Biology subjects

Paraschiv, A.

Publications and source records attributed to Paraschiv, A..

3 recordsLinked to original sources

bioRxiv2021

Durotaxis of passive nanoparticles on elastic membranes

The transport of macromolecules and nanoscopic particles to a target cellular site is a crucial aspect in many physiological processes. This directional motion is generally controlled via active mechanical and chemical processes. Here we show, by means of molecular dynamics simulations and an analytical theory, that completely passive nanoparticles can exhibit directional motion when embedded in non-uniform mechanical environments. Specifically, we study the motion of a passive nanoparticle adhering to a mechanically non-uniform elastic membrane. We observe a non-monotonic affinity of the particle to the membrane as a function of the membranes rigidity, which results in the particle transport. This transport can be both up or down the rigidity gradient, depending on the absolute values of the rigidities that the gradient spans across. We conclude that rigidity gradients can be used to direct average motion of passive macromolecules and nanoparticles on deformable membranes, resulting in the preferential accumulation of the macromolecules in regions of certain mechanical properties.

biophysics↗

bioRxiv2020

Influence of membrane-cortex linkers on the extrusion of membrane tubes

The cell membrane is an inhomogeneous system composed of phospholipids, sterols and proteins that can be directly attached to underlying cytoskeleton. The linkers between the membrane and the cytoskeleton are believed to have a profound effect on the mechanical properties of the cell membrane and its ability to reshape. Here we investigate the role of membrane-cortex linkers on the extrusion of membrane tubes using computer simulations and experiments. In simulations we find that the force for tube extrusion has a non-linear dependence on the density of membrane-cortex attachments: at a wide range of low and intermediate densities of linkers the force is not significantly influenced by the presence of membrane linking proteins and resembles that of the bare membrane. For large concentrations of linkers however the force substantially increases compared to the bare membrane. In both cases the linkers provided membrane tubes with increased stability against coalescence. We then pulled tubes from HEK cells using optical-tweezers for varying expression levels of the membrane-cortex attachment protein Ezrin. In line with simulations, we observed that overexpression of Ezrin led to an increased extrusion force, while Ezrin depletion had negligible effect on the force. Our results shed light on the importance of local effects in membrane reshaping at the nanoscopic scales.

biophysics↗

bioRxiv2019

Dynamic clustering regulates activity of mechanosensitive membrane channels

Mechanosensitive channels regulate the flux of solutes between the cell and its environment in response to mechanical stimuli. Recent in vitro experiments have suggested that bacterial mechanosensitive channels separate into 2D liquid-like clusters, exhibiting cooperative activity. To understand the functional role of the process and its physical mechanism, we develop a coarse-grained model of mechanosensitive channels embedded in a membrane, exposed to an osmotic shock. We find that the channel aggregation into liquid-like clusters promotes the closure of individual channels. The extent of clustering is highly dependent on the channel concentration and membrane stress. We show that this behaviour yields a tightly regulated gating system, whereby at high tensions channels gate individually, and at lower tensions the channels spontaneously aggregate and inactivate. We suggest that this positive feedback protects the cell against excessive loss of cytoplasmic content. Our results point to a novel role of functional micro-phase separation in the cell membrane.

biophysics↗