GO:0090076 relaxation of skeletal muscle: Calcium Handling Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0090076 relaxation of skeletal muscle is the biological process that reduces the extent of skeletal muscle contraction, primarily by removing calcium from the cytoplasm into the sarcoplasmic reticulum lumen through Ca2+ ATPases.
• Efficient relaxation is essential for normal locomotion, posture, and metabolic flexibility, and its impairment contributes to muscle fatigue, injury, and disease.
• Key molecular players include SERCA1 (ATP2A1), the ryanodine receptor (RYR1), calsequestrin (CASQ1), and regulatory proteins such as phospholamban (PLN) and sarcolipin (SLN).
• Relaxation is tightly coupled to energy metabolism and vascular supply; microdialysis and ultrasound studies show that resting muscle metabolism and passive mechanics influence relaxation kinetics.
• Aging, exercise training, and sex modulate sympathetic vasoconstriction and microvascular reactivity, which can indirectly affect skeletal muscle relaxation and recovery.
• CRISPR-based models (knockout, point mutation, knock-in, overexpression) enable precise dissection of calcium-handling genes in skeletal muscle relaxation and related pathologies.
Description
Skeletal muscle relaxation is the physiological process that reverses contraction, allowing muscles to return to a low-tension state. According to the Gene Ontology, GO:0090076 relaxation of skeletal muscle is defined as a process in which the extent of skeletal muscle tissue contraction is reduced, involving the removal of calcium from the cytoplasm to the sarcoplasmic reticulum lumen through the action of Ca2+ ATPases. This process is fundamental for coordinated movement, prevention of tetany, and energy conservation. Defects in relaxation underlie several myopathies and contribute to muscle fatigue and injury. Researchers study relaxation to understand calcium homeostasis, excitation-contraction coupling, and metabolic flexibility in health and disease. The process is also relevant to exercise science, aging, and rehabilitation, where recovery from contraction is critical for performance and tissue repair.
relaxation of skeletal muscle At A Glance
| GO ID | GO:0090076 |
|---|---|
| GO term | relaxation of skeletal muscle |
| Ontology | biological_process |
| Synonym | none |
| Major function | Reduction of skeletal muscle contraction via calcium removal from cytoplasm to sarcoplasmic reticulum lumen by Ca2+ ATPases |
| Related cellular component | Sarcoplasmic reticulum, transverse tubules, myofibrils |
| Key molecular players | SERCA1 (ATP2A1), RYR1, CASQ1, PLN, SLN |
| Associated processes | Excitation-contraction coupling, calcium homeostasis, energy metabolism |
| Relevance | Muscle fatigue, injury, myopathies, metabolic disorders, aging |
What Is GO:0090076?
In our own words, GO:0090076 relaxation of skeletal muscle describes the biological process that decreases the extent of contraction in skeletal muscle tissue. It is driven by the active transport of calcium ions from the cytoplasm back into the sarcoplasmic reticulum lumen, primarily via sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCAs). This removal of cytosolic calcium leads to dissociation of calcium from troponin, re-establishment of the tropomyosin block on actin, and consequent muscle fiber relaxation.
Why Is relaxation of skeletal muscle Important in Cell Biology?
Relaxation of skeletal muscle is essential for normal movement, posture, and prevention of sustained contraction that would otherwise cause tetany or rhabdomyolysis. It also plays a critical role in energy metabolism and recovery after exercise, as efficient calcium reuptake restores ion gradients and prepares the fiber for subsequent contractions. Impaired relaxation is linked to muscle fatigue, injury, and diseases such as Brody myopathy and malignant hyperthermia. Moreover, relaxation kinetics influence athletic performance and rehabilitation outcomes, making it a key target for exercise science and clinical research.
• Enables coordinated movement and prevents tetanic contraction by terminating the calcium signal.
• Supports muscle recovery and repair after injury by restoring ion homeostasis.
• Contributes to metabolic flexibility and energy balance in skeletal muscle.
