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https://www.readbyqxmd.com/read/28743005/xenopus-laevis-m18bp1-directly-binds-existing-cenp-a-nucleosomes-to-promote-centromeric-chromatin-assembly
#1
Bradley T French, Frederick G Westhorpe, Charles Limouse, Aaron F Straight
Vertebrate centromeres are epigenetically defined by nucleosomes containing the histone H3 variant, CENP-A. CENP-A nucleosome assembly requires the three-protein Mis18 complex (Mis18α, Mis18β, and M18BP1) that recruits the CENP-A chaperone HJURP to centromeres, but how the Mis18 complex recognizes centromeric chromatin is unknown. Using Xenopus egg extract, we show that direct, cell-cycle-regulated binding of M18BP1 to CENP-A nucleosomes recruits the Mis18 complex to interphase centromeres to promote new CENP-A nucleosome assembly...
July 24, 2017: Developmental Cell
https://www.readbyqxmd.com/read/28739643/histone-methyltransferase-dot1l-is-a-coactivator-for-thyroid-hormone-receptor-during-xenopus-development
#2
Luan Wen, Liezhen Fu, Yun-Bo Shi
Histone modifications are associated with transcriptional regulation by diverse transcription factors. Genome-wide correlation studies have revealed that histone activation marks and repression marks are associated with activated and repressed gene expression, respectively. Among the histone activation marks is histone H3 K79 methylation, which is carried out by only a single methyltransferase, disruptor of telomeric silencing-1-like (DOT1L). We have been studying thyroid hormone (T3)-dependent amphibian metamorphosis in two highly related species, the pseudo-tetraploid Xenopus laevis and diploid Xenopus tropicalis, as a model for postembryonic development, a period around birth in mammals that is difficult to study...
July 24, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/28739571/splice-variants-of-ph-sensitive-chloride-channel-identify-a-key-determinant-of-ivermectin-sensitivity-in-the-larvae-of-the-silkworm-bombyx-mori
#3
Daiki Okuhara, Shogo Furutani, Katsuhiko Ito, Makoto Ihara Ihara, Kazuhiko Matsuda
The pH-sensitive chloride channels (pHCls) are broadly expressed in insects, but little is known about their physiological role, diversity and sensitivity to insecticides acting on relevant chloride channels. Here we have sequenced 50 transcripts of the pHCl-1 gene from the brain, third thoracic ganglion (T3G) and midgut of larvae of silkworm Bombyx mori. It was found that >50 variants were expressed with distinct splicing in the T3G compared to the brain and midgut. Of the variants detected, variant 9, which was expressed most abundantly in the larvae, was reconstituted in Xenopus laevis oocytes to characterise its pH- and ivermectin sensitivity...
July 24, 2017: Molecular Pharmacology
https://www.readbyqxmd.com/read/28736919/a-g326e-substitution-in-the-glutamate-gated-chloride-channel-3-glucl3-of-the-two-spotted-spider-mite-tetranychus-urticae-abolishes-the-agonistic-activity-of-macrocyclic-lactones
#4
Catherine Mermans, Wannes Dermauw, Sven Geibel, Thomas Van Leeuwen
BACKGROUND: The macrocyclic lactones abamectin and milbemectin are frequently used to control phytophagous mites such as Tetranychus urticae. Consequently, resistance has developed and was genetically linked with substitutions in the glutamate-gated chloride channel (GluCl) subunits TuGluCl1 and TuGluCl3. Here, we functionally validated a G326E substitution in TuGluCl3 by functional expression in Xenopus laevis oocytes followed by two-electrode voltage-clamp electrophysiology. RESULTS: Homomeric wild-type and mutated GluCl3 were successfully expressed...
July 24, 2017: Pest Management Science
https://www.readbyqxmd.com/read/28733581/structural-determinants-at-the-m2-muscarinic-receptor-modulate-the-rgs4-girk-response-to-pilocarpine-by-impairment-of-the-receptor-voltage-sensitivity
#5
I-Shan Chen, Kazuharu Furutani, Yoshihisa Kurachi
Membrane potential controls the response of the M2 muscarinic receptor to its ligands. Membrane hyperpolarization increases response to the full agonist acetylcholine (ACh) while decreasing response to the partial agonist pilocarpine. We previously have demonstrated that the regulator of G-protein signaling (RGS) 4 protein discriminates between the voltage-dependent responses of ACh and pilocarpine; however, the underlying mechanism remains unclear. Here we show that RGS4 is involved in the voltage-dependent behavior of the M2 muscarinic receptor-mediated signaling in response to pilocarpine...
