GO:0016314 phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016314 describes the enzymatic removal of the 3-phosphate from phosphatidylinositol-3,4,5-trisphosphate (PIP3), converting it to phosphatidylinositol-4,5-bisphosphate (PIP2).
• PTEN (phosphatase and tensin homolog) is the principal human enzyme with this activity and functions as a tumor suppressor by antagonizing PI3K/AKT signaling.
• Loss-of-function mutations in PTEN cause PTEN hamartoma tumor syndromes, including Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome.
• The reaction is a key node in phosphoinositide signaling, controlling AKT activation, cell survival, proliferation, and neutrophil spontaneous death.
• Beyond PTEN, other enzymes such as voltage-sensing phosphatases (VSP) and microbial cytolethal distending toxin subunit B exhibit related 3-phosphatase activity toward PIP3 or PI(3,4)P2.
• CRISPR-based knockout, knock-in, and point-mutation models are essential to dissect the role of GO:0016314 in cancer, autism-related syndromes, and immune cell biology.
Description
Phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity (GO:0016314) is a molecular function that catalyzes the hydrolysis of phosphatidylinositol-3,4,5-trisphosphate (PIP3) to phosphatidylinositol-4,5-bisphosphate (PIP2) and inorganic phosphate. This reaction directly opposes the action of phosphoinositide 3-kinases (PI3Ks) and serves as a critical brake on the PI3K/AKT signaling axis, which governs cell growth, survival, and metabolism. The most extensively studied enzyme carrying this activity is PTEN (phosphatase and tensin homolog), a tumor suppressor frequently mutated in human cancers. The importance of GO:0016314 extends beyond oncology. Germline mutations in PTEN cause PTEN hamartoma tumor syndrome (PHTS), a spectrum of disorders that includes Cowden syndrome and autism-related features. Functional analysis of PTEN mutations has revealed distinct genotype-phenotype correlations, linking specific catalytic impairments to tumor predisposition or neurodevelopmental phenotypes. Additionally, the reaction is involved in immune regulation, as deactivation of PIP3/AKT signaling mediates neutrophil spontaneous death. Researchers study GO:0016314 to understand how cells terminate PI3K signaling, how mutations in PTEN and related enzymes drive disease, and how to target these pathways therapeutically. The enzymatic activity is also a benchmark for evaluating synthetic PIP3 analogues and for characterizing microbial effectors that mimic host phosphatases.
phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity At A Glance
| GO ID | GO:0016314 |
|---|---|
| GO term | phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity |
| Ontology | molecular_function |
| Synonym | PI(3,4,5)P3 3-phosphatase activity; PtdIns(3,4,5)P3 3-phosphatase activity; MMAC1; phosphatidylinositol-3,4,5-trisphosphate 3-phosphohydrolase activity |
| Major function | Hydrolyzes PIP3 to PIP2, thereby terminating PI3K/AKT signaling |
| Reaction | phosphatidylinositol-3,4,5-trisphosphate + H2O = phosphatidylinositol-4,5-bisphosphate + phosphate |
| Cofactors | Requires Mg2+ or Mn2+ for catalysis (inferred from PTEN biochemistry) |
| Major enzyme | PTEN (phosphatase and tensin homolog) |
| Related enzymes | Voltage-sensing phosphatase (VSP) acts on PI(3,4)P2; cytolethal distending toxin subunit B exhibits PIP3 phosphatase activity |
What Is GO:0016314?
GO:0016314 is defined by the Gene Ontology as the catalysis of the reaction: phosphatidylinositol-3,4,5-trisphosphate + H2O = phosphatidylinositol-4,5-bisphosphate + phosphate. In other words, it is the enzymatic activity that removes the phosphate group at the 3-position of the inositol ring of PIP3, producing PIP2. This activity is synonymous with PI(3,4,5)P3 3-phosphatase, PtdIns(3,4,5)P3 3-phosphatase, and MMAC1 (the original name for PTEN). It belongs to the molecular_function ontology aspect and is a key component of phosphoinositide metabolism.
