GO:0017018 myosin phosphatase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0017018 myosin phosphatase activity is defined as the catalysis of the reaction: phosphomyosin + H2O = myosin + phosphate.
• The holoenzyme is a trimeric complex of a catalytic PP1c subunit, a myosin-binding targeting subunit (MYPT1 or MYPT2), and a small 20-kDa subunit.
• Myosin phosphatase activity is inhibited by phosphorylation of the MYPT1 subunit by kinases such as Raf-1, providing a key regulatory node.
• The enzyme is central to smooth muscle relaxation and to non-muscle cell processes including cytokinesis and cell migration.
• Dysregulated myosin phosphatase activity has been linked to airway hyperresponsiveness, cardiovascular disease, and cancer.
• CRISPR-based knockout, point-mutation, and knock-in models enable causal dissection of myosin phosphatase subunit function.
Description
Myosin phosphatase activity (GO:0017018) is a molecular function that removes phosphate groups from phosphorylated myosin, directly opposing the action of myosin light chain kinase. This enzymatic activity is essential for the regulation of smooth muscle contraction and relaxation, as well as for non-muscle cell motility, cytokinesis, and morphology. The enzyme is a holoenzyme composed of a catalytic subunit (PP1c) bound to a myosin-targeting subunit (MYPT1 or MYPT2) and a small 20-kDa subunit. Because it controls the phosphorylation state of myosin, myosin phosphatase activity is a critical determinant of cellular contractility and has been implicated in diseases ranging from asthma to cancer. Researchers study this activity to understand how cells regulate force generation and to identify therapeutic targets for contractile disorders.
myosin phosphatase activity At A Glance
| GO ID | GO:0017018 |
|---|---|
| GO term | myosin phosphatase activity |
| Ontology | molecular_function |
| Synonym | myosin phosphatase, intrinsic catalyst activity; myosin phosphatase myosin binding |
| Major function | Catalysis of the reaction: phosphomyosin + H2O = myosin + phosphate |
| Enzyme class | Protein phosphatase (hydrolase) |
| Substrate | Phosphorylated myosin (phosphomyosin) |
| Products | Myosin and phosphate |
| Cofactors | Metal ions (e.g., Mn2+) may be required for PP1c activity |
What Is GO:0017018?
Myosin phosphatase activity (GO:0017018) is the catalysis of the reaction: phosphomyosin + H2O = myosin + phosphate. In other words, it is the enzymatic removal of a phosphate group from a phosphorylated myosin molecule, converting it back to its dephosphorylated form. This activity is intrinsic to the catalytic subunit of the myosin phosphatase holoenzyme, which is a member of the protein phosphatase 1 (PP1) family.
Why Is myosin phosphatase activity Important in Cell Biology?
Myosin phosphatase activity is a fundamental regulator of cellular contractility and motility, acting as the primary counterbalance to myosin light chain kinase. By dephosphorylating myosin, it controls smooth muscle relaxation, non-muscle cell cytokinesis, and cell migration. Its dysfunction is associated with pathological conditions such as airway hyperresponsiveness, hypertension, and cancer progression. Understanding its regulation provides insights into basic cell biology and offers potential therapeutic avenues for contractile and proliferative diseases.
• Regulates smooth muscle contraction and relaxation by dephosphorylating myosin.
• Controls non-muscle cell motility, cytokinesis, and morphology.
• Its inhibition by Raf-1-mediated phosphorylation of MYPT1 links signaling pathways to contractility.
• Dysregulation contributes to airway hyperresponsiveness in asthma models.
• Implicated in cardiovascular diseases such as hypertension and heart failure.
• Plays a role in cancer cell invasion and metastasis.
• Targeted by cell-penetrating peptides for modulating activity.
• Subject to regulation by FAT10-mediated stabilization of MYPT2 isoforms.
• A key node for understanding protein phosphatase 1 targeting and specificity.
• Potential therapeutic target for smooth muscle disorders.
What Happens During myosin phosphatase activity?
Substrate recognition and binding
In simple terms: The enzyme first grabs onto its target, the phosphorylated myosin.
The myosin phosphatase holoenzyme recognizes and binds to phosphorylated myosin through its myosin-binding subunit, MYPT1 or MYPT2. This targeting subunit anchors the catalytic PP1c subunit to the substrate, ensuring specificity. The small 20-kDa subunit also contributes to the holoenzyme stability and substrate presentation.
