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81.
Francois Korbmacher Benjamin Drepper Theo Sanderson Peer Martin Thomas Stach Alexander G. Maier Kai Matuschewski Joachim M. Matz 《Cellular microbiology》2021,23(1)
Malaria parasites are fast replicating unicellular organisms and require substantial amounts of folate for DNA synthesis. Despite the central role of this critical co‐factor for parasite survival, only little is known about intraparasitic folate trafficking in Plasmodium. Here, we report on the expression, subcellular localisation and function of the parasite's folate transporter 2 (FT2) during life cycle progression in the murine malaria parasite Plasmodium berghei. Using live fluorescence microscopy of genetically engineered parasites, we demonstrate that FT2 localises to the apicoplast. In invasive P. berghei stages, a fraction of FT2 is also observed at the apical end. Upon genetic disruption of FT2, blood and liver infection, gametocyte production and mosquito colonisation remain unaltered. But in the Anopheles vector, FT2‐deficient parasites develop inflated oocysts with unusual pulp formation consisting of numerous single‐membrane vesicles, which ultimately fuse to form large cavities. Ultrastructural analysis suggests that this defect reflects aberrant sporoblast formation caused by abnormal vesicular traffic. Complete sporogony in FT2‐deficient oocysts is very rare, and mutant sporozoites fail to establish hepatocyte infection, resulting in a complete block of parasite transmission. Our findings reveal a previously unrecognised organellar folate transporter that exerts critical roles for pathogen maturation in the arthropod vector. 相似文献
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Thomas Horn Brian D. Warner Joyce A. Running Kristi Downing Jennifer Clyne Mickey S. Urdea 《Nucleosides, nucleotides & nucleic acids》2013,32(5-6):875-877
Abstract Branched oligonucleotides have been synthesized using phosphoramidite derivatives with two protected hydroxyl functions. These molecules are employed for a label amplification strategy used in DNA probe diagnostics. 相似文献
84.
Svetlana Dashevskaya Ruth Horn Ivana Chudobova Stefan Schillberg Sol Maiam Rivera Vélez Teresa Capell Paul Christou 《Molecular breeding : new strategies in plant improvement》2013,32(2):463-484
Plants adapt to abiotic stress by undergoing diverse biochemical and physiological changes that involve hormone-dependent signaling pathways. The effects of plant hormones can be mimicked by exogenous chemical regulators such as herbicide safeners, which not only enhance stress tolerance but also confer hormetic benefits such as increased vigor and yield. In this study, rice plants growing in normal and saline soils were exposed to abscisic acid (ABA), the safener cyprosulfamide or both compounds together. We found that cyprosulfamide, either alone or in combination with ABA, protected the plants from salinity stress and induced vigorous growth, including the formation of new tillers and early flowering. Proteomic analysis identified several proteins that were induced by stress and/or the chemical treatments, including the late embryogenesis abundant protein OsLEA3, a putative mitochondrial translocase and a putative fumarylacetoacetate hydrolase. The corresponding genes were induced by stress and/or the individual chemical treatments, but expression dropped back when the stress was removed. However, the combination of ABA and cyprosulfamide prolonged the expression of all three genes beyond the stress period, and allowed the plants to maintain their enhanced growth characteristics. These data support a model involving cooperation between the cyprosulfamide and ABA signaling pathways. Accordingly, it was found that cyprosulfamide induces ABA synthesis more robustly than salinity stress, allowing the two regulators to converge on certain downstream target genes. We discuss the impact of our results on current models for the hormonal regulation of stress response pathways in rice and other plants. 相似文献
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Ruth Muchekehu Dingguo Liu Mark Horn Lioudmila Campbell Joselyn Del Rosario Michael Bacica Haim Moskowitz Trina Osothprarop Anouk Dirksen Venkata Doppalapudi Allan Kaspar Steven R. Pirie-Shepherd Julia Coronella 《Translational oncology》2013,6(5):562-IN6
Poor drug delivery and penetration of antibody-mediated therapies pose significant obstacles to effective treatment of solid tumors. This study explored the role of pharmacokinetics, valency, and molecular weight in maximizing drug delivery. Biodistribution of a fibroblast growth factor receptor 4 (FGFR4) targeting CovX-body (an FGFR4-binding peptide covalently linked to a nontargeting IgG scaffold; 150 kDa) and enzymatically generated FGFR4 targeting F(ab)2 (100 kDa) and Fab (50 kDa) fragments was measured. Peak tumor levels were achieved in 1 to 2 hours for Fab and F(ab)2versus 8 hours for IgG, and the percentage injected dose in tumors was 0.45%, 0.5%, and 2.5%, respectively, compared to 0.3%, 2%, and 6% of their nontargeting controls. To explore the contribution of multivalent binding, homodimeric peptides were conjugated to the different sized scaffolds, creating FGFR4 targeting IgG and F(ab)2 with four peptides and Fab with two peptides. Increased valency resulted in an increase in cell surface binding of the bivalent constructs. There was an inverse relationship between valency and intratumoral drug concentration, consistent with targeted consumption. Immunohistochemical analysis demonstrated increased size and increased cell binding decreased tumor penetration. The binding site barrier hypothesis suggests that limited tumor penetration, as a result of high-affinity binding, could result in decreased efficacy. In our studies, increased target binding translated into superior efficacy of the IgG instead, because of superior inhibition of FGFR4 proliferation pathways and dosing through the binding site barrier. Increasing valency is therefore an effective way to increase the efficacy of antibody-based drugs. 相似文献
89.
