AChBP-targeted α-conotoxin correlates distinct binding orientations with nAChR subtype selectivity

Neuronal nAChRs are a diverse family of pentameric ion channels with wide distribution throughout cells of the nervous and immune systems. However, the role of specific subtypes in normal and pathological states remains poorly understood due to the lack of selective probes. Here, we used a binding assay based on acetylcholine-binding protein (AChBP), a homolog of the nicotinic acetylcholine ligand-binding domain, to discover a novel α-conotoxin (α-TxIA) in the venom of Conus textile. α-TxIA bound with high affinity to AChBPs from different species and selectively targeted the α3β2 nAChR subtype. A co-crystal structure of Ac-AChBP with the enhanced potency analog TxIA(A10L), revealed a 20° backbone tilt compared to other AChBP–conotoxin complexes. This reorientation was coordinated by a key salt bridge formed between Arg5 (TxIA) and Asp195 (Ac-AChBP). Mutagenesis studies, biochemical assays and electrophysiological recordings directly correlated the interactions observed in the co-crystal structure to binding affinity at AChBP and different nAChR subtypes. Together, these results establish a new pharmacophore for the design of novel subtype-selective ligands with therapeutic potential in nAChR-related diseases

Income inequality and cardiovascular disease risk factors in a highly unequal country: a fixed-effects analysis from South Africa

Background: Chronic stress associated with high income inequality has been hypothesized to increase CVD risk and other adverse health outcomes. However, most evidence comes from high-income countries, and there is limited evidence on the link between income inequality and biomarkers of chronic stress and risk for CVD. This study examines how changes in income inequality over recent years relate to changes in CVD risk factors in South Africa, home to some of the highest levels of income inequality globally. Methods: We linked longitudinal data from 9356 individuals interviewed in the 2008 and 2012 National Income Dynamics Study to district-level Gini coefficients estimated from census and survey data. We investigated whether subnational district income inequality was associated with several modifiable risk factors for cardiovascular disease (CVD) in South Africa, including body mass index (BMI), waist circumference, blood pressure, physical inactivity, smoking, and high alcohol consumption. We ran individual fixed-effects models to examine the association between changes in income inequality and changes in CVD risk factors over time. Linear models were used for continuous metabolic outcomes while conditional Poisson models were used to estimate risk ratios for dichotomous behavioral outcomes. Results: Both income inequality and prevalence of most CVD risk factors increased over the period of study. In longitudinal fixed-effects models, changes in district Gini coefficients were not significantly associated with changes in CVD risk factors. Conclusions: Our findings do not support the hypothesis that subnational district income inequality is associated with CVD risk factors within the high-inequality setting of South Africa

Mass spectral identification of Vc1.1 and differential distribution of conopeptides in the venom duct of conus victoriae. Effect of post-translational modifications and disulfide isomerisation on bioactivity

Molluscs of the genus Conus (cone shells) are carnivorous, feeding on marine worms, small fish and other marine molluscs. They capture their prey by injecting venom containing hundreds of neurally active peptide components. These peptides are classed as conotoxins and consist of small disulfide-bonded peptides exhibiting a high degree of post-translational modifications (PTMs). The functional roles of these modifications remain largely unknown. Two of the most frequently observed modifications are γ-carboxylation of glutamate and hydroxylation of proline (Buczek et al. Cell Mol Life Sci 62:3067, 2005). Vc1.1 is an α-conotoxin from Conus victoriae (Sandall et al. Biochemistry 42(22):6904–6911, 2003) and the only form of this peptide which has been detected in the venom is the γ-glutamate and hydroxyproline (Vc1.1.P6O:E14- Gla) version of the molecule (Jakubowski et al. Toxicon 47(6):688–699, 2006). In order to investigate the role of PTMs, we did mass spectral profiling of the venom duct of C. victoriae looking at changes in mass and the number of peptides detected. We synthesised a number of predicted Vc1.1-PTM peptides together with the three possible disulfide isoforms of Vc1.1 and assessed the possible functional role of the PTM conopeptides by measuring the in vitro activity at the cognate neuronal nicotinic acetylcholine receptors (nAChRs). In addition we looked for their presence Vc1.1 venom by mass spectrometry and by this approach we were able to detect unmodified Vc1.1 in C. victoriae venom for the first time.A. Townsend, B.G. Livett, J.-P. Bingham, H.-T. Truong, J.A. Karas, P. O’Donnell, N.A. Williamson, A.W. Purcell and D. Scanlo