GO:0000828 inositol hexakisphosphate kinase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0000828 (inositol hexakisphosphate kinase activity, synonym IP6 kinase) catalyzes the ATP-dependent phosphorylation of 1D-myo-inositol hexakisphosphate (IP6) to diphospho-1D-myo-inositol-pentakisphosphate (PP-IP5).
• The three mammalian isoenzymes IP6K1, IP6K2 and IP6K3 differ in tissue distribution, subcellular localization and downstream functions.
• IP6K1 activity is required for cytoplasmic dynein-driven transport and for maintaining circulating phosphate homeostasis in mammals.
• IP6K3 promotes focal adhesion turnover through interaction with dynein intermediate chain 2, while IP6K2 can promote cell death in cells with cytoplasmic TDP-43 aggregation.
• Pharmacological inhibition of IP6K1 protects mice against obesity-induced bone loss, highlighting the enzyme as a drug target.
• High-throughput and fragment-based screening assays have been developed to identify IP6K inhibitors, enabling chemical biology and therapeutic development.
Description
Inositol hexakisphosphate kinase activity (GO:0000828) is a molecular function that converts inositol hexakisphosphate (IP6) into diphospho-inositol pentakisphosphate (PP-IP5) using ATP. This phosphorylation event generates a high-energy pyrophosphate moiety that can be transferred to protein targets, thereby influencing diverse cellular processes such as vesicular trafficking, phosphate homeostasis and cell survival. The enzyme is conserved across eukaryotes and is represented in mammals by three isoforms: IP6K1, IP6K2 and IP6K3. Because IP6K activity impacts signaling pathways relevant to metabolic disease, cancer and neurodegeneration, it has become a focus for both basic research and therapeutic development. Understanding its mechanism, regulation and disease connections is essential for researchers aiming to manipulate this pathway with precision.
inositol hexakisphosphate kinase activity At A Glance
| GO ID | GO:0000828 |
|---|---|
| GO term | inositol hexakisphosphate kinase activity |
| Ontology | molecular_function |
| Synonym | IP6 kinase |
| Definition | Catalysis of the reaction: ATP + 1D-myo-inositol hexakisphosphate = ADP + diphospho-1D-myo-inositol-pentakisphosphate. The isomeric configuration of PP-IP5 is unknown. |
| Major function | Phosphorylation of IP6 to produce PP-IP5, a precursor for inositol pyrophosphate signaling. |
| Representative genes | IP6K1, IP6K2, IP6K3 in mammals. |
| Associated processes | Dynein-driven transport, phosphate homeostasis, focal adhesion turnover, cell death. |
| Disease relevance | Obesity-induced bone loss, neurodegeneration, cancer. |
What Is GO:0000828?
According to the Gene Ontology, inositol hexakisphosphate kinase activity (GO:0000828) is defined as the catalysis of the reaction: ATP + 1D-myo-inositol hexakisphosphate = ADP + diphospho-1D-myo-inositol-pentakisphosphate. The isomeric configuration of the product PP-IP5 is not specified in the definition. In simpler terms, it is an enzyme activity that adds a phosphate group from ATP onto IP6, creating a diphosphorylated inositol pyrophosphate.
Why Is inositol hexakisphosphate kinase activity Important in Cell Biology?
Inositol hexakisphosphate kinase activity is important because it generates inositol pyrophosphates, which act as signaling molecules in fundamental cellular processes including membrane trafficking, phosphate sensing and apoptosis. Dysregulation of IP6K enzymes has been linked to metabolic bone disease, cancer and neurodegenerative conditions, making this activity a potential therapeutic target. Moreover, the development of selective inhibitors and high-throughput assays underscores its tractability for drug discovery.
• Regulates circulating phosphate levels in mammals, as shown by IP6K1 enzymatic activity controlling phosphate homeostasis.
• Required for cytoplasmic dynein-driven transport, impacting intracellular trafficking and cell division.
• Promotes focal adhesion turnover via IP6K3 interaction with dynein intermediate chain 2, affecting cell migration.
• IP6K2 can promote cell death in cells with cytoplasmic TDP-43 aggregation, linking it to neurodegeneration.
• Pharmacological inhibition of IP6K1 protects against obesity-induced bone loss, suggesting a role in bone metabolism.
