At its core, glutamylation involves the enzymatic addition of glutamate moieties to target proteins, a process that can be reversed by specific enzymes that remove them. This reversibility is what distinguishes glutamylation from a static structural feature and elevates it to the status of a genuine signaling modification. By modulating protein activity, stability, subcellular localization, and molecular interactions, glutamylation allows cells to respond rapidly and reversibly to internal and external cues. The review emphasizes that this dynamic quality, long appreciated in the context of microtubule regulation, applies equally to a growing list of non-structural substrates that participate in signal transduction, gene expression, and immune defense.

The enzymatic machinery responsible for glutamylation comprises two opposing families. The tubulin tyrosine ligase-like (TTLL) family catalyzes the initiation and elongation of glutamate chains on the C-terminal tails of alpha- and beta-tubulin, while cytosolic carboxypeptidases (CCPs) mediate the trimming and complete removal of these chains through deglutamylation. This push-and-pull system creates a finely tuned equilibrium that determines the glutamylation state of individual proteins at any given moment. Disruption of this balance, whether through mutation, altered expression, or pathological stress, can have profound consequences for cellular function, and the review highlights how imbalances in TTLL and CCP activity are increasingly linked to human disease.

The classical territory of glutamylation remains the cytoskeleton. Tubulin glutamylation fine-tunes microtubule properties and contributes to a remarkable range of cellular processes, including ciliary function, neuronal development and function, endoplasmic reticulum organization, centrosome and mitotic spindle dynamics, and overall cytoskeletal organization. In cilia, the hair-like projections that sense fluid flow and transmit developmental signals, precise glutamylation patterns are essential for structural integrity and signaling fidelity. In neurons, where microtubules form the scaffolding of axons and dendrites, glutamylation helps maintain the specialized architecture required for long-distance communication. During cell division, the modification influences centrosome behavior and spindle assembly, ensuring accurate chromosome segregation.

What has transformed the field, however, is the discovery that glutamylation extends well beyond tubulin. The review catalogs a growing repertoire of nontubulin substrates whose modification by glutamate addition alters fundamental cellular decisions. Among the most consequential are cGAS, the cytosolic DNA sensor that initiates innate immune responses; KLF4, a transcription factor governing cell-fate determination; IL-7Rα, a receptor subunit critical for lymphocyte development; BAP1, a tumor suppressor involved in chromatin regulation; TAB1, a signaling adaptor in inflammatory pathways; and YAP1, a transcriptional coactivator central to organ growth and regeneration. Glutamylation of these molecules modulates innate immunity, cell-fate choices, hematopoietic homeostasis, metabolic adaptation, tumor progression, and immune evasion.

The implications for immunology are particularly striking. Modification of cGAS, the enzyme that detects cytosolic DNA and triggers antiviral and antimicrobial defenses, demonstrates that glutamylation can tune the sensitivity of the innate immune system. Alterations in IL-7Rα glutamylation affect signaling through a receptor essential for T-cell and B-cell development, linking the modification directly to hematopoietic homeostasis. On the other side of the immune equation, the review notes that glutamylation-dependent changes can contribute to immune evasion, a process by which tumor cells and other threats avoid detection and destruction by the immune system. This dual role, as both a regulator of immune activation and a potential contributor to immune escape, makes the glutamylation machinery a compelling target for therapeutic intervention.

In oncology, the connection between glutamylation and cancer is reinforced through substrates such as BAP1 and YAP1. BAP1, a deubiquitinase with tumor-suppressive functions, and YAP1, a key effector of the Hippo signaling pathway that controls cell proliferation and organ size, are both subject to glutamylation-dependent regulation. TAB1, which participates in inflammatory signaling cascades, adds another layer by connecting the modification to the tumor microenvironment and inflammation-driven malignancy. The review proposes that these substrates, and the enzymes that modify them, could serve as biomarkers for disease progression and as pharmacological targets for novel cancer therapies.