Catalytic dephosphorylation
In simple terms: The enzyme then removes the phosphate group from myosin.
Once bound, the catalytic PP1c subunit hydrolyzes the phosphoester bond on phosphomyosin, releasing inorganic phosphate and regenerating unphosphorylated myosin. This reaction is metal-dependent and proceeds via a nucleophilic attack by a water molecule.
Regulation by inhibitory phosphorylation
In simple terms: The enzyme can be switched off by adding a phosphate to its targeting subunit.
Phosphorylation of MYPT1 at specific residues (e.g., Thr696 and Thr853) by kinases such as Raf-1 inhibits myosin phosphatase activity. This provides a dynamic mechanism to modulate contractility in response to cellular signals.
Role in smooth muscle relaxation
In simple terms: By removing phosphate from myosin, the enzyme helps muscles relax.
In smooth muscle, myosin phosphatase activity counteracts myosin light chain kinase-mediated phosphorylation, leading to decreased myosin ATPase activity and muscle relaxation. This process is essential for maintaining vascular tone and airway diameter.
Participation in non-muscle cell functions
In simple terms: The enzyme also helps cells divide and move.
In non-muscle cells, myosin phosphatase activity regulates cytokinesis, cell migration, and focal adhesion dynamics by controlling the phosphorylation state of myosin II. Disruption of this activity leads to defects in cell division and motility.
Key Genes Involved in GO:0017018 myosin phosphatase activity
The following genes encode subunits and regulators of the myosin phosphatase holoenzyme and its associated pathways.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PPP1CB | Catalytic subunit PP1c beta | Enzymatic core of myosin phosphatase |
| PPP1CA | Catalytic subunit PP1c alpha | Alternative catalytic isoform |
| PPP1CC | Catalytic subunit PP1c gamma | Alternative catalytic isoform |
| PPP1R12A | Myosin-binding subunit MYPT1 | Targeting and regulation of myosin phosphatase |
| PPP1R12B | Myosin-binding subunit MYPT2 | Targeting subunit in muscle and brain |
| PPP1R12C | Myosin-binding subunit MYPT3 | Related targeting subunit |
| PPP1R14A | CPI-17, inhibitor of myosin phosphatase | Mediates PKC-dependent inhibition |
| PPP1R14B | PHI-1, inhibitor of myosin phosphatase | Modulates activity in smooth muscle |
| PPP1R14C | KEPI, inhibitor of myosin phosphatase | Regulates activity in specific tissues |
| MYLK | Myosin light chain kinase | Opposing enzyme that phosphorylates myosin |
| MYL9 | Myosin regulatory light chain | Substrate of myosin phosphatase |
| MYL12A | Myosin regulatory light chain | Substrate of myosin phosphatase |
| MYL12B | Myosin regulatory light chain | Substrate of myosin phosphatase |
| RAF1 | Raf-1 kinase | Phosphorylates and inhibits MYPT1 |
| FAT10 | Ubiquitin-like modifier | Stabilizes MYPT2 isoforms |
| RIPOR2 | p116Rip | Promotes myosin phosphatase activity in airway smooth muscle |
| ROCK1 | Rho-associated kinase | Inhibits myosin phosphatase via MYPT1 phosphorylation |
How Is myosin phosphatase activity Regulated?
Myosin phosphatase activity is regulated by multiple mechanisms. Phosphorylation of the MYPT1 subunit by kinases such as Raf-1 and Rho-associated kinase (ROCK) inhibits the enzyme, thereby promoting myosin phosphorylation and contraction. Conversely, dephosphorylation of MYPT1 or binding of activator proteins like p116Rip can enhance activity. Additionally, the ubiquitin-like protein FAT10 differentially stabilizes MYPT2 isoforms, affecting enzyme levels. Inhibitor proteins such as CPI-17 and PHI-1 also modulate activity in a phosphorylation-dependent manner.
myosin phosphatase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PPP1R12A | Airway hyperresponsiveness | Knockout mouse or smooth muscle cell line |
| PPP1R12B | Cardiovascular disease | Knock-in mouse with phospho-mutant MYPT2 |
| PPP1R14A | Asthma and hypertension | Overexpression in smooth muscle cells |
| RAF1 | Cancer and contractile disorders | Point mutation to prevent MYPT1 phosphorylation |
| RIPOR2 | Airway smooth muscle relaxation | Knockout in airway smooth muscle cells |
Airway hyperresponsiveness and asthma
Decreased myosin phosphatase activity in airway smooth muscle contributes to enhanced contractility and airway hyperresponsiveness, a hallmark of asthma. Studies in ragweed pollen-sensitized canine tracheal smooth muscle showed reduced myosin light chain phosphatase activity. p116Rip promotes myosin phosphatase activity and may protect against hyperresponsiveness.
