Significance: The α9α10 nicotinic AChR (nAChR) subtype is a recently identified target for the development of breast cancer chemotherapeutics and analgesics, particularly to treat neuropathic pain. Structure/function analyses of antagonists of this subtype are therefore essential for the development of specific therapeutic compounds. TheConusgenus is a rich source of pharmacologically active peptides, and we report here that the αO-conotoxin GeXIVA is a potent and selective antagonist of the α9α10 nAChR subtype. GeXIVA displays unique structural properties among otherConuspeptides and represents a previously unidentified template for molecules active against neuropathic pain.

Titanium dioxide nanoparticles (TiO₂ NPs) have become a widely used nanomaterial due to the photocatalytic activity and absorption of ultraviolet light of specific wavelengths. This study investigated the toxic effects of rutile TiO₂ NPs on zebrafish by examining its embryos and adults. In the embryo acute toxicity test, exposure to 100 mg/L TiO₂ NPs didn’t affect the hatching rate of zebrafish embryos, and there was no sign of deformity. In the adult toxicity test, the effects of TiO₂ NPs on oxidative damage in liver, intestine and gill tissue were studied. Enzyme linked immunosorbent assay (ELISA) and fluorescence-based quantitative real-time reverse transcription PCR (qRT-PCR) were used to detect the three antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT) and glutathione S transferase (GSTs) in the above mentioned zebrafish organs at protein and gene levels. The results showed that long-term exposure to TiO₂ NPs can cause oxidative damage to organisms; and compared with the control group, the activity of the three kinds of enzyme declined somewhat at the protein level. In addition, long-term exposure to TiO₂ NPs could cause high expression of CAT, SOD and GSTs in three organs of adult zebrafish in order to counter the adverse reaction. The effects of long-term exposure to TiO₂ NPs to adult zebrafish were more obvious in the liver and gill.

This study was performed to discover and characterize the first potent α3β2‐subtype‐selective nicotinic acetylcholine receptor (nAChR) ligand. A novel α4/7‐conotoxin, α‐CTxLvIA, was cloned from Conus lividus. Its pharmacological profile at Xenopus laevis oocyte‐expressed rat nAChR subtypes was determined by 2‐electrode voltage‐clamp electrophysiology, and its 3‐dimensional (3D) structure was determined by NMR spectroscopy. α‐CTx LvIA is a 16‐aa C‐terminallyamidated peptide with 2‐disulfide bridges. Using rat subunits expressed in Xenopus oocytes, we found the highest affinity of α‐CTxLvIA was for α3β2 nAChRs (IC ₅₀ 8.7 nM), where blockade was reversible within 2 min. IC ₅₀ values were >100 nM at α6/α3β2β3, α6/α3β4, and α3β4 nAChRs, and ≥3 μM at all other subtypes tested. α3β2 vs. α6β2 subtype selectivity was confirmed for human‐subunit nAChRs with much greater preference (300‐fold) for α3β2 over α6β2 nAChRs. This is the first α‐CTx reported to show high selectivity for human α3β2 vs. α6β2 nAChRs. α‐CTxLvIA adopts two similarly populated conformations water: one (assumed to be bioactive) is highly structured, whereas the other is mostly random coil in nature. Selectivity differences with the similarly potent, but less selective, α3β2 nAChR antagonist α‐CTx PeIA probably reside within the three residues, which differ in loop 2, given their otherwise similar 3D structures. α4/7‐CTx LvIA is a new, potent, selective α3β2 nAChR antagonist, which will enable detailed studies of α3β2 nAChR structure, function, and physiological roles.—Luo, S., Zhangsun, D., Schroeder, C. I., Zhu, X., Hu, Y., Wu, Y., Weltzin, M. M., Eberhard, S., Kaas, Q., Craik, D. J., McIntosh, J. M., Whiteaker, P. A novel α4/7‐conotoxin LvIA from Conus lividus that selectively blocks α3β2 vs. α6/α3β2β3 nicotinic acetylcholine receptors. FASEB J. 28, 1842–1853 (2014). www.fasebj.org

α6β2 Nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic neurons in the CNS are potential therapeutic targets for the treatment of several neuropsychiatric diseases, including nicotine addiction and Parkinson disease. However, recent studies indicate that the α6 subunit can also associate with the β4 subunit to form α6β4 nAChRs that are difficult to pharmacologically distinguish from α6β2, α3β4, and α3β2 subtypes. The current study characterized a novel 16-amino acid α-conotoxin (α-CTx) TxIB from Conus textile whose sequence is GCCSDPPCRNKHPDLC-amide as deduced from gene cloning. The peptide and an analog with an additional C-terminal glycine were chemically synthesized and tested on rat nAChRs heterologously expressed in Xenopus laevis oocytes. α-CTx TxIB blocked α6/α3β2β3 nAChR with an IC₅₀ of 28 nm. In contrast, the peptide showed little or no block of other tested subtypes at concentrations up to 10 μm. The three-dimensional solution structure of α-CTx TxIB was determined using NMR spectroscopy. α-CTx TxIB represents a uniquely selective ligand for probing the structure and function of α6β2 nAChRs.

Conotoxins (CTxs) selectively target a range of ion channels and receptors, making them widely used tools for probing nervous system function. Conotoxins have been previously grouped into superfamilies according to signal sequence and into families based on their cysteine framework and biological target. Here we describe the cloning and characterization of a new conotoxin, from Conus vexillum, named αB-conotoxin VxXXIVA. The peptide does not belong to any previously described conotoxin superfamily and its arrangement of Cys residues is unique among conopeptides. Moreover, in contrast to previously characterized conopeptide toxins, which are expressed initially as prepropeptide precursors with a signal sequence, a ‘‘pro’’ region, and the toxin-encoding region, the precursor sequence of αB-VxXXIVA lacks a ‘‘pro’’ region. The predicted 40-residue mature peptide, which contains four Cys, was synthesized in each of the three possible disulfide arrangements. Investigation of the mechanism of action of αB-VxXXIVA revealed that the peptide is a nicotinic acetylcholine receptor (nAChR) antagonist with greatest potency against the α9α10 subtype. ¹H nuclear magnetic resonance (NMR) spectra indicated that all three αB-VxXXIVA isomers were poorly structured in aqueous solution. This was consistent with circular dichroism (CD) results which showed that the peptides were unstructured in buffer, but adopted partially helical conformations in aqueous trifluoroethanol (TFE) solution. The α9α10 nAChR is an important target for the development of analgesics and cancer chemotherapeutics, and αB-VxXXIVA represents a novel ligand with which to probe the structure and function of this protein.