GO:0043491 phosphatidylinositol 3-kinase/protein kinase B signal transduction: Signaling Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0043491 describes the intracellular signaling cassette that begins with PI3K activation, proceeds through PI3P production and PDK1 recruitment, and culminates in activation of protein kinase B (PKB/Akt).
• The pathway is a central regulator of cell growth, survival, metabolism, and proliferation, and its dysregulation is a hallmark of many cancers and metabolic disorders.
• PTEN acts as the principal negative regulator by dephosphorylating PI(3,4,5)P3, thereby opposing PI3K-driven Akt activation.
• Key nodes include receptor tyrosine kinases (e.g., HER2), PI3K catalytic and regulatory subunits, PDK1, Akt, and downstream effectors such as mTOR and FoxO3a.
• Experimental modulation of the pathway is achieved by natural compounds (e.g., quercetin), peptides (e.g., irisin), and traditional medicines, as shown in multiple in vivo models.
• CRISPR-based knockout, point mutation, knock-in, and overexpression models are essential for dissecting causal roles of pathway components in disease.
Description
Phosphatidylinositol 3-kinase/protein kinase B signal transduction (GO:0043491) is a fundamental intracellular signaling cassette that converts extracellular cues into changes in cell growth, survival, and metabolism. It is initiated by activation of phosphatidylinositol 3-kinase (PI3K) at the plasma membrane, leading to production of phosphatidylinositol 3-phosphate (PI3P) and recruitment of PDK1, which in turn activates protein kinase B (PKB, also known as Akt). This pathway is highly conserved and is one of the most frequently dysregulated signaling axes in human cancer and other diseases. For researchers, GO:0043491 provides a precise ontological framework to annotate genes and processes involved in PI3K-Akt signaling. The pathway integrates inputs from receptor tyrosine kinases, G-protein-coupled receptors, and focal adhesions, and its spatial organization is critical for signal fidelity. Because the pathway is amenable to genetic and pharmacological manipulation, it serves as a paradigm for studying signal transduction mechanisms and for developing targeted therapeutics. Understanding the molecular steps, regulatory feedback loops, and disease associations of GO:0043491 is essential for designing experiments that test causality, identify biomarkers, and evaluate drug responses. This article synthesizes authoritative QuickGO definitions and verified PubMed literature to provide a research-grade overview of the pathway, its key genes, and the methods used to study it.
phosphatidylinositol 3-kinase/protein kinase B signal transduction At A Glance
| GO ID | GO:0043491 |
|---|---|
| GO term | phosphatidylinositol 3-kinase/protein kinase B signal transduction |
| Ontology | biological_process |
| Synonym | AKT signaling; PI3K/Akt signal transduction; PI3K-PKB/Akt pathway; PKB signaling; protein kinase B signaling cascade |
| Major function | Transduces signals from cell surface receptors to Akt, regulating cell growth, survival, proliferation, and metabolism |
| Key upstream activator | Phosphatidylinositol 3-kinase (PI3K) |
| Key downstream effector | Protein kinase B (PKB/Akt) |
| Negative regulator | PTEN (dephosphorylates PI(3,4,5)P3) |
| Spatial organization | Focal adhesions contribute to PI3K-PI(3,4,5)P3-AKT signaling organization |
What Is GO:0043491?
GO:0043491, phosphatidylinositol 3-kinase/protein kinase B signal transduction, is defined as an intracellular signaling cassette that starts with phosphatidylinositol 3-kinase (PI3K) activation, production of phosphatidylinositol 3-phosphate (PI3P), activation of PDK1, which recruits and ends with the activation of protein kinase B (PKB, also known as Akt). PI3K is activated by cell surface receptors. Note that PTEN is an inhibitor of the pathway. In simpler terms, it is the molecular relay that transmits signals from activated receptors to Akt, controlling cell survival, growth, and metabolism.
Why Is phosphatidylinositol 3-kinase/protein kinase B signal transduction Important in Cell Biology?
GO:0043491 is critically important because it governs fundamental cellular decisions such as survival, proliferation, growth, and glucose metabolism, and its aberrant activation is a driving force in many human diseases, particularly cancer. The pathway is also a major target for therapeutic intervention, with numerous inhibitors in clinical use or development. Moreover, its role in metabolic and reproductive disorders, such as polycystic ovary syndrome and premature ovarian failure, highlights its broad physiological significance.
• Central regulator of cell survival and apoptosis resistance in cancer.
