GO:0008568 microtubule severing ATPase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0008568 microtubule severing ATPase activity describes the ATP-dependent catalysis of cutting a microtubule at a specific point along its length, coupling ATP hydrolysis to mechanical severing.
• The term is a molecular_function and includes synonyms such as katanin activity, microtubule-severing ATPase activity, and ATP phosphohydrolase (tubulin-dimerizing).
• Severing enzymes are AAA+ ATPases that use the energy of ATP hydrolysis to pull tubulin dimers out of the microtubule lattice, creating new plus and minus ends.
• Katanin, spastin, fidgetin, and related enzymes are the principal proteins annotated with this activity, and they regulate spindle assembly, neuronal remodeling, and cytoskeletal dynamics.
• Dysregulation of microtubule severing is linked to neurodevelopmental and neurodegenerative conditions, meiotic spindle defects, and cancer-related cytoskeletal changes.
• CRISPR knockout, point-mutation, knock-in, and overexpression models are essential for testing how specific residues and domains contribute to severing activity in cells and organisms.
Description
Microtubule severing ATPase activity (GO:0008568) is a molecular function that couples the hydrolysis of ATP to the cutting of a microtubule at a specific spot along its length. This activity is performed by specialized AAA+ ATPases that bind the microtubule lattice, hydrolyze ATP, and use the resulting conformational changes to remove tubulin dimers, thereby creating internal breaks in the polymer. The reaction is not a simple nuclease-like cut; it is a mechanochemical process in which ATP binding and hydrolysis are tightly linked to tubulin extraction and to the GTP state of the tubulin dimer.
microtubule severing ATPase activity At A Glance
| GO ID | GO:0008568 |
|---|---|
| GO term | microtubule severing ATPase activity |
| Ontology | molecular_function |
| Synonym | katanin activity; microtubule-severing ATPase activity; ATP phosphohydrolase (tubulin-dimerizing) |
| Major function | ATP-dependent severing of microtubules at internal sites along the polymer |
| Reaction | ATP + H2O = ADP + phosphate, coupled to microtubule severing |
| Representative enzymes | Katanin, spastin, fidgetin, and related AAA+ ATPases |
| Biological context | Spindle assembly, neuronal remodeling, cytoskeletal dynamics |
What Is GO:0008568?
According to the Gene Ontology, GO:0008568 microtubule severing ATPase activity is defined as the catalysis of the reaction ATP + H2O = ADP + phosphate, coupled to the severing of a microtubule at a specific spot along its length. In other words, the same protein uses the energy released by ATP hydrolysis to break the microtubule lattice internally, rather than simply depolymerizing it from the ends. The term is a molecular_function and is synonymous with katanin activity, microtubule-severing ATPase activity, and ATP phosphohydrolase (tubulin-dimerizing).
Why Is microtubule severing ATPase activity Important in Cell Biology?
Microtubule severing ATPase activity is important because it controls where and when microtubules are broken, which in turn determines microtubule number, length, and organization in cells. This activity is required for meiotic spindle assembly, for neuronal remodeling, and for the dynamic reorganization of the cytoskeleton during development and differentiation. Because severing enzymes are ATPases, their activity can be regulated by nucleotide state, by microtubule post-translational modifications such as polyglutamylation, and by protein-protein interactions, making GO:0008568 a central node in cytoskeletal regulation.
• Controls microtubule number and length by creating new plus and minus ends.
• Essential for female meiotic spindle assembly through katanin activity.
• Drives neuronal remodeling and microtubule reorganization in the nervous system.
• Regulated by polyglutamylation of microtubules, linking post-translational modifications to severing.
• Modulated by protein-protein interactions, such as fidgetin binding to spastin.
• Required for proper spindle function and chromosome segregation in dividing cells.
• Implicated in neurodegenerative and neurodevelopmental conditions when dysregulated.
• Provides a mechanistic target for studying AAA+ ATPase function and mechanochemistry.
• Supports cytoskeletal plasticity in response to developmental and environmental cues.
• Offers a functional readout for CRISPR-based perturbation of severing enzyme genes.
What Happens During microtubule severing ATPase activity?
Microtubule binding and target site recognition
In simple terms: The severing enzyme first attaches to the microtubule surface and finds the spot it will cut.
Severing ATPases bind along the microtubule lattice and recognize specific structural or chemical features that mark a severing site. This binding is mediated by microtubule-binding domains, and in the katanin p80 subunit these domains are essential for severing activity in C. elegans. The enzyme does not cut randomly; it selects a specific spot along the microtubule length, consistent with the GO definition of severing at a specific spot.
