of this residue in the allosteric interaction of sMT7. All these results and the different charge distributions observed at the two toxin surfaces of their structure models support the hypothesis that the two toxins recognize the M 1 receptor differently.

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Section: Discussionsupporting

confidence: 88%

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confidence: 99%

Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M₁ Muscarinic Receptor

et al. 2003

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“…In TC neurons, inhibition of TASK-1, TASK-3, and TREK-1 (this study) channels is the molecular correlate of I KL modulation by ACh [36][37][38]. Based on immunohistochemical staining as well as on the effects of antagonistic substances with preferential binding to special subtypes, namely, pirenzepine [21] and 4-DAMP [40] and the highly specific muscarinic toxins MT-1 and MT-7 [25,49], it is concluded that M 1 AChR and M 3 AChR largely mediate the effect of muscaric stimulation on I SO and the membrane potential. Our conclusion is in good agreement with findings from mice where M 1 AChR and M 3 AChR couple to Gα q to inhibit I SO [4].…”

Section: Muscarinic Signaling In the Thalamusmentioning

confidence: 94%

Identification of the muscarinic pathway underlying cessation of sleep-related burst activity in rat thalamocortical relay neurons

Bista

Meuth

Kanyshkova

et al. 2011

Pflugers Arch - Eur J Physiol

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Modulation of the standing outward current (I (SO)) by muscarinic acetylcholine (ACh) receptor (MAChR) stimulation is fundamental for the state-dependent change in activity mode of thalamocortical relay (TC) neurons. Here, we probe the contribution of MAChR subtypes, G proteins, phospholipase C (PLC), and two pore domain K(+) (K(2P)) channels to this signaling cascade. By the use of spadin and A293 as specific blockers, we identify TWIK-related K(+) (TREK)-1 channel as new targets and confirm TWIK-related acid-sensitve K(+) (TASK)-1 channels as known effectors of muscarinic signaling in TC neurons. These findings were confirmed using a high affinity blocker of TASK-3 and TREK-1, namely, tetrahexylammonium chloride. It was found that the effect of muscarinic stimulation was inhibited by M(1)AChR-(pirenzepine, MT-7) and M(3)AChR-specific (4-DAMP) antagonists, phosphoinositide-specific PLCβ (PI-PLC) inhibitors (U73122, ET-18-OCH(3)), but not the phosphatidylcholine-specific PLC (PC-PLC) blocker D609. By comparison, depleting guanosine-5'-triphosphate (GTP) in the intracellular milieu nearly completely abolished the effect of MAChR stimulation. The block of TASK and TREK channels was accompanied by a reduction of the muscarinic effect on I (SO). Current-clamp recordings revealed a membrane depolarization following MAChR stimulation, which was sufficient to switch TC neurons from burst to tonic firing under control conditions but not during block of M(1)AChR/M(3)AChR and in the absence of intracellular GTP. These findings point to a critical role of G proteins and PLC as well as TASK and TREK channels in the muscarinic modulation of thalamic activity modes.

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“…Muscarinic toxins (MTs) are small proteins in Dendroaspis snake venom that show very high selectivity for some mAChR subtypes and have been used both in vitro and in vivo [13][14][15]. MT1 and MT2 selectively bind to M 1 and M 4 receptor subtypes; MT1 shows similar affinities for both receptors, while MT2 has a 4-fold higher affinity for M 1 than for M 4 .…”

Section: Introductionmentioning

confidence: 99%

Muscarinic Inhibition of Hippocampal and Striatal Adenylyl Cyclase is Mainly Due to the M4 Receptor

et al. 2009

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The five muscarinic acetylcholine receptors (M(1)-M(5)) are differentially expressed in the brain. M(2) and M(4) are coupled to inhibition of stimulated adenylyl cyclase, while M(1), M(3) and M(5) are mainly coupled to the phosphoinositide pathway. We studied the muscarinic receptor regulation of adenylyl cyclase activity in the rat hippocampus, compared to the striatum and amygdala. Basal and forskolin-stimulated adenylyl cyclase activity was higher in the striatum but the muscarinic inhibition was much lower. Highly selective muscarinic toxins MT1 and MT2-affinity order M(1) > or = M(4) >> others-and MT3-highly selective M(4) antagonist-did not show significant effects on basal or forskolin-stimulated cyclic AMP production but, like scopolamine, counteracted oxotremorine inhibition. Since MTs have negligible affinity for M(2), M(4) would be the main subtype responsible for muscarinic inhibition of forskolin-stimulated enzyme. Dopamine stimulated a small fraction of the enzyme (3.1% in striatum, 1.3% in the hippocampus). Since MT3 fully blocked muscarinic inhibition of dopamine-stimulated enzyme, M(4) receptor would be responsible for this regulation.

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Muscarinic toxins: novel pharmacological tools for the muscarinic cholinergic system

Cited by 53 publications

References 42 publications

Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M₁ Muscarinic Receptor

Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M₁ Muscarinic Receptor

Identification of the muscarinic pathway underlying cessation of sleep-related burst activity in rat thalamocortical relay neurons

Muscarinic Inhibition of Hippocampal and Striatal Adenylyl Cyclase is Mainly Due to the M4 Receptor

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Muscarinic toxins: novel pharmacological tools for the muscarinic cholinergic system

Cited by 53 publications

References 42 publications

Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M1 Muscarinic Receptor

Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M1 Muscarinic Receptor

Identification of the muscarinic pathway underlying cessation of sleep-related burst activity in rat thalamocortical relay neurons

Muscarinic Inhibition of Hippocampal and Striatal Adenylyl Cyclase is Mainly Due to the M4 Receptor

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Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M₁ Muscarinic Receptor

Chemical Synthesis of MT1 and MT7 Muscarinic Toxins: Critical Role of Arg-34 in Their Interaction with M₁ Muscarinic Receptor