Force Generated by Two Kinesin Motors Depends on the Load Direction and Intermolecular Coupling

Khataee, Hamid; Howard, Jonathon

doi:10.1103/physrevlett.122.188101

Cited by 61 publications

(93 citation statements)

References 39 publications

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“…For different cellular processes in which the microtubule-kinesin complex can be subject to opposing forces such as during cargo transport and mitotic division the 3D orientation of the force vector can be significantly different between the two cases. A significant difference in the force vector due to the presence of a larger force component vertical to the microtubule in the single-bead assay 9 relative to three-bead assay is most likely the reason for the observed differences in <median-t > of the microtubule-kinesin complex between the two assays, supporting a recent theoretical study 7 . Moreover, when opposing forces are oriented mainly along the microtubule axis (dumbbell assay), kinesin's load-bearing capacity depends on the relative angular position of the pairs of opposing forces around the circumference of the microtubule.…”

Section: Main Textsupporting

confidence: 70%

Modulation of kinesin’s load-bearing capacity by force geometry and the microtubule track

Pyrpassopoulos

Shuman

Ostap

2019

Preprint

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Kinesin motors and their associated microtubule tracks are essential for long-distance transport of cellular cargos 1 . Intracellular activity and proper recruitment of kinesins is regulated by biochemical signaling, cargo adaptors and microtubule associated proteins 2-4 . Here we report on a novel regulatory mechanism of kinesin's load-bearing capacity by forces across the microtubule track. Using optical tweezers and the three-bead assay 5,6 to specifically apply forces parallel to the long-axis of the microtubule, we found that the median attachment duration between kinesin and microtubules under opposing forces is up to 10-fold longer than observed previously using the more conventional single-bead assay, which is likely due to vertical forces imposed by the single bead 7 . Using the threebead assay, we also found that not all the protofilaments are equivalent interacting substrates for kinesin and that the median attachment duration of kinesin varies by more than 10-fold, depending on the relative angular position of the forces along the circumference of the microtubule. Thus, depending on the geometry of forces across the microtubule, kinesin can switch from a fast detaching motor (< 0.2 s) to a persistent motor that sustains attachment (> 3 s) at high forces (5 pN). Our data show that the load-bearing capacity of the kinesin motor is highly variable and can be dramatically affected by offaxis forces and forces across the microtubule lattice which has implications for a range of cellular activites including cell division and organelle transport.

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Section: Main Textsupporting

confidence: 70%

Modulation of kinesin’s load-bearing capacity by force geometry and the microtubule track

Pyrpassopoulos

Shuman

Ostap

2019

Preprint

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“…For vertical loads, velocity remains almost load-independent. To model the effect of the vectorial character of the load on the detachment process, we follow our recent model [22] that describes the detachment of a kinesin from a MT as a two-step process, which passes through three states: strongly bound state k1 − → weakly bound state k2 − → detached state k 1 and k 2 are the fast and slow detachment rates, respectively, that depend on the load F and displacement δ j = (δ xj , δ zj ) vectors according to k j = k 0 j e F ·δ j /k B T , where k 0 j (for j = 1, 2) are the unloaded rates. The effective detachment rate is then given by [22]:…”

Section: Resultsmentioning

confidence: 99%

“…By fitting Equation (6) to the load-dependent detachment rate data [14], the two-step detachment model described the data by a continuous curve, where k 0 1 = 0.91 ± 0.38 s −1 , δ x1 = 2.90 ± 1.24 nm, δ z1 = 2.25 ± 0.75 nm, k 0 2 = 7.62 ± 0.74 s −1 , and δ z2 = 0.18 ± 0.01 nm (mean ± SE) [22]. This two-step model explained the effects of the load geometry on the detachment process [22]: i) detachment rate decreases with horizontal forces (i.e., catch-bond behaviour) when the force is resisting, and increases for assisting forces (see Fig. 3(A), dashed curve); and ii) detachment rate increases with vertical forces (i.e., slip-bond behaviour); see Fig.…”

Section: Resultsmentioning

confidence: 99%

“…They modelled single-kinesin load-velocity data [13,21] by quantifying the load-dependence of the mechanical kinetics underlying a stepping process of the motor [19,20]. Recently, we also modelled the mechanics of force generation by kinesin motors by quantifying the detachment process of the motor as a function of a 3D applied load F [22]. These models for the stepping and detachment processes as functions of the 3D applied load geometry suggest kinesin motor as a model system for studying the 3D load-dependence of the processivity of molecular motors (i.e., the average distance that a motor moves per interaction with a filament [23][24][25]), which remains elusive.…”