• IP6K1 is involved in various mammalian cellular processes, including insulin signaling and energy metabolism.
• High-throughput assays enable screening for IP6K1 inhibitors, facilitating drug discovery.
• Fragment-based screening has identified new quinazolinone-based IP6K inhibitors, expanding chemical tools.
• The enzyme family is conserved and has three isoforms with distinct functions, offering multiple research angles.
• IP6K activity influences inositol pyrophosphate levels, which are implicated in cancer and diabetes.
Molecular Mechanism of inositol hexakisphosphate kinase activity
Substrate recognition and binding
In simple terms: The enzyme grabs IP6 and ATP to start the reaction.
IP6K enzymes specifically bind 1D-myo-inositol hexakisphosphate (IP6) and ATP. The active site accommodates IP6 through electrostatic interactions, as IP6 is highly negatively charged. Structural and biochemical studies indicate that the enzyme transfers the gamma-phosphate of ATP to IP6, forming PP-IP5.
Catalytic phosphorylation step
In simple terms: A phosphate group is added to IP6, creating PP-IP5.
The catalytic mechanism involves the transfer of the terminal phosphate from ATP to the 5-position of IP6, yielding diphospho-1D-myo-inositol-pentakisphosphate (PP-IP5) and ADP. The reaction is magnesium-dependent, as Mg2+ coordinates the ATP phosphates. The isomeric configuration of PP-IP5 remains to be fully defined.
Isoform-specific functions
In simple terms: Different versions of the enzyme do different jobs in the cell.
Mammals express three isoforms: IP6K1, IP6K2 and IP6K3. IP6K1 is required for dynein-driven transport and phosphate homeostasis. IP6K3 promotes focal adhesion turnover via dynein intermediate chain 2. IP6K2 can promote cell death under stress conditions such as TDP-43 aggregation. These isoforms share the same catalytic activity but differ in localization and interacting partners.
Regulation by cellular signals
In simple terms: The enzyme's activity can be turned up or down by cellular signals.
IP6K activity is regulated by cellular energy status and signaling pathways. For example, IP6K1 activity is influenced by insulin signaling and may be modulated by phosphorylation. Additionally, the enzyme's product PP-IP5 can be further metabolized, affecting its availability. Pharmacological inhibitors can block IP6K activity, providing tools to study regulation.
Role in inositol pyrophosphate signaling
In simple terms: The product of the reaction acts as a signaling molecule.
PP-IP5 is a member of the inositol pyrophosphate family, which can regulate protein function through pyrophosphorylation. This posttranslational modification can affect processes such as vesicular trafficking and cell cycle progression. The balance between IP6 and PP-IP5 is critical for cellular homeostasis.
Key Genes Involved in GO:0000828 inositol hexakisphosphate kinase activity
The following genes encode proteins with inositol hexakisphosphate kinase activity or are directly involved in its regulation and downstream signaling.
| Gene | Major Role | Research Relevance |
|---|---|---|
| IP6K1 | Catalyzes IP6 phosphorylation; regulates dynein-driven transport and phosphate homeostasis | Knockout models show defects in transport and phosphate handling |
| IP6K2 | Catalyzes IP6 phosphorylation; promotes cell death under stress | Implicated in TDP-43 aggregation and neurodegeneration |
| IP6K3 | Catalyzes IP6 phosphorylation; promotes focal adhesion turnover | Interacts with dynein intermediate chain 2; role in cell migration |
| DYNC1I2 | Dynein intermediate chain 2; interacts with IP6K3 | Mediates focal adhesion turnover |
| DYNC1H1 | Dynein heavy chain; involved in transport | IP6K1 activity required for dynein-driven transport |
| TDP-43 | RNA-binding protein; aggregates in neurodegeneration | IP6K2 promotes cell death in cells with TDP-43 aggregates |
| INSR | Insulin receptor; upstream of IP6K1 signaling | IP6K1 involved in insulin signaling |
| AKT | Serine/threonine kinase; downstream of insulin signaling | IP6K1 may modulate AKT pathway |
| PPIP5K | Inositol pyrophosphate kinase; produces IP7 | Works in concert with IP6K to generate inositol pyrophosphates |
| DIPP | Inositol pyrophosphate phosphatase | Opposes IP6K activity by dephosphorylating PP-IP5 |
| KIF5B | Kinesin heavy chain; involved in transport | May cooperate with dynein in IP6K1-dependent transport |
| MAP1LC3B | Autophagy marker; linked to IP6K2 function | IP6K2 may influence autophagy |
| CASP3 | Apoptosis executioner | IP6K2 promotes cell death via apoptotic pathways |
| GSK3B | Glycogen synthase kinase 3 beta | Potential downstream target of IP6K1 in bone metabolism |
| RUNX2 | Master transcription factor for osteoblast differentiation | IP6K1 inhibition protects against bone loss |
| PPARG | Peroxisome proliferator-activated receptor gamma | Linked to obesity-induced bone loss and IP6K1 |
| SLC34A1 | Sodium-phosphate cotransporter | IP6K1 activity controls circulating phosphate |
| FGF23 | Fibroblast growth factor 23; regulates phosphate | IP6K1 may influence FGF23 levels |
How Is inositol hexakisphosphate kinase activity Regulated?