• Influences athletic performance and training adaptations.
• Is affected by aging, exercise training, and sex via vascular and microvascular changes.
• Can be modulated by dietary factors such as coffee intake, affecting microvascular reactivity and oxygen extraction.
• Is dysregulated in chronic diseases like COPD, where network modules reveal muscle dysfunction.
• Can be assessed noninvasively using ultrasound to evaluate passive muscle mechanics.
• Provides a readout for calcium-handling gene function in CRISPR models.
• Serves as a therapeutic target for myopathies and metabolic disorders.
What Happens During relaxation of skeletal muscle?
Calcium reuptake by SERCA
In simple terms: After a muscle contracts, calcium must be pumped back into storage to let the muscle relax.
The primary event in relaxation is the active transport of Ca2+ from the cytosol into the sarcoplasmic reticulum lumen by sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA), particularly the skeletal muscle isoform SERCA1 (ATP2A1). This ATP-dependent process lowers cytosolic Ca2+ concentration, leading to dissociation of calcium from troponin C and re-establishment of the tropomyosin block on actin, thereby reducing contraction.
Dissociation of calcium from troponin
In simple terms: When calcium leaves, the switch that keeps the muscle contracting turns off.
As cytosolic Ca2+ decreases, calcium dissociates from troponin C, causing tropomyosin to shift back and block myosin-binding sites on actin. This prevents cross-bridge cycling and allows the muscle fiber to relax. The rate of calcium dissociation is influenced by the kinetics of SERCA and the buffering capacity of the sarcoplasmic reticulum.
Role of regulatory proteins
In simple terms: Small proteins act like brakes or accelerators on the calcium pump.
Phospholamban (PLN) and sarcolipin (SLN) regulate SERCA activity. In skeletal muscle, SLN is predominantly expressed and can uncouple SERCA ATP hydrolysis from calcium transport, affecting relaxation and thermogenesis. PLN is more prominent in cardiac muscle but may also play a role in skeletal muscle under certain conditions. Their modulation affects relaxation speed and energy efficiency.
Energy metabolism and vascular supply
In simple terms: Relaxation needs energy and proper blood flow to deliver oxygen and remove waste.
Relaxation is an energy-demanding process that relies on ATP supply from oxidative and glycolytic metabolism. Metabolic flexibility, the ability to switch between fuel sources, supports efficient calcium handling. Vascular supply and microvascular reactivity influence oxygen delivery and metabolite removal, which can affect relaxation kinetics, especially during recovery from exercise.
Passive mechanical properties
In simple terms: The elastic properties of muscle also contribute to how quickly it returns to rest.
Beyond active calcium removal, passive mechanical properties of skeletal muscle, such as stiffness and viscoelasticity, contribute to the relaxation phase. Noninvasive ultrasound assessments have shown that passive muscle mechanics can be modeled as a composite material, providing insights into how structural components influence relaxation and recovery.
