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Found 34783 matches. Displaying 161-170
Wang GP, Simon DJ, Wu ZH, Belsky DM, Heller E, O'Rourke MK, Hertz NT, Molina H, Zhong GS, Tessier-Lavigne M, Zhuang XW
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Structural plasticity of actin-spectrin membrane skeleton and functional role of actin and spectrin in axon degeneration

ELIFE 2019 MAY 1; 8(?):? Article e38730
Axon degeneration sculpts neuronal connectivity patterns during development and is an early hallmark of several adult-onset neurodegenerative disorders. Substantial progress has been made in identifying effector mechanisms driving axon fragmentation, but less is known about the upstream signaling pathways that initiate this process. Here, we investigate the behavior of the actin-spectrin-based Membrane-associated Periodic Skeleton (MPS), and effects of actin and spectrin manipulations in sensory axon degeneration. We show that trophic deprivation (TD) of mouse sensory neurons causes a rapid disassembly of the axonal MPS, which occurs prior to protein loss and independently of caspase activation. Actin destabilization initiates TD-related retrograde signaling needed for degeneration; actin stabilization prevents MPS disassembly and retrograde signaling during TD. Depletion of beta II-spectrin, a key component of the MPS, suppresses retrograde signaling and protects axons against degeneration. These data demonstrate structural plasticity of the MPS and suggest its potential role in early steps of axon degeneration.
Schuch R, Pelzek AJ, Nelson DC, Fischetti VA
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The PlyB Endolysin of Bacteriophage vB_BanS_Bcp1 Exhibits Broad-Spectrum Bactericidal Activity against Bacillus cereus Sensu Lato Isolates

Lytic bacteriophages (or phages) drive bacterial mortality by elaborating exquisite abilities to bind, breach, and destroy bacterial cell membranes and subjugate critical bacterial cell functions. These antimicrobial activities make phages ideal candidates to serve as, or provide sources of, biological control measures for bacterial pathogens. In this study, we isolated the Myoviridae phage vB_BanS_Bcp1 (here referred to as Bcp1) from landfill soil, using a Bacillus anthracis host. The antimicrobial activities of both Bcp1 and its encoded endolysin, PlyB, were examined across different B. cereus sensu lato group species, including B. cereus sensu stricto, Bacillus thuringiensis, and Bacillus anthracis, with pathogenic potential in humans and multiple different uses in biotechnological applications. The Bcp1 phage infected only a subset (11 to 66%) of each B. cereus sensu lato species group tested. In contrast, functional analysis of purified PlyB revealed a potent bacteriolytic activity against all B. cereus sensu lato isolates tested (n = 79). plyB was, furthermore, active across broad temperature, pH, and salt ranges, refractory to the development of resistance, bactericidal as a single agent, and synergistic with a second endolysin, PlyG. To confirm the potential for PlyB as an antimicrobial agent, we demonstrated the efficacy of a single intravenous treatment with PlyB alone or combination with PlyG in a murine model of lethal B. anthracis infection. Overall, our findings show exciting potential for the Bcp1 bacteriophage and the PlyB endolysin as potential new additions to the antimicrobial armamentarium. IMPORTANCE Organisms of the Bacillus cereus sensu lato lineage are ubiquitous in the environment and are responsible for toxin-mediated infections ranging from severe food poisoning (B. cereus sensu stricto) to anthrax (Bacillus anthracis). The increasing incidence of many of these infections, combined with the specter of antibiotic resistance, has created a need for novel antimicrobials with potent activity, including bacteriophages (or phages) and phage-encoded products (i.e., endolysins). In this study, we describe a broadly infective phage, Bcp1, and its encoded endolysin, PlyB, which exhibited a rapidly bacteriolytic effect against all B. cereus sensu lato isolates tested with no evidence of evolving resistance. Importantly, PlyB was highly efficacious in a mouse model of lethal bacteremia with B. anthracis. Both the Bcp1 phage and the PlyB endolysin represent novel mechanisms of action compared to antibiotics, with potential applications to address the evolving problem of antimicrobial resistance.
Trimmer C, Keller A, Murphy NR, Snyder LL, Willer JR, Nagai MH, Katsanis N, Vosshall LB, Matsunami H, Mainland JD
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Genetic variation across the human olfactory receptor repertoire alters odor perception

