Biology subjects

Terentjev, E. M.

Publications and source records attributed to Terentjev, E. M..

4 recordsLinked to original sources

bioRxiv2021

Cell minor-axis length is a critical feature for breast cancer cell migration on straight, wavy, loop and grid microfibre patterns

Cell migration plays an important role in physiological and pathological processes where the fibrillar morphology of extracellular matrice (ECM) could regulate the migration dynamics. To mimic the morphological characteristics of fibrillar matrix structures, low-voltage continuous electrospinning was adapted to construct straight, wavy, looped and gridded fibre patterns made of polystyrene (of fibre diameter ca. 3 m). With microfibres deposited onto non-passivated surfaces, cells were permitted to explore their different shapes in response to the directly-adhered fibre, as well as to the neighbouring patterns. For all the patterns studied, analysing cellular migration dynamics of MDA-MB-231 (a highly migratory breast cancer cell line) demonstrated a switch in behaviour when the pattern features approach the upper limit of the cell minor axis. Our findings suggest that, although cells dynamically adjust their shapes in response to different fibrillar environments during migration, their ability to divert from an existing fibre track is limited by the size along the cell minor axis. We therefore conclude that the upper limit of cell minor axis might act as a guide for the design of microfibre patterns for different purposes of cell migration.

bioengineering↗

bioRxiv2020

Bioassemblying Macro-Scale, Lumnized Airway Tubes of Defined Shape via Multi-Organoid Patterning and Fusion

Epithelial, stem-cell derived organoids are ideal building blocks for tissue engineering, however, scalable and shape-controlled bioassembly of epithelial organoids into larger and anatomical structures has yet to be achieved. Here, a robust organoid engineering approach, Multi-Organoid Patterning and Fusion (MOrPF), is presented to assemble individual airway organoids of different sizes into upscaled, scaffold-free airway tubes with pre-defined shapes. Multi-Organoid Aggregates (MOAs) undergo accelerated fusion in a matrix-depleted, free-floating environment, possess a continuous lumen and maintain prescribed shapes without an exogenous scaffold interface. MOAs in the floating culture exhibit a well-defined three-stage process of inter-organoid surface integration, luminal material clearance and lumina connection. The observed shape stability of patterned MOAs is confirmed by theoretical modelling based on organoid morphology and the physical forces involved in organoid fusion. Immunofluorescent characterization shows that fused MOA tubes possess an unstratified epithelium consisting mainly of tracheal basal stem cells. By generating large, shape-controllable organ tubes, MOrPF enables upscaled organoid engineering towards integrated organoid-devices and structurally complex organ tubes.

bioengineering↗

bioRxiv2020

FliI6-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

The role of rotational molecular motors of the ATP synthase class is integral to the metabolism of cells. Yet the function of FliI6-FliJ complex - a homolog of the F1 ATPase motor - within the flagellar export apparatus remains unclear. We use a simple two-state model adapted from studies of linear molecular motors to identify key features of this motor. The two states are the locked ground state where the FliJ coiled coil filament experiences fluctuations in an asymmetric torsional potential, and a free excited state in which FliJ undergoes rotational diffusion. Michaelis-Menten kinetics was used to treat transitions between these two states, and obtain the average angular velocity of the FliJ filament within the FliI6 stator:{omega} max {approx} 9.0 rps. The motor was then studied under external counter torque conditions in order to ascertain its maximal power output: Pmax {approx} 42 kBT/s, and the stall torque: Gstall {approx} 3 kBT/rad. Two modes of action within the flagellar export apparatus are proposed, in which the motor performs useful work either by continuously grinding through the resistive environment, or by exerting equal and opposite stall force on it. In both cases, the resistance is provided by flagellin subunits entering the flagellar export channel prior to their unfolding. We therefore propose that the function of the FliI6-FliJ complex is to lower the energy barrier and therefore assist in unfolding of the flagellar proteins before feeding them into the transport channel.

biophysics↗

bioRxiv2017

Cooperative mechanosensitivity and allostery of focal adhesion clusters

We analyse an Ising-like Hamiltonian describing the free energy of cell adhesion on a substrate as a lattice of 3-state mechanosensing sites involving focal adhesion kinase (FAK). We use Monte Carlo stochastic algorithm to find equilibrium configurations of these mechanosensors in two representative geometries: on a 1D ring representing the rim of a cell on flat surface, and a 2D bounded surface representing the whole area of cell contact with flat surface. The level of FAK activation depend on the pulling force applied to the individual FAKintegrin via actin-myosin contractile networks, and the details of the coupling between individual sensors in a cluster. Strong coupling is shown to make the FAK sensors experience a sharp on-off behaviour in their activation, while at low coupling the activation/autoinhibition transition occurs over a broad range of pulling force. We find that the activation/autoinhibition transition of FAK in the 2D system with strong coupling occurs with a hysteresis, the width of which depends on the rate of change of force. The effect of introducing a mediating protein (such as Src) in limited quantity to control FAK activation is explored, and visualizations of clustering in both topologies are presented. In particular the results on the bounded 2D surface indicate that clustering of active FAK occurs preferentially at the boundary, in agreement with experimental observations of focal adhesions in cells.

biophysics↗