• Controls cell cycle progression and proliferation via downstream effectors like mTOR and FoxO3a.
• Mediates metabolic effects of insulin and growth factors, influencing glucose homeostasis.
• Frequently mutated or amplified in solid tumors, including HER2-positive breast cancer.
• Modulated by natural products and dietary compounds, offering chemopreventive strategies.
• Involved in reproductive biology, including ovarian function and polycystic ovary syndrome.
• Plays a role in gastric mucosal pathology and chronic atrophic gastritis.
• Target of approved and investigational drugs (e.g., PI3K inhibitors, Akt inhibitors).
• Spatial regulation by focal adhesions influences signaling specificity and output.
• Key pathway for CRISPR-based functional genomics to identify causal genes in disease models.
What Happens During phosphatidylinositol 3-kinase/protein kinase B signal transduction?
Receptor Activation and PI3K Recruitment
In simple terms: A signal from outside the cell turns on a receptor, which then activates PI3K at the membrane.
The pathway begins when cell surface receptors, such as receptor tyrosine kinases (e.g., HER2), are activated by ligands or are constitutively active in cancer. This activation leads to recruitment of phosphatidylinositol 3-kinase (PI3K) to the plasma membrane, where it becomes catalytically active. PI3K is a lipid kinase that phosphorylates phosphatidylinositol 4,5-bisphosphate (PIP2) to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3), often referred to as PI3P in the GO definition. This lipid second messenger serves as a docking site for downstream signaling proteins.
PDK1 Recruitment and Akt Activation
In simple terms: The lipid signal recruits PDK1, which then switches on Akt by adding a phosphate group.
Accumulation of PIP3 at the membrane recruits pleckstrin homology (PH) domain-containing proteins, including PDK1 and Akt (PKB). PDK1 phosphorylates Akt at Thr308 within its activation loop, a critical step for Akt activation. Full activation of Akt also requires phosphorylation at Ser473 by mTORC2, although the core GO definition ends with PDK1-mediated activation. Once active, Akt translocates to various subcellular compartments to phosphorylate downstream substrates.
Downstream Effectors and Cellular Outcomes
In simple terms: Active Akt sends signals that tell the cell to grow, survive, and divide.
Activated Akt phosphorylates numerous downstream targets, including mTOR, FoxO transcription factors, GSK3, and Bad, thereby promoting protein synthesis, cell cycle progression, survival, and metabolic reprogramming. For example, Akt-mediated phosphorylation of FoxO3a leads to its exclusion from the nucleus and inhibition of pro-apoptotic gene expression. The pathway also crosstalks with the MAPK/ERK cascade, as shown in ovarian cells where irisin modulates both PI3K/Akt and MAPK/ERK pathways. These downstream events collectively drive the cellular phenotypes associated with GO:0043491.
Negative Regulation by PTEN
In simple terms: PTEN acts as a brake by removing the lipid signal that Akt needs to stay active.
The tumor suppressor PTEN is a lipid phosphatase that dephosphorylates PIP3 back to PIP2, thereby terminating PI3K signaling and preventing Akt activation. Loss of PTEN function is a common event in cancer and leads to constitutive pathway activation. The balance between PI3K and PTEN activity determines the intensity and duration of GO:0043491 signaling, making PTEN a critical node for experimental manipulation.
Spatial Organization and Signal Specificity
In simple terms: Where the signaling happens inside the cell matters for what the signal does.
Recent evidence indicates that focal adhesions spatially organize PI3K-PI(3,4,5)P3-AKT signaling, influencing the specificity and magnitude of downstream outputs. This spatial compartmentalization ensures that Akt activation occurs at precise locations and times, contributing to distinct cellular responses. Understanding this spatial dimension is essential for interpreting experimental results and for designing targeted interventions.
