α-Selenoconotoxins, a New Class of Potent α7 Neuronal Nicotinic Receptor Antagonists

Armishaw, Christopher J.; Daly, Norelle L.; Nevin, Simon T.; Adams, David J.; Craik, David J.; Alewood, Paul F.

doi:10.1074/jbc.m512419200

Cited by 176 publications

(212 citation statements)

References 54 publications

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“…3). ␣-Conotoxin analogues possessing a similar consensus fold to the native conotoxin exhibit distinct CD spectra with characteristic minima occurring at ϳ200 nm (64,65). Their helical content was also estimated by measuring their molar ellipticity at 222 nm ( Fig.…”

Section: Design and Synthesis Of ␣-Conotoxinmentioning

confidence: 99%

Rational Design of α-Conotoxin Analogues Targeting α7 Nicotinic Acetylcholine Receptors

Armishaw

Jensen

Balle

et al. 2009

Journal of Biological Chemistry

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Nicotinic acetylcholine receptors (nAChRs) are ligandgated ion channels that belong to the superfamily of Cys loop receptors. Valuable insight into the orthosteric ligand binding to nAChRs in recent years has been obtained from the crystal structures of acetylcholine-binding proteins (AChBPs) that share significant sequence homology with the amino-terminal domains of the nAChRs. ␣-Conotoxins, which are isolated from the venom of carnivorous marine snails, selectively inhibit the signaling of neuronal nAChR subtypes. Co-crystal structures of ␣-conotoxins in complex with AChBP show that the side chain of a highly conserved proline residue in these toxins is oriented toward the hydrophobic binding pocket in the AChBP but does not have direct interactions with this pocket. In this study, we have designed and synthesized analogues of ␣-conotoxins ImI and PnIA[A10L], by introducing a range of substituents on the Pro 6 residue in these toxins to probe the importance of this residue for their binding to the nAChRs. Pharmacological characterization of the toxin analogues at the ␣ 7 nAChR shows that although polar and charged groups on Pro 6 result in analogues with significantly reduced antagonistic activities, analogues with aromatic and hydrophobic substituents in the Pro 6 position exhibit moderate activity at the receptor. Interestingly, introduction of a 5-(R)-phenyl substituent at Pro 6 in ␣-conotoxin ImI gives rise to a conotoxin analogue with a significantly higher binding affinity and antagonistic activity at the ␣ 7 nAChR than those exhibited by the native conotoxin. Nicotinic acetylcholine receptors (nAChRs)6 belong to the superfamily of Cys loop ligand-gated ion channels, which also includes serotonin (5-hydroxytryptamine, 5-HT 3 ), ␥-aminobutyric acid type A, and glycine receptors (1). As presynaptic heteroreceptors, nAChRs regulate the release of several important neurotransmitters, including dopamine, glutamate, and ␥-aminobutyric acid. Postsynaptic nAChRs are crucial mediators of the fast excitatory cholinergic neurotransmission in the central and peripheral nervous systems, which also influence the activity in several other important neurotransmitter systems (2, 3). The nAChRs are pentameric complexes composed of combinations of ␣ 1-10 , ␤ 1-4 , ␦, and ⑀/␥ subunits, each consisting of an extracellular ligand binding domain, four transmembrane helices, and an extended intracellular region arranged around a central cation-conducting pore (2). Muscle-type nAChRs are composed of two ␣ 1 -subunits and ␤ 1 -, ␦-, and ⑀/␥-subunits, whereas neuronal nAChRs are either heteromeric combinations of ␣ 2-6 -and ␤ 2-4 -subunits, ␣ 9 ␣ 10 complexes, or homomeric complexes consisting exclusively of ␣ 7 -or ␣ 9 -subunits (4). The different nAChR subtypes are involved in a wide range of distinct physiological functions, and the vast multitude of different subunit combinations underlines the importance of developing subtype-specific ligands for nAChRs as tools for studying cholinergic neurotransmission and for determining t...

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Section: Design and Synthesis Of ␣-Conotoxinmentioning

confidence: 99%

Rational Design of α-Conotoxin Analogues Targeting α7 Nicotinic Acetylcholine Receptors

Armishaw

Jensen

Balle

et al. 2009

Journal of Biological Chemistry

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“…There have been reports of disulphide replacements with thioethers [5][6][7][8], dicarba bridges [9,10] and diselenides [11] to generate redox-stable analogues without significantly compromising the binding affinity or activity of the parent peptide. However, it cannot be assumed a priori that replacement of a disulphide with a thioether will necessarily return biologically active compounds and each example needs to be investigated in a context-and sequence-specific manner.…”

