GO:0060001 minus-end directed microfilament motor activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0060001 describes a molecular motor activity that moves along actin filaments toward the minus (pointed) end using ATP hydrolysis.
• Myosin VI (MYO6) is the only known myosin that moves toward the minus end of actin filaments, making it the central protein for this GO term [1,3].
• MYO6 interacts with adaptor complexes such as Tom1, LMTK2, and others to coordinate endosomal trafficking and cytoskeletal dynamics.
• Mutations in MYO6 alter filopodia formation and endosome clustering, demonstrating the importance of minus-end directed motility in cell morphogenesis.
• Minus-end directed motor activity cooperates with microtubule motors during organelle transport, highlighting integrated cytoskeletal regulation.
• Studying GO:0060001 requires live-cell imaging, in vitro motility assays, and CRISPR-based genetic models to dissect its roles in health and disease [1,3].
Description
Minus-end directed microfilament motor activity (GO:0060001) is a molecular function that generates movement along actin filaments toward the minus end, driven by ATP hydrolysis. Unlike conventional myosins that move toward the plus (barbed) end, this activity is exemplified by myosin VI, which moves toward the pointed end of actin filaments. This counter-directional motility is essential for processes such as endocytosis, vesicle trafficking, and cell migration [1,3]. Researchers study GO:0060001 to understand how cells organize their actin cytoskeleton and how defects in this motor activity contribute to disease [1,3]. The unique directionality of myosin VI allows it to perform specialized roles that cannot be compensated by plus-end directed motors. As a result, GO:0060001 represents a critical node in cytoskeletal biology with broad implications for cell biology and medicine [1,3].
minus-end directed microfilament motor activity At A Glance
| GO ID | GO:0060001 |
|---|---|
| GO term | minus-end directed microfilament motor activity |
| Ontology | molecular_function |
| Synonym | minus-end directed actin filament motor activity; minus-end directed actin-filament motor activity; pointed-end directed actin-filament motor activity |
| Major function | ATP-dependent movement along actin filaments toward the minus end |
| Representative protein | Myosin VI (MYO6) |
| Cellular context | Actin cytoskeleton, endosomes, filopodia, and other actin-rich structures |
| Associated processes | Endocytosis, vesicle trafficking, cell migration, filopodia formation |
What Is GO:0060001?
GO:0060001, minus-end directed microfilament motor activity, is defined as a motor activity that generates movement along a microfilament toward the minus end, powered by ATP hydrolysis. The minus end of an actin filament is the end that does not preferentially add actin monomers. This activity is synonymous with minus-end directed actin filament motor activity and pointed-end directed actin-filament motor activity. In practice, it refers to the ability of certain myosin motors, notably myosin VI, to step toward the pointed end of actin filaments.
Why Is minus-end directed microfilament motor activity Important in Cell Biology?
GO:0060001 is important because it defines a unique directionality of actin-based motility that is essential for specialized cellular functions such as endocytosis, vesicle sorting, and cell migration [1,3]. Myosin VI, the primary motor for this activity, is recruited to endosomes and other compartments by specific adaptor proteins, and its dysfunction leads to defects in endosomal trafficking and cytoskeletal organization. Understanding this activity provides insight into how cells achieve spatial and temporal control of actin-based transport, and it offers potential therapeutic targets for diseases linked to myosin VI dysfunction [1,3].
• Enables endosome clustering and filopodia formation, processes critical for cell signaling and migration.
• Coordinates with microtubule motors to regulate bidirectional organelle transport.
• Required for proper endosomal trafficking through interactions with adaptor complexes.
• Contributes to actin cytoskeleton organization in polarized cells.
• Dysfunction of myosin VI is associated with deafness and other disorders.
• Provides a model for studying mechanochemical coupling in unconventional myosins.
• Plays a role in spindle polarity and astral microtubule capture in yeast.
• Influences cell growth and organelle motility in plant pollen tubes.
• Modulates the lethality of dynein mutants, indicating cross-talk with microtubule motors.
• Serves as a target for CRISPR-based functional studies to dissect its roles in disease [1,3].
Molecular Mechanism of minus-end directed microfilament motor activity
ATP Hydrolysis and Force Generation
In simple terms: The motor uses ATP as fuel to move along actin.