ATP binding and conformational activation
In simple terms: ATP binding changes the shape of the enzyme so it can pull on the microtubule.
After binding the microtubule, the enzyme binds ATP, which induces conformational changes in the AAA+ ATPase ring. These changes prime the enzyme for mechanical work and are coupled to the nucleotide state of the tubulin dimer, a process described as tubulin GTPase spring loading. ATP binding is therefore a key step that converts chemical energy into a poised mechanical state.
Tubulin dimer extraction and lattice breakage
In simple terms: The enzyme uses ATP energy to pull tubulin dimers out, breaking the microtubule.
ATP hydrolysis drives the extraction of tubulin dimers from the microtubule lattice, creating a gap that breaks the polymer. This severing event generates new microtubule ends and can release short tubulin oligomers. The reaction is coupled to ATP hydrolysis, as stated in the GO definition, and the energy of hydrolysis is used to overcome the lateral and longitudinal bonds holding tubulin in the lattice.
Release and recycling of the enzyme
In simple terms: After cutting, the enzyme lets go and can cut again elsewhere.
Following severing, the enzyme releases ADP and phosphate and dissociates from the newly created microtubule ends, allowing it to recycle to other sites. This catalytic cycle enables a single enzyme molecule to perform multiple severing events, which is important for rapid cytoskeletal remodeling. Regulation by interacting proteins, such as fidgetin binding to spastin, can attenuate this cycle and modulate severing activity.
Key Genes Involved in GO:0008568 microtubule severing ATPase activity
The following genes and proteins are representative of the microtubule severing ATPase activity (GO:0008568) and are commonly studied in cytoskeletal and developmental research.
| Gene | Major Role | Research Relevance |
|---|---|---|
| KATNA1 | Catalytic subunit of katanin, a microtubule severing ATPase | Studied for spindle assembly and meiotic division |
| KATNB1 | Regulatory p80 subunit of katanin | Microtubule-binding domains in p80 are essential for severing in C. elegans |
| SPAST | Spastin, a AAA+ ATPase that severs microtubules | Regulated by fidgetin binding; linked to neuronal function |
| FIGN | Fidgetin, a microtubule severing ATPase | Binds spastin to attenuate severing activity |
| FIGNL1 | Fidgetin-like 1, a severing enzyme | Studied in cytoskeletal dynamics and development |
| VPS4A | AAA+ ATPase related to severing enzymes | Model for AAA+ mechanochemistry |
| VPS4B | AAA+ ATPase related to severing enzymes | Model for AAA+ mechanochemistry |
| TTLL1 | Tubulin polyglutamylation enzyme | Polyglutamylation drives neuronal remodeling via severing |
| TTLL4 | Tubulin polyglutamylation enzyme | Modifies microtubules to regulate severing |
| TTLL6 | Tubulin polyglutamylation enzyme | Modifies microtubules to regulate severing |
| CCP1 | Tubulin deglutamylase | Counteracts polyglutamylation and modulates severing |
| CCP5 | Tubulin deglutamylase | Counteracts polyglutamylation and modulates severing |
| SPAST (mutants) | Disease-associated spastin variants | Used to study neurodegeneration and severing defects |
| KATNA1 (mutants) | Disease-associated katanin variants | Used to study meiotic spindle defects |
| KATNB1 (mutants) | Disease-associated p80 variants | Used to study severing in C. elegans |
| TUBB | Beta-tubulin, substrate of severing | Tubulin GTPase spring loading affects severing |
| TUBA1A | Alpha-tubulin, substrate of severing | Tubulin modifications affect severing |
How Is microtubule severing ATPase activity Regulated?
Microtubule severing ATPase activity is regulated at multiple levels. Post-translational polyglutamylation of microtubules drives neuronal remodeling and modulates severing by severing enzymes. Protein-protein interactions also regulate activity; for example, fidgetin binds spastin to attenuate its microtubule-severing activity. In addition, the nucleotide state of tubulin and the spring-loading mechanism couple ATP hydrolysis to tubulin GTPase activity, providing a built-in regulatory link between the enzyme and its substrate. These layers of regulation ensure that severing occurs at the right time and place during spindle assembly and neuronal development.
microtubule severing ATPase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SPAST | Neurodegeneration and neuronal remodeling | Knockout or point-mutation in neuronal cell lines |
| KATNA1 | Meiotic spindle defects | Knockout in oocyte or meiotic cell models |
| KATNB1 | Severing defects in C. elegans | Knockout or knock-in in C. elegans |
| TTLL1 | Polyglutamylation-driven neuronal remodeling | Overexpression or knockout in neurons |
| FIGN | Attenuation of spastin severing activity | Knockout or overexpression in neuronal cells |
Neurodegeneration and neuronal remodeling
Microtubule severing enzymes are critical for neuronal remodeling, and their dysregulation is linked to neurodegenerative conditions. Polyglutamylation of microtubules drives neuronal remodeling, and perturbations in this pathway can affect severing activity. Spastin, a severing ATPase, is regulated by fidgetin, and this interaction can attenuate severing activity, which is relevant to neuronal function.