Section: Introductionmentioning

confidence: 99%

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Processivity of molecular motors under vectorial loads

Khataee

Neufeld

2020

Preprint

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Molecular motors are cellular machines that drive the spatial organization of the cells by transporting cargoes along intracellular filaments. Although the mechanical properties of single molecular motors are relatively well characterised, it remains elusive how the three-dimensional geometry of a load imposed on a motor affects its processivity, i.e., the average distance that a motor moves per interaction with a filament. Here, we theoretically explore this question for a single kinesin molecular motor by analysing the load-dependence of the stepping and detachment processes. We find that the processivity of kinesin increases with lowering the load angle between kinesin and microtubule, due to the deceleration of the detachment rate. When the load angle is large, it is predicted that processivity can be enhanced if the velocity becomes less sensitive to load, through an optimal distribution of the load over the kinetic transition rates underlying a mechanical step of the motor. These results provide new insights into understanding of the design of potential synthetic biomolecular machines that can travel long distances with high velocities.

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“…7A; see Methods). The rates predicted from the trap data are slightly slower than experimentally observed in gliding assays, which may be due to geometric differences between the two types of study (42). Notably, based on the force-dependent fits from the optical trapping experiments, an assisting load of -2.8 pN on KIF3CC is predicted to have the same speed as unloaded KIFAC (103 nm/s), which is the same speed as KIF3AA under 2.8 pN hindering load ( Fig.…”

Section: Discussionmentioning

confidence: 68%

Strain-Dependent Kinetic Properties of KIF3A and KIF3C Tune the Mechanochemistry of the KIF3AC Heterodimer

Bensel

Woody

Pyrpassopoulos

et al. 2019

Preprint

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250 max) 249 words KIF3AC is a mammalian neuron-specific kinesin-2 implicated in intracellular cargo transport. It is a heterodimer of KIF3A and KIF3C motor polypeptides which have distinct biochemical and motile properties as engineered homodimers. Single-molecule motility assays show that KIF3AC moves processively along microtubules at a rate faster than expected given the motility rates of the KIF3AA and much slower KIF3CC homodimers. To resolve the stepping kinetics of KIF3A and KIF3C motors in homoand heterodimeric constructs, and to determine their transport potential under mechanical load, we assayed motor activity using interferometric scattering (iSCAT) microscopy and optical trapping. The distribution of stepping durations of KIF3AC molecules is described by a rate (k1 = 11 s -1 ) without apparent kinetic asymmetry in stepping. Asymmetry was also not apparent under hindering or assisting mechanical loads of 1 pN in the optical trap. KIF3AC shows increased force sensitivity relative to KIF3AA, yet is more capable of stepping against mechanical load than KIF3CC. Microtubule gliding assays containing 1:1 mixtures of KIF3AA and KIF3CC result in speeds similar to KIF3AC, indicating the homodimers mechanically impact each other's motility to reproduce the behavior of the heterodimer. We conclude that the stepping of KIF3C can be activated by KIF3A in a strain-dependent manner which is similar to application of an assisting load, and the behavior of KIF3C mirrors prior studies of kinesins with increased interhead compliance. These results suggest that KIF3AC-based cargo transport likely requires multiple motors, and its mechanochemical properties arise due to the strain-dependences of KIF3A and KIF3C.Key Words: kinesin  molecular motors single-molecule motility high-speed optical trapping iSCAT microscopy  neuron  microtubule  intracellular transport  cytoskeleton Significance Statement -(120 max) 120 words Kinesins are important long-range intracellular transporters in neurons required by the extended length of the axon and dendrites and selective cargo transport to each. The mammalian kinesin-2, KIF3AC, is a neuronal heterodimer of fast and slow motor polypeptides. Our results show that KIF3AC has a single observed stepping rate in the presence and absence of load and detaches from the microtubule rapidly under load. Interestingly, both KIF3A and assisting loads accelerate the kinetics of KIF3C. These results suggest that KIF3AC is an unconventional cargo transporter and its motile properties do not represent a combination of alternating fast and slow step kinetics. We demonstrate that the motile properties of KIF3AC represent a mechanochemistry that is specific to KIF3AC and may provide functional advantages in neurons.

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Force Generated by Two Kinesin Motors Depends on the Load Direction and Intermolecular Coupling

Cited by 61 publications

References 39 publications

Modulation of kinesin’s load-bearing capacity by force geometry and the microtubule track

Modulation of kinesin’s load-bearing capacity by force geometry and the microtubule track

Processivity of molecular motors under vectorial loads

Strain-Dependent Kinetic Properties of KIF3A and KIF3C Tune the Mechanochemistry of the KIF3AC Heterodimer

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