Kinesin-1 translocation: Surprising differences between bovine brain and MCF7-derived microtubules

Biochemistry and Biophysics Reports

Hernandez

Breslin

et al. 2019

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Growing evidence continues to point toward the critical role of beta tubulin isotypes in regulating some intracellular functions. Changes that were observed in the microtubules’ intrinsic dynamics, the way they interact with some chemotherapeutic agents, or differences on translocation specifications of some molecular motors along microtubules, were associated to their structural uniqueness in terms of beta tubulin isotype distributions. These findings suggest that the effects of microtubule associated proteins (MAPs) may also vary on structurally different microtubules. Among different microtubule associated proteins, Tau proteins, which are known as neuronal MAPs, bind to beta tubulin, stabilize microtubules, and consequently promote their polymerizations.In this study, in a set of well controlled experiments, the direct effect of Tau proteins on the polymerization of two structurally different microtubules, porcine brain and breast cancer (MCF7), were tested and compared. Remarkably, we found that in contrast with the promoted effect of Tau proteins on brain microtubules’ polymerization, MCF7 expressed a demoted polymerization while interacting with Tau proteins. This finding can potentially be a novel insight into the mechanism of drug resistance in some breast cancer cells.It has been reported that microtubules show destabilizing behavior in some MCF7 cells with overexpression of Tau protein when treated with a microtubules’ stabilizing agent, Taxol. This behavior has been classified by others as drug resistance, but it may instead be potentially caused by a competition between the destabilizing effect of the Tau protein and the stabilizing effect of the drug on MCF7 microtubules. Also, we quantified the polarization coefficient of MCF7 microtubules in the presence and absence of Tau proteins by the electro-orientation method and compared the values. The two significantly different values obtained can possibly be one factor considered to explain the effect of Tau proteins on the polymerization of MCF7 microtubules.

Section: Discussionsupporting

confidence: 57%

The regulatory effect of Tau protein on polymerization of MCF7 microtubules in vitro

Biochemistry and Biophysics Reports

Hernandez

Breslin

et al. 2019

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“…We first studied single Kin‐1 (KIF5B) 1–560 aa motors (henceforth ‘K560’) attached to beads, moving along either bovine or MCF7 MTs. We previously reported that under no load, K560's processivity on MCF7 MTs was reduced by approximately 50% while its velocity remained unchanged . We now studied the effect of load, by keeping the optical trap engaged.…”

Section: Resultsmentioning

confidence: 99%

“…The general procedure, which has previously been explained for kinesin , was modified to include also a second molecular motor, Eg5. Here, although most studies were carried out with a moderately high‐force setting higher laser power (∼110 mW, with corresponding trap stiffness of ∼0.05 pN/nm), a few experiments were also performed in a lower force regime (laser power [∼20 mW], with corresponding trap stiffness of ∼0.005 pN/nm).…”

Section: Methodsmentioning

confidence: 99%

Microtubule C‐Terminal Tails Can Change Characteristics of Motor Force Production

Narayanareddy

Vadpey

et al. 2015

Traffic

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Control of intracellular transport is poorly understood, and functional ramifications of tubulin isoform differences between cell types are mostly unexplored. Motors' force production and detachment kinetics are critical for their group function, but how microtubule (MT) details affect these properties -if at all -is unknown. We investigated these questions using both a vesicular transport human kinesin, kinesin-1, and also a mitotic kinesin likely optimized for group function, kinesin-5, moving along either bovine brain or MCF7(breast cancer) MTs. We found that kinesin-1 functioned similarly on the two sets of MTs -in particular, its mean force production was approximately the same, though due to its previously reported decreased processivity, the mean duration of kinesin-1 force production was slightly decreased on MCF7 MTs. In contrast, kinesin-5's function changed dramatically on MCF7 MTs: its average detachment force was reduced and its force-velocity curve was different. In spite of the reduced detachment force, the force-velocity alteration surprisingly improved high-load group function for kinesin-5 on the cancer-cell MTs, potentially contributing to functions such as spindle-mediated chromosome separation. Significant differences were previously reported for C-terminal tubulin tails in MCF7 versus bovine brain tubulin. Consistent with this difference being functionally important, elimination of the tails made transport along the two sets of MTs similar.

“…The outcomes of previous studies suggest that the diversity of beta tubulin isotypes may directly affect the dynamic and mechanical properties of MTs [9,10]. Recent studies have added more insight into the role of tubulin isotypes by revealing that a motor's mechanical properties, such as processivity, velocity, binding time, and stepping mechanism, can be regulated as a result of the architectural composition of the MT track [11][12][13].…”

Section: Introductionmentioning

confidence: 95%

The Contribution of the C-Terminal Tails of Microtubules in Altering the Force Production Specifications of Multiple Kinesin-1

2016

Cell Biochem Biophys

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The extent to which beta tubulin isotypes contribute to the function of microtubules and the microtubule-driven transport of molecular motors is poorly understood. The major differences in these isotypes are associated with the structure of their C-terminal tails. Recent studies have revealed a few aspects of the C-terminal tails' regulatory role on the activities of some of the motor proteins on a single-molecule level. However, little attention is given to the degree to which the function of a team of motor proteins can be altered by the microtubule's tail. In a set of parallel experiments, we investigated this open question by studying the force production of several kinesin-1 (kinesin) molecular motors along two groups of microtubules: regular ones and those microtubules whose C-terminals are cleaved by subtilisin digestion. The results indicate that the difference between the average of the force production of motors along two types of microtubules is statistically significant. The underlying mechanism of such production is substantially different as well. As compared to untreated microtubules, the magnitude of the binding time of several kinesin-1 is almost three times greater along subtilisin-treated microtubules. Also, the velocity of the group of kinesin molecules shows a higher sensitivity to external loads and reduces significantly under higher loads along subtilisin-treated microtubules. Together, this work shows the capacity of the tails in fine-tuning the force production characteristics of several kinesin molecules.