Cardiovascular disease
Altered myosin phosphatase activity is implicated in hypertension, heart failure, and vascular remodeling. Inhibition of the enzyme by Rho-kinase pathways leads to increased vascular tone. Dysregulation of MYPT1 phosphorylation has been observed in cardiovascular pathologies.
Cancer
Myosin phosphatase activity influences cell migration, invasion, and cytokinesis, processes critical for cancer metastasis. Loss of MYPT1 expression or function has been associated with tumor progression in various cancers. Targeting myosin phosphatase may offer therapeutic opportunities.
From myosin phosphatase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of MYPT1 knockout on smooth muscle contraction? | PPP1R12A knockout mouse or cell line |
| How does phosphorylation of MYPT1 at Thr696 regulate activity? | Point mutation (T696A) knock-in |
| What is the role of MYPT2 in cardiac function? | PPP1R12B knockout or knock-in mouse |
| Can overexpression of p116Rip enhance myosin phosphatase activity? | Overexpression of RIPOR2 in airway smooth muscle cells |
| How does FAT10 stabilize MYPT2 isoforms? | Knock-in of tagged MYPT2 or FAT10 knockout |
| What is the impact of CPI-17 phosphorylation on myosin phosphatase? | Point mutation of PPP1R14A at Thr38 |
How to Study the myosin phosphatase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Malachite green phosphatase assay | Release of inorganic phosphate | Quantifying myosin phosphatase activity in vitro |
| Western blot with p-MLC antibodies | Phosphorylation state of myosin | Assessing activity in cells and tissues |
| Western blot with p-MYPT1 antibodies | Inhibitory phosphorylation of MYPT1 | Monitoring regulation by kinases |
| In vitro kinase assay | Phosphorylation of MYPT1 by Raf-1 | Studying inhibitory mechanisms |
| Cell-penetrating peptide treatment | Modulation of activity in live cells | Functional studies of myosin phosphatase |
| Immunoprecipitation | Holoenzyme composition | Isolating active complexes |
| CRISPR knockout | Loss-of-function phenotypes | Determining subunit necessity |
| Proteomics | Interaction partners and post-translational modifications | Identifying novel regulators |
Phosphatase activity assays
Myosin phosphatase activity is typically measured using phosphorylated myosin light chains as substrate and detecting released phosphate via colorimetric or fluorometric assays. These assays can be performed on immunoprecipitated holoenzyme or recombinant subunits.
Phosphorylation-specific antibodies and Western blotting
Western blotting with antibodies against phosphorylated myosin light chain (e.g., p-MLC) and phosphorylated MYPT1 (e.g., p-MYPT1 Thr696) allows assessment of myosin phosphatase activity in cells and tissues.
In vitro kinase/phosphatase assays
Recombinant kinases such as Raf-1 can be used to phosphorylate MYPT1, followed by measuring the resulting inhibition of myosin phosphatase activity. This approach dissects regulatory phosphorylation events.
Cell-penetrating peptide delivery
Cell-penetrating peptides based on the MYPT1 sequence can be introduced into cells to modulate myosin phosphatase activity, enabling studies of downstream effects on contractility and motility.
How CRISPR Can Be Used to Study GO:0017018 myosin phosphatase activity
Knockout
CRISPR knockout of PPP1R12A (MYPT1) or PPP1CB (PP1c) eliminates myosin phosphatase activity, leading to increased myosin phosphorylation and enhanced contractility. Such models are valuable for studying the role of the enzyme in smooth muscle and non-muscle cells.
Point Mutation
Point mutations can be introduced to prevent or mimic phosphorylation of regulatory sites, such as MYPT1 Thr696 or Thr853, to dissect their role in enzyme inhibition. For example, a T696A mutation blocks Raf-1-mediated inhibition.
Knock-in
Knock-in of tagged MYPT1 or MYPT2 (e.g., GFP or FLAG) allows visualization and purification of the holoenzyme for interaction studies. Knock-in of disease-associated mutations can model human pathologies.
Overexpression
Overexpression of wild-type or mutant MYPT1, PP1c, or activator proteins like p116Rip can enhance myosin phosphatase activity and reverse hypercontractile phenotypes. This approach is useful for gain-of-function studies.
