Biology subjects

El Alaoui, F.

Publications and source records attributed to El Alaoui, F..

3 recordsLinked to original sources

bioRxiv2024

Septin filament assembly assists the lateral organization of membranes

Compartmentalized interactions of plasma membrane components are essential to support many cell functions, from signaling to cell division, adhesion, migration, or phagocytosis. Cytoskeletal-membrane interactions play an important role in forming membrane compartments, and this feature has been primarily studied through the actin cytoskeleton. Unlike actin, septins directly interact with membranes, acting as scaffolds to recruit proteins to specific cellular locations and as structural diffusion barriers for membrane components. However, how septins interact with and remodel the local membrane environment is unclear. Here we combined minimal reconstituted systems based on fluorescence microscopy and quantitative atomic force microscopy together with live yeast cell imaging and STED microscopy to study septin-mediated membrane organization. Our results show that septins self-assembly into filament-based sub-micrometric patches and high-order structures prompt their membrane-organizing role in vitro and in yeast cells, respectively. Furthermore, we show that the polybasic domain of Cdc11, in addition to the amphipathic helix of Cdc12, plays an essential role in supporting the membrane remodeling and curvature-sensing properties of yeast septins. Collectively, our work provides a framework for understanding the molecular mechanisms by which septins can support cellular functions intimately linked to membranes.

cell biology↗

bioRxiv2021

Structure and dynamics of FCHo2 docking on membranes

Clathrin-mediated endocytosis (CME) is a central trafficking pathway in eukaryotic cells regulated by phosphoinositides. The plasma membrane phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) plays an instrumental role in driving CME initiation. The F-BAR domain only protein 1 and 2 complex (FCHo1/2) is among the early proteins that reach the plasma membrane, but the exact mechanisms triggering its recruitment remains elusive. Here, we show the molecular dynamics of FCHo2 self-assembly on membranes by combining bottom-up synthetic approaches on in vitro and cellular membranes. Our results indicate that PI(4,5)P2 domains assist FCHo2 docking at specific membrane regions, where it self-assembles into ring-like shape protein patches. We show that binding of FCHo2 on cellular membranes promotes PI(4,5)P2 clustering at the boundary of cargo receptors and that this accumulation enhances clathrin assembly. Thus, our results provide a mechanistic framework that could explain the recruitment of early PI(4,5)P2-interacting proteins at endocytic sites.

biophysics↗

bioRxiv2019

Nanoscale topography templates the organization of stable clathrin/AP-2 structures

Membrane shape is a key feature of many cellular processes, including cell differentiation, division, migration, and trafficking. The development of nanostructured surfaces allowing for the in situ manipulation of membranes in living cells is crucial to understand these processes, but this requires complicated and limited-access technologies. Here, we investigate the self-organization of cellular membranes by using a customizable and bench top method allowing to engineer 1D SiO2 nanopillar arrays of defined sizes and shapes on high-performance glass compatible with advanced microscopies. As a result of this original combination, we provide a mapping of the morphology-induced modulation of the cell membrane mechanics, dynamics and steady-state organization of key protein complexes implicated in cellular trafficking and signal transduction.

biophysics↗