1,720,972 research outputs found
Tuning intermediate filament mechanics by variation of pH and ion charges
No full textThe cytoskeleton is formed by three types of filamentous proteins – microtubules, actin filaments, and
intermediate filaments (IFs) – and enables cells to withstand external and internal forces. Vimentin is the
most abundant IF protein in humans and assembles into 10 nm diameter filaments with remarkable
mechanical properties, such as high extensibility and stability. It is, however, unclear to which extent these
properties are influenced by the electrostatic environment. Here, we study the mechanical properties of
single vimentin filaments by employing optical trapping combined with microfluidics. Force-strain curves,
recorded at varying ion concentrations and pH values, reveal that the mechanical properties of single
vimentin IFs are influenced by pH and ion concentration. By combination with Monte Carlo simulations,
we relate these altered mechanics to electrostatic interactions of subunits within the filaments. We thus
suggest possible mechanisms that allow cells to locally tune their stiffness without remodeling the entire
cytoskeleton
Tuning intermediate filament mechanics by indirect and direct charge variations
No full textThe cytoskeleton is formed by three types of filamentous proteins – microtubules, actin filaments, and intermediate filaments (IFs) – and enables cells to withstand external and internal forces. Vimentin is the most abundant IF in humans and has remarkable mechanical properties, such as high extensibility and stability. It is, however, unclear to which extent these properties are influenced by the electrostatic environment. Here, we study the mechanical properties of single vimentin filaments by employing optical trapping combined with microfluidics. Force-strain curves, recorded at varying ion concentrations and pH values, reveal that the mechanical properties of single vimentin IFs are influenced by direct (pH) and indirect (ionic) charge variations. By combination with Monte Carlo simulations, we connect these altered mechanics to electrostatic interactions of subunits within the filaments. We thus find possible mechanisms that allow cells to locally tune their stiffness without remodelling the entire cytoskeleton
Multiscale mechanics and temporal evolution of vimentin intermediate filament networks
No full textThe cytoskeleton, an intricate network of protein filaments, motor proteins, and crosslinkers, largely determines the mechanical properties of cells. Among the three filamentous components, F-actin, microtubules, and intermediate filaments (IFs), the IF network is by far the most extensible and resilient to stress. We present a multiscale approach to disentangle the three main contributions to vimentin IF network mechanics – single filament mechanics, filament length, and interactions between filaments – including their temporal evolution. Combining particle tracking, quadruple optical trapping and computational modeling, we derive quantitative information on the strength and kinetics of filament interactions. Specifically, we find that hydrophobic contributions to network mechanics enter mostly via filament elongation kinetics, whereas electrostatics have a direct influence on filament–filament interactions. These results indicate that cells might need to explicitly suppress attractive interactions to re-organize the extremely stable cellular vimentin network
Multiscale mechanics and temporal evolution of vimentin intermediate filament networks
No full textThe cytoskeleton, an intricate network of protein filaments, motor proteins, and cross-linkers, largely determines the mechanical properties of cells. Among the three filamentous components, F-actin, microtubules, and intermediate filaments (IFs), the IF network is by far the most extensible and resilient to stress. We present a multiscale approach to disentangle the three main contributions to vimentin IF network mechanics—single-filament mechanics, filament length, and interactions between filaments—including their temporal evolution. Combining particle tracking, quadruple optical trapping, and computational modeling, we derive quantitative information on the strength and kinetics of filament interactions. Specifically, we find that hydrophobic contributions to network mechanics enter mostly via filament-elongation kinetics, whereas electrostatics have a direct influence on filament–filament interactions
Lateral Subunit Coupling Determines Intermediate Filament Mechanics
No full textThe cytoskeleton is a composite network of three types of protein filaments, among which in-termediate filaments (IFs) are the most extensible ones. Two very important IFs are keratin and vimentin, which have similar molecular architectures, but different mechanical behaviors. Here we compare the mechanical response of single keratin and vimentin filaments using optical tweezers. We show that the mechanics of vimentin strongly depends on the ionic strength of the buffer and that its force-strain curve suggests a high degree of cooperativity between subunits. Indeed, a computational model indicates that in contrast to keratin, vimentin is characterized by strong lateral subunit coupling of its charged monomers during unfolding of α-helices. We conclude that cells can tune their mechanics by differential use of keratin versus vimentin
Vimentin intermediate filaments stabilize dynamic microtubules by direct interactions
No full textThe tasks of the cytoskeleton depend on the fine-tuned interplay between the three filamentous components: actin filaments, microtubules, and intermediate filaments. Here, the authors show in a reconstituted in vitro system that vimentin intermediate filaments stabilize microtubules against depolymerization and support microtubule rescue by direct interactions
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