Why Is phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity Important in Cell Biology?
GO:0016314 is a central node in cellular signal transduction because it directly reverses the production of PIP3, the lipid second messenger that recruits and activates AKT and other pleckstrin-homology domain-containing proteins. By converting PIP3 to PIP2, this activity acts as a tumor suppressor mechanism, and its loss leads to constitutive PI3K/AKT signaling, which drives uncontrolled proliferation and survival in many cancers. Moreover, the reaction is critical for normal physiology, including immune cell homeostasis and neutrophil death, and its dysregulation is linked to neurodevelopmental disorders such as autism-related syndromes. Understanding this activity is therefore essential for cancer biology, immunology, and neurodevelopment.
• Tumor suppression: PTEN, the main enzyme with this activity, is one of the most frequently mutated tumor suppressors in human cancers.
• PI3K/AKT pathway regulation: The conversion of PIP3 to PIP2 directly opposes PI3K signaling, controlling cell growth and survival.
• PTEN hamartoma tumor syndrome: Germline PTEN mutations cause Cowden syndrome and related disorders.
• Autism-related syndromes: Functional analysis of PTEN mutations has implications for autism-related phenotypes.
• Immune regulation: Deactivation of PIP3/AKT signaling mediates neutrophil spontaneous death.
• Microbial pathogenesis: Some bacterial toxins, such as cytolethal distending toxin subunit B, exhibit PIP3 phosphatase activity to manipulate host cells.
• Drug discovery: PTEN-resistant PIP3 analogues are used to probe signaling and develop inhibitors.
• Enzyme diversity: Voltage-sensing phosphatases broaden the family of 3-phosphatases acting on phosphoinositides.
• Biochemical assays: Purification and characterization of PIP3 5-phosphatases provide tools to distinguish 3- vs 5-phosphatase activities.
• CRISPR modeling: Gene editing enables precise dissection of PTEN and related genes in disease models.
Molecular Mechanism of phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity
Substrate recognition and binding
In simple terms: The enzyme grabs PIP3 and positions it for phosphate removal.
The primary substrate for GO:0016314 is phosphatidylinositol-3,4,5-trisphosphate (PIP3), a membrane-embedded phosphoinositide. PTEN, the canonical enzyme, binds PIP3 through its phosphatase domain and a C2 domain that facilitates membrane association. The active site accommodates the inositol headgroup, allowing specific recognition of the 3-phosphate. Synthetic PTEN-resistant analogues of PIP3 have been used to confirm substrate specificity and to study downstream signaling.
Catalytic hydrolysis of the 3-phosphate
In simple terms: The enzyme uses water to cut off the phosphate at the 3-position.
Catalysis proceeds via a nucleophilic attack by water on the 3-phosphate of PIP3, yielding phosphatidylinositol-4,5-bisphosphate (PIP2) and inorganic phosphate. This reaction requires divalent metal ions such as Mg2+ for optimal activity. The catalytic mechanism is characteristic of the protein tyrosine phosphatase superfamily, to which PTEN belongs. The reaction is highly specific for the 3-position, distinguishing it from 5-phosphatases that remove the 5-phosphate.
Product formation and signaling termination
In simple terms: The product PIP2 no longer recruits AKT, so the signal is turned off.
The conversion of PIP3 to PIP2 terminates the membrane recruitment of AKT and other PIP3-binding effectors, thereby shutting down downstream survival and proliferation signals. This deactivation is crucial for preventing constitutive AKT activation. In neutrophils, deactivation of PIP3/AKT signaling mediates spontaneous cell death, highlighting the physiological importance of this reaction.
Related enzymes and alternative substrates
In simple terms: Other enzymes can also remove phosphates from similar lipids, but with different specificities.