July 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28730637/identification-and-functional-characterization-of-an-odorant-receptor-in-pea-aphid-acyrthosiphon-pisum
#6
Rui-Bin Zhang, Yang Liu, Shan-Chun Yan, Gui-Rong Wang
The sensitive olfactory system is necessary for survival of insects. Odorant receptors (ORs) are located on the dendrites of olfactory receptor neurons and play a critical role in odor detection. Insect ORs are functionally analyzed via heterologous expression in a Xenopus oocyte system using a two-electrode voltage-clamp (TEVC) electrophysiological recording. Here, we have identified a novel OR in the pea aphid, Acyrthosiphon pisum, then we cloned and named it ApisOR4. We analyzed the ApisOR4 tissue expression patterns and found expression only in antennae tissues...
July 21, 2017: Insect Science
https://www.readbyqxmd.com/read/28729424/molecular-determinants-of-acidic-ph-dependent-transport-of-human-equilibrative-nucleoside-transporter-3
#7
Md Fazlur Rahman, Candice Askwith, Rajgopal Govindarajan
Equilibrative nucleoside transporters (ENTs) translocate hydrophilic nucleosides across cellular membranes and are essential for salvage nucleotide synthesis and purinergic signaling. Unlike the prototypic human ENT members hENT1 and hENT2, which mediate plasma membrane nucleoside transport at pH 7.4, hENT3 is an acidic pH-activated lysosomal transporter partially localized to mitochondria. Recent studies demonstrate that hENT3 is indispensable for lysosomal homeostasis, and that mutations in hENT3 can result in a spectrum of lysosomal storage-like disorders...
July 20, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28722544/the-greatwall-kinase-is-dominant-over-pka-in-controlling-the-antagonistic-function-of-arpp19-in-xenopus-oocytes
#8
Aude-Isabelle Dupré, Olivier Haccard, Catherine Jessus
The small protein ARPP19 plays a dual role during oocyte meiosis resumption. In Xenopus, ARPP19 phosphorylation at S109 by PKA is necessary for maintaining oocytes arrested in prophase of the first meiotic division. Progesterone downregulates PKA, leading to the dephosphorylation of ARPP19 at S109. This initiates a transduction pathway ending with the activation of the universal inducer of M-phase, the kinase Cdk1. This last step depends on ARPP19 phosphorylation at S67 by the kinase Greatwall. Hence, phosphorylated by PKA at S109, ARPP19 restrains Cdk1 activation while when phosphorylated by Greatwall at S67, ARPP19 becomes an inducer of Cdk1 activation...
July 19, 2017: Cell Cycle
https://www.readbyqxmd.com/read/28720818/structural-and-rheological-properties-conferring-fertilization-competence-to-xenopus-egg-coating-envelope
#9
Mayu Hanaue, Naofumi Miwa
The extracellular egg-coating envelope that comprises a meshwork of filaments polymerized by glycoproteins plays a pivotal role in species-selective sperm recognition and subsequent fertilization; however, the structural and rheological properties conferring fertilization competence to the egg-coating envelope remain poorly unveiled. Here we show several nanoscale-structural and viscoelastic properties of the egg-coat using the transmission electron microscopy and the quartz crystal microbalance experiments, following clamp of the egg-coat at either fertilization-competent or -incompetent statuses by short-term pretreatment with synthetic peptides...
July 18, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28720508/to-swim-or-not-to-swim-a-population-level-model-of-xenopus-tadpole-decision-making-and-locomotor-behaviour
#10
Roman Borisyuk, Robert Merrison-Hort, Steve R Soffe, Stella Koutsikou, Wen-Chang Li
We present a detailed computational model of interacting neuronal populations that mimic the hatchling Xenopus tadpole nervous system. The model includes four sensory pathways, integrators of sensory information, and a central pattern generator (CPG) network. Sensory pathways of different modalities receive inputs from an "environment"; these inputs are then processed and integrated to select the most appropriate locomotor action. The CPG populations execute the selected action, generating output in motor neuron populations...
