Biology subjects

Beaudet, D.

Publications and source records attributed to Beaudet, D..

5 recordsLinked to original sources

bioRxiv2025

Tau hyperphosphorylation impairs cooperative binding tomicrotubules and perturbs organelle trafficking in neurons

Tau, a neuronal microtubule-associated protein (MAP), organizes the axonal cytoskeleton and regulates intracellular transport. Tau hyperphosphorylation is linked to neurodegeneration in tauopathies including Alzheimers disease. Tau binds microtubules cooperatively to form cohesive envelopes, which are thought to control access to the microtubule lattice and regulate the activity of motor proteins and other microtubule-associated proteins. However, how disease-related perturbations affect tau dynamics and its function as a selective barrier to intracellular transport remains unclear. Using tau phospho-variants in vitro and in live neurons, we show that tau hyperphosphorylation disrupts cooperative microtubule binding and dysregulates lysosome transport. Hyperphosphorylated tau does not form envelopes, distributes more uniformly along the axon, and dissociates faster from microtubules. Tau weakly inhibits KIF5C motility, but strongly inhibits KIF1A. Hyperphosphorylation reduces KIF5C inhibition but increases KIF1A inhibition by decreasing processivity and accelerating detachment. Consistent with these effects, hyperphosphorylated tau alters lysosome transport in neurons. While phospho-resistant tau inhibits processive lysosome motility, hyperphosphorylated tau weakens tau-mediated regulation of lysosome transport, mimicking tau knockout neurons that exhibit enhanced processivity. Altogether, these findings show that hyperphosphorylation disrupts tau envelopes and impairs lysosome trafficking, likely contributing to early defects in degradative pathways that drive neurodegeneration.

biophysics↗

bioRxiv2025

Axonal Mechanotransduction Drives Cytoskeletal Responses to Physiological Mechanical Forces

Axons experience strong mechanical forces due to animal movement. While these forces serve as sensory cues in mechanosensory neurons, their impact on other neuron types remains poorly defined. Here, we uncover signaling that controls an axonal cytoskeletal response to external physiological forces and plays a key role in axonal integrity. Live imaging of microtubules at single-polymer resolution in a C. elegans motor neuron reveals local oscillatory movements that fine-tune polymer positioning. Combining cell-specific chemogenetic silencing with targeted degradation alleles to distinguish neuron-intrinsic from extrinsic regulators of these movements, we find that they are driven by muscle contractions and require the mechanosensitive protein Talin, the small GTPase RhoA, and actomyosin activity in the axon. Genetic perturbation of the axons ability to buffer tension by disrupting the spectrin-based membrane-associated skeleton leads to RhoA hyperactivation, actomyosin relocalization to foci at microtubule ends, and converts local oscillations into processive bidirectional movements. This results in large gaps between microtubules, disrupting coverage of the axon and leading to its breakage and degeneration. Notably, hyperpolarizing muscle or degrading components of the mechanotransduction signaling pathway in the axon rescues cytoskeletal defects in spectrin-deficient axons. These results identify mechanisms of an axonal cytoskeletal response to physiological forces and highlight the importance of force-buffering and mechanotransduction signaling for axonal integrity.

neuroscience↗

bioRxiv2024

Huntingtin polyglutamine expansions misdirect axonal transport by perturbing motor and adaptor recruitment

Huntingtons disease (HD) is caused by polyglutamine (polyQ) expansions in huntingtin (HTT). Polyglutamine repeat lengths >35Q lead to neurodegeneration and longer repeats correspond to earlier symptom onset. HTT scaffolds kinesin-1 and dynein to a variety of vesicles and organelles directly and through adaptors. To characterize the effects of HTT polyQ expansions on axonal transport, we tracked BDNF vesicles, mitochondria, and lysosomes in neurons induced from an isogenic set of human stem cell lines with repeat lengths of 30, 45, 65, and 81Q. Mild and intermediate pathogenic polyQ expansions caused increased BDNF motility, while HTT-81Q misdirected BDNF towards the distal tip. In comparison, mitochondria and lysosome transport showed mild defects with polyQHTT. We next examined the effect of polyQHTT in combination with neuroinflammatory stress. Under stress, BDNF cargoes in HTT-30Q neurons were more processive. Stress in HTT-81Q resulted in a stark decrease in the number of BDNF cargoes. However, the few remaining BDNF cargoes displayed more frequent long-range motility in both directions. Under neuroinflammatory stress, lysosomes were more abundant in HTT-81Q neurons, and motile lysosomes moved less processively and had an anterograde bias while lysosomes in HTT-30Q where not strongly affected. To examine how HTT-polyQ expansions altered the motors and adaptors on vesicular cargoes, we isolated BDNF cargoes from neurons and quantified the proteins associated with them. BDNF-endosomes isolated from HTT-81Q neurons associated with 2.5 kinesin-1 and 3.9 HAP1 molecules on average, compared to 1.0 kinesin-1 and 1.0 HAP1 molecule for HTT-30Q neurons. Together, these results show that polyQ expansions in HTT cause aberrant motor and adaptor recruitment to cargoes, resulting in dysregulated transport and responses to neuroinflammatory stress.

cell biology↗

bioRxiv2022

Tau inhibits the long-range, dynein-mediated motility of early phagosomes

The misregulation of tau, a neuronal microtubule-associated protein, is linked to defective axonal transport and neurodegenerative disease. We reconstituted the motility of isolated phagosomes along microtubules to ask how the sets of motors transporting a cargo determine its motility and response to tau. Using quantitative photobleaching, we find that early phagosomes (EPs) and late phagosomes (LPs) are associated with different sets of kinesin-1, -2, -3, and dynein. While EPs exhibit unidirectional retrograde transport, LPs move bidirectionally. Previously, we found that tau biases LP transport towards the microtubule minus-end. Here, we find that tau strongly inhibits long-range retrograde EP motility. Tau impedes the forces generated by multi-dynein teams and accelerates dynein unbinding under load. Thus, specific cargoes differentially respond to tau, where dynein-complexes on EPs are more sensitive to tau than those on LPs.

biophysics↗

bioRxiv2019

Intramolecular regulation of anillin during cytokinesis

Cytokinesis occurs by the ingression of an actomyosin ring that cleaves a cell into two daughters. This process is tightly controlled to avoid aneuploidy, and we previously showed that active Ran coordinates ring positioning with chromatin. Active Ran is high around chromatin, and forms an inverse gradient to cargo-bound importins. We found that the ring component anillin contains an NLS that binds to importin and is required for its function. Anillin contains a RhoA-binding domain (RBD), which we revealed autoinhibits the adjacent NLS-containing C2 domain. Here, we show that active RhoA relieves inhibition of the C2 domain. Furthermore, FRAP experiments show that the NLS regulates anillins cortical properties, supporting feedback to the RBD. Indeed, mutations that disrupt the interface between the RBD and C2 domain disrupt anillins localization and function. Thus, active RhoA induces a conformational change that increases accessibility to the C2 domain, which is maintained by importin-binding for recruitment to the equatorial cortex.

cell biology↗