In vivo Multimotor Force–Velocity Curves by Tracking and Sizing Sub-Diffraction Limited Vesicles

Shtridelman, Yuri; Holzwarth, G.; Bauer, Clayton T.; Gassman, Natalie R.; DeWitt, David A.; Macosko, Jed C.

doi:10.1007/s12195-009-0064-8

Cited by 18 publications

(19 citation statements)

References 47 publications

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“…Rather than exploring the discrete-continuous connection in detail here, however, we build our model at the mesoscale, based on single-motor force-velocity and force-diffusivity relations. The qualitative features of these relations are informed by the robust literature of experimental measurements [67,32,62,63]. Furthermore, while the models of [37,34,28,36,72] do have spatial detail and incorporate force-velocity relationships comparable to our model, our formulation permits a more flexible and faithful rendering of the random diffusive component of the motor dynamics.…”

Section: Experimental Considerationsmentioning

confidence: 97%

Asymptotic analysis of microtubule-based transport by multiple identical molecular motors

McKinley

Athreya

Fricks

et al. 2012

Journal of Theoretical Biology

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We describe a system of stochastic differential equations (SDEs) which model the interaction between processive molecular motors, such as kinesin and dynein, and the biomolecular cargo they tow as part of microtubule-based intracellular transport. We show that the classical experimental environment fits within a parameter regime which is qualitatively distinct from conditions one expects to find in living cells. Through an asymptotic analysis of our system of SDEs, we develop a means for applying in vitro observations of the nonlinear response by motors to forces induced on the attached cargo to make analytical predictions for two parameter regimes that have thus far eluded direct experimental observation: 1) highly viscous in vivo transport and 2) dynamics when multiple identical motors are attached to the cargo and microtubule.

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Section: Experimental Considerationsmentioning

confidence: 97%

Asymptotic analysis of microtubule-based transport by multiple identical molecular motors

McKinley

Athreya

Fricks

et al. 2012

Journal of Theoretical Biology

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“…S5). A mean diameter (ϭ 657 Ϯ 53 nm) was measured from the peak-to-trough distance in a DIC image (38) of endosomes that were used to estimate force. Silica beads of known size served as a reference.…”

Section: Preparation and Motility Of Dictyostelium Endosomes On Polarmentioning

confidence: 99%

Tug-of-war between dissimilar teams of microtubule motors regulates transport and fission of endosomes

Soppina

Kumar

Ramaiya

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

322

416

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Intracellular transport is interspersed with frequent reversals in direction due to the presence of opposing kinesin and dynein motors on organelles that are carried as cargo. The cause and the mechanism of reversals are unknown, but are a key to understanding how cargos are delivered in a regulated manner to specific cellular locations. Unlike established single-motor biophysical assays, this problem requires understanding of the cooperative behavior of multiple interacting motors. Here we present measurements inside live Dictyostelium cells, in a cell extract and with purified motors to quantify such an ensemble function of motors. We show through precise motion analysis that reversals during endosome motion are caused by a tug-of-war between kinesin and dynein. Further, we use a combination of optical trap-based force measurements and Monte Carlo simulations to make the surprising discovery that endosome transport uses many (approximately four to eight) weak and detachment-prone dyneins in a tug-of-war against a single strong and tenacious kinesin. We elucidate how this clever choice of dissimilar motors and motor teams achieves net transport together with endosome fission, both of which are important in controlling the balance of endocytic sorting. To the best of our knowledge, this is a unique demonstration that dynein and kinesin function differently at the molecular level inside cells and of how this difference is used in a specific cellular process, namely endosome biogenesis. Our work may provide a platform to understand intracellular transport of a variety of organelles in terms of measurable quantities.asymmetric motor competition ͉ coordination of motors ͉ molecular motor dynein kinesin ͉ regulation of bidirectional motion ͉

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“…An alternative approach is to use dynamic light scattering to estimate the average number of motors bound to each bead, and then to determine the fraction of this average, which, from geometric considerations, could bind to a nearby microtubule [11]. The number of motors pulling a cargo in vivo has been estimated from both stall force [12][13][14] and cargo velocity [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Measuring the number and spacing of molecular motors propelling a gliding microtubule

2011

Self Cite

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The molecular motor gliding assay, in which a microtubule or other filament moves across a surface coated with motors, has provided much insight into how molecular motors work. The kinesin-microtubule system is also a strong candidate for the job of nanoparticle transporter in nanotechnology devices. In most cases, several motors transport each filament. Each motor serves both to bind the microtubule to a stationary surface and to propel the microtubule along the surface. By applying a uniform transverse force of 4-19 pN to a superparamagnetic bead attached to the trailing end of the microtubule, we have measured the distance d between binding points (motors). The average value of d was determined as a function of motor surface density σ. The measurements agree well with the scaling model of Duke, Holy, and Liebler, which predicts that (d)~σ(-2/5) if 0.05≤σ≤20 μm(-2) [Phys. Rev. Lett. 74, 330 (1995)]. The distribution of d fits an extension of the model. The radius of curvature of a microtubule bent at a binding point by the force of the magnetic bead was ≈1 μm, 5000-fold smaller than the radius of curvature of microtubules subjected only to thermal forces. This is evidence that at these points of high bending stress, generated by the force on the magnetic bead, the microtubule is in the more flexible state of a two-state model of microtubule bending proposed by Heussinger, Schüller, and Frey [Phys. Rev. E 81, 021904 (2010)].

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In vivo Multimotor Force–Velocity Curves by Tracking and Sizing Sub-Diffraction Limited Vesicles

Cited by 18 publications

References 47 publications

Asymptotic analysis of microtubule-based transport by multiple identical molecular motors

Asymptotic analysis of microtubule-based transport by multiple identical molecular motors

Tug-of-war between dissimilar teams of microtubule motors regulates transport and fission of endosomes

Measuring the number and spacing of molecular motors propelling a gliding microtubule

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