Key Genes Involved in GO:0043491 phosphatidylinositol 3-kinase/protein kinase B signal transduction
The following genes and proteins are core components or regulators of GO:0043491, as documented in the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PIK3CA | Catalytic subunit of PI3K; phosphorylates PIP2 to PIP3 | Frequently mutated in cancers; target for knockout and point mutation studies |
| PIK3R1 | Regulatory subunit of PI3K; modulates catalytic activity | Mutations affect pathway activation; studied via knock-in models |
| AKT1 | Serine/threonine kinase; central effector of the pathway | Key node for point mutation (e.g., E17K) and knockout studies |
| AKT2 | Akt isoform involved in insulin signaling and metabolism | Knockout models reveal metabolic roles |
| AKT3 | Akt isoform predominantly expressed in brain | Implicated in neurodevelopment; knockout models available |
| PDK1 | Phosphorylates Akt at Thr308; essential for activation | Knockout is lethal; conditional models used |
| PTEN | Lipid phosphatase; negative regulator of the pathway | Tumor suppressor; knockout leads to constitutive Akt activation |
| MTOR | Kinase in mTORC1 and mTORC2; downstream of Akt and in feedback loops | Target for rapamycin and CRISPR knockout |
| FOXO3A | Transcription factor inhibited by Akt phosphorylation | Reporter and knockout models for ovarian function |
| HER2 (ERBB2) | Receptor tyrosine kinase upstream of PI3K | Amplified in breast cancer; target for overexpression and knockout |
| IRS1 | Adaptor protein linking insulin receptor to PI3K | Knockout models for insulin resistance |
| TFF3 | Trefoil factor family 3; upregulates PI3K/Akt in liver | Overexpression studies in diabetic models |
| ANXA5 | Annexin A5; mediates PI3K/Akt signaling in HCC | Knockdown suppresses pathway; target for knockout |
| Gastrin | Regulates PI3K/Akt/mTORC2 in gastric mucosa | Measured in chronic atrophic gastritis models |
| MAPK1/ERK2 | Crosstalks with PI3K/Akt pathway | Dual pathway studies in PCOS |
| GSK3B | Substrate of Akt; regulates metabolism and survival | Point mutation and knockout models |
| BAD | Pro-apoptotic protein phosphorylated by Akt | Phospho-mimetic knock-in models |
How Is phosphatidylinositol 3-kinase/protein kinase B signal transduction Regulated?
GO:0043491 is tightly regulated at multiple levels. PTEN acts as a major negative regulator by dephosphorylating PIP3, thereby opposing PI3K activity. mTORC2 phosphorylates Akt at Ser473 to fully activate it, while mTORC1 mediates feedback inhibition of upstream signaling. Spatial organization by focal adhesions further modulates pathway output. Additionally, crosstalk with the MAPK/ERK cascade can influence PI3K/Akt signaling, as observed in ovarian cells treated with irisin. These regulatory mechanisms ensure that the pathway responds appropriately to extracellular cues and are frequently disrupted in disease.
phosphatidylinositol 3-kinase/protein kinase B signal transduction and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| HER2 (ERBB2) | HER2-positive breast cancer | Knockout or overexpression in breast cancer cell lines |
| PIK3CA | Various cancers (e.g., breast, colorectal) | Point mutation knock-in (e.g., H1047R) in cell lines |
| PTEN | Cancer predisposition, metabolic disorders | Knockout in mice or cell lines |
| FOXO3A | Premature ovarian failure | Knockout or reporter knock-in in rat models |
| TFF3 | Diabetes and liver dysfunction | Overexpression in Zucker diabetic fatty rats |
Cancer
Hyperactivation of GO:0043491 is a hallmark of many cancers, including HER2-positive breast cancer, where the HER2/PI3K/AKT axis drives proliferation and survival. Mutations in PIK3CA, loss of PTEN, and amplification of AKT are common oncogenic events. Targeting this pathway with natural products or synthetic inhibitors has shown therapeutic promise in preclinical models. In hepatocellular carcinoma, blocking Annexin A5-mediated PI3K/Akt signaling suppresses tumor progression.
Metabolic and Reproductive Disorders
The pathway is involved in metabolic homeostasis, as shown by improved liver and glucose homeostasis in diabetic rats following Roux-en-Y gastric bypass, which activates hepatic PI3K/Akt. In polycystic ovary syndrome, irisin modulates ovarian PI3K/Akt and MAPK/ERK pathways. Quercetin regulates the ovarian PI3K/Akt/FoxO3a pathway and oxidative stress in a rat model of cyclophosphamide-induced premature ovarian failure. These findings highlight the pathway's role in reproductive and metabolic health.
Gastrointestinal Pathology
In chronic atrophic gastritis, a traditional Chinese medicine decoction (Jiawei Huangqi Guizhi) affects gastrin content and PI3K/Akt/mTORC2 signaling in rats. This suggests that the pathway contributes to gastric mucosal pathology and may be a target for therapeutic intervention.
