GO:0009931 calcium-dependent protein serine/threonine kinase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0009931 describes the molecular function of calcium-dependent protein serine/threonine kinase activity, defined as calcium-dependent catalysis of ATP transfer to protein serine or threonine residues.
• This activity is executed by calcium-dependent protein kinases (CPKs/CDPKs) and related calcium/calmodulin-dependent kinases that decode calcium signals into phosphorylation events.
• CPK family members such as CPK3, CPK4, CPK6, CPK11, CPK27 and CPK28 respond to osmotic, cold and pathogen-related calcium signals.
• Downstream substrates include SnRK2 kinases, NADPH oxidase RBOHD and ion channels, linking GO:0009931 to stress adaptation and immunity.
• In human cells, calcium-dependent kinases such as CaMKK2 and PKCα contribute to cancer signaling and diabetic nephropathy, making this activity disease-relevant.
• CRISPR knockout, point-mutation, knock-in and overexpression models are essential to test causality of specific calcium-dependent kinase genes.
Description
GO:0009931, calcium-dependent protein serine/threonine kinase activity, is a molecular function ontology term that captures the calcium-dependent transfer of phosphate from ATP to serine or threonine residues on protein substrates. This activity is central to signal transduction because it converts transient changes in intracellular calcium concentration into durable phosphorylation-based cellular responses. Calcium-dependent protein kinases (CPKs, also called CDPKs) are the canonical enzymes carrying this activity in plants, while calcium/calmodulin-dependent protein kinase kinases and protein kinase C family members perform analogous calcium-dependent phosphorylation in animal cells. Researchers study GO:0009931 because it sits at the intersection of calcium signaling, protein phosphorylation and stress or disease responses, and because its dysregulation is implicated in processes ranging from osmotic stress adaptation to cancer cell signaling. The activity is experimentally tractable: kinase assays, phosphoproteomics and genetic perturbation allow precise mapping of which kinases phosphorylate which substrates under defined calcium conditions.
calcium-dependent protein serine/threonine kinase activity At A Glance
| GO ID | GO:0009931 |
|---|---|
| GO term | calcium-dependent protein serine/threonine kinase activity |
| Ontology | molecular_function |
| Synonym | none listed in QuickGO |
| Major function | Calcium-dependent phosphorylation of protein serine and threonine residues using ATP |
| Catalytic reaction | ATP + protein serine = ADP + protein serine phosphate; ATP + protein threonine = ADP + protein threonine phosphate |
| Calcium dependence | Requires calcium binding, often via EF-hand domains or calmodulin |
| Representative enzymes | CPK/CDPK family kinases and calcium/calmodulin-dependent kinases |
| Biological context | Stress signaling, immunity, ion channel regulation and cell division control |
What Is GO:0009931?
In plain terms, GO:0009931 describes an enzyme activity in which calcium binding enables a kinase to add phosphate groups to serine or threonine residues of target proteins. The official QuickGO definition states that this activity catalyzes the calcium-dependent reactions ATP + a protein serine = ADP + protein serine phosphate, and ATP + a protein threonine = ADP + protein threonine phosphate. The defining feature that distinguishes GO:0009931 from generic protein serine/threonine kinase activity is the explicit requirement for calcium, which typically acts through calcium-binding domains such as EF-hand motifs or through calcium-bound calmodulin. This activity is classified under molecular_function and is often annotated to CPK/CDPK family enzymes and calcium/calmodulin-dependent kinases.
Why Is calcium-dependent protein serine/threonine kinase activity Important in Cell Biology?
GO:0009931 matters because calcium-dependent protein serine/threonine kinases are primary decoders of calcium signals, and their phosphorylation outputs control ion transport, gene expression, immune activation and cell cycle progression. In plants, CPK3, CPK4, CPK6, CPK11 and CPK27 respond to osmotic stress and activate SnRK2 kinases, directly connecting this activity to abscisic acid and osmotic stress pathways. CPK28 undergoes phosphorylation-dependent subfunctionalization, showing that even within one kinase family the activity can be tuned for distinct physiological roles. In animals, calcium/calmodulin-dependent protein kinase kinase 2 mediates pleiotropic epidermal growth factor effects in cancer cells, and PKCα contributes to podocyte injury in diabetic nephropathy, illustrating disease relevance. Because the activity is defined by calcium dependence, it is also a prime target for chemical and genetic perturbation studies that aim to separate calcium-dependent from calcium-independent phosphorylation events.