Beyond cancer, the reach of glutamylation into neurodevelopment, metabolism, and cell-fate decisions suggests a modification of extraordinary breadth. KLF4, whose glutamylation influences cell-fate determination, sits at the intersection of stem cell biology and differentiation. Metabolic adaptation, the ability of cells to reprogram energy use in response to nutrient availability and stress, is also modulated through glutamylation-dependent mechanisms. The review integrates these threads into a coherent argument: glutamylation is not a niche modification confined to microtubule tails but a versatile signaling-related post-translational modification that operates across cellular compartments and biological contexts.

The therapeutic opportunities highlighted in the review are twofold. First, targeting TTLL and CCP enzymes directly offers a strategy to modulate glutamylation states in disease, whether by inhibiting excessive modification in tumors or restoring deficient modification in degenerative conditions. Second, the glutamylation status of specific substrates, such as cGAS, YAP1, or BAP1, could serve as biomarkers that guide diagnosis, prognosis, and treatment selection. The authors discuss emerging pharmacological approaches that exploit these possibilities, positioning the glutamylation system as a frontier for drug discovery.

By synthesizing evidence across cytoskeletal biology, cell signaling, and disease mechanisms, the review marks a conceptual shift in how the scientific community understands protein glutamylation. What began as a description of microtubule decoration has matured into a framework that connects cilia, neurons, dividing cells, immune sentinels, and cancer cells through a shared chemical language of reversible glutamate addition and removal. As research continues to uncover new substrates and refine the tools for measuring and manipulating glutamylation, the modification is likely to assume an increasingly prominent place in the study of cellular regulation and in the development of therapies for conditions ranging from neurodevelopmental disorders to metastatic cancer.

Subject of Research: Protein glutamylation as a reversible post-translational modification regulating cytoskeletal and signaling pathways

Article Title: Protein glutamylation: From cytoskeleton to signaling

Article References: Protein glutamylation: From cytoskeleton to signaling. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: protein glutamylation, post-translational modification, TTLL enzymes, cytosolic carboxypeptidases, tubulin code, cGAS, YAP1, BAP1, cilia, tumor progression, immune evasion, biomarkers

The protein at the heart of this story is GEF-H1, a guanine nucleotide exchange factor that activates the small GTPase RhoA, a master regulator of cell contractility, migration and shape. In healthy interphase cells, most GEF-H1 sits parked on microtubules in an inactive state, like a loaded spring held in check. When microtubules fall apart, for example under the influence of the destabilizing drug nocodazole, GEF-H1 is released, rushes to the plasma membrane and switches on RhoA. Because taxanes stabilize microtubules rather than destroy them, the textbook expectation was that they should leave GEF-H1 untouched. The new work overturns that assumption and shows that stabilization itself, when it comes with a specific structural change, can be just as effective at liberating the signalling protein.

To follow RhoA activity in living cells, the team used HT1080 fibrosarcoma cells equipped with a Förster resonance energy transfer biosensor called RhoA2G, which reports RhoA activation as a changing fluorescence ratio. Serum-starved cells had low baseline activity, which surged when serum was added. Adding nocodazole, which dismantles the microtubule network completely, produced a slower but persistent RhoA rise, and paclitaxel did the same, albeit more weakly. Crucially, when the researchers deleted the GEF-H1 gene using CRISPR-Cas9, both drug responses largely vanished, while the response to serum survived intact. This genetic control established that taxanes, like microtubule poisons, drive RhoA activation through GEF-H1 rather than through any of the alternative pathways that growth factors use.

The most telling comparison came from discodermolide, a marine sponge-derived compound that also binds the taxane site on tubulin and stabilizes microtubules just as effectively as paclitaxel. Despite blocking microtubule growth in cells just as efficiently, discodermolide failed to activate RhoA, failed to displace GEF-H1 and left the actin cytoskeleton looking essentially normal. The difference between the two drugs lies not in what they do to microtubule dynamics but in the geometry they impose on the microtubule wall. Taxanes expand the lattice, increasing the longitudinal spacing between tubulin dimers, whereas discodermolide locks the lattice into a compacted state that closely resembles the conformation found in normal, dynamic microtubules.

