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The majority of commercialized insecticides target the insect nervous system and therefore, neural proteins are well-validated targets for insecticide development. Considering that only a few neural targets are exploited for insecticidal action and the development of insecticide resistance has reduced the efficacy of current insecticidal classes, we sought to test the toxicological potential of the potassium-chloride cotransporter (KCC). In mammals, KCC proteins have seminal roles in shaping GABAergic signaling and inhibitory neurotransmission, thus ion transport through KCC is critical for proper neurotransmission. Therefore, we hypothesized that mosquito KCC represents a putative insecticide target site and that pharmacological inhibition of KCC constructs in Aedes aegypti will be lethal. To test this hypothesis, we developed a robust, cell-based fluorescence assay that enables in vitro characterization of small-molecules against Ae. aegypti KCC and performed a proof-of-concept study employing well characterized mammalian KCC modulators to determine the toxicological potential of Ae. aegypti KCC. The selective inhibitor of mammalian KCC, termed VU0463271, was found to be a potent inhibitor Ae. aegypti KCC and microinjection induced lethality in a concentration-dependent manner to susceptible and pyrethroid resistant strains. Importantly, an analog of VU0463271 was shown to be >40-fold less potent and did not induce toxicity, suggesting that the observed physiological effects and mortality are likely due to KCC inhibition. This proof-of-concept study suggests that Ae. aegypti KCC represents a putative target site for mosquitocide design that can mitigate the current mechanisms of insecticide resistance.
Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.
Zika virus (ZIKV) is a major human pathogen and member of the genus in the Flaviviridae family. In contrast to most other insect-transmitted flaviviruses, ZIKV also can be transmitted sexually and from mother to fetus in humans. During recent outbreaks, ZIKV infections have been linked to microcephaly, congenital disease, and Guillain-Barré syndrome. Neutralizing antibodies have potential as therapeutic agents. We report here a 4-Å-resolution cryo-electron microscopy structure of the ZIKV virion in complex with Fab fragments of the potently neutralizing human monoclonal antibody ZIKV-195. The footprint of the ZIKV-195 Fab fragment expands across two adjacent envelope (E) protein protomers. ZIKV neutralization by this antibody is presumably accomplished by cross-linking the E proteins, which likely prevents formation of E protein trimers required for fusion of the viral and cellular membranes. A single dose of ZIKV-195 administered 5 days after virus inoculation showed marked protection against lethality in a stringent mouse model of infection.
infection (CDI) is a major public health threat worldwide. The use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with enhanced susceptibility to and severity of CDI; however, the mechanisms driving this phenomenon have not been elucidated. NSAIDs alter prostaglandin (PG) metabolism by inhibiting cyclooxygenase (COX) enzymes. Here, we found that treatment with the NSAID indomethacin prior to infection altered the microbiota and dramatically increased mortality and the intestinal pathology associated with CDI in mice. We demonstrated that in -infected animals, indomethacin treatment led to PG deregulation, an altered proinflammatory transcriptional and protein profile, and perturbed epithelial cell junctions. These effects were paralleled by increased recruitment of intestinal neutrophils and CD4 cells and also by a perturbation of the gut microbiota. Together, these data implicate NSAIDs in the disruption of protective COX-mediated PG production during CDI, resulting in altered epithelial integrity and associated immune responses. infection (CDI) is a spore-forming anaerobic bacterium and leading cause of antibiotic-associated colitis. Epidemiological data suggest that use of nonsteroidal anti-inflammatory drugs (NSAIDs) increases the risk for CDI in humans, a potentially important observation given the widespread use of NSAIDs. Prior studies in rodent models of CDI found that NSAID exposure following infection increases the severity of CDI, but mechanisms to explain this are lacking. Here we present new data from a mouse model of antibiotic-associated CDI suggesting that brief NSAID exposure prior to CDI increases the severity of the infectious colitis. These data shed new light on potential mechanisms linking NSAID use to worsened CDI, including drug-induced disturbances to the gut microbiome and colonic epithelial integrity. Studies were limited to a single NSAID (indomethacin), so future studies are needed to assess the generalizability of our findings and to establish a direct link to the human condition.
Copyright © 2019 Maseda et al.
In the developing pancreas, transient Neurog3-expressing progenitors give rise to four major islet cell types: α, β, δ, and γ; when and how the Neurog3 cells choose cell fate is unknown. Using single-cell RNA-seq, trajectory analysis, and combinatorial lineage tracing, we showed here that the Neurog3 cells co-expressing Myt1 (i.e., Myt1Neurog3) were biased toward β cell fate, while those not simultaneously expressing Myt1 (Myt1Neurog3) favored α fate. Myt1 manipulation only marginally affected α versus β cell specification, suggesting Myt1 as a marker but not determinant for islet-cell-type specification. The Myt1Neurog3 cells displayed higher Dnmt1 expression and enhancer methylation at Arx, an α-fate-promoting gene. Inhibiting Dnmts in pancreatic progenitors promoted α cell specification, while Dnmt1 overexpression or Arx enhancer hypermethylation favored β cell production. Moreover, the pancreatic progenitors contained distinct Arx enhancer methylation states without transcriptionally definable sub-populations, a phenotype independent of Neurog3 activity. These data suggest that Neurog3-independent methylation on fate-determining gene enhancers specifies distinct endocrine-cell programs.