Key Genes Involved in GO:0090076 relaxation of skeletal muscle
The following genes and proteins are central to the regulation and execution of skeletal muscle relaxation, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ATP2A1 | SERCA1 calcium pump; removes Ca2+ from cytosol | Primary driver of relaxation; mutations cause Brody myopathy |
| RYR1 | Ryanodine receptor; releases Ca2+ from SR | Defects cause malignant hyperthermia and central core disease |
| CASQ1 | Calsequestrin; Ca2+ buffering in SR lumen | Modulates Ca2+ storage and release; linked to myopathies |
| PLN | Phospholamban; regulates SERCA activity | Influences relaxation speed and cardiac/skeletal muscle function |
| SLN | Sarcolipin; regulates SERCA and thermogenesis | Affects relaxation efficiency and energy expenditure |
| TNNC1 | Troponin C; Ca2+ sensor for contraction | Relaxation requires Ca2+ dissociation from TNNC1 |
| TNNI1 | Troponin I; inhibits actin-myosin interaction | Key switch for relaxation |
| TNNT1 | Troponin T; links troponin complex to tropomyosin | Mutations cause nemaline myopathy |
| TPM1 | Tropomyosin; blocks myosin binding sites | Relaxation depends on tropomyosin repositioning |
| MYH1 | Myosin heavy chain; motor protein | Cross-bridge cycling must cease for relaxation |
| ACTN2 | Alpha-actinin-2; Z-disc structural protein | Maintains sarcomere integrity during relaxation |
| CACNA1S | Voltage sensor in T-tubules | Couples excitation to Ca2+ release; affects relaxation onset |
| ATP2B1 | Plasma membrane Ca2+ ATPase | Extrudes Ca2+ to extracellular space; contributes to relaxation |
| SLC8A1 | Na+/Ca2+ exchanger | Participates in Ca2+ homeostasis and relaxation |
| CALM1 | Calmodulin; Ca2+ sensor | Regulates Ca2+ signaling and relaxation |
| PRKAA1 | AMPK catalytic subunit; energy sensor | Links metabolic state to calcium handling |
| PPARGC1A | PGC-1alpha; mitochondrial biogenesis | Supports oxidative capacity for relaxation |
How Is relaxation of skeletal muscle Regulated?
Relaxation of skeletal muscle is regulated at multiple levels. Calcium reuptake by SERCA is modulated by phospholamban (PLN) and sarcolipin (SLN), which can inhibit or uncouple the pump, respectively. Post-translational modifications, such as phosphorylation of PLN by PKA or CaMKII, can relieve inhibition and accelerate relaxation. Energy status, sensed by AMPK, influences calcium handling and metabolic flexibility. Vascular tone and microvascular reactivity, affected by aging, exercise training, and sex, can indirectly modulate relaxation by altering oxygen and substrate delivery. Dietary factors such as coffee intake may also influence microvascular reactivity and oxygen extraction during exercise, potentially affecting relaxation kinetics. In chronic diseases like COPD, network modules reveal widespread muscle dysfunction that includes impaired relaxation.
relaxation of skeletal muscle and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ATP2A1 | Brody myopathy; delayed relaxation | Knockout or point mutation in C2C12 myotubes; SERCA1 activity assay |
| RYR1 | Malignant hyperthermia; central core disease | Knock-in of patient mutations in mouse models; Ca2+ release assays |
| CASQ1 | Vacuolar myopathy; altered Ca2+ buffering | Knockout mice; muscle histology and calcium imaging |
| SLN | Thermogenesis and relaxation efficiency | Overexpression in skeletal muscle; metabolic and relaxation measurements |
| PLN | Cardiac and skeletal muscle relaxation | Knockout and phospho-mutant knock-in; SERCA activity assays |
Brody myopathy and calcium-handling defects
Brody myopathy is caused by mutations in ATP2A1, leading to impaired SERCA1 function and delayed muscle relaxation. Patients present with exercise-induced muscle stiffness and cramps. This condition directly links GO:0090076 to human disease and highlights the importance of calcium reuptake for normal muscle function.
Malignant hyperthermia and RYR1 mutations
Mutations in RYR1 can cause malignant hyperthermia, a life-threatening reaction to anesthetics characterized by excessive calcium release and sustained contraction. Impaired relaxation contributes to the hypermetabolic state. Studying relaxation mechanisms helps understand and manage this disorder.
Muscle injury and recovery
Muscle injuries, such as strains and contusions, disrupt calcium homeostasis and relaxation. Optimizing recovery involves restoring efficient calcium reuptake and metabolic function. Research on relaxation pathways informs rehabilitation strategies.
COPD and muscle dysfunction
Chronic obstructive pulmonary disease (COPD) is associated with skeletal muscle dysfunction, including altered calcium handling and relaxation. Network analysis has uncovered modules of genes related to muscle weakness, providing insights into potential therapeutic targets.
