Taxol acts differently on different tubulin isotypes

Abstract

Taxol is a critically important cancer drug that stabilises microtubules. We report that taxol acts differently on different metazoan tubulin isotypes. 50 nM taxol blocks catastrophe of human or zebrafish α1β4 but has no effect on human α1β3 microtubules. 500 nM taxol blocks catastrophe in both α1β3 and α1β4 microtubules but introduces kinks only into α1β4 microtubules. Taxol washout relaxes the kinks, suggesting taxol expands α1β4 but not α1β3 lattices. Kinesin-driven microtubule gliding detects this conformational shift - α1β4 microtubules glide at ~450 nm/sec in 400 nM taxol, but at ~750 nm/sec in 10 μM taxol, whereas α1β3 microtubules glide at ~450 nm/sec, even in 10 μM taxol. Thus, taxol readily stabilises α1β4 GDP-tubulin lattices and shifts them to a fast-gliding conformation, but stabilises α1β3 lattices much less readily and without shifting their conformation. These isotype-specific actions of taxol may drive the switch to β3 tubulin commonly seen in taxol-resistant tumours.

β3 accelerates microtubule plus end maturation through a divergent lateral interface

“…This suggests that microtubules containing β3full tubulin are more stable than wild-type microtubules. This was surprising, since purified mammalian heterodimers containing 3 have been shown to increase catastrophe frequency compared to other isotypes (Vemu et al, 2016, Pamula et al, 2016, Chew and Cross, 2023. Our results suggest that in the context of yeast tubulin, the 3 variant residues may stabilize microtubules.…”

“…Due to its association with disease, β3 has been studied in reconstitution experiments to examine its biochemical activity. These studies consistently show that microtubules assembled from heterodimers containing 3 exhibit a higher frequency of catastrophe, the switch from polymerization to depolymerization, and some studies show an increased rate of depolymerization (Panda et al, 1994, Pamula et al, 2016, Ti et al, 2018, Cross and Chew, 2023, Vemu et al, 2016. These observations have led to a model where 3 increases microtubule dynamics and promotes a more rapid turnover of microtubules.…”

“…In addition, 3 has been implicated in resistance to the MTA paclitaxel, which stabilizes the microtubule lattice. (Parker et al, 2017, Stengel et al, 2010, Chew and Cross, 2023 What remains to be understood is the mechanism through which β3 alters interactions between heterodimers and the transit between zones in a microtubule. The domains of -tubulin that are responsible for increasing catastrophe frequency are unknown and the mechanism through which 3 promotes resistance to paclitaxel remains to be investigated.…”

Cellular cartography: Towards an atlas of the neuronal microtubule cytoskeleton

“…Furthermore, high-resolution mapping of the localization of tubulin isotypes and whether these partially segregate to different microtubules will hopefully become possible with the help of techniques such as ORANGE ( Willems et al, 2020 ). For example, these isotypes may differ in their dynamicity or stability ( Chew and Cross, 2023 ). Further advances in labeling technologies and the development of live-cell markers for different microtubule properties, as well as developments in light and electron microscopy will surely advance our continued study and comprehensive mapping of microtubule subsets including their MAPs, PTMs, isotypes, orientations, stability, and motor proteins, allowing us to fill in the blanks in our atlas of the neuronal microtubule cytoskeleton.…”

Determinants of cytoplasmic microtubule depolymerization during ciliogenesis inChlamydomonas reinhardtii

“…In addition, it is well known that higher concentrations of taxol, a paclitaxel equivalent, can induce different processes from lower concentrations, and lower concentrations of taxol can inhibit microtubule dynamics without altering tubulin polymer mass which occurs with higher concentrations (Derry et al, 1998;Jordan et al, 1993). Taxol can also differentially impact microtubule processivity depending on the organism and tubulin isoform (Chew & Cross, 2023).…”