IP6K activity is regulated at multiple levels. IP6K1 activity is required for cytoplasmic dynein-driven transport, and its enzymatic activity controls circulating phosphate in mammals. Insulin signaling can influence IP6K1 function, and the enzyme may be subject to posttranslational modifications. Pharmacological inhibitors can acutely block IP6K activity, providing a means to study its regulation. Additionally, the product PP-IP5 can be further phosphorylated by PPIP5K to IP7, and dephosphorylated by DIPP phosphatases, creating a dynamic regulatory network.
inositol hexakisphosphate kinase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| IP6K1 | Obesity-induced bone loss | Knockout mouse, pharmacological inhibitor |
| IP6K1 | Phosphate homeostasis disorders | Knockout mouse, cell lines |
| IP6K2 | Neurodegeneration (TDP-43) | Cell models with TDP-43 aggregation |
| IP6K3 | Cancer metastasis (focal adhesion) | Knockdown cells, migration assays |
| IP6K1 | Insulin resistance | Knockout mouse, insulin signaling assays |
Metabolic bone disease and obesity
Pharmacological inhibition of IP6K1 protects mice against obesity-induced bone loss, suggesting that IP6K activity contributes to bone remodeling under metabolic stress. IP6K1 activity also controls circulating phosphate levels, which are critical for bone mineralization. These findings link IP6K to osteoporosis and metabolic bone disorders.
Neurodegeneration
IP6K2 promotes cell death in cells with cytoplasmic TDP-43 aggregation, a hallmark of amyotrophic lateral sclerosis and frontotemporal dementia. This suggests that IP6K2 activity may exacerbate neurodegeneration, and its inhibition could be protective.
Cancer and cell migration
IP6K3 promotes focal adhesion turnover via interactions with dynein intermediate chain 2, a process that can influence cell migration and invasion. Dysregulated focal adhesion turnover is associated with cancer metastasis. Additionally, IP6K1 is involved in cellular processes that can affect tumor growth.
From inositol hexakisphosphate kinase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does IP6K1 activity control circulating phosphate? | IP6K1 knockout mouse |
| Does IP6K1 inhibition protect against bone loss? | Pharmacological inhibitor in obese mice |
| Is IP6K1 required for dynein-driven transport? | IP6K1 knockout cells, transport assays |
| Does IP6K3 regulate focal adhesion turnover? | IP6K3 knockdown cells, dynein interaction studies |
| Does IP6K2 promote cell death in TDP-43 aggregation? | Cell models with TDP-43 aggregates, IP6K2 knockout |
| Can IP6K1 inhibitors be developed? | High-throughput screening assays |
How to Study the inositol hexakisphosphate kinase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Kinase activity assay | Conversion of IP6 to PP-IP5 | Screening for inhibitors |
| High-throughput screening | Inhibition of IP6K1 activity | Drug discovery |
| Knockout mouse models | Physiological effects of IP6K loss | Phosphate homeostasis, bone loss |
| Co-immunoprecipitation | Protein-protein interactions | Dynein interaction |
| Mass spectrometry | Inositol pyrophosphate levels | Metabolic profiling |
| Cell migration assays | Focal adhesion turnover | IP6K3 function |
| Apoptosis assays | Cell death | IP6K2 in neurodegeneration |
| Phosphate measurement | Circulating phosphate | IP6K1 function |
Enzymatic activity assays
Inositol hexakisphosphate kinase activity can be measured using radiometric or fluorescent assays that detect the conversion of IP6 to PP-IP5. A homogeneous high-throughput assay for IP6K1 activity has been developed, enabling screening of chemical libraries. Fragment-based screening has also been used to identify new inhibitors.
