GO:1990036 calcium ion import into sarcoplasmic reticulum: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990036 describes the directed movement of calcium ions into the sarcoplasmic reticulum, a process essential for muscle relaxation and intracellular calcium signaling.
• The sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) family, particularly SERCA2 in cardiac and skeletal muscle, is the primary pump driving this import.
• Redox regulation by ERdj5 and SEPN1 modulates SERCA activity and protects against oxidative stress, linking calcium import to cellular redox homeostasis.
• Dysregulation of sarcoplasmic reticulum calcium import is implicated in cardiac arrhythmias such as catecholaminergic polymorphic ventricular tachycardia (CPVT) and skeletal muscle pathologies.
• Key research methods include live-cell calcium imaging, SERCA activity assays, and CRISPR-based gene editing to dissect gene function.
• Understanding this process is critical for developing therapies targeting calcium handling in heart failure, myopathies, and metabolic disorders.
Description
Calcium ion import into the sarcoplasmic reticulum (SR) is a fundamental biological process that maintains intracellular calcium homeostasis and enables muscle contraction-relaxation cycles. This process is primarily mediated by the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pumps, which actively transport calcium ions from the cytosol into the SR lumen against a concentration gradient. The importance of this process extends beyond muscle physiology, as SR calcium stores regulate diverse signaling pathways, including apoptosis, gene expression, and metabolic control. Researchers study GO:1990036 to understand how calcium handling defects contribute to diseases such as heart failure, arrhythmias, and skeletal muscle myopathies. Recent advances in CRISPR gene editing and live-cell imaging have provided new tools to dissect the molecular players and regulatory mechanisms involved in SR calcium import.
calcium ion import into sarcoplasmic reticulum At A Glance
| GO ID | GO:1990036 |
|---|---|
| GO term | calcium ion import into sarcoplasmic reticulum |
| Ontology | biological_process |
| Synonym | None |
| Major function | Active transport of calcium ions into the sarcoplasmic reticulum lumen |
| Cellular location | Sarcoplasmic reticulum membrane |
| Key proteins | SERCA1, SERCA2, phospholamban, sarcolipin, ERdj5, SEPN1 |
| Associated diseases | CPVT, heart failure, skeletal muscle myopathies |
| Research methods | Calcium imaging, SERCA activity assays, CRISPR knockout, proteomics |
What Is GO:1990036?
GO:1990036, calcium ion import into sarcoplasmic reticulum, is defined as the directed movement of calcium ions (Ca2+) into the sarcoplasmic reticulum, a specialized endoplasmic reticulum compartment in muscle cells. This process requires energy and is typically mediated by ATP-dependent calcium pumps that translocate calcium from the cytoplasm into the SR lumen, thereby lowering cytosolic calcium concentrations and replenishing SR stores.
Why Is calcium ion import into sarcoplasmic reticulum Important in Cell Biology?
Calcium ion import into the sarcoplasmic reticulum is essential for muscle relaxation, as it removes calcium from the cytosol following contraction. This process also maintains the SR calcium store required for subsequent contraction cycles and modulates calcium-dependent signaling pathways that influence cell survival, metabolism, and gene expression. Defects in SR calcium import are linked to severe cardiac and skeletal muscle disorders, making it a critical area of biomedical research.
• Enables muscle relaxation by clearing cytosolic calcium after contraction.
• Maintains SR calcium stores necessary for excitation-contraction coupling.
• Regulates calcium-dependent signaling pathways involved in cell survival and metabolism.
• Dysfunction is associated with cardiac arrhythmias such as CPVT.
• Implicated in skeletal muscle pathologies including SEPN1-related myopathy.
• Redox regulation of SERCA by ERdj5 and SEPN1 links calcium import to oxidative stress responses.
• Target for therapeutic intervention in heart failure and muscle diseases.
• Provides a model system for studying active transport and membrane protein function.
• Essential for normal cardiac and skeletal muscle physiology.
• Involved in cellular calcium homeostasis across diverse cell types.
What Happens During calcium ion import into sarcoplasmic reticulum?
Calcium binding and pump activation
In simple terms: Calcium ions bind to the SERCA pump, which then gets ready to move them.
The sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) is a P-type ATPase that undergoes conformational changes upon calcium binding. In cardiac muscle, SERCA2a is the predominant isoform, and its activity is regulated by phospholamban and sarcolipin. Calcium binding to the cytosolic domain of SERCA triggers phosphorylation and activation of the pump, initiating the transport cycle.
ATP-dependent calcium translocation
In simple terms: The pump uses energy from ATP to push calcium ions into the SR.
SERCA hydrolyzes ATP to ADP and inorganic phosphate, using the released energy to transport two calcium ions across the SR membrane into the lumen per ATP molecule consumed. This active transport maintains a steep calcium gradient between the cytosol (low nanomolar) and the SR lumen (high micromolar to millimolar).
Redox regulation of SERCA activity
In simple terms: Oxidative stress can modify the pump, and certain proteins help protect it.
The endoplasmic reticulum disulfide reductase ERdj5 regulates calcium homeostasis by reducing disulfide bonds in SERCA2, thereby modulating its activity. SEPN1, an ER-localized selenoprotein, counteracts hyperoxidation of SERCA2 and preserves its pump function under oxidative stress. These redox-regulatory mechanisms are critical for maintaining SR calcium import in muscle cells.
Calcium storage and buffering in the SR lumen
In simple terms: Once inside, calcium is stored safely until needed.
Inside the SR lumen, calcium ions are buffered by calcium-binding proteins such as calsequestrin and calreticulin, which prevent calcium precipitation and provide a readily releasable pool for signaling. The stored calcium can be rapidly released through ryanodine receptors (RyR) during muscle contraction, and the import process replenishes this store during relaxation.
Key Genes Involved in GO:1990036 calcium ion import into sarcoplasmic reticulum
The following genes and proteins are central to calcium ion import into the sarcoplasmic reticulum, based on published literature [1-5].
| Gene | Major Role | Research Relevance |
|---|---|---|
| ATP2A1 (SERCA1) | Fast-twitch skeletal muscle calcium pump | Target for skeletal muscle disorders |
| ATP2A2 (SERCA2) | Cardiac and slow-twitch muscle calcium pump | Central to cardiac contractility and CPVT |
| ATP2A3 (SERCA3) | Ubiquitous calcium pump | Less studied in SR import |
| PLN (Phospholamban) | Regulates SERCA2 activity | Modulates cardiac relaxation |
| SLN (Sarcolipin) | Regulates SERCA1 and SERCA2 | Involved in thermogenesis and muscle function |
| RYR1 | Calcium release channel in skeletal muscle | Couples SR import to contraction |
| RYR2 | Calcium release channel in cardiac muscle | Mutations cause CPVT |
| CASQ1 | Calsequestrin 1, SR calcium buffer | Maintains SR calcium store |
| CASQ2 | Calsequestrin 2, cardiac SR buffer | Mutations linked to CPVT |
| ERDJ5 (DNAJC10) | ER disulfide reductase | Regulates SERCA2 redox state |
| SEPN1 (SELENON) | ER selenoprotein | Protects SERCA2 from hyperoxidation |
| VDAC2 | Mitochondrial outer membrane channel | Indirectly affects calcium crosstalk |
| CALR | Calreticulin, ER calcium buffer | Buffers SR/ER calcium |
| HSPA5 (BiP) | ER chaperone | Indirect role in ER calcium homeostasis |
| ATF6 | ER stress transcription factor | Links calcium imbalance to ER stress |
| XBP1 | ER stress response factor | Modulates calcium handling genes |
| ERO1A | ER oxidoreductin | Redox regulation of ER calcium |
How Is calcium ion import into sarcoplasmic reticulum Regulated?
