Structure–activity relationship and site of binding of polyamine derivatives at the nicotinic acetylcholine receptor

Bixel, M. Gabriele; Krauß, Michael; Liu, Ying; Bolognesi, María Laura; Rosini, Michela; Mellor, Ian S.; Usherwood, P.N.R.; Melchiorre, Carlo; Nakanishi, Koji; Hucho, Ferdinand

doi:10.1046/j.1432-1327.2000.00971.x

Cited by 32 publications

(63 citation statements)

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“…nAChR by PhTX-343 have been reported. The noncompetitive nature of philanthotoxin inhibition of nAChR is supported by Bixel et al (2000), who showed that the binding of N 3 -Ph-PhTX-343-Lys to resting (12) 1 M 1.62 Ϯ 0.27 (5) state Torpedo californica nAChR is unaffected by the presence of ␣-BgTX and slightly enhanced by the presence of carbamylcholine. Bixel et al (2001) also showed that binding of a related philanthotoxin, 125 I-MR44, was largely unaffected by either ␣-BgTX or carbamylcholine.…”

Section: Discussionmentioning

confidence: 93%

“…1), a structurally close analog of PhTX-433, is one of many synthetic analogs of the natural product Bruce et al, 1990;Benson et al, 1992Benson et al, , 1993Strømgaard et al, 1999Strømgaard et al, , 2000Bixel et al, 2000). It is a potent antagonist of ionotropic glutamate receptors mediating neuromuscular transmission in insects (Eldefrawi et al, 1988;Bruce et al, 1990), of ionotropic glutamate receptors of rat brain (Ragsdale et al, 1989;Jones et al, 1990;Brackley et al, 1993), and of recombinant, ionotropic glutamate receptors from rat (Brackley et al, 1993;Bä hring and Mayer, 1998).…”

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confidence: 99%

“…Biochemical studies of philanthotoxin action on nAChR of Torpedo nobiliana electric organ (e.g., Anis et al, 1990) include the use of photosensitive analogs of PhTX-343 (Nakanishi et al, 1997). Recently, Bixel et al (2000) showed that the photoactive compound N 3 -phenyl-PhTX-343-lysine binds to nAChR with a stoichiometry of 2:1 and that a related compound, MR44 (a 3-6-8-6 polyamine linked via an amide group to an aromatic head group), labels, via its aromatic 'head group', the ␣-subunits of Torpedo californica nAChR at a region (Ser-162 to Glu-175) thought to form the outer vestibule of the nAChR channel (Bixel et al, 2001).…”

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confidence: 99%

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Contrasting Actions of Philanthotoxin-343 and Philanthotoxin-(12) on Human Muscle Nicotinic Acetylcholine Receptors

Brier¹,

Mellor²,

Tikhonov³

et al. 2003

Mol Pharmacol

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Whole-cell recordings and outside-out patch recordings from TE671 cells were made to investigate antagonism of human muscle nicotinic acetylcholine receptors (nAChR) by the philanthotoxins, . When coapplied with acetylcholine (ACh), PhTX-343 caused activation-dependent, noncompetitive inhibition (IC 50 ϭ 17 M at Ϫ100 mV) of wholecell currents that was strongly voltage-dependent. However, preapplication of PhTX-343 unveiled a voltage-independent antagonism that also required receptor activation, which is suggestive of desensitization enhancement.

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Section: Discussionmentioning

confidence: 93%

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confidence: 99%

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confidence: 99%

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Contrasting Actions of Philanthotoxin-343 and Philanthotoxin-(12) on Human Muscle Nicotinic Acetylcholine Receptors

Brier¹,

Mellor²,

Tikhonov³

et al. 2003

Mol Pharmacol

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“…Synthetic analogues of this polyamine amide, such as PhTX-343, have been shown to noncompetitively antagonize a range of ionotropic receptors (21), including nAChR (22)(23)(24)(25)(26). These low molecular weight compounds have a hydrophobic head group linked to a polyamine tail.…”

mentioning

confidence: 99%

“…We have synthesized a series of polyamine-containing analogues of PhTX-343 in the search for a ligand with high affinity and specificity for Torpedo californica nAChR for photocross-linking studies. This approach resulted in the discovery of a photoactivable compound, MR44, which binds to the nAChR with high affinity (26,29).…”

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confidence: 99%

Location of the Polyamine Binding Site in the Vestibule of the Nicotinic Acetylcholine Receptor Ion Channel