Meiotic spindle defects and reproductive biology
The microtubule-severing activity of the AAA+ ATPase katanin is essential for female meiotic spindle assembly. Loss of katanin function leads to spindle defects, highlighting the importance of GO:0008568 in meiosis. The p80 subunit of katanin, which contains microtubule-binding domains, is also essential for severing activity in C. elegans, linking structural domains to reproductive phenotypes.
Cancer and cytoskeletal dynamics
Altered microtubule severing can affect spindle assembly and chromosome segregation, processes that are central to cancer cell division. Although direct cancer links are still being defined, the role of severing enzymes in spindle function makes them candidates for further study in cancer biology. Research on TBEV-infected neurons and astrocytes has also revealed potential pathogenic effectors related to cytoskeletal and severing pathways, suggesting broader disease relevance.
From microtubule severing ATPase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of katanin affect meiotic spindle assembly? | KATNA1 knockout in oocyte models |
| Do microtubule-binding domains in p80 mediate severing? | KATNB1 point mutations in C. elegans |
| Does fidgetin binding regulate spastin severing? | FIGN knockout or overexpression in neuronal cells |
| Does polyglutamylation drive neuronal remodeling? | TTLL1 overexpression or knockout in neurons |
| What is the catalytic mechanism of severing ATPases? | Recombinant protein with point mutations in ATPase domain |
| How does tubulin GTP state affect severing? | TUBB knock-in or point mutation in cell lines |
How to Study the microtubule severing ATPase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging | Microtubule severing events and dynamics | Quantify severing frequency in cells |
| In vitro severing assay | ATP hydrolysis and microtubule breakage | Test purified enzyme activity |
| RNA profiling | Expression of severing enzymes and related genes | Disease model transcriptomics |
| Proteomics | Tubulin post-translational modifications | Detect polyglutamylation |
| CRISPR knockout | Loss-of-function effects on severing | Study gene requirement |
| Point mutation | Specific residue contributions to catalysis | Dissect ATPase mechanism |
| Knock-in | Tagged or mutant protein expression | Track localization and dynamics |
| Overexpression | Gain-of-function effects on severing | Test sufficiency in cells |
Live-cell imaging of microtubule severing
Live-cell imaging with fluorescently labeled tubulin allows direct visualization of microtubule severing events in real time. This method can quantify severing frequency, microtubule length, and the appearance of new ends after severing. It is particularly useful for studying how mutations in severing enzymes alter dynamics in cells.
In vitro severing assays with purified proteins
In vitro assays using purified severing ATPases and microtubules measure ATP hydrolysis and microtubule breakage under controlled conditions. These assays can test the effects of nucleotide state, tubulin modifications, and interacting proteins on severing activity. They are essential for dissecting the mechanochemical cycle of GO:0008568.
RNA profiling and transcriptomics
Integrative RNA profiling can reveal changes in expression of severing enzymes and related cytoskeletal genes in disease models. For example, RNA profiling of TBEV-infected neurons and astrocytes identified potential pathogenic effectors, including cytoskeletal pathways. Such approaches help link severing activity to broader cellular responses.
Proteomics and post-translational modification analysis
Proteomic methods can detect polyglutamylation and other modifications on tubulin that regulate severing. Mass spectrometry-based approaches allow quantification of tubulin modification states and their impact on severing enzyme recruitment. These methods complement functional assays to provide a mechanistic understanding of GO:0008568 regulation.
How CRISPR Can Be Used to Study GO:0008568 microtubule severing ATPase activity
Knockout
CRISPR knockout of severing enzyme genes such as KATNA1, KATNB1, SPAST, or FIGN can abolish microtubule severing activity and reveal its role in spindle assembly, neuronal remodeling, and cytoskeletal organization. Knockout models are useful for testing whether a gene is required for a specific severing-dependent process.