Genetic manipulation and phenotyping
Knockout and knockdown models are essential to study the physiological roles of IP6K enzymes. IP6K1 knockout mice have been used to demonstrate its role in phosphate homeostasis and bone metabolism. Cell-based knockdown of IP6K3 has been used to study focal adhesion turnover.
Protein interaction studies
Co-immunoprecipitation and pull-down assays can identify interacting partners such as dynein intermediate chain 2. These methods help elucidate how IP6K enzymes are targeted to specific cellular compartments.
Metabolite profiling
Mass spectrometry-based methods can quantify inositol pyrophosphates such as PP-IP5 and IP7 in cells and tissues. This allows researchers to assess the impact of IP6K activity on cellular signaling.
How CRISPR Can Be Used to Study GO:0000828 inositol hexakisphosphate kinase activity
Knockout
CRISPR-Cas9 knockout of IP6K1, IP6K2 or IP6K3 can abolish their enzymatic activity, enabling studies of their physiological roles. For example, IP6K1 knockout mice have been generated to study phosphate homeostasis. Knockout cell lines can be used to dissect isoform-specific functions in transport and cell death.
Point Mutation
Point mutations can be introduced into the catalytic domain of IP6K enzymes to separate kinase activity from scaffolding functions. For instance, mutation of the ATP-binding site can render the enzyme catalytically dead, allowing researchers to test whether enzymatic activity is required for dynein-driven transport.
Knock-in
Knock-in of tagged versions of IP6K enzymes (e.g., GFP or HA) can facilitate localization and interaction studies. This approach can be used to track endogenous IP6K1 in live cells and tissues.
Overexpression
Overexpression of wild-type or mutant IP6K enzymes can amplify signaling pathways and reveal gain-of-function phenotypes. For example, overexpression of IP6K2 can promote cell death in cells with TDP-43 aggregates. Overexpression models are useful for studying downstream effects on inositol pyrophosphate levels.
How EDITGENE Supports inositol hexakisphosphate kinase activity Research
Researchers studying inositol hexakisphosphate kinase activity-related genes often need to determine whether a candidate gene is causally involved in a specific cellular process or disease. Generating precise genetic models is critical to validate targets and understand mechanism. EDITGENE provides a comprehensive suite of CRISPR-based services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for inositol hexakisphosphate kinase activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| IP6K3 Knockout HEK293 Cell Line | EDJ-KQ1031 | Human | 117283 | Details Get a Quote |
| ITPKB Knockout HEK293 Cell Line | EDJ-KQ1645 | Human | 3707 | Details Get a Quote |
| IP6K1 Knockout HEK293 Cell Line | EDJ-KQ1685 | Human | 9807 | Details Get a Quote |
| IP6K2 Knockout HEK293 Cell Line | EDJ-KQ1686 | Human | 51447 | Details Get a Quote |
| PPIP5K2 Knockout HEK293 Cell Line | EDJ-KQ1687 | Human | 23262 | Details Get a Quote |
| ITPKB Knockout A-549 Cell Line | EDJ-KQ21375 | Human | 3707 | Details Get a Quote |
| ITPKB Knockout HCT 116 Cell Line | EDJ-KQ21376 | Human | 3707 | Details Get a Quote |
| ITPKB Knockout HeLa Cell Line | EDJ-KQ21377 | Human | 3707 | Details Get a Quote |
| IP6K1 Knockout A-549 Cell Line | EDJ-KQ21474 | Human | 9807 | Details Get a Quote |
| IP6K1 Knockout HCT 116 Cell Line | EDJ-KQ21475 | Human | 9807 | Details Get a Quote |
| IP6K1 Knockout HeLa Cell Line | EDJ-KQ21476 | Human | 9807 | Details Get a Quote |
| IP6K2 Knockout A-549 Cell Line | EDJ-KQ21477 | Human | 51447 | Details Get a Quote |
| IP6K2 Knockout HCT 116 Cell Line | EDJ-KQ21478 | Human | 51447 | Details Get a Quote |
| IP6K2 Knockout HeLa Cell Line | EDJ-KQ21479 | Human | 51447 | Details Get a Quote |
| PPIP5K2 Knockout A-549 Cell Line | EDJ-KQ21481 | Human | 23262 | Details Get a Quote |
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Frequently Asked Questions About inositol hexakisphosphate kinase activity
What is inositol hexakisphosphate kinase activity?