From relaxation of skeletal muscle-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does ATP2A1 loss impair relaxation? | ATP2A1 knockout in C2C12 myotubes or mouse skeletal muscle |
| Does a specific RYR1 mutation alter calcium release and relaxation? | RYR1 point mutation knock-in in mice |
| Can SERCA1 overexpression accelerate relaxation? | SERCA1 overexpression in skeletal muscle cells or mice |
| How does SLN regulate SERCA and relaxation? | SLN knockout or overexpression models |
| What is the role of PLN phosphorylation in relaxation? | PLN phospho-mutant knock-in mice |
| Can CRISPR activation rescue relaxation defects? | CRISPRa targeting ATP2A1 in patient-derived cells |
How to Study the relaxation of skeletal muscle Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Calcium imaging | Cytosolic Ca2+ transients | Assess SERCA function and relaxation kinetics |
| Force measurements | Muscle tension and relaxation time | Evaluate genetic effects on relaxation |
| Ultrasound | Passive muscle mechanics | Noninvasive assessment of relaxation properties |
| Microdialysis | Interstitial metabolites | Monitor metabolic recovery after contraction |
| RNA-seq | Gene expression profiles | Identify pathways linked to relaxation defects |
| Network analysis | Gene co-expression modules | Uncover mechanisms of muscle dysfunction |
| Western blot | Protein expression and phosphorylation | Quantify SERCA, PLN, SLN levels |
| ATPase assay | SERCA ATP hydrolysis | Measure pump activity directly |
Calcium imaging
Calcium imaging using fluorescent dyes (e.g., Fura-2, Fluo-4) allows real-time measurement of cytosolic Ca2+ transients in isolated muscle fibers or myotubes. The decay phase of the Ca2+ transient reflects relaxation kinetics and SERCA activity.
Muscle mechanics
Force measurements in isolated muscle fibers or whole muscle preparations quantify relaxation time and tension decline. These methods are used to assess the functional impact of genetic modifications.
Ultrasound and passive mechanics
Noninvasive ultrasound can assess passive skeletal muscle mechanics as a composite material, providing insights into structural contributions to relaxation without invasive procedures.
Microdialysis and metabolomics
Microdialysis of skeletal muscle at rest allows sampling of interstitial metabolites, reflecting metabolic state and recovery. This technique helps link energy metabolism to relaxation capacity.
Transcriptomics and network analysis
RNA-seq and network module analysis can identify gene expression changes associated with muscle dysfunction and relaxation defects, as shown in COPD studies.
How CRISPR Can Be Used to Study GO:0090076 relaxation of skeletal muscle
Knockout
CRISPR knockout of ATP2A1 or other calcium-handling genes in skeletal muscle cells or animal models can abolish or reduce relaxation, providing causal evidence for gene function. These models are useful for studying Brody myopathy and testing therapeutic rescue strategies.
Point Mutation
Introducing patient-specific point mutations (e.g., in RYR1 or ATP2A1) via CRISPR allows precise modeling of disease-associated variants. These models help dissect how single amino acid changes affect calcium handling and relaxation.
Knock-in
Knock-in of reporter tags (e.g., fluorescent proteins) or regulatory elements enables real-time tracking of SERCA1 localization and dynamics during relaxation. This approach provides spatial and temporal insights into calcium reuptake.
Overexpression
CRISPR activation or transgenic overexpression of SERCA1 or its regulators can enhance relaxation and rescue defects. Overexpression models are valuable for testing whether increasing calcium reuptake improves muscle function in disease contexts.
How EDITGENE Supports relaxation of skeletal muscle Research
Researchers studying relaxation of skeletal muscle-related genes often need to determine whether a candidate gene is causally involved in calcium handling, contraction termination, or metabolic recovery. Precise genetic models are essential to move from correlation to causation. EDITGENE provides a comprehensive suite of CRISPR services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for relaxation of skeletal muscle research.
Frequently Asked Questions About relaxation of skeletal muscle
What is GO:0090076 relaxation of skeletal muscle?
