Biology subjects

Ramirez-Rios, S.

Publications and source records attributed to Ramirez-Rios, S..

6 recordsLinked to original sources

bioRxiv2026

VASH1 phosphorylation regulates tubulin detyrosination via CNP/PRKG1α signaling in DRG neurons.

Functional neuronal circuit formation requires precise regulation of axon growth and branching through dynamic cytoskeletal remodeling. Although microtubule detyrosination/re-tyrosination critically controls microtubule dynamics, how extracellular signals regulate this process remains unclear. Here, we identify a direct link between C-type natriuretic peptide, protein kinase cGMP-dependent 1 (CNP/cGMP/PRKG1) signaling and microtubule detyrosination in dorsal root ganglion (DRG) neurons. CNP stimulation induces growth cone enlargement, increases tyrosinated tubulin within growth cones, and reduces detyrosinated tubulin along axons, effects abolished by PRKG1 inhibition. Pharmacological inhibition or genetic deletion of the detyrosinating enzyme VASH1 phenocopies CNP-induced growth cone remodeling. In vitro kinase assays identify VASH1 as a direct PRKG1 substrate and reveal a specific C-terminal serine phosphorylation site (serine 337) that suppresses VASH1-SVBP microtubule association and detyrosination activity. Together, these findings establish VASH1-SVBP as a key downstream effector linking extracellular guidance signaling to microtubule remodeling during DRG neuronal development.

cell biology↗

bioRxiv2026

Neprilysin inhibition reduces microtubule detyrosination in cardiomyocytes through a cGMP-PRKG1-VASH1 axis

Microtubule detyrosination and re-tyrosination on the C-terminus of -tubulin are mediated by the vasohibin (VASH)-small vasohibin-binding protein (SVBP) complex and tubulin tyrosine ligase (TTL), respectively. Elevated levels of detyrosinated -tubulin (dTyr-tub) are observed in heart failure, and reducing this modification improves cardiac function, suggesting that clinically used heart failure therapies may modulate microtubule detyrosination. We investigated whether sacubitrilat and valsartan, the active components of the angiotensin receptor-neprilysin inhibitor LCZ696, influence dTyr-tub levels in endothelin-1 (ET1)-induced hypertrophy in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). While both sacubitrilat and valsartan prevented hypertrophy, only sacubitrilat prevented ET1-induced dTyr-tub accumulation. RNA sequencing revealed that sacubitrilat normalized several ET1-induced dysregulated pathways. Sacubitrilat slightly increased cyclic guanosine 3,5-monophosphate (cGMP) levels and lowered dTyr-tub, whereas inhibition or knockdown of the cGMP-dependent protein kinase 1 (PRKG1) increased dTyr-tub level. Mechanistically, PRKG1 alpha phosphorylated native VASH1. Incubation of microtubules with the VASH1-SVBP complex containing wild-type VASH1 increased detyrosination, while incubation of the complex containing a VASH1 phosphomimic, in which seven C-terminal serine residues were mutated to glutamate (VASH1-7E) did not. Consistently, overexpression of VASH1-7E gave rise to lower dTyr-tub level than overexpression of a non-phosphorylatable form of VASH1 (VASH1-7A) in hiPSC-CMs deficient in VASH1. In conclusion, these findings identify a cGMP-PRKG1-VASH1 signaling axis that reduces microtubule detyrosination in cardiomyocytes. Our work provides mechanistic insight into how neprilysin inhibition may contribute to therapeutic benefit in heart failure. One Sentence SummaryWe establish a neprilysin-cGMP-PRKG1-VASH1 signaling axis that reduces microtubule detyrosination in cardiomyocytes.

cell biology↗

bioRxiv2026

SHANK3-CAMSAP2 interaction links synapses to dendritic microtubule organisation in PV neurons

The microtubule cytoskeleton plays an essential role in establishing and maintaining neuronal polarity. In neurons, microtubules are initially generated at the centrosome which gradually loses this role in development. In mature neurons, microtubules are stabilised by the microtubule minus end-binding protein CAMSAP2. How and where microtubule minus ends are anchored within dendrites of mammalian neurons remains an open question. Here, we show that microtubules are directly attached to the postsynaptic density of excitatory synapses through an interaction of CAMSAP2 with the scaffolding protein SHANK3. This process is particularly relevant in parvalbumin-positive GABAergic neurons, in which excitatory synapses are predominantly located directly on the dendritic shaft in direct proximity to microtubules. Notably, this association is strongly enhanced by the Autism Spectrum Disorder (ASD)-associated SHANK3L68P mutation, leading to an increase of synaptic levels of CAMSAP2. This promotes an increased microtubule association with the synapse and alters microtubule dynamics. Downregulation of CAMSAP2 in SHANK3L68P parvalbumin neurons tips the balance between site-specific microtubule stabilisation and dynamics, reshaping dendritic architecture, connecting SHANK3-CAMSAP2 dependent microtubule regulation to synaptic ASD pathology. TeaserInteraction between synapses and microtubules is enhanced in parvalbumin neurons bearing the ASD-associated SHANK3 L68P mutation.