Voltage-sensing phosphatase (VSP) exhibits 3-phosphatase activity toward phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2], expanding the repertoire of enzymes that can dephosphorylate phosphoinositides at the 3-position. Additionally, the cytolethal distending toxin subunit B from bacteria displays phosphatidylinositol 3,4,5-trisphosphate phosphatase activity, representing a microbial strategy to manipulate host signaling. These examples illustrate the broader biological context of GO:0016314.
Regulation by PTEN and interacting proteins
In simple terms: The activity is controlled by how much PTEN is present and how it is modified.
PTEN activity is regulated at multiple levels, including transcription, post-translational modifications (phosphorylation, ubiquitination, oxidation), and protein-protein interactions. Mutations in PTEN that impair its catalytic activity lead to accumulation of PIP3 and hyperactivation of AKT. Functional analysis of PTEN mutations has revealed that different mutations can differentially affect tumor suppression versus neurodevelopmental functions. The regulation of PTEN is therefore central to the control of GO:0016314 in cells.
Key Genes Involved in GO:0016314 phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity
The following genes and proteins are directly or functionally associated with phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity (GO:0016314), based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PTEN | Primary 3-phosphatase that converts PIP3 to PIP2; tumor suppressor | Most studied enzyme for GO:0016314; mutations in cancer and autism |
| PIK3CA | Catalytic subunit of PI3K; produces PIP3, the substrate of PTEN | Oncogene frequently mutated in cancers; opposes PTEN function |
| PIK3R1 | Regulatory subunit of PI3K; modulates PIP3 production | Mutations affect PI3K signaling and PTEN-dependent phenotypes |
| AKT1 | Serine/threonine kinase activated by PIP3; downstream effector | Readout of PTEN activity; target for pathway inhibitors |
| AKT2 | AKT isoform involved in insulin signaling and survival | Implicated in metabolic and cancer phenotypes |
| AKT3 | AKT isoform enriched in brain; linked to neurodevelopment | Relevant to autism-related syndromes and PTEN mutations |
| TP53 | Tumor suppressor; interacts with PTEN pathway in cancer | Co-mutations with PTEN influence tumor progression |
| BRCA1 | DNA repair gene; synthetic lethality with PTEN loss | Potential therapeutic target in PTEN-mutant cancers |
| VSP (voltage-sensing phosphatase) | 3-phosphatase activity toward PI(3,4)P2 | Model for studying phosphoinositide 3-phosphatase mechanism |
| CdtB (cytolethal distending toxin subunit B) | Microbial PIP3 phosphatase | Bacterial effector that mimics host phosphatase activity |
| INPP4B | Inositol polyphosphate 4-phosphatase; indirectly affects PIP3 levels | Modulates PI3K/AKT signaling in cancer |
| INPP5D (SHIP1) | 5-phosphatase that converts PIP3 to PI(3,4)P2 | Distinct from 3-phosphatase; regulates immune signaling |
| OCRL | 5-phosphatase involved in phosphoinositide metabolism | Mutations cause Lowe syndrome; related to PIP3 turnover |
| MTM1 | Myotubularin, a 3-phosphatase for PI(3)P and PI(3,5)P2 | Related to VSP and PTEN in phosphoinositide dephosphorylation |
| PIP4K2A | Phosphatidylinositol-5-phosphate 4-kinase; generates PIP2 | Contributes to substrate availability for PIP3 synthesis |
| PTENP1 | Pseudogene of PTEN; regulates PTEN expression | Modulates PTEN levels and thus GO:0016314 activity |
| SUMO1 | Post-translational modifier of PTEN | Regulates PTEN stability and localization |
| NEDD4 | E3 ubiquitin ligase that ubiquitinates PTEN | Controls PTEN degradation and PIP3 levels |
How Is phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity Regulated?
