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Publications de l’équipe
Microscopie Moléculaire des Membranes (MMM)
Année de publication : 2014
Lin Jia, Di Cui, Jérôme Bignon, Aurelie Di Cicco, Joanna Wdzieczak-Bakala, Jianmiao Liu, Min-Hui Li
(2014 May 19)
Reduction-responsive cholesterol-based block copolymer vesicles for drug
delivery.
Biomacromolecules : 2206-17 : DOI : 10.1021/bm5003569
Résumé
We developed a new robust reduction-responsive polymersome based on the amphiphilic
block copolymer PEG-SS-PAChol. The stability and robustness were achieved by the smectic
physical cross-linking of cholesterol-containing liquid crystal polymer PAChol in the
hydrophobic layer. The reduction-sensitivity was introduced by the disulfide bridge (-S-S-)
that links the hydrophilic PEG block and the hydrophobic PAChol block. We used a versatile
synthetic strategy based on atom transfer radical polymerization (ATRP) to synthesize the
reduction-responsive amphiphilic block copolymers. The reductive cleavage of the disulfide
bridge in the block copolymers was first evidenced in organic solution. The partial
destruction of PEG-SS-PAChol polymersomes in the presence of a reducing agent was then
demonstrated by cryo-electron microscopy. Finally, the calcein release from PEG-SS-PAChol
polymersomes triggered by glutathione (GSH) was observed both in PBS suspension and in
vitro inside the macrophage cells. High GSH concentrations (≥35 mM in PBS or artificially
enhanced in macrophage cells by GSH-OEt pretreatment) and long incubation time (in the
order of hours) were, however, necessary to get significant calcein release. These
polymersomes could be used as drug carriers with very long circulation profiles and slow
release kinetics.
Ayako Yamada, Alexandre Mamane, Jonathan Lee-Tin-Wah, Aurélie Di Cicco, Coline Prévost,
Daniel Lévy, Jean-François Joanny, Evelyne Coudrier, Patricia Bassereau (2014 Apr 7)
Catch-bond behaviour facilitates membrane tubulation by non-processive
myosin 1b.
Nature communications : 3624 : DOI : 10.1038/ncomms4624
Résumé
Myosin 1b is a single-headed membrane-associated motor actin filaments to That Bind with a
catch-hop behavior in response to load. In vivo, myosin 1b is required to form membrane
tubules at Both endosomes and the trans-Golgi network. To suit les the link entre thesis
Fundamental two properties, here we Investigate the capacity of myosin 1b to extract
membrane tubes along bundled actin filaments in a minimum reconstituted system. We that
show single-headed non-processive myosin 1b can extract membrane tubes at biologically
relevant low density. In contrast to kinesins we do not observe motor accumulation at the
tip, Suggesting que la Underlying mechanism for tube formation is different. In our
theoretical model, myosin 1b catch-bond properties Facilitate tube extraction under the
conditions of membrane voltage by Increasing Reducing the density of myo1b required to
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 1
Publications de l’équipe
Microscopie Moléculaire des Membranes (MMM)
pull tubes.
Année de publication : 2013
Bibiana Peralta, David Gil-Carton, Daniel Castaño-Díez, Aurelie Bertin, Claire Boulogne, Hanna M
Oksanen, Dennis H Bamford, Nicola G A Abrescia (2013 Oct 3)
Mechanism of membranous tunnelling nanotube formation in viral genome
delivery.
PLoS biology : e1001667 : DOI : 10.1371/journal.pbio.1001667
Résumé
In internal membrane-containing viruses, a lipid vesicle enclosed by the icosahedral capsid
protects the genome. It has been postulated that this internal membrane is the genome
delivery device of the virus. Viruses built with this architectural principle infect hosts in all
three domains of cellular life. Here, using a combination of electron microscopy techniques,
we investigate bacteriophage PRD1, the best understood model for such viruses, to unveil
the mechanism behind the genome translocation across the cell envelope. To deliver its
double-stranded DNA, the icosahedral protein-rich virus membrane transforms into a tubular
structure protruding from one of the 12 vertices of the capsid. We suggest that this viral
nanotube exits from the same vertex used for DNA packaging, which is biochemically distinct
from the other 11. The tube crosses the capsid through an aperture corresponding to the
loss of the peripentonal P3 major capsid protein trimers, penton protein P31 and membrane
protein P16. The remodeling of the internal viral membrane is nucleated by changes in
osmolarity and loss of capsid-membrane interactions as consequence of the de-capping of
the vertices. This engages the polymerization of the tail tube, which is structured by
membrane-associated proteins. We have observed that the proteo-lipidic tube in vivo can
pierce the gram-negative bacterial cell envelope allowing the viral genome to be shuttled to
the host cell. The internal diameter of the tube allows one double-stranded DNA chain to be
translocated. We conclude that the assembly principles of the viral tunneling nanotube take
advantage of proteo-lipid interactions that confer to the tail tube elastic, mechanical and
functional properties employed also in other protein-membrane systems.
Pierre Frederic Fribourg, Mohamed Chami, Carlos Oscar S Sorzano, Francesca Gubellini, Roberto
Marabini, Sergio Marco, Jean-Michel Jault, Daniel Lévy (2013 Aug 7)
3D cryo-electron reconstruction of BmrA, a bacterial multidrug ABC transporter
in an inward-facing conformation and in a lipidic environment.
Journal of molecular biology : 2059-69 : DOI : 10.1016/j.jmb.2014.03.002
Résumé
ABC (ATP-binding cassette) membrane exporters are efflux transporters of a wide diversity of
molecule across the membrane at the expense of ATP. A key issue regarding their catalytic
cycle is whether or not their nucleotide-binding domains (NBDs) are physically disengaged in
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 2
Publications de l’équipe
Microscopie Moléculaire des Membranes (MMM)
the resting state. To settle this controversy, we obtained structural data on BmrA, a bacterial
multidrug homodimeric ABC transporter, in a membrane-embedded state. BmrA in the
apostate was reconstituted in lipid bilayers forming a mixture of ring-shaped structures of 24
or 39 homodimers. Three-dimensional models of the ring-shaped structures of 24 or 39
homodimers were calculated at 2.3 nm and 2.5 nm resolution from cryo-electron microscopy,
respectively. In these structures, BmrA adopts an inward-facing open conformation similar to
that found in mouse P-glycoprotein structure with the NBDs separated by 3 nm. Both lipidic
leaflets delimiting the transmembrane domains of BmrA were clearly resolved. In planar
membrane sheets, the NBDs were even more separated. BmrA in an ATP-bound
conformation was determined from two-dimensional crystals grown in the presence of ATP
and vanadate. A projection map calculated at 1.6 nm resolution shows an open outwardfacing conformation. Overall, the data are consistent with a mechanism of drug transport
involving large conformational changes of BmrA and show that a bacterial ABC exporter can
adopt at least two open inward conformations in lipid membrane.
INSTITUT CURIE, 20 rue d’Ulm, 75248 Paris Cedex 05, France | 3