α-Conotoxin Vc1.1 specifically and potently inhibits the nicotinic acetylcholine receptor subtype α9α10 (α9α10 nAChR) and is a potential novel treatment for neuropathic pain. Here, we used a combination of computational modeling and electrophysiology experiments to determine the Vc1.1 binding site on the α9α10 nAChR. Interactions of Vc1.1 with two probable binding sites, α9α10 and α10α9, were modeled. Mutational energies calculated by assuming specific interactions in the α10α9 binding site correlated better with electrophysiological recordings than those assuming interactions with the α9α10 binding site. Two novel Vc1.1 analogues, [N9F]Vc1.1 and [N9W]Vc1.1, were predicted to have large differences in affinity between the two binding sites. Data from functional studies were consistent with computational predictions that assumed preferred binding of Vc1.1 to the α10α9 pocket. Moreover, our modeling study suggested that a single hydrogen bond formed between Vc1.1 and position 59 of the α10α9 pocket confers specificity to rat versus human α9α10 nAChRs.

Nicotinic acetylcholine receptors (nAChRs) play essential roles in transmitting acetylcholine-mediated neural signals across synapses and neuromuscular junctions, and are also closely linked to various diseases and clinical conditions. Therefore, novel nAChR-specific compounds have great potential for both neuroscience research and clinical applications. Conotoxins, the peptide neurotoxins produced by cone snails, are a rich reservoir of novel ligands that target receptors, ion channels and transporters in the nervous system. From the venom of Conus generalis, we identified a novel dimeric nAChR-inhibiting αD-conotoxin GeXXA. By solving the crystal structure and performing structure-guided dissection of this toxin, we demonstrated that the monomeric C-terminal domain of αD-GeXXA, GeXXA-CTD, retains inhibitory activity against the α9α10 nAChR subtype. Furthermore, we identified that His7 of the rat α10 nAChR subunit determines the species preference of αD-GeXXA, and is probably part of the binding site of this toxin. These results together suggest that αD-GeXXA cooperatively binds to two inter-subunit interfaces on the top surface of nAChR, thus allosterically disturbing the opening of the receptor. The novel antagonistic mechanism of αD-GeXXA via a new binding site on nAChRs provides a valuable basis for the rational design of new nAChR-targeting compounds.

Conotoxins have emerged as useful leads for the development of novel therapeutic analgesics. These peptides, isolated from marine molluscs of the genus Conus, have evolved exquisite selectivity for receptors and ion channels of excitable tissue. One such peptide, α-conotoxin Vc1.1, is a 16-mer possessing an interlocked disulfide framework. Despite its emergence as a potent analgesic lead, the molecular target and mechanism of action of Vc1.1 have not been elucidated to date. In this paper we describe the regioselective synthesis of dicarba analogues of Vc1.1 using olefin metathesis. The ability of these peptides to inhibit acetylcholine-evoked current at rat α9α10 and α3β4 nicotinic acetylcholine receptors (nAChR) expressed in Xenopus oocytes has been assessed in addition to their ability to inhibit high voltage-activated (HVA) calcium channel current in isolated rat DRG neurons. Their solution structures were determined by NMR spectroscopy. Significantly, we have found that regioselective replacement of the native cystine framework with a dicarba bridge can be used to selectively tune the cyclic peptide's innate biological activity for one receptor over another. The 2,8-dicarba Vc1.1 isomer retains activity at γ-aminobutyric acid (GABAB) G protein-coupled receptors, whereas the isomeric 3,16-dicarba Vc1.1 peptide retains activity at the α9α10 nAChR subtype. These singularly acting analogues will enable the elucidation of the biological target responsible for the peptide's potent analgesic activity.

Air pollution is associated with detrimental effects on human health, including decreased cardiovascular function. However, the causative mechanisms behind these effects have yet to be fully elucidated. Here we review the current epidemiological, clinical and experimental evidence linking pollution with cardiovascular dysfunction. Our focus is on particulate matter (PM) and the associated low molecular weight polycyclic aromatic hydrocarbons (PAHs) as key mediators of cardiotoxicity. We begin by reviewing the growing epidemiological evidence linking air pollution to cardiovascular dysfunction in humans. We next address the pollution‐based cardiotoxic mechanisms first identified in fish following the release of large quantities of PAHs into the marine environment from point oil spills (e.g. Deepwater Horizon). We finish by discussing the current state of mechanistic knowledge linking PM and PAH exposure to mammalian cardiovascular patho‐physiologies such as atherosclerosis, cardiac hypertrophy, arrhythmias, contractile dysfunction and the underlying alterations in gene regulation. Our aim is to show conservation of toxicant pathways and cellular targets across vertebrate hearts to allow a broad framework of the global problem of cardiotoxic pollution to be established. AhR; Aryl hydrocarbon receptor. Dark lines indicate topics discussed in this review. Grey lines indicate topics reviewed elsewhere.

α-Conotoxin RgIA is both an antagonist of the α9α10 nicotinic acetylcholine receptor (nAChR) subtype and an inhibitor of high-voltage-activated N-type calcium channel currents. RgIA has therapeutic potential for the treatment of pain, but reduction of the disulfide bond framework under physiological conditions represents a potential liability for clinical applications. We synthesized four RgIA analogues that replaced native disulfide pairs with nonreducible dicarba bridges. Solution structures were determined by NMR, activity assessed against biological targets, and stability evaluated in human serum. [3,12]-Dicarba analogues retained inhibition of ACh-evoked currents at α9α10 nAChRs but not N-type calcium channel currents, whereas [2,8]-dicarba analogues displayed the opposite pattern of selectivity. The [2,8]-dicarba RgIA analogues were effective in HEK293 cells stably expressing human Cav2.2 channels and transfected with human GABAB receptors. The analogues also exhibited improved serum stability over the native peptide. These selectively acting dicarba analogues may represent mechanistic probes to explore analgesia-related biological receptors.