Minus-end directed microfilament motor activity is driven by ATP hydrolysis, which induces conformational changes in the motor domain that are converted into directed movement along the actin filament. Myosin VI, the archetypal motor for this activity, has a unique insert that reverses its directionality compared to plus-end directed myosins.
Actin Filament Polarity and Directionality
In simple terms: Actin filaments have two ends, and this motor moves toward the pointed end.
The minus end of an actin filament is the end that does not preferentially add actin monomers, also known as the pointed end. Myosin VI moves toward this end, allowing it to transport cargo away from the leading edge in migrating cells.
Cargo Binding and Adaptor Recruitment
In simple terms: The motor attaches to cargo via adaptor proteins.
Myosin VI interacts with a variety of adaptor proteins, such as Tom1 and LMTK2, which link the motor to endosomal membranes and other cargo. These interactions are essential for coordinating early endosome and cytoskeletal dynamics.
Coordination with Microtubule Motors
In simple terms: Actin and microtubule motors work together to move cargo.
Minus-end directed actin motors cooperate with microtubule motors during organelle transport, as shown in melanophores where myosin cooperates with dynein and kinesin. This coordination ensures efficient bidirectional movement and proper cargo distribution.
Regulation by Calcium and Calmodulin
In simple terms: Calcium signals can tune the motor's activity.
Myosin VI is regulated by calcium via calmodulin binding, which can affect its motility and cargo binding. This regulation allows the motor to respond to local calcium signals during processes like endocytosis.
Key Genes Involved in GO:0060001 minus-end directed microfilament motor activity
The following genes and proteins are directly implicated in minus-end directed microfilament motor activity or its regulation, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| MYO6 | Minus-end directed actin motor; moves toward pointed end | Central to GO:0060001; mutations cause deafness and affect endocytosis [1,3] |
| TOM1 | Adaptor linking MYO6 to endosomes | Regulates endosomal trafficking and cytoskeletal dynamics |
| LMTK2 | Adaptor and kinase interacting with MYO6 | Coordinates early endosome and cytoskeletal dynamics |
| DHC-1 | Microtubule motor dynein heavy chain | Cross-talk with actin motors; mutants show lethality modulated by actin regulators |
| KCBP | Calmodulin-binding kinesin | Regulates polarized growth and organelle motility in pollen tubes |
| BUD6 | Cortical protein involved in spindle polarity | Priming spindle polarity and astral microtubule capture |
| ACT1 | Actin | Substrate for motor activity; filament polarity determines directionality |
| CALM1 | Calmodulin | Calcium sensor regulating myosin VI activity |
| DYNC1H1 | Dynein heavy chain | Cooperates with myosin during organelle transport |
| KIF5B | Kinesin heavy chain | Microtubule motor cooperating with myosin |
| MYO5A | Plus-end directed myosin | Contrasts with minus-end directed activity; used in comparative studies |
| RAB5 | Early endosome marker | Endosomal cargo for MYO6-mediated transport |
| RAB7 | Late endosome marker | Endosomal cargo for MYO6-mediated transport |
| EEA1 | Early endosome antigen | Marker for endosome clustering affected by MYO6 mutants |
| CDC42 | Rho GTPase | Regulates actin dynamics and filopodia formation |
| ARP2/3 | Actin nucleation complex | Generates branched actin networks for motor tracks |
| WASL | Actin nucleation promoting factor | Regulates filopodia and endosome dynamics |
| TPM1 | Tropomyosin | Stabilizes actin filaments and modulates motor activity |
How Is minus-end directed microfilament motor activity Regulated?
Minus-end directed microfilament motor activity is regulated at multiple levels, including calcium signaling through calmodulin binding to myosin VI, which can alter motor activity and cargo interactions. Adaptor proteins such as Tom1 and LMTK2 modulate the recruitment of myosin VI to specific endosomal compartments, thereby controlling the spatial and temporal aspects of minus-end directed transport. Additionally, phosphorylation events and interactions with other cytoskeletal motors, such as dynein and kinesin, coordinate bidirectional transport and ensure proper cargo distribution.
minus-end directed microfilament motor activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MYO6 | Nonsyndromic deafness, cancer progression | Knockout or point-mutation in cell lines; mouse models |
| TOM1 | Endosomal trafficking defects | Knockout in HeLa cells; rescue with wild-type |
| LMTK2 | Neurodegeneration, endosomal sorting | Knock-in of kinase-dead mutant |
| DHC-1 | Lethality modulated by actin regulators | C. elegans dhc-1 mutant with actin gene knockdown |
| KCBP | Pollen tube growth defects | Plant knockout or overexpression |
Hearing Loss and Myosin VI Dysfunction
Mutations in MYO6, the gene encoding the minus-end directed motor myosin VI, are associated with nonsyndromic deafness and other auditory disorders. The unique motility of myosin VI is essential for maintaining the structure and function of hair cells in the inner ear, and its disruption leads to progressive hearing loss.