From phosphatidylinositol 3-kinase/protein kinase B signal transduction-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of PIK3CA abolish PI3K/Akt signaling? | CRISPR knockout of PIK3CA in cancer cell lines |
| Does the AKT1 E17K mutation drive constitutive pathway activation? | Point mutation knock-in of AKT1 E17K |
| Can PTEN restoration suppress tumor growth? | Knock-in of wild-type PTEN in PTEN-null cells |
| How does FOXO3A phosphorylation affect ovarian function? | Knock-in of phospho-deficient FOXO3A in rat models |
| What is the effect of TFF3 overexpression on hepatic PI3K/Akt? | Overexpression of TFF3 in diabetic rat liver |
| Does Annexin A5 mediate PI3K/Akt in HCC? | Knockout of ANXA5 in hepatocellular carcinoma cells |
How to Study the phosphatidylinositol 3-kinase/protein kinase B signal transduction Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Western blot | Phospho-Akt (Thr308/Ser473) levels | Pathway activation status in cells and tissues |
| Phospho-proteomics | Global phosphorylation changes | Identifying downstream targets and crosstalk |
| Live-cell imaging | PIP3 dynamics and localization | Spatial regulation at focal adhesions |
| RNA-seq | Transcriptional changes | FOXO target gene expression |
| Luciferase reporter | Akt or FOXO transcriptional activity | High-throughput compound screening |
| CRISPR knockout screen | Gene essentiality and pathway regulators | Discovery of novel pathway components |
| Immunohistochemistry | Protein expression and localization in tissues | Clinical correlation in cancer |
| Co-immunoprecipitation | Protein-protein interactions | Complex formation (e.g., PI3K subunits) |
Phospho-Proteomics and Western Blotting
Measuring phosphorylation status of Akt (Thr308, Ser473) and downstream substrates is standard for assessing pathway activity. Phospho-proteomics can quantify multiple nodes simultaneously.
Lipid Imaging and Live-Cell Microscopy
Visualizing PIP3 dynamics using fluorescently tagged PH domains allows real-time monitoring of PI3K activity at the membrane. Focal adhesion components can be co-imaged to study spatial organization.
Transcriptomics and Pathway Reporter Assays
RNA-seq and luciferase reporters for FOXO or Akt activity reveal transcriptional outputs of the pathway. These methods are useful for high-throughput screening of pathway modulators.
CRISPR Screening and Functional Genomics
Genome-wide CRISPR knockout or activation screens can identify genes that regulate PI3K/Akt signaling and drug resistance. These screens are powerful for discovering novel pathway components.
How CRISPR Can Be Used to Study GO:0043491 phosphatidylinositol 3-kinase/protein kinase B signal transduction
Knockout
CRISPR knockout of core pathway genes such as PIK3CA, AKT1, or PTEN is used to determine their necessity for PI3K/Akt signaling and cellular phenotypes. For example, knocking out ANXA5 in hepatocellular carcinoma cells suppresses PI3K/Akt signaling and tumor progression. Knockout models are also valuable for validating drug targets.
Point Mutation
Point mutations such as AKT1 E17K or PIK3CA H1047R are introduced via CRISPR to model oncogenic activation and study constitutive signaling. These models help dissect the specific contribution of individual mutations to pathway output and drug response.
Knock-in
Knock-in of wild-type PTEN into PTEN-null cells restores negative regulation and suppresses pathway activity. Similarly, knock-in of phospho-deficient or phospho-mimetic variants of FOXO3A or Akt substrates allows precise interrogation of phosphorylation-dependent functions.
Overexpression
CRISPR activation (CRISPRa) or traditional overexpression constructs can drive high-level expression of pathway components like HER2 or TFF3 to study their effects on PI3K/Akt signaling. Overexpression models are useful for identifying gain-of-function phenotypes and resistance mechanisms.
How EDITGENE Supports phosphatidylinositol 3-kinase/protein kinase B signal transduction Research
Researchers studying phosphatidylinositol 3-kinase/protein kinase B signal transduction-related genes often need to determine whether a candidate gene is causally involved in pathway regulation or disease phenotypes. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such functional studies with high precision and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for phosphatidylinositol 3-kinase/protein kinase B signal transduction research.
Frequently Asked Questions About phosphatidylinositol 3-kinase/protein kinase B signal transduction
What is phosphatidylinositol 3-kinase/protein kinase B signal transduction?
It is an intracellular signaling pathway (GO:0043491) that starts with PI3K activation, produces PI3P, recruits PDK1, and ends with activation of protein kinase B (Akt), regulating cell growth and survival.
What genes are involved in phosphatidylinositol 3-kinase/protein kinase B signal transduction?