• Decodes calcium signals into phosphorylation-based cellular responses.
• Controls osmotic stress adaptation through CPK-mediated activation of SnRK2 kinases.
• Regulates plant immunity via phosphorylation of NADPH oxidase RBOHD.
• Participates in cold stress signaling through CPK3 and calmodulin-gated channels.
• Shapes pathogen pattern-triggered immunity through calcium channel and kinase coupling.
• Contributes to cancer cell signaling via CaMKK2 and related calcium-dependent kinases.
• Is implicated in diabetic nephropathy through PKCα/p66SHC-mediated podocyte injury.
• Provides a druggable node for modulating calcium-dependent phosphorylation in disease.
• Enables phosphoproteomic mapping of calcium-dependent versus calcium-independent substrates.
• Supports CRISPR-based causal testing of individual kinase genes in stress and disease models.
GO:0009931 calcium-dependent protein serine/threonine kinase activity
Calcium binding and kinase activation
In simple terms: Calcium acts like a key that switches the kinase on.
The activity begins when intracellular calcium rises and binds to calcium-sensing domains within or associated with the kinase. In CPK/CDPK enzymes, EF-hand calcium-binding domains relieve autoinhibition and allow the kinase domain to adopt an active conformation. In animal cells, calcium-bound calmodulin can activate calcium/calmodulin-dependent kinase kinases such as CaMKK2, which then phosphorylate downstream targets. This calcium-gated activation step is the defining feature of GO:0009931 and distinguishes it from constitutively active serine/threonine kinases.
Substrate recognition and phosphorylation
In simple terms: The active kinase then tags target proteins with phosphate.
Once activated, the kinase binds protein substrates and transfers the gamma-phosphate of ATP to serine or threonine residues. In Arabidopsis, CPK3, CPK4, CPK6, CPK11 and CPK27 respond to osmotic stress and activate SnRK2 kinases through phosphorylation. CPK28 undergoes phosphorylation-dependent subfunctionalization, indicating that substrate specificity can be modulated by prior phosphorylation events. The NADPH oxidase RBOHD is directly regulated by the PRR-associated kinase BIK1, illustrating how calcium-dependent phosphorylation controls immune oxidative bursts.
Signal integration with ion channels and second messengers
In simple terms: The kinase activity is wired into calcium channels and other signals.
Calcium-dependent kinases operate within feedback loops that include calcium channels and calmodulin. A calmodulin-gated calcium channel links pathogen patterns to plant immunity, providing calcium entry that can feed into calcium-dependent kinase activation. CPK3 and CaM2 coordinately control calcium signaling via cyclic nucleotide-gated channels in response to cold stress, showing that the kinase activity is embedded in channel-regulatory networks. These interactions ensure that phosphorylation outputs are spatially and temporally matched to calcium microdomains.
Downstream physiological outputs
In simple terms: Phosphorylation changes what the cell does next.
The phosphorylation events catalyzed by GO:0009931 alter the activity, localization or stability of substrate proteins, leading to physiological outcomes such as osmotic stress gene expression, immune activation, ion transport changes and cell division. Mechanical stretch triggers rapid epithelial cell division through Piezo1, a process in which calcium-dependent signaling contributes to cell cycle control. In human disease contexts, calcium-dependent kinase activity mediated by PKCα and CaMKK2 influences podocyte injury and cancer cell signaling, respectively.
