Basal body positioning is controlled by flagellum formation in Trypanosoma brucei

To perform their multiple functions, cilia and flagella are precisely positioned at the cell surface by mechanisms that remain poorly understood. The protist Trypanosoma brucei possesses a single flagellum that adheres to the cell body where a specific cytoskeletal structure is localised, the flagellum attachment zone (FAZ). Trypanosomes build a new flagellum whose distal tip is connected to the side of the old flagellum by a discrete structure, the flagella connector. During this process, the basal body of the new flagellum migrates towards the posterior end of the cell. We show that separate inhibition of flagellum assembly, base-to-tip motility or flagella connection leads to reduced basal body migration, demonstrating that the flagellum contributes to its own positioning. We propose a model where pressure applied by movements of the growing new flagellum on the flagella connector leads to a reacting force that in turn contributes to migration of the basal body at the proximal end of the flagellum.     

Studies of membranotropic and fusogenic activity of two putative HCV fusion peptides

Over the past decades, membranotropic peptides such as positively charged cell-penetrating peptides (CPPs) or amphipathic antimicrobial peptides (AMPs) have received increasing interest in order to improve therapeutic agent cellular uptake.As far as we are concerned, we were interested in studying HCV fusion peptides as putative anchors. Two peptides, HCV6 and HCV7, were identified and conjugated to a fluorescent tag NBD and tested for their interaction with liposomes as model membranes. DSC and spectrofluorescence analyses demonstrate HCV7 propensity to insert or internalize in vesicles containing anionic lipids DMPG whereas no activity was observed with zwitterionic DMPC. This behavior could be explained by the peptide sequence containing a cationic arginine residue. On the contrary, HCV6 did not exhibit any membranotropic activity but was the only sequence able to induce liposomes' fusion or aggregation monitored by spectrofluorescence and DLS. This two peptides mild activity was related to their inefficient structuration in contact with membrane mimetics, which was demonstrated by CD and NMR experiments.Altogether, our data allowed us to identify two promising membrane-active peptides from E1 and E2 HCV viral proteins, one fusogenic (HCV6) and the other membranotropic (HCV7). The latter was also confirmed by fluorescence microscopy with CHO cells, indicating that HCV7 could cross the plasma membrane via an endocytosis process. Therefore, this study provides new evidences supporting the identification of HCV6 as the HCV fusion peptide as well as insights on a novel membranotropic peptide from the HCV-E2 viral protein.     

The conjugating green alga Zygnema sp. (Zygnematophyceae) from the Arctic shows high frost tolerance in mature cells (pre-akinetes)

Protoplasma - Green algae of the genus Zygnema form extensive mats and produce large amounts of biomass in shallow freshwater habitats. Environmental stresses including freezing may perturb these...     

Synthesis and larvicidal activity of indole derivatives against Aedes aegypti (Diptera: Culicidae)

In light of the challenges to control Aedes aegypti and the critical role that it plays as arbovirus vector, it is imperative to adopt strategies that provide fast, efficient and environmentally safe control of the insect population. In the present study, we synthesized six indole derivatives (C1‐C6) and examined their larvicidal activity and persistence against Ae. aegypti larvae, as well as their toxicity towards Raw 264.7 macrophages, Vero cells, Chlorella vulgaris BR017, Scenedesmus obliquus BR003, Caenorhabditis elegans N2 and Galleria mellonella. Among the bioactive compounds (C1, C2, C4 and C5), C2 exerted the strongest larvicidal activity against Ae. aegypti, with LC50 = 1.5 μg/ml (5.88 µM) and LC90 = 2.4 μg/ml (9.50 µM), indicating that the presence of chlorine or bromine groups in the aromatic ring improved the larvicidal activity of the indole derivatives. C1, C2, C4 and C5 did not reduce viability of RAW 264.7 macrophages, Vero cells, C. elegans N2 and G. mellonella. Compounds C1, C2 and C5 did not affect the growth of C. vulgaris BR017 and S. obliquus BR003. Analysis of larvicidal persistence under laboratory conditions revealed that the effect of compounds C1, C2, C4 and C5 lasted for 30 days and caused 100% of larvae mortality within few hours. Altogether, our findings demonstrate that the indole derivatives C1, C2, C4 and C5 effectively control Ae. aegypti larvae population, without clear signs of toxicity to mammalian cells, algae, C. elegans and G. mellonella.     

Dual role of sequence-dependent DNA curvature in nucleosome stability: the critical test of highly bent Crithidia fasciculata DNA tract

In spite of the knowledge of the nucleosome molecular structure, the role of DNA intrinsic curvature in determining nucleosome stabilization is still an open question. In this paper, we describe a general model that allows the prediction of the nucleosome stability, tested on 83 different DNA sequences, in surprising good agreement with the experimental data, carried out in ours as well as in many other laboratories. The model is based on the dual role of DNA curvature in nucleosome thermodynamic stabilization. A critical test is the evaluation of the nucleosome free energy relative to a Crithidia fasciculata kinetoplast DNA fragment, which represents the most curved DNA found so far in biological systems and, therefore, is generally believed to form a highly stable nucleosome.     

Tuber borchii fruit body: 2-dimensional profile and protein identification

The formation of the fruit body represents the final phase of the ectomycorrhizal fungus T. borchii life cycle. Very little is known concerning the molecular and biochemical processes involved in the fructification phase. 2-DE maps of unripe and ripe ascocarps revealed different protein expression levels and the comparison of the electropherograms led to the identification of specific proteins for each developmental phase. Associating micropreparative 2-DE to microchemical approaches, such as N-terminal sequencing and 2-D gel-electrophoresis mass-spectrometry, proteins playing pivotal roles in truffle physiology were identified.     

A possible transport mechanism for aluminum in biological membranes

The transport mechanism of aluminum in lysosomes extracted from rat liver has been investigated in this paper. The experimental evidence supports the hypothesis that aluminum is transported inside lysosomes in the form of an Al(OH)(3) electroneutral compound, the driving force being the internal acidic pH. This mechanism could help to explain the presence of aluminum in cells in many illnesses.     

Low electromagnetic field (50 Hz) induces differentiation on primary human oral keratinocytes (HOK)

This work concerns the effect of low frequency electromagnetic fields (ELF) on biochemical properties of human oral keratinocytes (HOK). Cells exposed to a 2 mT, 50 Hz, magnetic field, showed by scanning electron microscopy (SEM) modification in shape and morphology; these modifications were also associated with different actin distribution, revealed by phalloidin fluorescence analysis. Moreover, exposed cells had a smaller clonogenic capacity, and decreased cellular growth. Indirect immunofluorescence with fluorescent antibodies against involucrin and beta-catenin, both differentiation and adhesion markers, revealed an increase in involucrin and beta-catenin expression. The advance in differentiation was confirmed by a decrease of expression of epidermal growth factor (EGF) receptor in exposed cells, supporting the idea that exposure to electromagnetic field carries keratinocytes to higher differentiation level. These observations support the hypothesis that 50 Hz electromagnetic fields may modify cell morphology and interfere in differentiation and cellular adhesion of normal keratinocytes.