Endosomal Trafficking Defects and Neurodegeneration
Defects in minus-end directed microfilament motor activity can impair endosomal trafficking, which is a hallmark of neurodegenerative diseases. Myosin VI interacts with adaptors like Tom1 and LMTK2 to regulate early endosome dynamics, and disruption of these interactions may contribute to neuronal dysfunction.
Cancer Cell Migration and Invasion
Minus-end directed motor activity contributes to cell migration and invasion, processes that are critical for cancer metastasis. Myosin VI is often overexpressed in cancer cells, where it supports filopodia formation and endosome clustering, promoting invasive behavior.
From minus-end directed microfilament motor activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does MYO6 knockout impair endosome clustering? | MYO6 knockout cell line (e.g., HeLa) |
| How does a specific MYO6 mutation affect motor directionality? | Point-mutation knock-in of MYO6 |
| Can tagged MYO6 rescue endosomal trafficking? | Knock-in of fluorescently tagged MYO6 |
| Does overexpression of MYO6 increase filopodia formation? | Overexpression of MYO6 in cultured cells |
| What adaptors are required for MYO6 recruitment? | Knockout of TOM1 or LMTK2 |
| How does dynein loss affect actin motor function? | dhc-1 mutant in C. elegans with actin regulators |
How to Study the minus-end directed microfilament motor activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging | Movement of fluorescently tagged motors and cargo | Visualizing endosome clustering and filopodia |
| In vitro motility assay | Speed and directionality of motor along actin | Characterizing myosin VI mutants |
| Affinity purification + mass spectrometry | Protein-protein interactions | Identifying adaptors like Tom1, LMTK2 |
| CRISPR knockout screen | Gene essentiality and modifiers | Finding actin regulators in dynein mutants |
| RNA-seq | Transcriptional changes upon motor perturbation | Assessing downstream effects of MYO6 loss |
| Proteomics | Global protein expression and modifications | Mapping signaling changes in motor mutants |
| FRAP | Dynamics of motor turnover at structures | Measuring exchange rates at endosomes |
| TIRF microscopy | Single-molecule motor stepping | Detailed mechanochemistry of myosin VI |
Live-Cell Imaging of Motor Dynamics
Live-cell imaging using fluorescently tagged myosin VI and endosomal markers allows researchers to visualize minus-end directed movement in real time. This approach can reveal defects in endosome clustering and filopodia formation in mutant cells.
In Vitro Motility Assays
In vitro motility assays using purified myosin VI and actin filaments can measure the speed and directionality of minus-end directed movement. These assays are essential for dissecting the mechanochemical properties of the motor.
Proteomic Identification of Adaptor Complexes
Affinity purification coupled with mass spectrometry can identify novel interactors of myosin VI, such as Tom1 and LMTK2, that regulate its function. This method helps map the interactome of minus-end directed motors.
CRISPR-Based Genetic Screens
CRISPR knockout screens can identify genes that modulate minus-end directed motor activity or compensate for its loss. Such screens have revealed actin regulators that mediate lethality in dynein mutants.
How CRISPR Can Be Used to Study GO:0060001 minus-end directed microfilament motor activity
Knockout
CRISPR knockout of MYO6 or its adaptors (e.g., TOM1, LMTK2) can abolish minus-end directed microfilament motor activity, leading to defects in endosomal trafficking and filopodia formation [1,3]. These models are valuable for studying the loss-of-function phenotypes associated with GO:0060001.
Point Mutation
Introducing point mutations into the motor domain of MYO6 via CRISPR can dissect the specific residues required for minus-end directed movement. Such models help distinguish between motor activity and cargo binding functions.
Knock-in
Knock-in of fluorescently tagged MYO6 allows real-time visualization of the motor in its endogenous context, enabling studies of its dynamics and localization. This approach preserves native regulation and can reveal subtle trafficking defects.