Humans use a family of more than 400 olfactory receptors (ORs) to detect odors, but there is currently no model that can predict olfactory perception from receptor activity patterns. Genetic variation in human ORs is abundant and alters receptor function, allowing us to examine the relationship between receptor function and perception. We sequenced the OR repertoire in 332 individuals and examined how genetic variation affected 276 olfactory phenotypes, including the perceived intensity and pleasantness of 68 odorants at two concentrations, detection thresholds of three odorants, and general olfactory acuity. Genetic variation in a single OR was frequently associated with changes in odorant perception, and we validated 10 cases in which in vitro OR function correlated with in vivo odorant perception using a functional assay. In 8 of these 10 cases, reduced receptor function was associated with reduced intensity perception. In addition, we used participant genotypes to quantify genetic ancestry and found that, in combination with single OR genotype, age, and gender, we can explain between 10% and 20% of the perceptual variation in 15 olfactory phenotypes, highlighting the importance of single OR genotype, ancestry, and demographic factors in the variation of olfactory perception.
Schmidt F, Keele BF, Del Prete GQ, Voronin D, Fennessey CM, Soll S, Kane M, Raymond A, Gifford RJ, KewalRamani V, Lifson JD, Bieniasz PD, Hatziioannou T
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Derivation of simian tropic HIV-1 infectious clone reveals virus adaptation to a new host

To replicate in a new host, lentiviruses must adapt to exploit required host factors and evade species-specific antiviral proteins. Understanding how host protein variation drives lentivirus adaptation allowed us to expand the host range of HIV-1 to pigtail macaques. We have previously derived a viral swarm(in the blood of infected animals) that can cause AIDS in this new host. To further exploit this reagent, we generated infectious molecular clones (IMCs) from the viral swarm. We identified clones with high replicative capacity in pigtail peripheral blood mononuclear cells (PBMC) in vitro and used in vivo replication to select an individual IMC, named stHIV-A19 (for simian tropic HIV-1 clone A19), which recapitulated the phenotype obtained with the viral swarm. Adaptation of HIV-1 in macaques led to the acquisition of amino acid changes in viral proteins, such as capsid (CA), that are rarely seen in HIV-1-infected humans. Using stHIV-A19, we show that these CA changes confer a partial resistance to the host cell inhibitor Mx2 from pigtail macaques, but that complete resistance is associated with a fitness defect. Adaptation of HIV-1 to a new host will lead to a more accurate animal model and a better understanding of virus-host interactions.
Garcia-Gomez S, Chaparro R, Safa A, Van den Rym A, Martinez-Barricarte R, Lorenzo L, Sanchez-Ramon S, Toledano V, Cubillos-Zapata C, Lopez-Collazo E, Martin-Arranz MD, Martin-Arranz E, Vela M, Gonzalez-Navarro P, Perez-Martinez A, Casanova JL, Recio MJ, de Diego RP
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Double-strand break repair through homologous recombination in autosomal-recessive BCL10 deficiency

Garone MG, de Turris V, Soloperto A, Brighi C, De Santis R, Pagani F, Di Angelantonio S, Rosa A
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Conversion of Human Induced Pluripotent Stem Cells (iPSCs) into Functional Spinal and Cranial Motor Neurons Using PiggyBac Vectors

We describe here a method to obtain functional spinal and cranial motor neurons from human induced pluripotent stem cells (iPSCs). Direct conversion into motor neuron is obtained by ectopic expression of alternative modules of transcription factors, namely Ngn2, Isl1 and Lhx3 (NIL) or Ngn2, Isl1 and Phox2a (NIP). NIL and NIP specify, respectively, spinal and cranial motor neuron identity. Our protocol starts with the generation of modified iPSC lines in which NIL or NIP are stably integrated in the genome via a piggyBac transposon vector. Expression of the transgenes is then induced by doxycycline and leads, in 5 days, to the conversion of iPSCs into MN progenitors. Subsequent maturation, for 7 days, leads to homogeneous populations of spinal or cranial MNs. Our method holds several advantages over previous protocols: it is extremely rapid and simplified; it does not require viral infection or further MN isolation; it allows generating different MN subpopulations (spinal and cranial) with a remarkable degree of maturation, as demonstrated by the ability to fire trains of action potentials. Moreover, a large number of motor neurons can be obtained without purification from mixed populations. iPSC-derived spinal and cranial motor neurons can be used for in vitro modeling of Amyotrophic Lateral Sclerosis and other neurodegenerative diseases of the motor neuron. Homogeneous motor neuron populations might represent an important resource for cell type specific drug screenings.
Fay A, Czudnochowski N, Rock JM, Johnson JR, Krogan NJ, Rosenberg O, Glickman MS
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Two Accessory Proteins Govern MmpL3 Mycolic Acid Transport in Mycobacteria