Key Genes Involved in GO:0009931 calcium-dependent protein serine/threonine kinase activity
The following genes and proteins are experimentally linked to calcium-dependent protein serine/threonine kinase activity or its downstream signaling.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CPK3 | Calcium-dependent protein kinase responding to osmotic and cold stress | Osmotic stress and cold signaling models |
| CPK4 | Calcium-dependent protein kinase activating SnRK2s under osmotic stress | Osmotic stress pathway dissection |
| CPK6 | Calcium-dependent protein kinase involved in osmotic stress responses | Stress kinase cascade studies |
| CPK11 | Calcium-dependent protein kinase contributing to osmotic stress signaling | SnRK2 activation research |
| CPK27 | Calcium-dependent protein kinase responding to osmotic stress | Stress signaling and phosphoproteomics |
| CPK28 | Calcium-dependent protein kinase with phosphorylation-dependent subfunctionalization | Kinase specificity and immunity studies |
| CaM2 | Calmodulin coordinating calcium signaling with CPK3 | Cold stress and channel regulation |
| SnRK2 | Downstream kinase activated by CPKs under osmotic stress | Stress signaling cascade research |
| RBOHD | NADPH oxidase regulated by calcium-dependent phosphorylation | Plant immunity oxidative burst studies |
| BIK1 | PRR-associated kinase regulating RBOHD | Pathogen immunity signaling |
| Piezo1 | Mechanosensitive calcium channel linked to cell division | Mechanical stretch and cell cycle research |
| CaMKK2 | Calcium/calmodulin-dependent kinase kinase mediating EGF effects | Cancer cell signaling studies |
| PKCα | Calcium-dependent protein kinase C isoform | Diabetic nephropathy podocyte injury models |
| p66SHC | Oxidative stress adaptor downstream of PKCα | Podocyte injury and oxidative stress research |
| CNGC | Cyclic nucleotide-gated calcium channel | Calcium signaling and cold stress studies |
How Is calcium-dependent protein serine/threonine kinase activity Regulated?
GO:0009931 is regulated at multiple levels. Calcium availability is the primary switch, as the activity is defined by calcium dependence and is triggered by calcium entry through channels such as calmodulin-gated channels and CNGCs. Phosphorylation of the kinase itself can modulate activity and substrate specificity, as shown for CPK28, which undergoes phosphorylation-dependent subfunctionalization. In osmotic stress signaling, CPK3, CPK4, CPK6, CPK11 and CPK27 activate SnRK2 kinases, placing them upstream of a major stress kinase cascade that can also feed back on calcium signaling. In animal cells, calcium/calmodulin-dependent kinase kinases such as CaMKK2 are regulated by calcium-bound calmodulin and contribute to growth factor signaling, while PKCα activity is influenced by lipid and calcium signals in disease contexts.
calcium-dependent protein serine/threonine kinase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CaMKK2 | Cancer cell signaling and EGF responses | Cancer cell line knockout and overexpression |
| PKCα | Diabetic nephropathy podocyte injury | Podocyte cell models with point mutation or knockout |
| p66SHC | Oxidative stress in kidney disease | Knockout and phospho-mutant models |
| CPK28 | Plant immunity and kinase subfunctionalization | Arabidopsis knockout and phospho-mutant lines |
| CPK3/CPK4/CPK6/CPK11/CPK27 | Osmotic stress signaling | Arabidopsis knockout and overexpression lines |
Cancer signaling
Calcium/calmodulin-dependent protein kinase kinase 2 mediates pleiotropic effects of epidermal growth factor in cancer cells, linking calcium-dependent phosphorylation to proliferative signaling. This makes GO:0009931-related kinases potential nodes for studying how calcium signals drive tumor cell behavior.
Diabetic nephropathy
Klotho inhibits PKCα/p66SHC-mediated podocyte injury in diabetic nephropathy, indicating that calcium-dependent protein kinase activity contributes to podocyte damage and oxidative stress in this disease. Modulating this activity is therefore of interest for kidney disease research.
Stress and immunity biology
In plants, calcium-dependent kinases are central to osmotic stress adaptation and pathogen immunity, with CPKs activating SnRK2s and BIK1 regulating RBOHD. These pathways inform general principles of calcium-dependent phosphorylation that are relevant to human cell stress responses.