Point Mutation
Point mutations in the ATPase domain or microtubule-binding domains of severing enzymes can dissect the catalytic mechanism and domain requirements for severing. For example, mutations in katanin p80 microtubule-binding domains impair severing in C. elegans, demonstrating the value of targeted point mutations.
Knock-in
Knock-in of tagged or mutant versions of severing enzymes allows tracking of protein localization and dynamics while preserving endogenous regulation. This approach can also introduce disease-associated mutations to study their effects on severing activity.
Overexpression
Overexpression of severing enzymes or their regulators can test sufficiency for severing and downstream phenotypes, such as neuronal remodeling or spindle defects. Overexpression of polyglutamylation enzymes like TTLL1 can also drive severing-dependent remodeling.
How EDITGENE Supports microtubule severing ATPase activity Research
Researchers studying microtubule severing ATPase activity-related genes often need to determine whether a candidate gene is causally involved in severing, spindle assembly, or neuronal remodeling. EDITGENE provides CRISPR-based cell model services that enable precise perturbation of these genes in relevant cellular contexts.
Contact EDITGENE today to design your custom CRISPR model for microtubule severing ATPase activity research.
Frequently Asked Questions About microtubule severing ATPase activity
What is microtubule severing ATPase activity?
It is a molecular function (GO:0008568) in which ATP hydrolysis is coupled to the cutting of a microtubule at a specific spot along its length.
What genes are involved in microtubule severing ATPase activity?
Key genes include KATNA1, KATNB1, SPAST, FIGN, and related AAA+ ATPases such as VPS4A and VPS4B.
What is the GO ID for microtubule severing ATPase activity?
The GO ID is GO:0008568.
How does katanin sever microtubules?
Katanin binds the microtubule lattice, hydrolyzes ATP, and extracts tubulin dimers to break the polymer, a process essential for meiotic spindle assembly.
What is the role of spastin in microtubule severing?
Spastin is a AAA+ ATPase that severs microtubules and is regulated by fidgetin binding, which attenuates its severing activity.
How is microtubule severing regulated?
It is regulated by tubulin polyglutamylation, protein-protein interactions such as fidgetin-spastin binding, and the nucleotide state of tubulin.
Why is microtubule severing important for neurons?
Severing drives neuronal remodeling, and polyglutamylation of microtubules is a key signal for this process.
What diseases are linked to microtubule severing defects?
Defects are linked to neurodegeneration, meiotic spindle abnormalities, and potentially cancer-related cytoskeletal changes.
What methods are used to study microtubule severing ATPase activity?
Common methods include live-cell imaging, in vitro severing assays, RNA profiling, proteomics, and CRISPR-based perturbation.
How can CRISPR help study microtubule severing?
CRISPR knockout, point mutation, knock-in, and overexpression models allow precise testing of gene function in severing pathways.
Conclusion
Microtubule severing ATPase activity (GO:0008568) is a mechanochemical function that couples ATP hydrolysis to the internal breakage of microtubules, controlling cytoskeletal organization in processes ranging from meiotic spindle assembly to neuronal remodeling. The activity is carried out by AAA+ ATPases such as katanin, spastin, and fidgetin, and is regulated by tubulin modifications and protein interactions. Understanding this activity requires integrated approaches, including CRISPR-based models, live imaging, and biochemical assays.
References
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- 2. Roll-Mecak A et al.. 2010. Microtubule-severing enzymes.. Curr Opin Cell Biol 22(1):96-103 PMID: 19963362
- 3. Bailey ME et al.. 2016. Invited review: Microtubule severing enzymes couple atpase activity with tubulin GTPase spring loading.. Biopolymers 105(8):547-56 PMID: 27037673
- 4. Sun Y et al.. 2025. Fidgetin binds spastin to attenuate the microtubule-severing activity.. Biochim Biophys Acta Mol Cell Res 1872(2):119890 PMID: 39681249
- 5. Joly N et al.. 2016. Microtubule-severing activity of the AAA+ ATPase Katanin is essential for female meiotic spindle assembly.. Development 143(19):3604-3614 PMID: 27578779
- 6. Selinger M et al.. 2022. Integrative RNA profiling of TBEV-infected neurons and astrocytes reveals potential pathogenic effectors.. Comput Struct Biotechnol J 20:2759-2777 PMID: 35685361
- 7. Gavoci A et al.. 2025. Polyglutamylation of microtubules drives neuronal remodeling.. Nat Commun 16(1):5384 PMID: 40562742
- 8. Beaumale E et al.. 2024. Microtubule-binding domains in Katanin p80 subunit are essential for severing activity in C. elegans.. J Cell Biol 223(4) PMID: 38329452