July 15, 2017: Bio Systems
https://www.readbyqxmd.com/read/28719101/neuronal-degeneration-and-regeneration-induced-by-axotomy-in-the-olfactory-epithelium-of-xenopus-laevis
#11
A S Cervino, D A Paz, J L Frontera
The olfactory epithelium (OE) has the remarkable capability to constantly replace olfactory receptor neurons (ORNs) due to the presence of neural stem cells (NSCs). For this reason, the OE provides an excellent model to study neurogenesis and neuronal differentiation. In the present work, we induced neuronal degeneration in the OE of Xenopus laevis larvae by bilateral axotomy of the olfactory nerves. We found that axotomy induces specific- neuronal death through apoptosis between 24 and 48h post-injury. In concordance, there was a progressive decrease of the mature-ORN marker OMP until it was completely absent 72h post-injury...
July 18, 2017: Developmental Neurobiology
https://www.readbyqxmd.com/read/28716930/conserved-gene-regulatory-module-specifies-lateral-neural-borders-across-bilaterians
#12
Yongbin Li, Di Zhao, Takeo Horie, Geng Chen, Hongcun Bao, Siyu Chen, Weihong Liu, Ryoko Horie, Tao Liang, Biyu Dong, Qianqian Feng, Qinghua Tao, Xiao Liu
The lateral neural plate border (NPB), the neural part of the vertebrate neural border, is composed of central nervous system (CNS) progenitors and peripheral nervous system (PNS) progenitors. In invertebrates, PNS progenitors are also juxtaposed to the lateral boundary of the CNS. Whether there are conserved molecular mechanisms determining vertebrate and invertebrate lateral neural borders remains unclear. Using single-cell-resolution gene-expression profiling and genetic analysis, we present evidence that orthologs of the NPB specification module specify the invertebrate lateral neural border, which is composed of CNS and PNS progenitors...
July 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28715428/cip29-is-phosphorylated-following-activation-of-the-dna-damage-response-in-xenopus-egg-extracts
#13
Janet Holden, Elaine M Taylor, Howard D Lindsay
Acting through a complex signalling network, DNA lesions trigger a range of cellular responses including DNA repair, cell cycle arrest, altered gene expression and cell death, which help to limit the mutagenic effects of such DNA damage. RNA processing factors are increasingly being recognised as important targets of DNA damage signalling, with roles in the regulation of gene expression and also more directly in the promotion of DNA repair. In this study, we have used a Xenopus laevis egg extract system to analyse the DNA damage-dependent phosphorylation of a putative RNA export factor, Cip29...
2017: PloS One
https://www.readbyqxmd.com/read/28715108/ivermectin-activates-girk-channels-in-a-pip2-dependent-g%C3%AE-%C3%AE-independent-manner-and-an-amino-acid-residue-at-the-slide-helix-governs-the-activation
#14
I-Shan Chen, Michihiro Tateyama, Yuko Fukata, Motonari Uesugi, Yoshihiro Kubo
Ivermectin (IVM) is a widely used antiparasitic drug in humans and pets which activates glutamate-gated Cl(-) channel in parasites. It is also known that IVM binds to the transmembrane domains (TMs) of several ligand-gated channels, such as Cys-loop receptors and P2X receptors. In this study, we found that the G-protein-gated inwardly rectifying K(+) (GIRK) channel is activated by IVM directly. By electrophysiological recordings in Xenopus oocytes, we observed that IVM activates GIRK channel in a phosphatidylinositol-4,5-biphosphate (PIP2 )-dependent manner, and that the IVM-mediated GIRK activation is independent of Gβγ ...
July 17, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28709293/fluorescence-correlation-spectroscopy-experiments-to-quantify-free-diffusion-coefficients-in-reaction-diffusion-systems-the-case-of-ca-2-and-its-dyes
#15
Lorena Sigaut, Cecilia Villarruel, María Laura Ponce, Silvina Ponce Dawson
Many cell signaling pathways involve the diffusion of messengers that bind and unbind to and from intracellular components. Quantifying their net transport rate under different conditions then requires having separate estimates of their free diffusion coefficient and binding or unbinding rates. In this paper, we show how performing sets of fluorescence correlation spectroscopy (FCS) experiments under different conditions, it is possible to quantify free diffusion coefficients and on and off rates of reaction-diffusion systems...