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confidence: 99%

Redox‐stable cyclic peptide inhibitors of the SPSB2–iNOS interaction

et al. 2016

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Edited by Barry HalliwellSPSB2 mediates the proteasomal degradation of iNOS. Inhibitors of SPSB2-iNOS interaction are expected to prolong iNOS lifetime and thereby enhance killing of persistent pathogens. Here, we describe the synthesis and characterization of two redox-stable cyclized peptides containing the DINNN motif required for SPSB2 binding. Both analogues bind with low nanomolar affinity to the iNOS binding site on SPSB, as determined by SPR and 19 F NMR, and efficiently displace full-length iNOS from binding to SPSB2 in macrophage cell lysates. These peptides provide a foundation for future development of redox-stable, potent ligands for SPSB proteins as a potential novel class of anti-infectives.Keywords: anti-infective; cyclic peptide; inducible nitric oxide synthase; redox-stable; SPRY domain of the SOCS-box protein 2 SPSB2 protein plays a key role in modulating the lifetime of iNOS in macrophages during infection [1]. It acts as a negative regulator that recruits an E3 ubiquitin ligase complex that polyubiquitinates iNOS and thereby mediates its proteasomal degradation [1]. SPSB2-deficient macrophages exhibit prolonged iNOS expression, NO production and ultimately enhanced killing of persistent pathogens such as Leishmania major parasites and Mycobacterium tuberculosis, suggesting that inhibitors of the SPSB2-iNOS interaction have potential as a new class of anti-infectives [1].Kuang et al. [1] showed that a linear peptide from the disordered N-terminal region of iNOS, KEEK-DINNNVKKT, bound to SPSB2 with a K D of 13 nM, and that the most important residues mediating this interaction were DINNN, in particular the first, third and fifth residues of this sequence motif. In addition, structural studies by X-ray crystallography revealed that the SPRY domain of SPSB2 binds to Asp184, Asn186 and Asn188 of the DINNN sequence of the VASA peptide, the same motif as in the N-terminal region of iNOS (where the corresponding residues are Asp23, Asn25Abbreviations SPSB2, SPRY domain of the SOCS-box protein 2; iNOS, inducible nitric oxide synthase; SPR, surface plasmon

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“…39 This approach was also used to study Sec fragments of Grx1 (10)(11)(12)(13)(14)(15)(16)(17) and analogs of α-conotoxin ImI. 40,41,42 The SPPS approach is significantly enhanced by the native chemical ligation (NCL) strategy, which allows the assembly of unprotected peptides to produce large proteins. 43,44 The NCL methodology has proven useful in the efficient preparation of many proteins, 44,45 and was recently applied to the semisynthesis of selenoproteins using Sec instead of Cys at the ligation site.…”

Section: Introductionmentioning

confidence: 99%

Synthetic Seleno-Glutaredoxin 3 Analogues Are Highly Reducing Oxidoreductases with Enhanced Catalytic Efficiency

2006

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Selenoenzymes have a central role in maintaining cellular redox potential. These enzymes have selenenylsulfide bonds in their active sites that catalyze the reduction of peroxides, sulfoxides and disulfides. The selenol/disufide exchange reaction is common to all of these enzymes and the active site redox potential reflects the ratio between the forward and reverse rates of this reaction. The preparation of enzymes containing selenocysteine (Sec) is experimentally challenging. As a result, little is known about the kinetic role of selenols in enzyme active sites, and the redox potential of a selenenylsulfide or diselenide bond in a protein has not been experimentally determined. In order to fully evaluate the effects of Sec on oxidoreductase redox potential and kinetics, glutaredoxin 3 (Grx3) and all three Sec variants of its conserved 11 CXX 14 C active site were chemically synthesized. Grx3, Grx3(C11U) and Grx3(C14U) exhibited redox potentials of −194, −260 and −275 mV, respectively. The position of redox equilibrium between Grx3(C11U-C14U) (−309 mV) and thioredoxin (Trx) (−270 mV) suggests a possible role for diselenide bonds in biological systems. Kinetic analysis is consistent with the hypothesis that the lower redox potentials of the Sec variants result primarily from the greater nucleophilicity of the active site selenium rather than its role as either a leaving group or a 'central atom' in the exchange reaction. The 10 2 to 10 4 -fold increase in the rate of Trx reduction by the seleno-Grx3 analogs demonstrates that Oxidoreductases containing either selenenylsulfide or diselenide bonds can have physiologically compatible redox potentials and enhanced reduction kinetics in comparison with their sulfide counterparts.

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α-Selenoconotoxins, a New Class of Potent α7 Neuronal Nicotinic Receptor Antagonists

Cited by 176 publications

References 54 publications

Rational Design of α-Conotoxin Analogues Targeting α7 Nicotinic Acetylcholine Receptors

Rational Design of α-Conotoxin Analogues Targeting α7 Nicotinic Acetylcholine Receptors

Redox‐stable cyclic peptide inhibitors of the SPSB2–iNOS interaction

Synthetic Seleno-Glutaredoxin 3 Analogues Are Highly Reducing Oxidoreductases with Enhanced Catalytic Efficiency

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