Amyloid- (A) oligomers play a crucial role in Alzheimer’s disease due to their neurotoxic aggregation properties. Fibrillar A oligomerization can lead to protofilaments and protofilament pairs via oligomer elongation and oligomer association, respectively. Small fibrillar oligomers adopt the protofilament topology, whereas fibrils contain at least protofilament pairs. To date, the underlying growth mechanism from oligomers to the mature fibril still remains to be elucidated. Here, we performed all-atom molecular dynamics simulations in explicit solvent on single layer-like protofilaments and fibril-like protofilament pairs of different size ranging from the tetramer to the 48-mer. We found that the initial U-shaped topology per monomer is maintained over time in all oligomers. The observed deviations of protofilaments from the starting structure increase significantly with size due to the twisting of the in-register parallel -sheets. This twist causes long protofilaments to be unstable and leads to a breakage. Protofilament pairs, which are stabilized by a hydrophobic interface, exhibit more fibril-like properties such as the overall structure and the twist angle. Thus, they can act as stable conformational templates for further fibril growth. Key properties like the twist angle, shape complementarity, and energetics show a size-dependent behavior so that small oligomers favor the protofilament topology, whereas large oligomers favor the protofilament pair topology. The region for this conformational transition is at the size of approximately twelve A monomers. From that, we propose the following growth mechanism from A oligomers to fibrils: (1) elongation of short protofilaments; (2) breakage of large protofilaments; (3) formation of short protofilament pairs; and (4) elongation of protofilament pairs. 相似文献
90.
Fabrice E. Graf Philipp Ludin Tanja Wenzler Marcel Kaiser Reto Brun Patient Pati Pyana Philippe Büscher Harry P. de Koning David Horn Pascal M?ser 《PLoS neglected tropical diseases》2013,7(10)
The predominant mechanism of drug resistance in African trypanosomes is decreased drug uptake due to loss-of-function mutations in the genes for the transporters that mediate drug import. The role of transporters as determinants of drug susceptibility is well documented from laboratory-selected Trypanosoma brucei mutants. But clinical isolates, especially of T. b. gambiense, are less amenable to experimental investigation since they do not readily grow in culture without prior adaptation. Here we analyze a selected panel of 16 T. brucei ssp. field isolates that (i) have been adapted to axenic in vitro cultivation and (ii) mostly stem from treatment-refractory cases. For each isolate, we quantify the sensitivity to melarsoprol, pentamidine, and diminazene, and sequence the genomic loci of the transporter genes TbAT1 and TbAQP2. The former encodes the well-characterized aminopurine permease P2 which transports several trypanocides including melarsoprol, pentamidine, and diminazene. We find that diminazene-resistant field isolates of T. b. brucei and T. b. rhodesiense carry the same set of point mutations in TbAT1 that was previously described from lab mutants. Aquaglyceroporin 2 has only recently been identified as a second transporter involved in melarsoprol/pentamidine cross-resistance. Here we describe two different kinds of TbAQP2 mutations found in T. b. gambiense field isolates: simple loss of TbAQP2, or loss of wild-type TbAQP2 allele combined with the formation of a novel type of TbAQP2/3 chimera. The identified mutant T. b. gambiense are 40- to 50-fold less sensitive to pentamidine and 3- to 5-times less sensitive to melarsoprol than the reference isolates. We thus demonstrate for the first time that rearrangements of the TbAQP2/TbAQP3 locus accompanied by TbAQP2 gene loss also occur in the field, and that the T. b. gambiense carrying such mutations correlate with a significantly reduced susceptibility to pentamidine and melarsoprol. 相似文献