From calcium-dependent protein serine/threonine kinase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is a specific CPK required for osmotic stress signaling? | CRISPR knockout of CPK3/4/6/11/27 in Arabidopsis |
| Does phosphorylation of CPK28 alter its function? | Point-mutation knock-in of phospho-null or phospho-mimetic residues |
| Can calcium-dependent kinase activity be tracked in live cells? | Tagged knock-in of kinase with fluorescent reporter |
| Does overexpression of CaMKK2 enhance cancer signaling? | Overexpression cell models |
| Does PKCα inhibition protect podocytes? | Knockout or point-mutation podocyte models |
| Which substrates are phosphorylated upon calcium elevation? | Phosphoproteomics with knockout controls |
How to Study the calcium-dependent protein serine/threonine kinase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| In vitro kinase assay | Calcium-dependent phosphate incorporation | Enzyme activity validation |
| Phosphoproteomics | Global serine/threonine phosphorylation sites | Substrate discovery |
| CRISPR knockout | Loss-of-function phenotype | Causal gene testing |
| Point-mutation knock-in | Effect of specific phospho-sites | Kinase regulation studies |
| Overexpression | Gain-of-function signaling output | Cancer and stress models |
| Live-cell calcium imaging | Calcium dynamics | Signal coupling studies |
| Co-immunoprecipitation | Protein-protein interactions | Kinase-substrate complex mapping |
| RNA-seq | Transcriptional consequences | Downstream pathway analysis |
Kinase activity assays
In vitro kinase assays using recombinant calcium-dependent kinases and substrate peptides measure phosphate incorporation under defined calcium concentrations, directly reporting GO:0009931 activity.
Phosphoproteomics
Mass spectrometry-based phosphoproteomics identifies serine and threonine phosphorylation sites that depend on calcium and on specific kinases, enabling substrate mapping for CPKs and related enzymes.
Genetic perturbation
Knockout, point-mutation and overexpression lines allow causal testing of individual kinase genes in stress, immunity and disease models.
Live-cell calcium and kinase imaging
Calcium indicators and genetically encoded kinase reporters visualize the spatiotemporal coupling between calcium signals and kinase activation in living cells.
How CRISPR Can Be Used to Study GO:0009931 calcium-dependent protein serine/threonine kinase activity
Knockout
CRISPR knockout of calcium-dependent kinase genes such as CPK3, CPK4, CPK6, CPK11, CPK27 or CPK28 removes the activity and reveals its requirement in osmotic stress, cold signaling or immunity. Knockout of CaMKK2 or PKCα in human cells tests disease-relevant functions.
Point Mutation
Point-mutation knock-in can substitute catalytic residues or phospho-acceptor sites to separate kinase activity from scaffolding functions, as illustrated by phosphorylation-dependent subfunctionalization of CPK28. This approach is valuable for dissecting calcium-dependent versus calcium-independent roles.
Knock-in
Tagged knock-in of calcium-dependent kinases with fluorescent or affinity tags enables live-cell localization and interaction studies while preserving endogenous regulation. Knock-in of reporter cassettes can also monitor pathway activation.
Overexpression
Overexpression of CPKs or CaMKK2 amplifies calcium-dependent phosphorylation and can phenocopy stress or growth factor responses, providing gain-of-function evidence for GO:0009931 in signaling.
How EDITGENE Supports calcium-dependent protein serine/threonine kinase activity Research
Researchers studying calcium-dependent protein serine/threonine kinase activity-related genes often need to determine whether a candidate gene is causally involved in a specific stress, immune or disease phenotype. EDITGENE provides CRISPR-based cell model services that enable precise knockout, point-mutation, knock-in and overexpression of calcium-dependent kinase genes, supported by library screening and bioinformatics to accelerate discovery.
Contact EDITGENE today to design your custom CRISPR model for calcium-dependent protein serine/threonine kinase activity research.
Frequently Asked Questions About calcium-dependent protein serine/threonine kinase activity
What is GO:0009931?
GO:0009931 is the Gene Ontology molecular function term for calcium-dependent protein serine/threonine kinase activity, defined as calcium-dependent catalysis of ATP transfer to protein serine or threonine residues.