Overexpression
Overexpression of wild-type or mutant MYO6 can amplify minus-end directed motor activity, leading to increased filopodia formation and endosome clustering. This is useful for gain-of-function studies and for testing dominant-negative effects.
How EDITGENE Supports minus-end directed microfilament motor activity Research
Researchers studying minus-end directed microfilament motor activity-related genes often need to determine whether a candidate gene is causally involved in motor function, cargo trafficking, or disease phenotypes. EDITGENE provides a comprehensive suite of CRISPR services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for minus-end directed microfilament motor activity research.
Frequently Asked Questions About minus-end directed microfilament motor activity
What is minus-end directed microfilament motor activity?
It is a molecular motor activity that moves along actin filaments toward the minus (pointed) end using ATP hydrolysis, exemplified by myosin VI.
What genes are involved in minus-end directed microfilament motor activity?
The primary gene is MYO6, which encodes myosin VI; adaptors such as TOM1 and LMTK2 also play key roles [1,3].
Which protein moves toward the minus end of actin filaments?
Myosin VI is the only known myosin that moves toward the minus end of actin filaments.
What is the function of GO:0060001?
GO:0060001 describes ATP-dependent movement along actin filaments toward the pointed end, important for endocytosis, vesicle trafficking, and cell migration [1,3].
How is minus-end directed motor activity regulated?
It is regulated by calcium/calmodulin binding, adaptor proteins, and phosphorylation, which control motor recruitment and activity [1,3].
What diseases are associated with minus-end directed motor dysfunction?
Mutations in MYO6 cause nonsyndromic deafness, and defects in this activity are linked to endosomal trafficking disorders and cancer progression [1,3].
How can I study minus-end directed microfilament motor activity?
Use live-cell imaging, in vitro motility assays, proteomics, and CRISPR-based genetic models to dissect its mechanisms and functions [1,3,4].
What is the difference between plus-end and minus-end directed motors?
Plus-end directed myosins (e.g., myosin V) move toward the barbed end, while minus-end directed myosin VI moves toward the pointed end, enabling distinct cellular roles.
Can CRISPR be used to study GO:0060001?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are powerful tools to investigate the function of MYO6 and its adaptors [1,3].
What model systems are used to study minus-end directed motor activity?
Common models include cultured mammalian cells, C. elegans, yeast, and plant pollen tubes, each offering unique advantages [1,4,6,7].
Conclusion
Minus-end directed microfilament motor activity (GO:0060001) is a specialized molecular function driven by myosin VI that moves cargo toward the pointed end of actin filaments. Its unique directionality is critical for endosomal trafficking, filopodia formation, and cell migration, and its dysfunction is linked to deafness and cancer [1,3]. Understanding this activity requires integrated approaches, including live-cell imaging, in vitro assays, and CRISPR-based genetics [1,3,4]. EDITGENE provides comprehensive CRISPR services to support research into GO:0060001 and its associated genes, helping to accelerate discoveries in cytoskeletal biology and disease [1,3].
References
- 1. Masters TA et al.. 2017. Filopodia formation and endosome clustering induced by mutant plus-end-directed myosin VI.. Proc Natl Acad Sci U S A 114(7):1595-1600 PMID: 28143933
- 3. O'Loughlin T et al.. 2018. The MYO6 interactome reveals adaptor complexes coordinating early endosome and cytoskeletal dynamics.. EMBO Rep 19(4) PMID: 29467281
- 4. Gil-Krzewska AJ et al.. 2010. Regulators of the actin cytoskeleton mediate lethality in a Caenorhabditis elegans dhc-1 mutant.. Mol Biol Cell 21(15):2707-20 PMID: 20554764
- 5. Rogers SL et al.. 1998. Myosin cooperates with microtubule motors during organelle transport in melanophores.. Curr Biol 8(3):161-4 PMID: 9443916
- 6. Lazzaro MD et al.. 2013. Polarized cell growth, organelle motility, and cytoskeletal organization in conifer pollen tube tips are regulated by KCBP, the calmodulin-binding kinesin.. Planta 238(3):587-97 PMID: 23784715
- 7. Ten Hoopen R et al.. 2012. Mechanism for astral microtubule capture by cortical Bud6p priming spindle polarity in S. cerevisiae.. Curr Biol 22(12):1075-83 PMID: 22608510
