Biology subjects

Velluz, M.-C.

Publications and source records attributed to Velluz, M.-C..

5 recordsLinked to original sources

bioRxiv2026

A biochemical probe for microtubule lattice integrity uncovers motor-caused lattice damage

Microtubules experience mechanical and enzymatic stresses that can compromise lattice integrity, yet where and how lattice damage forms remains poorly understood due to the lack of tools that directly visualize damage as it occurs. Existing approaches infer damage indirectly through repair events or rely on static ultrastructural snapshots, precluding dynamic analysis. Here, we introduce MT-DS (Microtubule Damage Sensor), a damage-selective fluorescent probe that directly labels microtubule lattice openings. MT-DS combines taxane-based microtubule binding with a multivalent protein scaffold to restrict intraluminal diffusion and selectively retain the probe at sites of lattice openings. Using MT-DS, we visualize intrinsic lattice defects in stabilized microtubules, uncover a strong enrichment of damage at annealing sites, and demonstrate that kinesin-1{Delta}6 actively generates de novo lattice damage during motility. By enabling direct, time-resolved detection of microtubule damage, MT-DS establishes lattice integrity as an experimentally accessible parameter and provides a chemical tool to investigate how mechanical stress reshapes the microtubule cytoskeleton.

biochemistry↗

bioRxiv2025

Microtubule lattice conformation and integrity regulate α-tubulin acetylation

Microtubule acetylation of lysine 40 of -tubulin is a hallmark of stable microtubules. This luminal modification is catalyzed by -tubulin acetyltransferase 1 (TAT1) and reversed by histone deacetylase 6 (HDAC6). However, acetylation regulation within the microtubule lumen and the influence of lattice architecture on enzymatic activity remain poorly understood. Here, we reconstitute microtubule acetylation in vitro using purified TAT1 and HDAC6 on microtubules assembled with defined lattice conformations. We show that TAT1 overwrites HDAC6 enzymatic activity, but its acetylation efficiency decreases upon microtubule damage. Importantly, TAT1 efficiently acetylates microtubules in expanded lattices and twisted tubulin states, while compacted lattices impede its activity. Our findings reveal that both microtubule integrity and lattice conformation are critical regulators for TAT1 enzymatic activity, suggesting that dynamic lattice transitions modulate the acetylation pattern of microtubules in cells.

cell biology↗

bioRxiv2025

Phase Separation and a Hydrodynamic Instability Localize Proteins at Growing Microtubule Ends

Regulating microtubule dynamics is essential for cellular function, and precise localization of regulatory proteins at microtubule ends is critical. End-binding protein EB3, a key regulator of microtubule growth, accumulates over an extended region at the growing end, forming a comet that gradually fragments into transient droplets along the microtubule shaft. Here, we combine in vitro reconstitution experiments with theoretical analysis to show that surface-mediated condensation of EB3 effectively localizes the protein at microtubule ends. Our results reveal that a Rayleigh-Plateau instability limits the condensates extent, producing a finite comet length and discrete droplets along the shaft. Remarkably, the comet size is independent of the GTP-cap size. This finding is supported by experiments on cells showing that modulation of microtubule growth velocity and hence GTP-cap size do not consistently alter EB3 comet length. Furthermore, our theory shows that rapid droplet evaporation requires a transition of EB3 to a non-phase-separating state. Overall, our work challenges the view that comet length directly reflects GTP-cap size and highlights a novel mechanism for regulating microtubule dynamics.

biophysics↗

bioRxiv2022

Running Kinesin-1 shapes the microtubule acetylation gradient

The properties of single microtubules within the microtubule network can be modulated through posttranslational modifications (PTMs), including acetylation within the lumen of microtubules. To access the lumen, the enzymes could either enter through the microtubule ends or at damage sites along the microtubule shaft. Here we show that the acetylation profile depends on damage sites, which can be caused by the motor protein kinesin-1. Indeed, the entry of the deacetylase HDAC6 into the microtubule lumen depends on kinesin-1-induced damage sites. In contrast, activity of the microtubule acetylase TAT1 is independent of kinesin-1 and shaft damage. On a cellular level, our results show that microtubule acetylation distributes in an exponential gradient. This gradient results from tight regulation of microtubule (de-)acetylation and scales with the size of the cells. The control of shaft damage represents a novel mechanism to regulate PTM inside the microtubule by giving access to the lumen.

cell biology↗

bioRxiv2021

A liquid +TIP-network drives microtubule dynamics through tubulin condensation

Regulation of microtubule dynamics is essential for diverse cellular functions, and proteins that bind to dynamic microtubule ends can regulate network dynamics. Here we show that two conserved microtubule end-binding proteins, CLIP-170 and EB3, undergo phase separation and form dense liquid-networks. When CLIP-170 and EB3 act together the multivalency of the network increases, which synergistically increases the amount of protein in the dense phase. In vitro and in cells these liquid networks can condense tubulin. In vitro in the presence of microtubules, EB3/CLIP-170 phase separation can co-condense tubulin all along the microtubule. At this condition microtubule growth speed increases up to two-fold and depolymerization events are strongly reduced, compared to conditions with phase separation deficient networks. Our data show that phase separated EB3/CLIP-170 networks impact microtubule growth dynamics beyond direct protein-microtubule interactions.

cell biology↗