Downstream of RhoA, the consequences were dramatic and visible within an hour. Serum-starved fibrosarcoma, Swiss 3T3 and U2OS cells, normally elongated with sparse stress fibres, responded to paclitaxel by forming dense actin stress fibres, membrane blebs and rounded morphologies, mirroring the response to nocodazole. In GEF-H1 knockout cells, none of these changes appeared. The team also detected increased levels of phosphorylated myosin light chain, a canonical readout of RhoA-driven actomyosin contractility, after paclitaxel treatment. Live imaging of breast cancer, melanoma and fibrosarcoma cells captured the sequence in real time: rapid rounding and blebbing, followed by partial re-spreading decorated with prominent stress fibres. Taxanes, in other words, hijack the same contractility programme that cells normally deploy during migration and invasion.

Direct visualization of GEF-H1 itself sealed the argument. The researchers expressed GFP-tagged GEF-H1 at near-endogenous levels in U2OS cells and watched it decorate microtubules along their length while avoiding the acetylated, long-lived subset. Within one minute of paclitaxel addition, the fluorescent protein peeled off the microtubules, an effect captured in striking live-cell movies. Discodermolide, again, did nothing. Because one minute is far too short for meaningful changes in tubulin acetylation, and because artificially boosting acetylation with the deacetylase inhibitor tubacin or the acetyltransferase αTAT1, or inducing detyrosination with VASH2-SVBP or MATCAP, did not remove GEF-H1 from microtubules, the team concluded that post-translational modifications could not explain the drug effect. The culprit had to be the lattice itself.

To prove the point with purified components, the group turned to in vitro reconstitution. Using total internal reflection fluorescence microscopy, they grew dynamic microtubules from stabilized seeds in the presence of nanomolar concentrations of purified GFP-GEF-H1. The protein bound avidly to the dynamic GDP lattice but conspicuously avoided the GMPCPP-stabilized seeds, which have an expanded conformation. This exclusion could not be attributed to nucleotide state, because microtubules polymerized with the non-hydrolysable analogue GTPγS, which keeps a compacted lattice, bound GEF-H1 just as well as GDP lattices. Interference reflection microscopy confirmed that the seeds and growing lattices contained the expected protofilament numbers, indicating that GEF-H1 is not fussy about protofilament count but is exquisitely sensitive to longitudinal lattice spacing.

The wash-in experiments provided the most elegant demonstration. When paclitaxel was flowed onto microtubules sparsely labelled with fluorescent tubulin, the speckles visibly shifted apart, a direct optical readout of lattice expansion, and simultaneously the bound GFP-GEF-H1 dissociated within seconds. Discodermolide wash-in produced neither expansion nor release. Cryo-electron microscopy and single-particle analysis then quantified the geometry: discodermolide-stabilized microtubules with 13 or 14 protofilaments had dimer rise values of 81.7 and 81.6 angstroms, essentially identical to compacted GTPγS lattices, confirming their compacted character. Remarkably, at high concentration GEF-H1 could flip the relationship and act as a code writer rather than a code reader: adding a 200-fold excess of the protein rapidly compacted microtubules that paclitaxel had expanded, imposing its preferred geometry on the drug-stabilized lattice. This concentration-dependent bidirectionality likely explains why earlier studies using strongly overexpressed GEF-H1 missed the taxane sensitivity altogether.