MBIO 2019 MAY-JUN; 10(3):? Article e00850-19
Mycolic acids are the signature lipid of mycobacteria and constitute an important physical component of the cell wall, a target of mycobacterium-specific antibiotics and a mediator of Mycobacterium tuberculosis pathogenesis. Mycolic acids are synthesized in the cytoplasm and are thought to be transported to the cell wall as a trehalose ester by the MmpL3 transporter, an antibiotic target for M. tuberculosis. However, the mechanism by which mycolate synthesis is coupled to transport, and the full MmpL3 transport machinery, is unknown. Here, we identify two new components of the MmpL3 transport machinery in mycobacteria. The protein encoded by MSMEG_0736/Rv0383c is essential for growth of Mycobacterium smegmatis and M. tuberculosis and is anchored to the cytoplasmic membrane, physically interacts with and colocalizes with MmpL3 in growing cells, and is required for trehalose monomycolate (TMM) transport to the cell wall. In light of these findings, we propose MSMEG_0736/Rv0383c be named "TMM transport factor A", TtfA. The protein encoded by MSMEG_5308 also interacts with the MmpL3 complex but is nonessential for growth or TMM transport. However, MSMEG_5308 accumulates with inhibition of MmpL3-mediated TMM transport and stabilizes the MmpL3/TtfA complex, indicating that it may stabilize the transport system during stress. These studies identify two new components of the mycobacterial mycolate transport machinery, an emerging antibiotic target in M. tuberculosis. IMPORTANCE The cell envelope of Mycobacterium tuberculosis, the bacterium that causes the disease tuberculosis, is a complex structure composed of abundant lipids and glycolipids, including the signature lipid of these bacteria, mycolic acids. In this study, we identified two new components of the transport machinery that constructs this complex cell wall. These two accessory proteins are in a complex with the MmpL3 transporter. One of these proteins, TtfA, is required for mycolic acid transport and cell viability, whereas the other stabilizes the MmpL3 complex. These studies identify two new components of the essential cell envelope biosynthetic machinery in mycobacteria.
McCarthy MW, de Asua DR, Gabbay E, Christos PJ, Fins JJ
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Frequency of Ethical Issues on a Hospitalist Teaching Service at an Urban, Tertiary Care Center

Little is known about the daily ethical conflicts encountered by hospitalists that do not prompt a formal clinical ethics consultation. We describe the frequencies of ethical issues identified during daily rounds on hospitalist teaching services at a metropolitan, tertiary-care, teaching hospital. Data were collected from September 2017 through May 2018 by two attending hospitalists from the ethics committee who were embedded on rounds. A total of 270 patients were evaluated and 113 ethical issues were identified in 77 of those patients. These issues most frequently involved discussions about goals of care, treatment refusals, decision-making capacity, discharge planning, cardiopulmonary resuscitation status, and pain management. Only five formal consults were brought to the Hospital Ethics Committee for these 270 patients. Our data are the first prospective description of ethical issues arising on academic hospitalist teaching services and are an important step in the development of a targeted ethics curriculum for hospitalists. (C) 2019 Society of Hospital Medicine
Cao BH, Lu TW, Fiesco JAM, Tomasini M, Fan LX, Simon SM, Taylor SS, Zhang P
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Structures of the PKA RI alpha Holoenzyme with the FLHCC Driver J-PKAc alpha or Wild-Type PKAc alpha

STRUCTURE 2019 MAY 7; 27(5):816-+
Fibrolamellar hepatocellular carcinoma (FLHCC) is driven by J-PKAc alpha, a kinase fusion chimera of the J domain of DnaJB1 with PKAc alpha, the catalytic subunit of protein kinase A (PKA). Here we report the crystal structures of the chimeric fusion RI alpha(2):J-PKAc alpha(2) holoenzyme formed by J-PKAc alpha and the PKA regulatory (R) subunit RI alpha, and the wild-type (WT) RI alpha(2):PKAc alpha(2) holoenzyme. The chimeric and WT RI alpha holoenzymes have quaternary structures different from the previously solved WT RI beta and RII beta holoenzymes. The WT RI alpha holoenzyme showed the same configuration as the chimeric RI alpha(2):J-PKAc alpha(2) holoenzyme and a distinct second conformation. The J domains are positioned away from the symmetrical interface between the two RI alpha:J-PKAc alpha heterodimers in the chimeric fusion holoenzyme and are highly dynamic. The structural and dynamic features of these holoenzymes enhance our understanding of the fusion chimera protein J-PKAc alpha that drives FLHCC as well as the isoform specificity of PKA.
Roongthumskul Y, Maoileidigh DO, Hudspeth AJ
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Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears

BIOPHYSICAL JOURNAL 2019 MAY 21; 116(10):2023-2034
Spontaneous otoacoustic emissions (SOAEs) are weak sounds that emanate from the ears of tetrapods in the absence of acoustic stimulation. These emissions are an epiphenomenon of the inner ear's active process, which enhances the auditory system's sensitivity to weak sounds, but their mechanism of production remains a matter of debate. We recorded SOAEs simultaneously from the two ears of the tokay gecko and found that binaural emissions could be strongly correlated: some emissions occurred at the same frequency in both ears and were highly synchronized. Suppression of the emissions in one ear often changed the amplitude or shifted the frequency of emissions in the other. Decreasing the frequency of emissions from one ear by lowering its temperature usually reduced the frequency of the contralateral emissions. To understand the relationship between binaural SOAEs, we developed a mathematical model of the eardrums as noisy nonlinear oscillators coupled by the air within an animal's mouth. By according with the model, the results indicate that some SOAEs are generated bilaterally through acoustic coupling across the oral cavity. The model predicts that sound localization through the acoustic coupling between ears is influenced by the active processes of both ears.