The activity of phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase is primarily regulated through the expression, localization, and post-translational modification of PTEN. PTEN is subject to phosphorylation by kinases such as CK2 and GSK3, which affect its stability and membrane recruitment. Ubiquitination by NEDD4 leads to proteasomal degradation, reducing 3-phosphatase activity and increasing PIP3 levels. Oxidation of the catalytic cysteine by reactive oxygen species transiently inactivates PTEN, allowing temporary PIP3 accumulation during growth factor signaling. Additionally, PTEN is regulated by SUMOylation and by interaction with PDZ domain-containing proteins. In immune cells, the balance between PI3K and PTEN activities determines the lifespan of neutrophils, with PIP3 dephosphorylation promoting spontaneous death. These regulatory layers ensure that GO:0016314 is tightly controlled in response to cellular cues.
phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PTEN | PTEN hamartoma tumor syndrome; Cowden syndrome; cancer | Knockout and point-mutation cell lines; mouse models |
| PTEN | Autism-related syndromes; macrocephaly | Patient-derived iPSCs; neuronal cultures with PTEN mutations |
| PIK3CA | Cancer; overactivation of PI3K/AKT pathway | Knock-in of activating mutations; organoids |
| AKT1 | Cancer; metabolic disorders | Overexpression and knockout models; xenografts |
| CdtB | Bacterial pathogenesis; host immune evasion | Recombinant toxin treatment; infection models |
PTEN hamartoma tumor syndrome and cancer predisposition
Germline mutations in PTEN cause PTEN hamartoma tumor syndrome (PHTS), which includes Cowden syndrome, Bannayan-Riley-Ruvalcaba syndrome, and Proteus-like syndrome. These conditions are characterized by multiple hamartomas and an increased risk of cancers such as breast, thyroid, and endometrial carcinoma. The loss of 3-phosphatase activity leads to PIP3 accumulation and constitutive AKT activation, driving tumorigenesis. Somatic PTEN mutations are also among the most common events in sporadic cancers, including glioblastoma and prostate cancer.
Autism spectrum disorders and neurodevelopment
Functional analysis of PTEN mutations has revealed implications in autism-related syndromes. Certain PTEN mutations that impair catalytic activity but retain other functions may contribute to neurodevelopmental phenotypes, including macrocephaly and autism spectrum disorder. The PI3K/AKT pathway, which is normally restrained by GO:0016314, is critical for neuronal growth and synaptic function, and its dysregulation can alter brain development.
Immune regulation and neutrophil homeostasis
Deactivation of phosphatidylinositol 3,4,5-trisphosphate/Akt signaling mediates neutrophil spontaneous death. This process is essential for resolving inflammation and preventing tissue damage. The 3-phosphatase activity that converts PIP3 to PIP2 is a key step in this deactivation, and its dysregulation can lead to prolonged neutrophil survival and inflammatory pathology.
Microbial pathogenesis and host manipulation
The cytolethal distending toxin subunit B from bacteria exhibits phosphatidylinositol 3,4,5-trisphosphate phosphatase activity, representing a novel mode of action for a microbial-derived immunotoxin. By depleting PIP3, this toxin can disrupt host cell signaling and immune responses, contributing to bacterial pathogenesis. This highlights how pathogens can mimic or hijack GO:0016314 for their own benefit.
From phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of PTEN 3-phosphatase activity drive tumorigenesis? | PTEN knockout cell lines and mouse models |
| How do specific PTEN point mutations affect catalytic activity versus protein interactions? | Point-mutation knock-in cell lines (e.g., C124S, G129E) |
| What is the effect of PTEN restoration on PIP3 levels and AKT signaling? | Knock-in of wild-type PTEN or overexpression |
| How does PTEN localization affect its 3-phosphatase activity? | Tagged knock-in (e.g., GFP-PTEN) for live imaging |
| Can PTEN-resistant PIP3 analogues bypass PTEN-mediated signaling? | Overexpression of PTEN with synthetic PIP3 analogues |
| What is the role of VSP in phosphoinositide regulation? | Knockout or overexpression of VSP in cell lines |
How to Study the phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Malachite green assay | Release of inorganic phosphate from PIP3 | In vitro PTEN activity |
| Radioactive PIP3 assay | Conversion of 32P-PIP3 to PIP2 | Enzyme kinetics and specificity |
| Phospho-AKT Western blot | AKT phosphorylation at Ser473/Thr308 | Readout of PTEN function |
| CRISPR knockout screen | Gene essentiality and pathway interactions | Discovery of regulators of PIP3 signaling |
| Live-cell imaging with PH-domain biosensors | PIP3 localization and dynamics | Spatiotemporal analysis of PTEN activity |
| Synthetic PIP3 analogues | Enzyme resistance and signaling | Probing PTEN substrate specificity |
| Neutrophil survival assays | Spontaneous cell death | Role of PIP3/AKT deactivation |
| Bacterial toxin assays | PIP3 phosphatase activity of CdtB | Microbial pathogenesis studies |
Biochemical phosphatase assays
Direct measurement of GO:0016314 activity can be performed using malachite green or radioactive assays with PIP3 as substrate. Purification and biochemical characterization of PIP3 5-phosphatases provide a framework for distinguishing 3-phosphatase activity. Synthetic PTEN-resistant PIP3 analogues can be used to probe substrate specificity and to assess enzyme kinetics.
CRISPR-based genetic screens
Genome-wide CRISPR knockout screens can identify genes that modulate PIP3 levels and AKT signaling. Such screens are valuable for discovering novel regulators of GO:0016314 and for mapping synthetic lethal interactions with PTEN loss.
Phospho-proteomics and signaling readouts
Mass spectrometry-based phosphoproteomics can quantify AKT phosphorylation at Ser473 and Thr308, which are readouts of PIP3 levels and PTEN activity. These methods are used to assess the impact of PTEN mutations on downstream signaling.
Live-cell imaging of phosphoinositides
Genetically encoded biosensors such as GFP-AKT-PH can visualize PIP3 distribution in live cells. Tagged knock-in of PTEN allows simultaneous tracking of enzyme localization and substrate conversion. These imaging approaches provide spatiotemporal insights into GO:0016314 in real time.
How CRISPR Can Be Used to Study GO:0016314 phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity
Knockout
CRISPR knockout of PTEN or related genes is used to eliminate 3-phosphatase activity, leading to PIP3 accumulation and constitutive AKT activation. These models are essential for studying the tumor suppressor function of PTEN and for testing targeted therapies. Knockout of VSP or other phosphatases can reveal their contributions to phosphoinositide metabolism.
Point Mutation
Point mutations in PTEN, such as C124S (catalytically dead) or G129E (lipid phosphatase deficient), can be introduced via CRISPR to dissect the specific contribution of 3-phosphatase activity versus protein-protein interactions. These models help distinguish between tumor-suppressive and neurodevelopmental functions of PTEN.
Knock-in
Knock-in of tagged PTEN (e.g., GFP or HA) allows for live-cell imaging and biochemical purification of the enzyme. Knock-in of patient-derived mutations can recreate disease-associated alleles in isogenic cell lines, enabling precise genotype-phenotype studies.
Overexpression
Overexpression of wild-type PTEN or other 3-phosphatases is used to reduce PIP3 levels and inhibit AKT signaling. This approach can reverse the effects of PTEN loss and is valuable for validating drug targets. Overexpression of PTEN-resistant PIP3 analogues can also be used to study signaling dynamics.
How EDITGENE Supports phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity Research
Researchers studying phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity-related genes often need to determine whether a candidate gene is causally involved in PIP3 metabolism, AKT signaling, or disease phenotypes. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity research.
Frequently Asked Questions About phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity
What is phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity?
It is the enzymatic activity that removes the 3-phosphate from PIP3 to produce PIP2, as defined by GO:0016314.
What genes are involved in phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity?