Calcium ion import into the sarcoplasmic reticulum is regulated at multiple levels. Phospholamban inhibits SERCA2a by direct interaction, and its phosphorylation by PKA or CaMKII relieves inhibition, enhancing calcium import. Sarcolipin similarly modulates SERCA activity and uncouples ATP hydrolysis from calcium transport to generate heat. Redox regulation by ERdj5 and SEPN1 modifies SERCA2 cysteine residues and protects against oxidative inactivation. Additionally, angiotensin II-induced calcium oscillations can influence SR calcium handling through signaling cascades.
calcium ion import into sarcoplasmic reticulum and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| RYR2 | CPVT | Knock-in mouse with CPVT mutation |
| CASQ2 | CPVT | KO mouse or patient iPSC-derived cardiomyocytes |
| SEPN1 | SEPN1-related myopathy | KO mouse or CRISPR knockout cell line |
| ATP2A2 | Heart failure | Overexpression or KO in cardiac cells |
| PLN | Cardiac dysfunction | Phospholamban KO or point mutant |
Cardiac arrhythmias and CPVT
Mutations in RYR2 or CASQ2 cause catecholaminergic polymorphic ventricular tachycardia (CPVT), a life-threatening arrhythmia characterized by defective SR calcium handling. Altered SERCA2a activity and phospholamban regulation contribute to arrhythmogenesis by disrupting calcium import and store refilling.
Skeletal muscle myopathies
SEPN1-related myopathy is caused by mutations in SEPN1, leading to hyperoxidation of SERCA2 and impaired SR calcium import in skeletal muscle. This results in muscle weakness, early-onset rigidity, and respiratory insufficiency.
Heart failure
In heart failure, reduced SERCA2a expression and activity impair SR calcium import, leading to prolonged cytosolic calcium transients and diastolic dysfunction. Phospholamban dysregulation further exacerbates calcium handling defects.
ER stress and metabolic disorders
Disruption of ER/SR calcium homeostasis activates the unfolded protein response, contributing to metabolic diseases and neurodegeneration. ERdj5 and other redox regulators link calcium import to ER stress pathways.
From calcium ion import into sarcoplasmic reticulum-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate SR calcium import? | CRISPR knockout in C2C12 or HL-1 cells |
| What is the effect of a disease mutation on SERCA2? | Point mutation knock-in in HEK293 or iPSC-derived cardiomyocytes |
| Can a candidate gene rescue calcium import? | Overexpression in SERCA2-deficient cells |
| Where does the protein localize during calcium import? | Tagged knock-in with fluorescent protein |
| What is the role of redox regulation in SR calcium import? | CRISPR knockout of ERDJ5 or SEPN1 |
| How does angiotensin II affect SR calcium oscillations? | Live-cell imaging in renal cells |
How to Study the calcium ion import into sarcoplasmic reticulum Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell calcium imaging | Cytosolic and SR calcium transients | Assessing SR import in real time |
| SERCA ATPase assay | ATP hydrolysis and calcium transport | Quantifying pump activity |
| CRISPR knockout | Gene function loss | Identifying essential genes for SR import |
| CRISPR knock-in | Mutant protein expression | Modeling disease mutations |
| Proteomics | Protein interactions and modifications | Discovering regulators of SERCA |
| Redox proteomics | Oxidative modifications | Linking redox state to calcium import |
| RNA-seq | Transcriptional changes | Identifying compensatory pathways |
| Immunofluorescence | Protein localization | Visualizing SR proteins |
Live-cell calcium imaging
Fluorescent calcium indicators such as Fura-2 or genetically encoded sensors (e.g., GCaMP) allow real-time measurement of cytosolic and SR calcium dynamics. This method is used to assess SR calcium import rates and store content in response to stimuli.
SERCA activity assays
ATPase activity of SERCA can be measured using coupled enzyme assays or by monitoring calcium uptake into isolated SR vesicles with calcium-sensitive dyes. These assays quantify the rate of calcium import and the effects of regulatory proteins.
CRISPR-based gene editing
CRISPR/Cas9 knockout, point mutation, and knock-in approaches enable precise manipulation of genes involved in SR calcium import, such as ATP2A2, PLN, and SEPN1. These models help establish causal relationships between gene function and calcium handling.
Proteomics and redox analysis
Mass spectrometry-based proteomics can identify post-translational modifications of SERCA and interacting proteins. Redox proteomics specifically detects oxidative modifications that regulate calcium import.
How CRISPR Can Be Used to Study GO:1990036 calcium ion import into sarcoplasmic reticulum
Knockout
CRISPR knockout of genes such as ATP2A2, PLN, or SEPN1 in muscle cell lines (e.g., C2C12, HL-1) can reveal their requirement for SR calcium import. Loss-of-function models show reduced calcium uptake and altered contractility.
