The rockefeller university

Despite the astonishing progress in treating chronic hepatitis C virus (HCV) infection with direct-acting antiviral agents, liver fibrosis remains a major health concern in HCV infected patients, in particular due to the treatment cost and insufficient HCV screening in many countries. Only a fraction of patients with chronic HCV infection develop liver fibrosis. While there is evidence that host genetic factors are involved in the development of liver fibrosis, the common variants identified so far, in particular by genome-wide association studies, were found to have limited effects. Here, we conducted an exome association study in 88 highly selected HCV-infected patients with and without fibrosis. A strategy focusing on TGF-beta pathway genes revealed an enrichment in rare variants of the endoglin gene (ENG) in fibrosis patients. Replication studies in additional cohorts (617 patients) identified one specific ENG variant, Thr5Met, with an overall odds ratio for fibrosis development in carriers of 3.04 (1.39-6.69). Our results suggest that endoglin, a key player in TGF-beta signaling, is involved in HCV-related liver fibrogenesis.

TRAAK is a membrane tension-activated K+ channel that has been associated through behavioral studies to mechanical nociception. We used specific monoclonal antibodies in mice to show that TRAAK is localized exclusively to nodes of Ranvier, the action potential propagating elements of myelinated nerve fibers. Approximately 80 percent of myelinated nerve fibers throughout the central and peripheral nervous system contain TRAAK in what is likely an all-nodes or no-nodes per axon fashion. TRAAK is not observed at the axon initial segment where action potentials are first generated. We used polyclonal antibodies, the TRAAK inhibitor RU2 and node clamp amplifiers to demonstrate the presence and functional properties of TRAAK in rat nerve fibers. TRAAK contributes to the 'leak' K+ current in mammalian nerve fiber conduction by hyperpolarizing the resting membrane potential, thereby increasing Na+ channel availability for action potential propagation. We speculate on why nodes of Ranvier contain a mechanosensitive K+ channel.

In the last years, the ionic conductance behavior of solid-state nanochannels (SSN) has been extensively studied with both basic and applied purposes. In particular, the interactions between confined groups and dissolved species have been widely used for the design of biosensors and smart devices. Being the species confined to the small volume of the SSN, the ionic equilibrium usually differs from that in the solution bulk and nanoconfinement effects appear. In this work, we study the binding equilibrium between surface-confined amine groups and phosphate anions taking place within SSN by measuring the changes in the iontronic transmembrane current response of single nanochannels at different phosphate concentrations. Phosphate binding is higher compared with other divalent anions and takes place even in electrostatically hindered conditions, which reinforces the idea of chemical specificity of the amine-phosphate interaction. The sensitivity of the iontronic response of asymmetric SSN to changes in the surface charge allowed the interpretation of the experimental results in terms of a simple binding model, which reveals that the nanoconfinement effects are responsible for a one order of magnitude increase in the effective constants for the anion binding to the surface amine groups in the nanochannel walls. Furthermore, polyphosphates show a more pronounced binding tendency toward amine moieties, which allows the detection and quantification of ATP in the micromolar range from the analysis of the iontronic response.

Objectives: We have previously shown associations between 4 genetic variants in opioid and stress-related genes (OPRM1, NPYR1/NPYR5, NR3C1, and CRHBP) and prolonged abstinence from heroin without methadone maintenance treatment (MMT). We currently assessed the associations between these variants and MMT patients' characteristics. Methods: A non-selective group of 351 patients who stayed at least 1 year in their first admission to MMT were genotyped and their characteristics and substance in urine on admission and after 1 year were studied. Results: The proportions of patients with both cocaine and benzodiazepine abuse were reduced significantly after 1 year in MMT; however, cocaine abuse cessation was significantly associated with the non-carriers of the CRHBP (corticotrophin releasing hormone binding protein) SNP rs1500 minor C allele (GG genotype) (P = 0.0009, PBonferroni = 0.0221). More carriers of the 2 C alleles (CC genotype) than carriers of the GC and GG genotypes abused cocaine on admission (32.3% vs 19.7%, respectively, P = 0.0414, recessive model), and more of the C allele carriers (GC and CC genotypes) than non-carriers (GG genotype) abused cocaine after 1 year in MMT (25.7% vs 15.8%, respectively, P = 0.0334, dominant model). Abusers of benzodiazepine were more prevalent among carriers of the C allele compared with non-carriers on admission 60.6% vs 45.9%, respectively, P = 0.0080, dominant model), as well as after 1 year in MMT (50.9% vs 39.1%, respectively, P = 0.0362). Conclusions: Reduction in cocaine abuse among MMTpatients may be mediated by a genetic effect in a stress-related gene (CRHBP SNP rs1500 minor C allele). Evaluations of larger samples, additional SNPs, and different populations are needed to support these findings.

