Synthesis of a novel archaeal tetraether-type lipid containing a diorthoester group as a helper lipid for gene delivery

International audienceAs an alternative to recombinant virus, synthetic carriers are widely developed for providing efficient and safe DNA delivery. To reach the nucleus where nucleic acid (NA) constructs are transcripted, chemical complexes have to overcome serious cellular traps such as endosomal escape and intracellular trafficking. Here, the design and the multi-step synthesis of a stabilizing tetraether lipid analogue of archaeal counterparts containing a diorthoester moiety in the middle of the bridging chain were described. The key step involved a double coupling reaction between two diether alcohols and a diketene acetal. Under aqueous acidic conditions, the diorthoester function of the tetraether lipid can be hydrolysed to yield two monopolar diether lipids. Applied to gene delivery in association with a cationic lipid, this new helper bipolar tetraether lipid led to lipid-DNA complexes with sizes and potential zeta values depending on the charge ratios (+/-). In addition, preliminary in vitro transfection assays supported the interest of these novel bipolar lipid-based lipoplex formulations compared to standard Lipofectamine-based formulations. © 2016 Elsevier Ltd. All rights reserved

The Ancestral N-Terminal Domain of Big Defensins Drives Bacterially Triggered Assembly into Antimicrobial Nanonets

International audienceBig defensins, ancestors of ␤-defensins, are composed of a ␤-defensin-like C-terminal domain and a globular hydrophobic ancestral N-terminal domain. This unique structure is found in a limited number of phylogenetically distant species , including mollusks, ancestral chelicerates, and early-branching cephalochor-dates, mostly living in marine environments. One puzzling evolutionary issue concerns the advantage for these species of having maintained a hydrophobic domain lost during evolution toward ␤-defensins. Using native ligation chemistry, we produced the oyster Crassostrea gigas BigDef1 (Cg-BigDef1) and its separate domains. Cg-BigDef1 showed salt-stable and broad-range bactericidal activity, including against multidrug-resistant human clinical isolates of Staphylococcus aureus. We found that the ancestral N-terminal domain confers salt-stable antimicrobial activity to the ␤-defensin-like domain, which is otherwise inactive. Moreover, upon contact with bacteria, the N-terminal domain drives Cg-BigDef1 assembly into nanonets that entrap and kill bacteria. We speculate that the hydrophobic N-terminal domain of big defensins has been retained in marine phyla to confer salt-stable interactions with bacterial membranes in environments where electrostatic interactions are impaired. Those remarkable properties open the way to future drug developments when physiological salt concentrations inhibit the antimicrobial activity of vertebrate ␤-defensins. IMPORTANCE ␤-Defensins are host defense peptides controlling infections in species ranging from humans to invertebrates. However, the antimicrobial activity of most human ␤-defensins is impaired at physiological salt concentrations. We explored the properties of big defensins, the ␤-defensin ancestors, which have been conserved in a number of marine organisms, mainly mollusks. By focusing on a big defensin from oyster (Cg-BigDef1), we showed that the N-terminal domain lost during evolution toward ␤-defensins confers bactericidal activity to Cg-BigDef1, even at high salt concentrations. Cg-BigDef1 killed multidrug-resistant human clinical isolates of Staphylococcus aureus. Moreover, the ancestral N-terminal domain drove the assembly of the big defensin into nanonets in which bacteria are entrapped and killed. This discovery may explain why the ancestral N-terminal domain has been maintained in diverse marine phyla and creates a new path of discovery to design ␤-defensin derivatives active at physiological and high salt concentrations

A Structure‐Activity Investigation on Modified Analogues of an Argininocalixarene Based Non‐viral Gene Vector

AbstractThe tetra‐L‐arginino‐tetrahexyloxycalix[4]arene 1 has shown extraordinary abilities to compact and internalize different types of Nucleid Acid cargos (DNA, microRNA, PNA) into cells even known to be transfected with great difficulties by commercial non‐viral gene delivery systems. This activity, accompanied by negligible toxicity, makes this calixarene a rather promising prototype of vector for Gene Therapy. In this study we report how small structural changes like i) the lower rim alkyl substituents, ii) the type of the terminal cationic headgroups (guanidinium or primary ammonium), iii) the length of the linker between the macrocycle and the terminal cationic headgroup, iv) the presence/absence of the basic α‐amino group of Arg, and v) the stereochemistry (L or D) of Arg, might affect the ability of the novel calixarene vectors to compact DNA and to deliver its cargo into the cells