Key genes include PIK3CA, PIK3R1, AKT1/2/3, PDK1, PTEN, MTOR, FOXO3A, and upstream receptors like HER2.
How is the PI3K/Akt pathway regulated?
It is positively regulated by receptor tyrosine kinases and negatively regulated by PTEN, with feedback from mTORC1 and spatial organization by focal adhesions.
What diseases are associated with PI3K/Akt signaling?
Cancer, metabolic disorders, polycystic ovary syndrome, premature ovarian failure, and chronic atrophic gastritis are linked to this pathway.
How can I study PI3K/Akt signaling in the lab?
Common methods include Western blotting for phospho-Akt, phospho-proteomics, live-cell imaging of PIP3, RNA-seq, and CRISPR screens.
What is the role of PTEN in this pathway?
PTEN is a lipid phosphatase that dephosphorylates PIP3 to PIP2, thereby inhibiting PI3K/Akt signaling and acting as a tumor suppressor.
Can natural products target the PI3K/Akt pathway?
Yes, compounds like quercetin and 2-hydroxy-3-methylanthraquinone have been shown to modulate PI3K/Akt signaling in cancer and ovarian models.
What CRISPR models are available for PI3K/Akt research?
Knockout, point mutation, knock-in, and overexpression models can be generated for genes such as PIK3CA, AKT1, PTEN, and FOXO3A.
How does the PI3K/Akt pathway crosstalk with MAPK/ERK?
In ovarian cells, irisin modulates both PI3K/Akt and MAPK/ERK pathways, indicating bidirectional crosstalk.
Why is spatial organization important for PI3K/Akt signaling?
Focal adhesions spatially organize PI3K-PI(3,4,5)P3-AKT signaling, which affects signal specificity and cellular outcomes.
Conclusion
GO:0043491 phosphatidylinositol 3-kinase/protein kinase B signal transduction is a central signaling cassette that controls fundamental cellular processes and is implicated in a wide range of diseases. Understanding its molecular steps, regulatory mechanisms, and disease associations is essential for both basic and translational research. With the help of CRISPR-based models and bioinformatics, researchers can dissect the causal roles of individual pathway components and accelerate the development of targeted therapies.
References
- 1. Pan L et al.. 2024. HER2/PI3K/AKT pathway in HER2-positive breast cancer: A review.. Medicine (Baltimore) 103(24):e38508 PMID: 38875362
- 2. Tewari D et al.. 2022. Natural products targeting the PI3K-Akt-mTOR signaling pathway in cancer: A novel therapeutic strategy.. Semin Cancer Biol 80:1-17 PMID: 31866476
- 3. Li CG et al.. 2024. Effect of irisin on ovarian phosphatidylinositol-3-kinase/protein kinase B signaling pathway and mitogen-activated protein kinase/extracellular signal-regulated kinase pathways of rats with polycystic ovary syndrome.. J Obstet Gynaecol Res 50(10):1945-1951 PMID: 39225708
- 4. Zheng S et al.. 2022. Effects of quercetin on ovarian function and regulation of the ovarian PI3K/Akt/FoxO3a signalling pathway and oxidative stress in a rat model of cyclophosphamide-induced premature ovarian failure.. Basic Clin Pharmacol Toxicol 130(2):240-253 PMID: 34841658
- 5. Wang J et al.. 2024. Spatial organization of PI3K-PI(3,4,5)P(3)-AKT signaling by focal adhesions.. Mol Cell 84(22):4401-4418.e9 PMID: 39488211
- 6. Luo M et al.. 2025. 2-Hydroxy-3-Methylanthraquinone Suppresses Hepatocellular Carcinoma Progression by Blocking Annexin A5-Mediated Phosphatidylinositol 3-Kinase/Protein Kinase B Signaling.. Chem Biol Drug Des 106(1):e70161 PMID: 40702694
- 7. Xia Z et al.. 2025. Effect of Jiawei Huangqi Guizhi decoction on the expression of gastrin content and phosphatidylinositol 3-kinase/ protein kinase B/mechanistic target of rapamycin complex 2 signalling pathways in rats with chronic atrophic gastritis.. J Tradit Chin Med 45(4):770-776 PMID: 40810222
- 8. Song K et al.. 2025. Roux-en-Y gastric bypass improves liver and glucose homeostasis in Zucker diabetic fatty rats by upregulating hepatic trefoil factor family 3 and activating the phosphatidylinositol 3-kinase/protein kinase B pathway.. Surg Obes Relat Dis 21(7):792-805 PMID: 39893149
