Biology subjects

Abou-Ghali, M.

Publications and source records attributed to Abou-Ghali, M..

2 recordsLinked to original sources

bioRxiv2019

Actin modulates shape and mechanics of tubular membranes

The actin cytoskeleton shapes cells and also organizes internal membranous compartments. In particular, it interacts with membranes in intracellular transport of material in mammalian cells, yeast or plant cells. Tubular membrane intermediates, pulled along microtubule tracks, are involved during these processes, and destabilize into vesicles. While the role of actin in this destabilization process is still debated, literature also provide examples of membranous structures stabilization by actin. To directly address this apparent contradiction, we mimic the geometry of tubular intermediates with preformed membrane tubes. The growth of an actin sleeve at the tube surface is monitored spatio-temporally. Depending on network cohesiveness, actin is able to stabilize, or maintain membrane tubes under pulling. Indeed, on a single tube, thicker portions correlate with the presence of actin. Such structures relax over several minutes, and may provide enough time and curvature geometries for other proteins to act on tube stability.

biophysics↗

bioRxiv2018

A direct proof that sole actin dynamics drive membrane deformations

Cell membrane deformations are crucial for proper cell function. Specialized protein assemblies initiate inward or outward membrane deformations that turn into, for example, filopodia or endocytic intermediates. Actin dynamics and actin-binding proteins are involved in this process, although their detailed role remains controversial. We show here that a dynamic, branched actin network is sufficient, in absence of any membrane-associated proteins, to initiate both inward and outward membrane deformation. With actin polymerization triggered at the membrane of liposomes, we produce inward filopodia-like structures at low tension, while outward endocytosis-like structures are robustly generated regardless of tension. Our results are reminiscent of endocytosis in mammalian cells, where actin polymerization forces are required when membrane tension is increased, and in yeast, where they are always required to overcome the opposing turgor pressure. By combining experimental observations with physical modeling, we propose a mechanism for actin-driven endocytosis under high tension or high pressure conditions.

biophysics↗