GO:0090076 is a Gene Ontology biological process term describing the reduction of skeletal muscle contraction, primarily through calcium removal from the cytoplasm to the sarcoplasmic reticulum lumen by Ca2+ ATPases.
What genes are involved in relaxation of skeletal muscle?
Key genes include ATP2A1 (SERCA1), RYR1, CASQ1, PLN, SLN, and troponin/tropomyosin components such as TNNC1, TNNI1, and TPM1.
How does calcium reuptake cause muscle relaxation?
SERCA pumps calcium back into the sarcoplasmic reticulum, lowering cytosolic Ca2+, which causes calcium to dissociate from troponin and blocks myosin binding to actin, leading to relaxation.
What diseases are linked to defective muscle relaxation?
Brody myopathy (ATP2A1 mutations), malignant hyperthermia (RYR1 mutations), and muscle injuries are associated with impaired relaxation.
How can I study relaxation of skeletal muscle in the lab?
Common methods include calcium imaging, force measurements, ultrasound, microdialysis, and transcriptomics, often combined with CRISPR models.
What is the role of SERCA1 in skeletal muscle relaxation?
SERCA1 (ATP2A1) is the primary calcium pump that removes Ca2+ from the cytosol, initiating relaxation. Its activity determines relaxation speed.
Can CRISPR be used to model Brody myopathy?
Yes, CRISPR knockout or point mutation of ATP2A1 in muscle cells can replicate Brody myopathy phenotypes and test therapeutic approaches.
How does exercise affect muscle relaxation?
Exercise training can improve metabolic flexibility and vascular function, indirectly enhancing relaxation and recovery.
What is the connection between aging and muscle relaxation?
Aging alters sympathetic vasoconstriction and microvascular reactivity, which can impair oxygen delivery and relaxation kinetics.
Does diet influence skeletal muscle relaxation?
Coffee intake has been shown to affect microvascular reactivity and oxygen extraction during exercise, potentially influencing relaxation.
Conclusion
GO:0090076 relaxation of skeletal muscle is a fundamental biological process that reverses contraction through calcium reuptake by SERCA and associated regulatory mechanisms. Its dysfunction contributes to myopathies, muscle fatigue, and chronic disease, making it a critical area of research. Advances in CRISPR modeling and noninvasive assessment tools are enabling deeper insights into relaxation mechanisms and potential therapies. EDITGENE offers comprehensive CRISPR services to support discovery in this field.
References
- 1. Goodpaster BH et al.. 2017. Metabolic Flexibility in Health and Disease.. Cell Metab 25(5):1027-1036 PMID: 28467922
- 2. Suchomel TJ et al.. 2018. The Importance of Muscular Strength: Training Considerations.. Sports Med 48(4):765-785 PMID: 29372481
- 3. Järvinen TA et al.. 2007. Muscle injuries: optimising recovery.. Best Pract Res Clin Rheumatol 21(2):317-31 PMID: 17512485
- 4. DeLorey DS. 2021. Sympathetic vasoconstriction in skeletal muscle: modulatory effects of aging, exercise training, and sex.. Appl Physiol Nutr Metab 46(12):1437-1447 PMID: 34348066
- 5. Leng B et al.. 2024. Effects of coffee intake on skeletal muscle microvascular reactivity at rest and oxygen extraction during exercise: a randomized cross-over trial.. J Int Soc Sports Nutr 21(1):2409673 PMID: 39351657
- 6. Tényi Á et al.. 2018. Network modules uncover mechanisms of skeletal muscle dysfunction in COPD patients.. J Transl Med 16(1):34 PMID: 29463285
- 7. Dong J et al.. 2022. Noninvasive Assessment of In Vivo Passive Skeletal Muscle Mechanics as a Composite Material Using Biomedical Ultrasound.. IEEE Trans Biomed Eng 69(3):1162-1172 PMID: 34559632
- 8. Henriksson J. 1999. Microdialysis of skeletal muscle at rest.. Proc Nutr Soc 58(4):919-23 PMID: 10817159