Bixel

Weise

Bolognesi

et al. 2001

Journal of Biological Chemistry

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To map the structure of a ligand-gated ion channel, we used the photolabile polyamine-containing toxin MR44 as photoaffinity label. MR44 binds with high affinity to the nicotinic acetylcholine receptor in its closed channel conformation. The binding stoichiometry was two molecules of MR44 per receptor monomer. Upon UV irradiation of the receptor-ligand complex, The nicotinic acetylcholine receptor (nAChR), 1 a prototypical member of the superfamily of ligand-gated ion channels, is an integral transmembrane protein with the subunit stoichiometry ␣ 2 ␤␥␦ (1-3). Each receptor subunit contains four hydrophobic sequences, which are presumed to span the plasma membrane (4, 5). The large N-terminal domain and the relatively short C-terminal part of the subunits are oriented toward the extracellular side. A large connecting loop, which is found between transmembrane sequences M3 and M4, is assumed to extend into the cytoplasm. The five subunits contribute their homologous M2 sequences to the formation of the ion channel (6), which is permeable for cations upon agonist binding. A selectivity filter formed by the five M2 helices contributes to the cation conductance properties of the channel.

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Tuning Wasp Toxin Structure for Nicotinic Receptor Antagonism: Cyclohexylalanine‐Containing Analogues as Potent and Voltage‐Dependent Blockers

Olsen¹,

Mellor²,

Wellendorph³

et al. 2006

ChemMedChem

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The wasp venom constituent philanthotoxin-433 1) [1] is a polyamine toxin that antagonizes ionotropic glutamate receptors (iGluRs) [2] and nicotinic acetylcholine receptors (nAChRs) [3] nonselectively (Figure 1). Thus, similar potencies have been reported for PhTX-433 and its synthetic sperminecontaining analogue PhTX-343 (2) toward a range of human and insect glutamate-and ACh-gated ion channels.[4] The broad selectivity observed for 1 is compatible with its natural role as a prey suppression tool. Attempts to improve selectivity toward human receptors, necessary for potential therapeutic applications, have been partly successful through manipulation of the parent polyamine structure, whereas no notable improvements in selectivity have yet been observed through structural modifications of the tyrosine head group. Thus, while PhTX-83 (3) has been shown to be a selective antagonist of the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), [5] PhTX-12 (4) is a selective human muscletype nAChR antagonist, which is inactive toward AMPAR. [5, 6] Herein, we report analogues in which the tyrosine moiety present in 1-4 has been replaced by cyclohexylalanine (Cha). These novel head-group analogues (compounds 5-10) show pronounced selectivity toward human muscle-type nAChR, with one of them exhibiting unprecedented potency at nanomolar concentrations.The synthesis of polyamine toxins is greatly facilitated by the use of solid-phase synthesis (SPS) strategies. [7] In particular, Fukuyama-Mitsunobu alkylation has been successfully applied as a means of stepwise construction of the polyamine moiety. [8][9][10][11] However, a large excess of reagents in three repetitive couplings is required to obtain satisfactory yields. Accordingly, a method that involves S N 2 amine alkylation was devised for the synthesis of 8 and 9 (Scheme 1). In preliminary alkylation experiments with various resin-bound sulfonates, mesylate proved superior, presumably owing to the absence of competing trans sulfonation, which becomes predominant in SPS with increasingly reactive sulfonates. [12] Hence, the mesylate displacement strategy [13,14] was chosen for the synthesis of 8 and 9. Argopore Wang resin 13 was derivatized with a mono-Teocprotected diamine (11 or 12; Scheme 1, Method A), and the resulting resins were treated successively with Boc 2 O and Bu 4 NF to give resin 15 or 16, respectively. Peptide and acyl couplings completed the syntheses, with isolation of the required analogues 8 and 9 in 8-9 % yield. Moreover, 9 was re-synthesized on a polystyrene trityl resin 14 by using a modified procedure in an attempt to improve the overall yield; instead of the repetitive polyamine chain elongation, the monoprotected diamine 12 was employed at a concentration of 1 m (Scheme 1, Method B), [13][14][15] to give 9 in 24 % yield. Compounds 5-7 were obtained by using Fukuyama-Mitsunobu alkylation in isolated yields of 30 %.[9] For the analogue 10, which contains the symmetrical spermine moiety, it was more rational to apply the...

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Structure–activity relationship and site of binding of polyamine derivatives at the nicotinic acetylcholine receptor

Cited by 32 publications

References 36 publications

Contrasting Actions of Philanthotoxin-343 and Philanthotoxin-(12) on Human Muscle Nicotinic Acetylcholine Receptors

Contrasting Actions of Philanthotoxin-343 and Philanthotoxin-(12) on Human Muscle Nicotinic Acetylcholine Receptors

Location of the Polyamine Binding Site in the Vestibule of the Nicotinic Acetylcholine Receptor Ion Channel

Tuning Wasp Toxin Structure for Nicotinic Receptor Antagonism: Cyclohexylalanine‐Containing Analogues as Potent and Voltage‐Dependent Blockers

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