June 2017: Physical Review. E
https://www.readbyqxmd.com/read/28708941/regulation-of-the-insulin-akt-signaling-pathway-and-glycolysis-during-dehydration-stress-in-the-african-clawed-frog-xenopus-laevis
#16
Cheng-Wei Wu, Shannon N Tessier, Kenneth B Storey
Estivation is an adaptive stress response utilized by some amphibians during periods of drought in the summer season. In this study, we examine the regulation of the insulin signaling cascade and glycolysis pathway in the African clawed frog Xenopus laevis during dehydration stress induced state of estivation. We show that in the brain and heart of X. laevis, dehydration reduces the phosphorylation of the insulin growth factor-1 receptor (IGF-1R), and this is followed by similar reductions in the phosphorylation of the Akt and mechanistic target of rapamycin (mTOR) kinase...
July 14, 2017: Biochemistry and Cell Biology, Biochimie et Biologie Cellulaire
https://www.readbyqxmd.com/read/28708422/epithelial-sodium-channel-enac-is-a-modifier-of-the-long-term-non-progressive-phenotype-associated-with-f508del-cftr-mutations
#17
Pankaj B Agrawal, Ruobing Wang, Hongmei Lisa Li, Klaus Schmitz-Abe, Chantelle Simone-Roach, Jingxin Chen, Jiahai Shi, Tin Louie, Shaohu Sheng, Meghan C Towne, Christine F Brainson, Michael A Matthay, Carla F Kim, Michael Bamshad, Mary J Emond, Norma P Gerard, Thomas R Kleyman, Craig Gerard
BACKGROUND: Cystic Fibrosis (CF) remains the most lethal genetic disease in the Caucasian population. However, there is great variability of clinical phenotype and survival, even among patients harboring the same genotype. We identified five CF patients with a homozygous F508del mutation in the CFTR gene living in their 5th or 6th decade of life, all with minimal change in lung function over longitudinal period of more than 20 years. Because of the rarity of this long-term non-progressive phenotype, we hypothesized those individuals may carry rare genetic variants in modifier genes that ameliorate disease severity...
July 14, 2017: American Journal of Respiratory Cell and Molecular Biology
https://www.readbyqxmd.com/read/28705808/molecular-basis-of-altered-herg1-channel-gating-induced-by-ginsenoside-rg3
#18
Alison Gardner, Wei Wu, Steven Thomson, Eva-Maria Zangerl-Plessl, Anna Stary-Weinzinger, Michael Sanguinetti
Outward current conducted by human ether-a-g-go-related gene type 1 (hERG1) channels is a major determinant of action potential repolarization in the human ventricle. Ginsenoside 20(S)-Rg3 (Rg3), an alkaloid isolated from the root of Panax ginseng slows the rate of hERG1 deactivation, induces channels to open at more negative potentials than normal and increases current magnitude. The onset of Rg3 action is extremely fast, suggesting that it binds to an extracellular accessible site on the channel to alter its gating...
July 13, 2017: Molecular Pharmacology
https://www.readbyqxmd.com/read/28702127/coordinating-heart-morphogenesis-a-novel-role-for-hyperpolarization-activated-cyclic-nucleotide-gated-hcn-channels-during-cardiogenesis-in-xenopus-laevis
#19
Emily Pitcairn, Hannah Harris, Justine Epiney, Vaibhav P Pai, Joan M Lemire, Bin Ye, Nian-Qing Shi, Michael Levin, Kelly A McLaughlin
Hyperpolarization-activated cyclic-nucleotide gated channel (HCN) proteins are important regulators of both neuronal and cardiac excitability. Among the 4 HCN isoforms, HCN4 is known as a pacemaker channel, because it helps control the periodicity of contractions in vertebrate hearts. Although the physiological role of HCN4 channel has been studied in adult mammalian hearts, an earlier role during embryogenesis has not been clearly established. Here, we probe the embryonic roles of HCN4 channels, providing the first characterization of the expression profile of any of the HCN isoforms during Xenopus laevis development and investigate the consequences of altering HCN4 function on embryonic pattern formation...
2017: Communicative & Integrative Biology
https://www.readbyqxmd.com/read/28700927/charged-antimicrobial-peptides-can-translocate-across-membranes-without-forming-channel-like-pores
#20
Jakob P Ulmschneider
How can highly charged, cationic antimicrobial peptides (AMPs) translocate across hydrophobic lipid bilayers despite the prohibitive energetic penalty to do so? A common explanation has been the formation of peptide-lined channels. However, for most AMPs, no structures of membrane pores have been found despite clear evidence of membrane leakage and antimicrobial activity. The study here suggests an alternative and simple reason: for the AMP PGLa from Xenopus laevis (charge +5), such pores are not needed to explain both leakage and peptide translocation...
July 11, 2017: Biophysical Journal
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