The structural logic is intriguing. Previous cryo-EM work showed that the C1 zinc-finger domain of GEF-H1, spanning amino acids 28 to 100, binds in a groove between two tubulin dimers in adjacent protofilaments, a site far from the exchangeable nucleotide pocket where taxane-induced expansion is thought to originate. The new study shows that a dimerized fragment containing the first 136 amino acids is sufficient to confer taxane sensitivity in cells, and that the GEF-H1-bound microtubule lattice adopts a partially compacted twist resembling that of GTPγS and discodermolide structures. How binding at the interdimer interface allosterically favours compaction near the β-tubulin E-site remains an open question, but the authors suggest that the drug and the protein compete for control of the same conformational degree of freedom.

The clinical implications are potentially far-reaching. Docetaxel, a taxane with higher microtubule affinity that is a mainstay of cancer chemotherapy, activated RhoA at concentrations as low as 100 nanomolar, well within the range measured in the plasma of treated patients, and the response grew stronger over hours as the drug accumulated in cells, a process the team followed directly with a fluorescent taxane probe. Because RhoA signalling can promote anti-tumour immune responses and drive apoptosis in cells that lose adhesion, taxane-induced RhoA activation may contribute to therapeutic efficacy, not just to toxicity. Conversely, misregulated RhoA contractility in neurons offers a plausible route to the dose-limiting peripheral neuropathy that plagues taxane therapy. Beyond the clinic, the study elevates lattice conformation to a recognized layer of the tubulin code, alongside isotypes and post-translational modifications, and provides the community with discodermolide as a powerful tool compound for separating conformational effects from effects on microtubule dynamics. If other microtubule-binding proteins turn out to read the lattice as keenly as GEF-H1 does, taxanes may be quietly rewiring many more signalling pathways than anyone suspected.

Subject of Research: How taxane-induced microtubule lattice expansion releases GEF-H1 to activate RhoA signalling

Article Title: Taxane-induced conformational changes in the microtubule lattice activate GEF-H1-dependent RhoA signalling

Article References: Meiring, J. C. M., Mahapatra, V., Liu, R., Gravett, M. S. C., Morren, D., Saunders, H. A. J., Choi, S. R., Pelster José, A., Karhanova, A., Metallidou, I., Moore, A., Spoelstra, M. F. M., Grigoriev, I. S., Giono, M., Iyer, S. S., Stehbens, S. J., Díaz, J. F., Lansky, Z., Stecker, K. E., … Akhmanova, A. (2026). Taxane-induced conformational changes in the microtubule lattice activate GEF-H1-dependent RhoA signalling. Nature Cell Biology. https://doi.org/10.1038/s41556-026-02079-4

Image Credits: AI Generated

DOI: 10.1038/s41556-026-02079-4

Keywords: microtubules, taxanes, paclitaxel, GEF-H1, RhoA, tubulin code, lattice conformation, discodermolide, actin cytoskeleton, chemotherapy, cryo-EM, cell signalling

The article, led by Carsten Janke of Institut Curie and Université Paris-Saclay together with Anna Akhmanova of Utrecht University and an international consortium of sixteen colleagues from institutions spanning Europe and the United States, lays out a coordinated agenda for the microtubule field. Its authors span structural biology, biophysics, cell biology, neuroscience, parasitology and computational modelling, reflecting their central conviction that progress will come not from any single discipline but from a deliberate fusion of them. The paper is punctuated by the admission that some of the most basic questions remain unexplored, including how the properties and functions of microtubules are affected by the chemical marks known as tubulin post-translational modifications, by disease-related mutations in tubulin genes, or by variation in the microtubule lattice itself.

Microtubules are hollow tubes assembled from αβ-tubulin dimers that stack into protofilaments, typically thirteen of which align laterally to form the wall of the polymer. What makes these structures extraordinary is their behaviour: individual microtubules stochastically switch between phases of growth and rapid shrinkage, a phenomenon called dynamic instability, which was first described by Tim Mitchison and Marc Kirschner in 1984. A stabilizing cap of GTP-bound tubulin at the growing plus end controls this behaviour, and its loss triggers catastrophic depolymerization. Beyond pure polymerization, microtubules can self-repair by incorporating new tubulin along damaged stretches of lattice, a property revealed in studies showing that lattice defects actually induce self-renewal and protect the polymers from destruction by molecular motors. These discoveries have transformed the view of microtubules from static beams into dynamic, self-healing machines.