What genes are involved in calcium-dependent protein serine/threonine kinase activity?
Key genes include plant CPK3, CPK4, CPK6, CPK11, CPK27 and CPK28, as well as animal CaMKK2 and PKCα, which carry out calcium-dependent phosphorylation.
How is calcium-dependent protein kinase activity regulated?
It is primarily regulated by calcium binding to EF-hand domains or calmodulin, and can be further modulated by phosphorylation of the kinase itself, as shown for CPK28.
What substrates are phosphorylated by calcium-dependent kinases?
Substrates include SnRK2 kinases in osmotic stress signaling, the NADPH oxidase RBOHD in immunity, and downstream targets of CaMKK2 and PKCα in animal cells.
Why is calcium-dependent protein serine/threonine kinase activity important in disease?
It contributes to cancer cell signaling through CaMKK2 and to diabetic nephropathy through PKCα/p66SHC-mediated podocyte injury.
How can I study GO:0009931 in the lab?
Common methods include in vitro kinase assays, phosphoproteomics, live-cell calcium imaging and CRISPR-based genetic perturbation.
What is the difference between GO:0009931 and general serine/threonine kinase activity?
GO:0009931 explicitly requires calcium for catalysis, whereas general serine/threonine kinase activity does not have this calcium dependence as a defining feature.
Which model organisms are used to study calcium-dependent protein kinases?
Arabidopsis is widely used for CPK/CDPK studies, while human cell lines are used for CaMKK2 and PKCα research.
Can CRISPR knockout help identify calcium-dependent kinase functions?
Yes, CRISPR knockout of CPK genes in Arabidopsis and of CaMKK2 or PKCα in human cells has been used to test their roles in stress and disease pathways.
What services does EDITGENE provide for calcium-dependent kinase research?
EDITGENE provides knockout, point-mutation, knock-in, overexpression cell models, CRISPR library screening and bioinformatics for calcium-dependent kinase genes.
Conclusion
GO:0009931, calcium-dependent protein serine/threonine kinase activity, is a molecular function that converts calcium signals into phosphorylation-based cellular responses. Its study spans plant stress and immunity biology as well as human cancer and kidney disease, with CPKs, CaMKK2 and PKCα as representative enzymes. CRISPR-based models and phosphoproteomic methods now allow precise causal testing of this activity in diverse biological contexts.
References
- 1. Li Q et al.. 2025. Calcium-dependent protein kinases CPK3/4/6/11 and 27 respond to osmotic stress and activate SnRK2s in Arabidopsis.. Dev Cell 60(10):1423-1438.e8 PMID: 39814016
- 2. Tian W et al.. 2019. A calmodulin-gated calcium channel links pathogen patterns to plant immunity.. Nature 572(7767):131-135 PMID: 31316205
- 3. Gudipaty SA et al.. 2017. Mechanical stretch triggers rapid epithelial cell division through Piezo1.. Nature 543(7643):118-121 PMID: 28199303
- 4. Jiang W et al.. 2019. Klotho inhibits PKCα/p66SHC-mediated podocyte injury in diabetic nephropathy.. Mol Cell Endocrinol 494:110490 PMID: 31207271
- 5. Kadota Y et al.. 2014. Direct regulation of the NADPH oxidase RBOHD by the PRR-associated kinase BIK1 during plant immunity.. Mol Cell 54(1):43-55 PMID: 24630626
- 6. Dai S et al.. 2022. Calcium/calmodulin-dependent protein kinase kinase 2 mediates pleiotropic effects of epidermal growth factor in cancer cells.. Biochim Biophys Acta Mol Cell Res 1869(7):119252 PMID: 35271909
- 7. Ming Y et al.. 2025. Coordinated control of calcium signaling by CPK3 and CaM2 via CNGCs in response to cold stress in Arabidopsis.. Dev Cell 60(23):3222-3235.e6 PMID: 40633536
- 8. Bredow M et al.. 2021. Phosphorylation-dependent subfunctionalization of the calcium-dependent protein kinase CPK28.. Proc Natl Acad Sci U S A 118(19) PMID: 33941701