How EDITGENE Supports myosin phosphatase activity Research
Researchers studying myosin phosphatase activity-related genes often need to determine whether a candidate gene is causally involved in contractility, motility, or disease. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell and animal models, enabling rigorous functional validation of myosin phosphatase components and regulators.
Contact EDITGENE today to design your custom CRISPR model for myosin phosphatase activity research.
Frequently Asked Questions About myosin phosphatase activity
What is myosin phosphatase activity?
Myosin phosphatase activity (GO:0017018) is the enzymatic removal of a phosphate group from phosphorylated myosin, catalyzing the reaction: phosphomyosin + H2O = myosin + phosphate.
What genes are involved in myosin phosphatase activity?
Key genes include PPP1CB (catalytic subunit), PPP1R12A (MYPT1), PPP1R12B (MYPT2), and regulators such as RAF1 and RIPOR2.
How is myosin phosphatase activity regulated?
It is regulated by phosphorylation of the MYPT1 subunit by kinases like Raf-1 and ROCK, which inhibits activity, and by activator proteins like p116Rip.
What diseases are associated with myosin phosphatase activity?
Dysregulation is linked to asthma, cardiovascular disease, and cancer.
What is the role of myosin phosphatase in smooth muscle?
It promotes smooth muscle relaxation by dephosphorylating myosin, counteracting myosin light chain kinase.
How can I study myosin phosphatase activity in the lab?
Common methods include phosphatase activity assays, Western blotting for phosphorylated myosin and MYPT1, and CRISPR knockout models.
What is the structure of myosin phosphatase?
It is a trimeric holoenzyme consisting of a catalytic PP1c subunit, a myosin-binding subunit (MYPT1/2), and a small 20-kDa subunit.
Can myosin phosphatase activity be targeted therapeutically?
Yes, it is considered a potential target for smooth muscle disorders and cancer, with cell-penetrating peptides and small molecules under investigation.
What are the substrates of myosin phosphatase?
The primary substrate is phosphorylated myosin regulatory light chain (e.g., MYL9, MYL12A/B).
How does FAT10 affect myosin phosphatase?
FAT10 differentially stabilizes MYPT2 isoforms, thereby influencing myosin phosphatase activity.
Conclusion
Myosin phosphatase activity (GO:0017018) is a critical molecular function that governs myosin phosphorylation and thereby controls smooth muscle contraction, non-muscle cell motility, and cytokinesis. Its holoenzyme structure and regulatory mechanisms have been well characterized, revealing multiple layers of control by kinases and inhibitor proteins. Dysregulation of this activity contributes to diseases such as asthma, cardiovascular disorders, and cancer, making it an attractive therapeutic target. Continued research using advanced CRISPR models and biochemical assays will further elucidate its roles and therapeutic potential.
References
- 1. Komatsu S et al.. 2020. p116(Rip) promotes myosin phosphatase activity in airway smooth muscle cells.. J Cell Physiol 235(1):114-127 PMID: 31347175
- 2. Kiss A et al.. 2019. Myosin phosphatase: Unexpected functions of a long-known enzyme.. Biochim Biophys Acta Mol Cell Res 1866(1):2-15 PMID: 30076859
- 3. Liu X et al.. 1994. Myosin light chain phosphatase activity in ragweed pollen-sensitized canine tracheal smooth muscle.. Am J Respir Cell Mol Biol 11(6):676-81 PMID: 7946396
- 4. Ito M et al.. 2004. Myosin phosphatase: structure, regulation and function.. Mol Cell Biochem 259(1-2):197-209 PMID: 15124925
- 5. Kiss A et al.. 2025. Cell-Penetrating Peptide Based on Myosin Phosphatase Target Subunit Sequence Mediates Myosin Phosphatase Activity.. Biomolecules 15(5) PMID: 40427598
- 6. Hartshorne DJ. 1998. Myosin phosphatase: subunits and interactions.. Acta Physiol Scand 164(4):483-93 PMID: 9887971
- 7. Song SE et al.. 2023. FAT10 differentially stabilizes MYPT2 isoforms.. Biochem Biophys Res Commun 676:115-120 PMID: 37506472
- 8. Broustas CG et al.. 2002. Phosphorylation of the myosin-binding subunit of myosin phosphatase by Raf-1 and inhibition of phosphatase activity.. J Biol Chem 277(4):3053-9 PMID: 11719507