The primary gene is PTEN, but other enzymes such as VSP and bacterial CdtB also exhibit related activities.
What is the role of PTEN in this activity?
PTEN is the main human enzyme that catalyzes the conversion of PIP3 to PIP2, acting as a tumor suppressor.
How is phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity regulated?
It is regulated by PTEN expression, phosphorylation, ubiquitination, oxidation, and protein interactions.
What diseases are associated with defects in this activity?
PTEN hamartoma tumor syndrome, cancer, autism-related syndromes, and immune disorders.
How can I study phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity in the lab?
Biochemical assays, CRISPR knockout/knock-in models, phospho-AKT Western blots, and live-cell imaging.
What is the difference between 3-phosphatase and 5-phosphatase activity?
3-phosphatase removes the phosphate at the 3-position of PIP3, while 5-phosphatase removes it at the 5-position, producing different products.
Can CRISPR be used to model PTEN mutations?
Yes, CRISPR knock-in can introduce specific PTEN mutations to study their effects on 3-phosphatase activity and disease.
What are PTEN-resistant PIP3 analogues?
Synthetic PIP3 analogues that cannot be dephosphorylated by PTEN, used to study signaling.
How does the microbial toxin CdtB relate to this activity?
CdtB exhibits PIP3 phosphatase activity, mimicking host enzymes to manipulate signaling.
Conclusion
Phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase activity (GO:0016314) is a fundamental enzymatic function that controls the levels of PIP3, a key lipid second messenger in cell survival and proliferation. PTEN is the principal enzyme responsible for this activity, and its dysfunction is linked to cancer, PTEN hamartoma tumor syndrome, autism-related phenotypes, and immune dysregulation. Understanding the molecular mechanism, regulation, and disease relevance of this activity is essential for developing targeted therapies. CRISPR-based models, including knockout, point-mutation knock-in, and overexpression, provide powerful tools to dissect the precise roles of PTEN and related enzymes. EDITGENE offers a full range of services to support such research, from custom cell line generation to CRISPR library screening and bioinformatics analysis.
References
- 1. Rodríguez-Escudero I et al.. 2011. A comprehensive functional analysis of PTEN mutations: implications in tumor- and autism-related syndromes.. Hum Mol Genet 20(21):4132-42 PMID: 21828076
- 2. Adam MP et al.. 1993. PTEN Hamartoma Tumor Syndrome.. PMID: 20301661
- 3. Kurokawa T et al.. 2012. 3' Phosphatase activity toward phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] by voltage-sensing phosphatase (VSP).. Proc Natl Acad Sci U S A 109(25):10089-94 PMID: 22645351
- 4. Zhang H et al.. 2006. Synthesis and biological activity of PTEN-resistant analogues of phosphatidylinositol 3,4,5-trisphosphate.. J Am Chem Soc 128(51):16464-5 PMID: 17177371
- 5. Woscholski R et al.. 1995. Purification and biochemical characterization of a mammalian phosphatidylinositol 3,4,5-trisphosphate 5-phosphatase.. J Biol Chem 270(52):31001-7 PMID: 8537357
- 6. Zhu D et al.. 2006. Deactivation of phosphatidylinositol 3,4,5-trisphosphate/Akt signaling mediates neutrophil spontaneous death.. Proc Natl Acad Sci U S A 103(40):14836-41 PMID: 16988010
- 7. Maehama T et al.. 1998. The tumor suppressor, PTEN/MMAC1, dephosphorylates the lipid second messenger, phosphatidylinositol 3,4,5-trisphosphate.. J Biol Chem 273(22):13375-8 PMID: 9593664
- 8. Shenker BJ et al.. 2007. A novel mode of action for a microbial-derived immunotoxin: the cytolethal distending toxin subunit B exhibits phosphatidylinositol 3,4,5-triphosphate phosphatase activity.. J Immunol 178(8):5099-108 PMID: 17404292
