Biology subjects

Moutin, M.-J.

Publications and source records attributed to Moutin, M.-J..

3 recordsLinked to original sources

bioRxiv2023

Myofibrillar malformations that arise in mdx muscle fibers are driven by detyrosinated microtubules

In Duchenne muscular dystrophy (DMD), alterations in the myofibrillar structure of skeletal muscle fibers that impair contractile function and increase injury susceptibility arise as a consequence of dystrophic pathology. In murine DMD (mdx), myofibrillar alterations are abundant in advanced pathology (>4 months), an age where we formerly established the densification of microtubules (MTs) post-translationally modified by detyrosination (deTyr-MTs) as a negative disease modifier. Given the essential role of MTs in myofibrillar growth, maintenance, and repair, we examined the increased abundance of deTyr-MTs as a potential mechanism for these myofibrillar alterations. Here we find increased levels of deTyr-MTs as an early event in dystrophic pathology (4 weeks) with no evidence of myofibrillar alterations. At 16 weeks, we show the level of deTyr-MTs is significantly increased and co-localized to areas of myofibrillar malformation. Profiling the enzyme complexes responsible for deTyr-tubulin, we identify vasohibin 2 (VASH2) and small vasohibin binding protein (SVBP) significantly elevated in the mdx muscle at 4 wks. We then use the genetic increase in VASH2/SVBP expression in 4 wk wild-type mice and find densified deTyr-MTs that co-segregate with myofibrillar malformations similar to those in the 16 wk mdx. Given that no changes were identified in fibers expressing EGFP as a control, we conclude that disease dependent densification of deTyr-MTs underscores the altered myofibrillar structure in dystrophic skeletal muscle fibers.

pathology↗

bioRxiv2022

VASH1-SVBP and VASH2-SVBP generate different detyrosination profiles on microtubules

The detyrosination/tyrosination cycle of -tubulin is critical for proper cell functioning. VASH1-SVBP and VASH2-SVBP are ubiquitous enzyme complexes involved in microtubule detyrosination. However, little is known about their mode of action. Here, we show in reconstituted systems and in cells that VASH1-SVBP and VASH2-SVBP drive global and local detyrosination of microtubules, respectively. We solved the cryo-electron microscopy structure of human VASH2-SVBP bound to microtubules, revealing a different microtubule-binding configuration of its central catalytic region compared to VASH1-SVBP. We further show that the divergent mode of detyrosination between the two enzymes is correlated with the microtubule-binding properties of their disordered N- and C-terminal regions. Specifically, the N-terminal region is responsible for a significantly longer residence time of VASH2-SVBP on microtubules compared to VASH1-SVBP. We suggest that this VASH domain is critical for microtubule-detachment and diffusion of VASH-SVBP enzymes on the lattice. Together, our results suggest a mechanism by which these enzymes could generate distinct microtubule subpopulations and confined areas of detyrosinated lattices to drive various microtubule-based cellular functions. SUMMARYVASH1-SVBP and VASH2-SVBP produce global and local detyrosination patterns of microtubule lattices, respectively. These activities rely on the interplay between the N- and C-terminal disordered regions of the enzymes, which determine their differential molecular mechanism of action. GRAPHICAL ABSTRACTSchematic representation of divergent molecular mechanisms of action of VASH-SVBP detyrosination complexes.

cell biology↗

bioRxiv2021

Impaired α-tubulin re-tyrosination leads to synaptic dysfunction and is a feature of Alzheimer's disease

In neurons, dynamic microtubules play regulatory roles in neurotransmission and synaptic plasticity. While stable microtubules contain detyrosinated tubulin, dynamic microtubules are composed of tyrosinated tubulin, suggesting that the tubulin tyrosination/detyrosination (Tyr/deTyr) cycle modulates microtubule dynamics and synaptic function. In the Tyr/deTyr cycle, the C-terminal tyrosine of -tubulin is re-added by tubulin-tyrosine-ligase (TTL). Here we show that TTL+/- mice exhibit decreased tyrosinated microtubules, synaptic plasticity and memory deficits, and that reduced TTL expression is a feature of sporadic and familial Alzheimers disease (AD), with human APPV717I neurons having less dynamic microtubules. We find that spines visited by dynamic microtubules are more resistant to Amyloid{beta}1-42 and that TTL, by promoting microtubule entry into spines, prevents A{beta}1-42-induced spine pruning. Our results demonstrate that the Tyr/deTyr cycle regulates synaptic plasticity, is protective against spine injury, and that tubulin re-tyrosination is lost in AD, providing evidence that a defective Tyr/deTyr cycle may contribute to neurodegeneration.

neuroscience↗