Published by Elsevier Inc.
Annexin proteins function as Ca-dependent regulators of membrane trafficking and repair that may also modulate membrane curvature. Here, using high-resolution confocal imaging, we report that the intestine-specific annexin A13 (ANX A13) localizes to the tips of intestinal microvilli and determined the crystal structure of the ANX A13a isoform to 2.6 Å resolution. The structure revealed that the N terminus exhibits an alternative fold that converts the first two helices and the associated helix-loop-helix motif into a continuous α-helix, as stabilized by a domain-swapped dimer. We also found that the dimer is present in solution and partially occludes the membrane-binding surfaces of annexin, suggesting that dimerization may function as a means for regulating membrane binding. Accordingly, as revealed by binding and cellular localization assays, ANX A13a variants that favor a monomeric state exhibited increased membrane association relative to variants that favor the dimeric form. Together, our findings support a mechanism for how the association of the ANX A13a isoform with the membrane is regulated.
© 2019 McCulloch et al.
Enterovirus D68 (EV-D68) is a pathogen that causes outbreaks of respiratory illness across the world, mostly in children, and can be especially severe in those with asthma. Clusters of acute flaccid myelitis, a poliomyelitis-like neuromuscular weakness syndrome, often occur concurrent with EV-D68 respiratory outbreaks. Seroepidemiologic studies have found that the serum of nearly everyone older than 2 to 5 years contains anti-EV-D68 neutralizing antibodies, which suggests that EV-D68 is a ubiquitous pathogen of childhood. However, knowledge of the viral epitopes against which the humoral immune response is directed is only inferred from previous studies of related viruses. Although neutralizing antibodies protect newborn mice from lethal EV-D68 inoculation via nonphysiologic routes, cotton rats have a mixed phenotype of both benefit and possible exacerbation when inoculated intranasally. The human antibody response to EV-D68 needs to be studied further to clarify the role of antibodies in protection versus pathogenesis, which might differ among respiratory and neurologic disease phenotypes.
In this trans-ethnic multi-omic study, we reinterpret the genetic architecture of blood pressure to identify genes, tissues, phenomes and medication contexts of blood pressure homeostasis. We discovered 208 novel common blood pressure SNPs and 53 rare variants in genome-wide association studies of systolic, diastolic and pulse pressure in up to 776,078 participants from the Million Veteran Program (MVP) and collaborating studies, with analysis of the blood pressure clinical phenome in MVP. Our transcriptome-wide association study detected 4,043 blood pressure associations with genetically predicted gene expression of 840 genes in 45 tissues, and mouse renal single-cell RNA sequencing identified upregulated blood pressure genes in kidney tubule cells.
Clostridium difficile is a Gram-positive, spore-forming anaerobic bacterium that infects the colon, causing symptoms ranging from infectious diarrhea to fulminant colitis. In the last decade, the number of C. difficile infections has dramatically risen, making it the leading cause of reported hospital acquired infection in the United States. Bacterial toxins produced during C. difficile infection (CDI) damage host epithelial cells, releasing erythrocytes and heme into the gastrointestinal lumen. The reactive nature of heme can lead to toxicity through membrane disruption, membrane protein and lipid oxidation, and DNA damage. Here we demonstrate that C. difficile detoxifies excess heme to achieve full virulence within the gastrointestinal lumen during infection, and that this detoxification occurs through the heme-responsive expression of the heme activated transporter system (HatRT). Heme-dependent transcriptional activation of hatRT was discovered through an RNA-sequencing analysis of C. difficile grown in the presence of a sub-toxic concentration of heme. HatRT is comprised of a TetR family transcriptional regulator (hatR) and a major facilitator superfamily transporter (hatT). Strains inactivated for hatR or hatT are more sensitive to heme toxicity than wild-type. HatR binds heme, which relieves the repression of the hatRT operon, whereas HatT functions as a heme efflux pump. In a murine model of CDI, a strain inactivated for hatT displayed lower pathogenicity in a toxin-independent manner. Taken together, these data suggest that HatR senses intracellular heme concentrations leading to increased expression of the hatRT operon and subsequent heme efflux by HatT during infection. These results describe a mechanism employed by C. difficile to relieve heme toxicity within the host, and set the stage for the development of therapeutic interventions to target this bacterial-specific system.