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[
Curr Biol,
2005]
Aurora B kinases play important roles during mitosis in eukaryotic cells; new work in Caenorhabditis elegans has identified the Tousled kinase TLK-1 as a substrate activator of the model nematode''''s Aurora B kinase AIR-2 which acts to ensure proper chromosome segregation during
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Trends in Cell Biology,
1996]
Cellular microtubules assemble and disassemble at a variety of rates and frequencies, and these properties contribute directly to the cell-cycle-associated rearrangements of the microtubule cytoskeleton and to the molecular basis of mitosis. The kinetics of assembly/disassembly are governed, in part, by the hydrolysis of GTP bound to the B-tubulin nucleotide-binding site. The B-tubulin GTP-binding site, therefore, lies at the heart of microtubule assembly-disassembly kinetics, and the elucidation of its structure is central to an understanding of the cellular behaviour of microtubules. Unfortunately, the crystallographic structure of B-tubulin is not yet available. In this review, we describe the progress being made using mutagenesis and biochemical studies to understand the structure of this unusual GTP-binding site.
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Microbiol Mol Biol Rev,
2021]
SUMMARYExtensive use of chemical insecticides adversely affects both environment and human health. One of the most popular biological pest control alternatives is bioinsecticides based on <i>Bacillus thuringiensis</i> This entomopathogenic bacterium produces different protein types which are toxic to several insect, mite, and nematode species. Currently, insecticidal proteins belonging to the Cry and Vip3 groups are widely used to control insect pests both in formulated sprays and in transgenic crops. However, the benefits of <i>B. thuringiensis</i>-based products are threatened by insect resistance evolution. Numerous studies have highlighted that mutations in genes coding for surrogate receptors are responsible for conferring resistance to <i>B. thuringiensis</i> Nevertheless, other mechanisms may also contribute to the reduction of the effectiveness of <i>B. thuringiensis</i>-based products for managing insect pests and even to the acquisition of resistance. Here, we review the relevant literature reporting how invertebrates (mainly insects and <i>Caenorhabditis elegans</i>) respond to exposure to <i>B. thuringiensis</i> as either whole bacteria, spores, and/or its pesticidal proteins.
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[
1986]
Wild-type body wall muscle cells of Caenorhabditis elegans produce at a constant ratio two myosin heavy chain isoforms, A and B, that form homodimeric myosins. Electron microscopy of negatively stained complexes of isoform-specific antibodies with isolated thick filaments shows that the surface of the 9.7 =B5m long filament is differentiated with respect to myosin content: a medial 1.8 =B5m zone contains myosin A and two polar 4.4 = =B5m zones contain myosin B. Biochemical and electron microscopic studies show that at 0.45 M KC1, pH 6.35, myosin B and paramyosin are solubilized. The medial all-myosin A region with novel core structures extending in a polar manner remain. These dissociation experiments suggest a sequential model for wild-type thick filament assembly in which myosins A and B would participate in the initiation and termination of assembly, respectively. Analysis of mutant thick filaments clarifies the relationship of the myosin isoforms. CB190 (
unc-54 I) thick filaments contain myosin A only and have normal length. CB1214 (
unc-15 I) mutants produce no paramyosin, and their thick filaments are composed of a medial myosin region
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Results Probl Cell Differ,
2017]
Asymmetric cell division is a common mode of cell differentiation during the invariant lineage of the nematode, C. elegans. Beginning at the four-cell stage, and continuing throughout embryogenesis and larval development, mother cells are polarized by Wnt ligands, causing an asymmetric inheritance of key members of a Wnt/B-catenin signal transduction pathway termed the Wnt/B-catenin asymmetry pathway. The resulting daughter cells are distinct at birth with one daughter cell activating Wnt target gene expression via B-catenin activation of TCF, while the other daughter displays transcriptional repression of these target genes. Here, we seek to review the body of evidence underlying a unified model for Wnt-driven asymmetric cell division in C. elegans, identify global themes that occur during asymmetric cell division, as well as highlight tissue-specific variations. We also discuss outstanding questions that remain unanswered regarding this intriguing mode of asymmetric cell division.
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Genome Biol,
2001]
SUMMARY: All G-protein-coupled receptors (GPCRs) share a common molecular architecture (with seven putative transmembrane segments) and a common signaling mechanism, in that they interact with G proteins (heterotrimeric GTPases) to regulate the synthesis of intracellular second messengers such as cyclic AMP, inositol phosphates, diacylglycerol and calcium ions. Historically, GPCRs have been classified into six families, which were thought to be unrelated; three of these are found in vertebrates. Recent work has identified several new GCPR families and suggested the possibility of a common evolutionary origin for all of them. Family B (the secretin-receptor family or ''family 2'') of the GPCRs is a small but structurally and functionally diverse group of proteins that includes receptors for polypeptide hormones, molecules thought to mediate intercellular interactions at the plasma membrane and a group of Drosophila proteins that regulate stress responses and longevity. Family-B GPCRs have been found in all animal species investigated, including mammals, Caenorhabditis elegans and Drosophila melanogaster, but not in plants, fungi or prokaryotes. In this article, I describe the structures and functions of family-B GPCRs and propose a simplified nomenclature for these proteins.