The Roadmap emphasizes that microtubule function is not determined by the polymer alone but by a dense layer of regulation encoded on the tubulin subunit itself. Enzymes of the tubulin tyrosine ligase-like family decorate the unstructured carboxy-terminal tails of tubulin with modifications such as tyrosination, detyrosination, acetylation, glutamylation and glycylation, creating what has become known as the tubulin code. Recent structural work has shown, for example, that enzymes involved in polyglutamylation recognize microtubules through a quadrivalent mechanism that links microtubule geometry to the generation of localized modification patterns, and that protofilament-specific nanopatterns of these marks tune the mechanics of beating cilia. The Roadmap argues that understanding how this chemical language is written, read and erased across cellular contexts is one of the field’s most pressing challenges, particularly because disruptions in the code are now firmly linked to neurodegeneration, ciliopathies and other disorders.

Nowhere is the clinical relevance more evident than in the nervous system. Neurons depend on microtubule tracks for the long-range transport of organelles, messenger RNAs and signalling endosomes along axons and dendrites, a process powered by kinesin and dynein motor proteins. Mutations in tubulin genes such as TUBA1A cause lissencephaly, a severe developmental brain malformation, by perturbing neuronal migration, and variants in a growing list of tubulin genes underlie a spectrum of neurodevelopmental disorders collectively known as tubulinopathies. Defective axonal transport is a shared hallmark of motor neuron diseases, and recent work has shown that excessive polyglutamylation of tubulin in the brain is sufficient to drive neurodegeneration by disrupting transport, while restoring the balance of these modifications can rescue affected neurons. The Roadmap positions a systems-level understanding of these processes as essential for translating molecular insight into therapies.

The heart and the immune system tell equally compelling stories. In beating cardiomyocytes, detyrosinated microtubules act as load-bearing elements that buckle under contraction and stiffen the cell, and suppressing this modification improves cardiac function in models of heart failure. In immune cells, microtubule networks orchestrate cell shape, migration and the directed release of lytic granules by natural killer cells, while platelets, whose tubulin repertoire is dominated by the β1-tubulin isotype, rely on precisely regulated microtubule assembly during their biogenesis; mutations in the TUBB1 gene cause congenital macrothrombocytopenia and thyroid dysgenesis. The Roadmap argues that these tissue-specific roles cannot be understood piecemeal and demand approaches that bridge the molecular properties of tubulin to the physiology of whole organs.

Technological innovation sits at the centre of the proposed strategy. Cryo-electron microscopy and cryo-electron tomography now reveal microtubules and their associated proteins at near-atomic and in situ resolution, while expansion microscopy and ultrastructure expansion microscopy allow researchers to visualize centrioles, cilia and mitotic spindles in whole cells and tissues with nanometre precision. In vitro reconstitution, a tradition stretching back to the pioneering work of Tim Mitchison and Marc Kirschner and continued in landmark experiments showing that purified microtubules and motors can self-organize into asters and vortices, remains indispensable for dissecting minimal systems. These experimental approaches are increasingly paired with computational and physical models that simulate spindle assembly, microtubule network organization and chromosome movement, and the Roadmap calls for tighter coupling between modelling and experiment, including the development of virtual cells powered by artificial intelligence.

