64,107 research outputs found
The role of microtubule movement in bidirectional organelle transport
We study the role of microtubule movement in bidirectional organelle
transport in Drosophila S2 cells and show that EGFP-tagged peroxisomes in cells
serve as sensitive probes of motor induced, noisy cytoskeletal motions.
Multiple peroxisomes move in unison over large time windows and show
correlations with microtubule tip positions, indicating rapid microtubule
fluctuations in the longitudinal direction. We report the first high-resolution
measurement of longitudinal microtubule fluctuations performed by tracing such
pairs of co-moving peroxisomes. The resulting picture shows that
motor-dependent longitudinal microtubule oscillations contribute significantly
to cargo movement along microtubules. Thus, contrary to the conventional view,
organelle transport cannot be described solely in terms of cargo movement along
stationary microtubule tracks, but instead includes a strong contribution from
the movement of the tracks.Comment: 24 pages, 5 figure
Microtubules gate tau condensation to spatially regulate microtubule functions.
Tau is an abundant microtubule-associated protein in neurons. Tau aggregation into insoluble fibrils is a hallmark of Alzheimer's disease and other types of dementia1, yet the physiological state of tau molecules within cells remains unclear. Using single-molecule imaging, we directly observe that the microtubule lattice regulates reversible tau self-association, leading to localized, dynamic condensation of tau molecules on the microtubule surface. Tau condensates form selectively permissible barriers, spatially regulating the activity of microtubule-severing enzymes and the movement of molecular motors through their boundaries. We propose that reversible self-association of tau molecules, gated by the microtubule lattice, is an important mechanism of the biological functions of tau, and that oligomerization of tau is a common property shared between the physiological and disease-associated forms of the molecule
Monitoring Microtubule Mechanical Vibrations via Optomechanical Coupling
The possible disruption of a microtubule during mitosis can control the
duplication of a cancer cell. Cancer detection and treatment may be possible
based on the detection and control of microtubule mechanical oscillations in
cells through external fields (e.g. electromagnetic or ultrasound). However,
little is known about the dynamic (high-frequency) mechanical properties of
microtubules. Here we propose to control the vibrations of a doubly clamped
microtubule by tip electrodes and to detect its motion via the optomechanical
coupling between the vibrational modes of the microtubule and an optical
cavity. In the presence of a red-detuned strong pump laser, this coupling leads
to optomechanical induced transparency of an optical probe field, which can be
detected with state-of the art technology. The center frequency and linewidth
of the transparency peak give the resonance frequency and damping rate of the
microtubule respectively, while the height of the peak reveals information
about the microtubule-cavity field coupling. Our method should yield new
knowledge about the physical properties of microtubules, which will enhance our
capability to design physical cancer treatment protocols as alternatives to
chemotherapeutic drugs
On the Nature and Shape of Tubulin Trails: Implications on Microtubule Self-Organization
Microtubules, major elements of the cell skeleton are, most of the time, well
organized in vivo, but they can also show self-organizing behaviors in time
and/or space in purified solutions in vitro. Theoretical studies and models
based on the concepts of collective dynamics in complex systems,
reaction-diffusion processes and emergent phenomena were proposed to explain
some of these behaviors. In the particular case of microtubule spatial
self-organization, it has been advanced that microtubules could behave like
ants, self-organizing by 'talking to each other' by way of hypothetic (because
never observed) concentrated chemical trails of tubulin that are expected to be
released by their disassembling ends. Deterministic models based on this idea
yielded indeed like-looking spatio-temporal self-organizing behaviors.
Nevertheless the question remains of whether microscopic tubulin trails
produced by individual or bundles of several microtubules are intense enough to
allow microtubule self-organization at a macroscopic level. In the present
work, by simulating the diffusion of tubulin in microtubule solutions at the
microscopic scale, we measure the shape and intensity of tubulin trails and
discuss about the assumption of microtubule self-organization due to the
production of chemical trails by disassembling microtubules. We show that the
tubulin trails produced by individual microtubules or small microtubule arrays
are very weak and not elongated even at very high reactive rates. Although the
variations of concentration due to such trails are not significant compared to
natural fluctuations of the concentration of tubuline in the chemical
environment, the study shows that heterogeneities of biochemical composition
can form due to microtubule disassembly. They could become significant when
produced by numerous microtubule ends located in the same place. Their possible
formation could play a role in certain conditions of reaction. In particular,
it gives a mesoscopic basis to explain the collective dynamics observed in
excitable microtubule solutions showing the propagation of concentration waves
of microtubules at the millimeter scale, although we doubt that individual
microtubules or bundles can behave like molecular ants
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