Following oxycodone conditioned place preference (CPP) in naive female and male Sprague Dawley rats, delta-and mu-opioid receptors (DORs and MORs) redistribute in hippocampal CA3 pyramidal cells and GABAergic interneurons in a manner that would promote opioid-associative learning processes, particularly in females. MORs and DORs similarly redistribute in CA3 and hilar neurons following chronic immobilization stress (CIS) in females, but not males, essentially "priming" the opioid system for oxycodone-associative learning. Following CIS, only females acquire oxycodone CPP. The present study determined whether sex and CIS differentially affect the levels of phosphorylated MORs and DORs (pMORs and pDORs) in the hippocampus following oxycodone CPP as phosphorylation is important for opioid receptor internationalization and trafficking. In naive oxycodone-injected (Oxy) female rats, the density of pMOR-immunoreactivity (ir) was increased in CA1 stratum oriens and CA3a,b strata lucidum and radiatum compared to saline-injected (Sal)-females. Additionally, the density of pDOR-ir increased in the pyramidal cell layer and stratum radiatum of CA2/3a in Oxy-males compared to Sal-males. In CIS females that acquire CPP, pDOR-ir levels were increased in the CA2/3a. These findings indicate only rats that acquire oxycodone CPP have activated MORs and DORs in the hippocampus but that the subregion containing activated opioid receptors differs in females and males. These results are consistent with previously observed sex differences in the hippocampal opioid system following Oxy-CPP.

Clostridium perfringens epsilon toxin (ETX) is responsible for causing the economically devastating disease, enterotoxaemia, in livestock. It is well accepted that ETX causes blood brain barrier (BBB) permeability, however the mechanisms involved in this process are not well understood. Using in vivo and in vitro methods, we determined that ETX causes BBB permeability in mice by increasing caveolae-dependent transcytosis in brain endothelial cells. When mice are intravenously injected with ETX, robust ETX binding is observed in the microvasculature of the central nervous system (CNS) with limited to no binding observed in the vasculature of peripheral organs, indicating that ETX specifically targets CNS endothelial cells. ETX binding to CNS microvasculature is dependent on MAL expression, as ETX binding to CNS microvasculature of MAL-deficient mice was not detected. ETX treatment also induces extravasation of molecular tracers including 376Da fluorescein salt, 60kDA serum albumin, 70kDa dextran, and 155kDA IgG. Importantly, ETX-induced BBB permeability requires expression of both MAL and caveolin-1, as mice deficient in MAL or caveolin-1 did not exhibit ETX-induced BBB permeability. Examination of primary murine brain endothelial cells revealed an increase in caveolae in ETX-treated cells, resulting in dynamin and lipid raft-dependent vacuolation without cell death. ETX-treatment also results in a rapid loss of EEA1 positive early endosomes and accumulation of large, RAB7-positive late endosomes and multivesicular bodies. Based on these results, we hypothesize that ETX binds to MAL on the apical surface of brain endothelial cells, causing recruitment of caveolin-1, triggering caveolae formation and internalization. Internalized caveolae fuse with early endosomes which traffic to late endosomes and multivesicular bodies. We believe that these multivesicular bodies fuse basally, releasing their contents into the brain parenchyma.

Intrinsically disordered regions (IDRs) of proteins are implicated in key macromolecular interactions. However, the molecular forces underlying IDR function within multicomponent assemblies remain elusive. By combining thermodynamic and structural data, we have discovered an allostery-based mechanism regulating the soluble core region of the nuclear pore complex (NPC) composed of nucleoporins Nup53, Nic96, and Nup157. We have identified distinct IDRs in Nup53 that are functionally coupled when binding to partner nucleoporins and karyopherins (Kaps) involved in NPC assembly and nucleocytoplasmic transport. We show that the Nup53.Kap121 complex forms an ensemble of structures that destabilize Nup53 hub interactions. Our study provides a molecular framework for understanding how disordered and folded domains communicate within macromolecular complexes.

DNA is both a fundamental building block of life and a fascinating natural polymer. The advent of single-molecule manipulation tools made it possible to exert controlled force on individual DNA molecules and measure their mechanical response. Such investigations elucidated the elastic properties of DNA and revealed its distinctive structural configurations across force regimes. In the meantime, a detailed understanding of DNA mechanics laid the groundwork for single-molecule studies of DNA-binding proteins and DNA-processing enzymes that bend, stretch, and twist DNA. These studies shed new light on the metabolism and transactions of nucleic acids, which constitute a major part of the cell's operating system. Furthermore, the marriage of single-molecule fluorescence visualization and force manipulation has enabled researchers to directly correlate the applied tension to changes in the DNA structure and the behavior of DNA-templated complexes. Overall, experimental exploitation of DNA mechanics has been and will continue to be a unique and powerful strategy for understanding how molecular machineries recognize and modify the physical state of DNA to accomplish their biological functions.