Recombinant tubulin technology is highlighted as a particularly transformative advance. For decades, biochemists were limited to native tubulin purified from brain tissue, a mixture of isotypes and modifications that obscured cause and effect. The ability to produce functional human tubulin dimers in defined isotypes, with controlled post-translational modifications, has now enabled researchers to show directly that different isotypes confer distinct dynamic properties, that detyrosination tunes microtubule stability through selective recruitment of associated factors, and that systematic mutagenesis can map the functional landscape of disease-linked variants. Combined with deep mutational scanning and artificial-intelligence-driven phenotyping, the authors argue, these tools will allow the effects of every clinically observed tubulin mutation to be predicted and tested, a goal that seemed out of reach only a few years ago.

The Roadmap also looks beyond animal cells, drawing attention to the diversity of microtubule arrays across eukaryotes, from the cortical arrays that guide plant cell morphogenesis to the subpellicular arrays of trypanosomes and the specialized mitotic machinery of parasites. Comparative studies of parasites such as Plasmodium have revealed that adaptations in tubulin sequence generate distinct microtubule architectures, mechanics and drug susceptibilities, opening avenues for species-selective therapeutics. The authors contend that this evolutionary breadth is not a curiosity but a resource: organisms that build microtubules with unusual lattices, modifications or assembly mechanisms offer natural experiments that can illuminate principles hidden in familiar model systems.

Ultimately, the Roadmap is an invitation to think bigger. Its authors conclude that the microtubule cytoskeleton will continue to inspire scientists for decades precisely because so many fundamental questions remain open: how microtubule arrays are organized and diversified in different cell types, how the tubulin code is orchestrated across space and time, how mechanical forces reshape and stabilize microtubule lattices in living cells, and how all of this integrates into the physiology of tissues and organisms in health, ageing and disease. By bridging the atomic structure of the tubulin dimer with the behaviour of mitotic spindles, migrating neurons and beating hearts, the field aims to transform its fragmented molecular knowledge into a coherent systems-level picture, one that could reshape how disorders ranging from neurodegeneration and cancer to ciliopathies and heart failure are understood and treated.

The historical depth of the field is worth appreciating. Microtubules were first visualized in the late nineteenth and early twentieth centuries, but their protein building block was only identified in the late 1960s, when colchicine-binding assays led to the isolation of what was soon named tubulin, and amino-acid analysis of sperm flagella confirmed it as the universal subunit of the polymer. The discovery of dynamic instability two decades later established that these polymers are fundamentally nonequilibrium structures, a insight that continues to shape how spindle assembly and chromosome movement are understood today.

Equally important is the cast of regulatory proteins that act on microtubules. Microtubule-associated proteins such as tau can condense on the lattice in regulated phases, altering how motors and severing enzymes engage the polymer, while enzymes that cut microtubules generate new seeds and reshape networks. Proteins like doublecortin, which is mutated in human brain malformations, illustrate how even lattice geometry itself can be read selectively, recognizing only specific protofilament numbers. These layered interactions, spanning motors, maps, severing enzymes and modifying enzymes, form the mechanistic vocabulary that any systems-level account of the cytoskeleton will ultimately need to integrate.

Subject of Research: Systems-level integration of microtubule cytoskeleton structure, regulation and function in physiology and disease

Article Title: Towards a systems-level view of the microtubule cytoskeleton and its functions in physiology and disease

Article References: Janke, C., Akhmanova, A., Bartolini, F., Bodakuntla, S., Del Bene, F., Hamel, V., Mitchison, T. J., Müller-Reichert, T., Nédélec, F., Nogales, E., Pigino, G., Roll-Mecak, A., Schiavo, G., Surrey, T., & Lansky, Z. (2026). Towards a systems-level view of the microtubule cytoskeleton and its functions in physiology and disease. Nature Reviews Molecular Cell Biology. https://doi.org/10.1038/s41580-026-01011-w

Image Credits: AI Generated

DOI: 10.1038/s41580-026-01011-w

Keywords: microtubules, tubulin code, post-translational modifications, dynamic instability, axonal transport, tubulinopathies, ciliopathies, neurodegeneration, mitotic spindle, cryo-electron tomography, in vitro reconstitution, systems biology