Hydrodynamic flow caused by active transport along cytoskeletal elements

Abstract

-We develop a simple lattice model to describe the hydrodynamic influence of active mass transport along bio-filaments on freely diffusing mass in the cell. To quantify the overall mass transport we include Brownian motion, excluded volume interactions, active transport along the filaments, and hydrodynamic interactions. The model shows that the hydrodynamic forces induced by molecular motors attached to the filaments give rise to a non-negligible flux close to the filament. This additional flux appears to have two effects. Depending on the degree of filament occupation it can exert a sufficiently large influence on unbound motors and cargo to modify their transport and also regulate the flux of motors bound to the filament. We expect such a mechanism is important in situations found in plant cells, where directional transport spans the entire cell. In particular, it can explain the cytoplasmic streaming observed in plant cells.

Flexibility contra Stiffness: The Phragmoplast as a Physical Barrier for Beads But Not for Vesicles

“…This would be comparable to the results from in vitro experiments shown by Koster et al (2003), where kinesin motor proteins could pull thin tubes from phospholipid (1,2-dioleoyl-sn-glycero-3-phosphocholine) 1997;Janson and Dogterom, 2004) and actin filaments (Kovar and Pollard, 2004) can buckle in vitro. We do not know whether the injected vesicles and beads are coated with motor proteins and actively moved or whether they are dragged by hydrodynamic flow created by motor-driven transport of endogenous vesicles (Houtman et al, 2007;Esseling-Ozdoba et al, 2008a). Where exactly is the physical barrier excluding the beads from the plane of the cell plate?…”

Running Faster Together: Huge Speed up of Thermal Ratchets due to Hydrodynamic Coupling

“…The velocity increase is significantly larger than that observed for hydrodynamically coupled particles that move on a surface under the influence of a constant external force that has been chosen such that it reproduces the average velocity of isolated particles (referred to as"sliders" in Fig. 2) [5]. The key difference between sliders and the ratchet motion characteristic of steppers is that sliders move smoothly, rather than in bursts.…”

“…The dynamic coupling of small suspended particles affects, for instance, the average velocity of particles driven by a constant force [1] and the correlation spectrum of pairs of freely diffusing particles [2,3]. All existing studies show that hydrodynamic coupling can increase the speed at which particles move, but the resulting speed-ups are typically quite modest [4,5] .In this Letter we show that hydrodynamic interactions can cause a very large speedup of particles that move asynchronously by a thermal ratchet mechanism: hydrodynamic coupling increases the speed of such motors by up to two orders of magnitude compared to the velocity of isolated particles. Physical realizations of such ratchet motors, to which we will refer generically as steppers, can be created in colloidal systems [6] and may be found in molecular motors [7] that move along polar biofilaments, such as microtubules or actin.…”

“…The dynamic coupling of small suspended particles affects, for instance, the average velocity of particles driven by a constant force [1] and the correlation spectrum of pairs of freely diffusing particles [2,3]. All existing studies show that hydrodynamic coupling can increase the speed at which particles move, but the resulting speed-ups are typically quite modest [4,5] .…”

Synthetic Lipid (DOPG) Vesicles Accumulate in the Cell Plate Region But Do Not Fuse

“…Furthermore, we cannot exclude the contribution of hydrodynamic flow on vesicle movement. Cytoplasmic movement by hydrodynamic flow is an additional way of transport and may well contribute to transport of large structures like vesicles and even organelles (Houtman et al, 2007;Esseling-Ozdoba et al, 2008).…”