Septin-based readout of PI(4,5)P2 incorporation into membranes of giant unilamellar vesicles.

Septins constitute a novel class of cytoskeletal proteins. Budding yeast septins self-assemble into non-polar filaments bound to the inner plasma membrane through specific interactions with l-α-phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). Biomimetic in vitro assays using giant unilamellar vesicles (GUVs) are relevant tools to dissect and reveal insights in proteins-lipids interactions, membrane mechanics and curvature sensitivity.

Drp1 polymerization stabilizes curved tubular membranes similar to those of constricted mitochondria.

Dynamin-related protein 1 (Drp1), an 80 kDa mechanochemical GTPase of the dynamin superfamily, is required for mitochondrial division in mammals. Despite the role of Drp1 dysfunction in human disease, its molecular mechanism remains poorly understood. Here, we examined the effect of Drp1 on membrane curvature using tubes pulled from giant unilamellar vesicles (GUVs).

Mechanism and Determinants of Amphipathic Helix-Containing Protein Targeting to Lipid Droplets.

Cytosolic lipid droplets (LDs) are the main storage organelles for metabolic energy in most cells. They are unusual organelles that are bounded by a phospholipid monolayer and specific surface proteins, including key enzymes of lipid and energy metabolism. Proteins targeting LDs from the cytoplasm often contain amphipathic helices, but how they bind to LDs is not well understood.

Pulling Membrane Nanotubes from Giant Unilamellar Vesicles.

The reshaping of the cell membrane is an integral part of many cellular phenomena, such as endocytosis, trafficking, the formation of filopodia, etc. Many different proteins associate with curved membranes because of their ability to sense or induce membrane curvature. Typically, these processes involve a multitude of proteins making them too complex to study quantitatively in the cell.

Ezrin enhances line tension along transcellular tunnel edges via NMIIa driven actomyosin cable formation.

Transendothelial cell macroaperture (TEM) tunnels control endothelium barrier function and are triggered by several toxins from pathogenic bacteria that provoke vascular leakage. Cellular dewetting theory predicted that a line tension of uncharacterized origin works at TEM boundaries to limit their widening. Here, by conducting high-resolution microscopy approaches we unveil the presence of an actomyosin cable encircling TEMs.

How curvature-generating proteins build scaffolds on membrane nanotubes.

Bin/Amphiphysin/Rvs (BAR) domain proteins control the curvature of lipid membranes in endocytosis, trafficking, cell motility, the formation of complex subcellular structures, and many other cellular phenomena. They form 3D assemblies that act as molecular scaffolds to reshape the membrane and alter its mechanical properties. It is unknown, however, how a protein scaffold forms and how BAR domains interact in these assemblies at protein densities relevant for a cell.

Physical basis of some membrane shaping mechanisms.

In vesicular transport pathways, membrane proteins and lipids are internalized, externalized or transported within cells, not by bulk diffusion of single molecules, but embedded in the membrane of small vesicles or thin tubules. The formation of these 'transport carriers' follows sequential events: membrane bending, fission from the donor compartment, transport and eventually fusion with the acceptor membrane. A similar sequence is involved during the internalization of drug or gene carriers inside cells.

IRSp53 senses negative membrane curvature and phase separates along membrane tubules.

BAR domain proteins contribute to membrane deformation in diverse cellular processes. The inverted-BAR (I-BAR) protein IRSp53, for instance, is found on the inner leaflet of the tubular membrane of filopodia; however its role in the formation of these structures is incompletely understood. Here we develop an original assay in which proteins are encapsulated in giant unilamellar vesicles connected to membrane nanotubes.

Methyl-branched lipids promote the membrane adsorption of α-synuclein by enhancing shallow lipid-packing defects.

Alpha-synuclein (AS) is a synaptic protein that is directly involved in Parkinson's disease due to its tendency to form protein aggregates. Since AS aggregation can be dependent on the interactions between the protein and the cell plasma membrane, elucidating the membrane binding properties of AS is of crucial importance to establish the molecular basis of AS aggregation into toxic fibrils. Using a combination of in vitro reconstitution experiments based on Giant Unilamellar Vesicles (GUVs), confocal microscopy and all-atom molecular dynamics simulations, we have investigated the membrane binding properties of AS, with a focus on the relative contribution of hydrophobic versus electrostatic interactions.

Catch-bond behaviour facilitates membrane tubulation by non-processive myosin 1b.

Myosin 1b is a single-headed membrane-associated motor that binds to actin filaments with a catch-bond behaviour in response to load. In vivo, myosin 1b is required to form membrane tubules at both endosomes and the trans-Golgi network. To establish the link between these two fundamental properties, here we investigate the capacity of myosin 1b to extract membrane tubes along bundled actin filaments in a minimal reconstituted system.