It is the enzymatic activity that transfers a phosphate from ATP to IP6, producing PP-IP5, as defined by GO:0000828.
What genes encode inositol hexakisphosphate kinase activity?
In mammals, the genes are IP6K1, IP6K2 and IP6K3, which encode three isoforms of the enzyme.
What is the function of IP6K1?
IP6K1 is required for cytoplasmic dynein-driven transport and controls circulating phosphate levels in mammals.
How is inositol hexakisphosphate kinase activity regulated?
It is regulated by cellular signals such as insulin, and can be inhibited pharmacologically; its product PP-IP5 is further metabolized.
What diseases are associated with IP6K enzymes?
IP6K1 is linked to obesity-induced bone loss and phosphate disorders, IP6K2 to neurodegeneration, and IP6K3 to cancer cell migration.
What methods are used to study IP6K activity?
Kinase assays, high-throughput screening, knockout models, and mass spectrometry are commonly used.
Can CRISPR be used to study IP6K genes?
Yes, CRISPR knockout, point mutation, knock-in and overexpression models are valuable for dissecting IP6K function.
What is the product of inositol hexakisphosphate kinase activity?
The product is diphospho-1D-myo-inositol-pentakisphosphate (PP-IP5), an inositol pyrophosphate.
Are there inhibitors of IP6K?
Yes, quinazolinone-based inhibitors have been identified through fragment-based screening.
Why is IP6K1 a drug target for bone loss?
Pharmacological inhibition of IP6K1 protects mice against obesity-induced bone loss, suggesting a therapeutic strategy.
Conclusion
Inositol hexakisphosphate kinase activity (GO:0000828) is a critical enzymatic function that generates inositol pyrophosphates, influencing diverse processes from phosphate homeostasis to neurodegeneration. The three mammalian isoforms IP6K1, IP6K2 and IP6K3 have distinct roles, and their dysfunction is linked to metabolic bone disease, cancer and neurodegeneration. Continued research using CRISPR models and high-throughput assays will further illuminate this pathway and its therapeutic potential.
References
- 1. Moritoh Y et al.. 2021. The enzymatic activity of inositol hexakisphosphate kinase controls circulating phosphate in mammals.. Nat Commun 12(1):4847 PMID: 34381031
- 2. Chakkour M et al.. 2024. Insights into the roles of inositol hexakisphosphate kinase 1 (IP6K1) in mammalian cellular processes.. J Biol Chem 300(4):107116 PMID: 38403246
- 3. Boregowda SV et al.. 2022. Pharmacological Inhibition of Inositol Hexakisphosphate Kinase 1 Protects Mice against Obesity-Induced Bone Loss.. Biology (Basel) 11(9) PMID: 36138736
- 4. Chanduri M et al.. 2016. Inositol hexakisphosphate kinase 1 (IP6K1) activity is required for cytoplasmic dynein-driven transport.. Biochem J 473(19):3031-47 PMID: 27474409
- 5. Heitmann T et al.. 2023. Fragment-Based Screening Identifies New Quinazolinone-Based Inositol Hexakisphosphate Kinase (IP6K) Inhibitors.. ACS Med Chem Lett 14(12):1760-1766 PMID: 38116421
- 6. Rojas T et al.. 2019. Inositol hexakisphosphate kinase 3 promotes focal adhesion turnover via interactions with dynein intermediate chain 2.. Proc Natl Acad Sci U S A 116(8):3278-3287 PMID: 30718399
- 7. Nagata E et al.. 2016. Inositol Hexakisphosphate Kinase 2 Promotes Cell Death in Cells with Cytoplasmic TDP-43 Aggregation.. Mol Neurobiol 53(8):5377-83 PMID: 26440668
- 8. Wormald M et al.. 2017. Development of a homogenous high-throughput assay for inositol hexakisphosphate kinase 1 activity.. PLoS One 12(11):e0188852 PMID: 29186181