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Trends Glycosci Glycotechnol,
2004]
Blood-group-ABH antigens have been attributed no physiological roles. While studying Ca2+ dependent cell-cell adhesion of Xenopus laevis, we found that blood-group-B active GPI-anchored lectin and blood-group-B active glycoconjugates are mediating cell adhesion of early embryonic cells. In mouse embryonic cells, not the blood-group-B antigens but the Lewis x blood-group-active molecules are playing similar roles in compaction. How did the surface glycomes playing roles in cell-cell adhesion evolve in these two species? In the nematode Caenorhabditis elegans, sugar chains of chondroitin proteoglycan play indispensable roles in completion of cell division. A decrease of chondroitin on the embryonic cell surfaces results in apparent reversion of cell division. Cytokinesis and chromosome partition becomes abnormal, and the embryonic cells die. Are chondroitin in the higher organisms playing similar roles in cell division, or are the roles of chondroitin replaced with different sugar chains? As seen in the two examples, comparison of glycomes between various organisms could be very powerful hypothesis generating tools in glycobiology. With the completion of genome DNA sequencing, it seems to be high time to study the evolution of glycomes with bioinformatics and functional glycomics.
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Ciba Found Symp,
1987]
Human lymphatic filariasis is caused mainly by Wuchereria bancrofti, Brugia malayi and Brugia timori. Of the estimated 90.2 million people infected, more than 90% have bancroftian and less than 10% brugian filariasis. The distribution and transmission of the disease are closely associated with socioeconomic and behavioural factors in endemic populations. Urban W. bancrofti infection, as seen in South-East Asia, is related to poor urban sanitation, which leads to intense breeding of Culex quiquefasciatus, the principal vector. Rural strains of W. bancrofti are transmitted primarily by Anopheles spp. and Aedes spp. mosquitoes. Brugian filariasis is mainly a rural disease transmitted by Mansonia, Anopheles and Aedes spp. mosquitoes. The periodic form of B. malayi is principally a human parasite, whereas the subperiodic form is zoonotically transmitted in some countries. The control of filariasis has relied on chemotherapy, vector control and reduction of human-vector contact. Although eradication of W. bancrofti and periodic B. malayi can be achieved, it is possible only to reduce transmission of zoonotic subperiodic B. malayi in some areas. A rational approach to control should consider ecological, socioeconomic and behavioural factors and, where feasible, integrate control programmes into the delivery system for primary health care.
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Cell Motility and the Cytoskeleton,
1995]
The tubilin family has been considered to have two members, the a- and B-tubulins, which interact to form the heterodimers which in turn assemble to form the eukaryotic microtubules. A third member, y-tubulin, was identified in 1989 and has since been shown to be specifically localized in Microtubule Organizing Centers and has been implicated in the nucleation of microtubules in vivo. Comparisons of individual a-, B-, and y-tubulin sequences within the three subfamilies yield homologies of 65-100% identity. By contrast, comparisons between the three subfamilies typically yield homologies of only about 30-40% identity. The Caenorhabditis and yeast genome projects have recently identified two putative y-tubulin sequences. Analysis of these sequences, however, shows that they are significantly different from those of bona fide y-tubulins...
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Ann Trop Med Parasitol,
1991]
An intense global collaborative effort under the leadership of the Steering Committee of the Filariasis Scientific Working Group of the Tropical Diseases Research Programme, World Health Organization, has brought together researchers, pharmaceutical chemists and clinicians in the development and search for antifilarial compounds which are more effective and more convenient to administer than diethylcarbamazine citrate, the current drug of choice for lymphatic filariasis. The Brugia spp.-rodent model has been used extensively for the primary screening and B. pahangi infections in the dog or cat for the secondary screening, of potential filaricides. Recently, the leaf-monkey (Presbytis spp.) infected with subperiodic B. malayi or Wuchereria kalimantani has been used for the tertiary evaluation and pharmacokinetic studies of compounds which have shown effectiveness in the primary and secondary screens. Both P. cristata and P. melalophos are extremely susceptible to subperiodic B. malayi infection, but the former is a better host as a higher peak microfilaremia and adult worm recovery rate were obtained. Although more than 30 potential filaricides have been evaluated in the tertiary screen, only a few compounds have shown some promise against lymphatic filariasis. CGP 20376, a 5-methoxyl-6-dithiocarbamic-S-(2-carboxy-ethyl) ester derivative of benzothiazole, had complete adulticidal and microfilaricidal activities against the parasite at a single oral dose of 20 mg kg-1. However, as the compound or its metabolites caused hepatotoxicity, its clinical use in the present formulation is not recommended.(ABSTRACT TRUNCATED AT 250 WORDS)