neuroscience↗

bioRxiv2024

L-Dopa incorporation into tubulin alters microtubule dynamics and reduces dendritic spine invasion and synapse maintenance

Previous studies have shown that L-Dopa, a tyrosine analog used in Parkinsons disease treatment, can be incorporated into -tubulin C-terminal tail via the tubulin tyrosine ligase (TTL) and polymerize into microtubules. In this work, we demonstrated that mature wild type hippocampal neurons treated with L-Dopa exhibited reduced dendritic spine density, primarily affecting mature dendritic spines. In these neurons, L-Dopa treatment significantly reduced tyrosinated -tubulin levels without altering detyrosinated or {Delta}2 -tubulin levels, suggesting the formation of a new tubulin pool, likely composed of L-Dopa--tubulin. In vitro analysis of the activity of the purified VASH1-SVBP complex, the most abundant tubulin carboxypeptidase in brain, revealed that L-Dopa incorporation into -tubulin modified the binding of the complex to microtubules and reduced its carboxypeptidase activity. These results suggest that L-Dopa incorporation into tubulin alters the properties of microtubules and affects their ability to interact with the enzyme. To confirm the implication of L-Dopa-microtubules in dendritic spine alterations observed in wild type neurons, we analyzed the effect of L-Dopa treatment in neurons lacking the enzymes of the -tubulin detyrosination/tyrosination cycle. In these cells, L-Dopa cannot be incorporated into -tubulin due to the absence of the ligase (in TTL KO neurons) or the reduction of detyrosinated -tubulin levels (in SVBP KO neurons). L-Dopa treatment did not modify dendritic spine density in TLL KO or SVBP KO neurons, clearly demonstrating that the alterations in dendritic spines seen in WT neurons are due to the incorporation of L-Dopa into tubulin. Further analysis revealed that L-Dopa treatment decreased the percentage of spines containing excitatory synapses in wild type neurons, but not in TTL KO or SVBP KO neurons, suggesting a cumulative synaptic defect due to L-Dopa incorporation into microtubules. Additionally, L-Dopa altered microtubule dynamics by increasing catastrophe frequency and reducing comet lifetime, which led to fewer microtubules entering dendritic spines and decreased spine resistance to pruning. Taken together, our results demonstrate that L-Dopa incorporation into -tubulin drastically affects synaptic homeostasis, reaffirming the importance of balanced detyrosination/tyrosination of tubulin within the synaptic compartment. The abnormal dynamics of L-Dopa-microtubules and the reduction of dendritic spines and excitatory synapses highlight a novel mechanism of L-Dopa-induced synaptotoxicity.

neuroscience↗

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↗

bioRxiv2020

Two antagonistic microtubule targeting drugs act synergistically to kill cancer cells

Paclitaxel is a microtubule stabilizing agent and a successful drug for cancer chemotherapy inducing, however, adverse effects. To reduce the effective dose of paclitaxel, we searched for drugs which could potentiate its therapeutic effect. We have screened a chemical library and selected Carba1, a carbazolone, which exerts synergistic cytotoxic effects on tumor cells grown in vitro, when co-administrated with a low dose of paclitaxel. Carba1 targets the colchicine binding-site of tubulin and is a microtubule-destabilizing agent. The Carba1-induced modulation of microtubule dynamics increases the accumulation of fluorescent paclitaxel inside microtubules, providing a mechanistic explanation of the observed synergy between Carba1 and paclitaxel. The synergistic effect of Carba1 with paclitaxel on tumor cell viability was also observed in vivo in xenografted mice. Thus, a new mechanism favoring paclitaxel accumulation in microtubules can be transposed to in vivo mouse cancer treatments, paving the way for new therapeutic strategies combining low doses of microtubule targeting agents with opposite mechanisms of action.

cancer biology↗