Point Mutation
Introducing disease-associated point mutations (e.g., in RYR2 or CASQ2) via CRISPR base editing or homology-directed repair allows study of their impact on SR calcium import and arrhythmogenesis.
Knock-in
Knock-in of fluorescent tags (e.g., GFP) into endogenous SERCA2 or ERdj5 loci enables live-cell tracking of protein localization and dynamics during calcium import.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of SERCA2a or SEPN1 can rescue calcium import defects in disease models and test therapeutic potential.
How EDITGENE Supports calcium ion import into sarcoplasmic reticulum Research
Researchers studying calcium ion import into sarcoplasmic reticulum-related genes often need to determine whether a candidate gene is causally involved in calcium handling, and how specific mutations affect pump function. EDITGENE provides comprehensive CRISPR-based services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for calcium ion import into sarcoplasmic reticulum research.
Frequently Asked Questions About calcium ion import into sarcoplasmic reticulum
What is GO:1990036?
GO:1990036 is the Gene Ontology term for calcium ion import into sarcoplasmic reticulum, describing the active transport of calcium ions into the SR lumen.
What genes are involved in calcium ion import into sarcoplasmic reticulum?
Key genes include ATP2A1, ATP2A2, PLN, SLN, RYR2, CASQ2, ERDJ5, and SEPN1.
How is calcium ion import into the sarcoplasmic reticulum regulated?
It is regulated by phospholamban, sarcolipin, redox modifications by ERdj5 and SEPN1, and signaling pathways such as angiotensin II.
What diseases are associated with defective SR calcium import?
CPVT, heart failure, SEPN1-related myopathy, and ER stress-related disorders.
What methods are used to study SR calcium import?
Live-cell calcium imaging, SERCA ATPase assays, CRISPR knockout/knock-in, proteomics, and redox analysis.
Which protein pumps calcium into the sarcoplasmic reticulum?
SERCA (sarco/endoplasmic reticulum Ca2+-ATPase) pumps, particularly SERCA1 and SERCA2, are the primary calcium pumps.
How does SEPN1 affect calcium import?
SEPN1 protects SERCA2 from hyperoxidation, preserving its calcium pump activity under oxidative stress.
What is the role of ERdj5 in SR calcium import?
ERdj5 is a disulfide reductase that regulates SERCA2 activity and ER calcium homeostasis.
Can CRISPR be used to study SR calcium import?
Yes, CRISPR knockout, point mutation, and knock-in models are powerful tools to dissect gene function in SR calcium import.
Why is SR calcium import important for muscle function?
It enables muscle relaxation by removing cytosolic calcium and refilling SR stores for subsequent contractions.
Conclusion
Calcium ion import into the sarcoplasmic reticulum (GO:1990036) is a vital biological process that maintains calcium homeostasis and supports muscle function. Dysregulation of this process contributes to cardiac arrhythmias, heart failure, and skeletal muscle myopathies. Advances in CRISPR gene editing and live-cell imaging continue to unravel the molecular mechanisms and regulatory networks involved. Targeting SR calcium import pathways holds promise for therapeutic development in calcium-related diseases.
References
- 1. Naghdi S et al.. 2016. VDAC2-specific cellular functions and the underlying structure.. Biochim Biophys Acta 1863(10):2503-14 PMID: 27116927
- 2. Ushioda R et al.. 2016. Redox-assisted regulation of Ca2+ homeostasis in the endoplasmic reticulum by disulfide reductase ERdj5.. Proc Natl Acad Sci U S A 113(41):E6055-E6063 PMID: 27694578
- 3. Edwards A et al.. 2008. Mechanisms underlying angiotensin II-induced calcium oscillations.. Am J Physiol Renal Physiol 295(2):F568-84 PMID: 18562632
- 4. Dulhunty AF. 2022. Molecular Changes in the Cardiac RyR2 With Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT).. Front Physiol 13:830367 PMID: 35222090
- 5. Marino M et al.. 2015. SEPN1, an endoplasmic reticulum-localized selenoprotein linked to skeletal muscle pathology, counteracts hyperoxidation by means of redox-regulating SERCA2 pump activity.. Hum Mol Genet 24(7):1843-55 PMID: 25452428
