Biology:PTEN (gene)

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Short description: Tumor suppressor gene


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example
Space-filling model of the PTEN protein (blue) complexed with tartaric acid (brown).[1]

Phosphatase and tensin homolog (PTEN) is a phosphatase in humans and is encoded by the PTEN gene.[2] Mutations of this gene are a step in the development of many cancers, specifically glioblastoma, lung cancer, breast cancer, and prostate cancer. Genes corresponding to PTEN (orthologs)[3] have been identified in most mammals for which complete genome data are available.

PTEN acts as a tumor suppressor gene through the action of its phosphatase protein product. This phosphatase is involved in the regulation of the cell cycle, preventing cells from growing and dividing too rapidly.[4] It is a target of many anticancer drugs.

The protein encoded by this gene is a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase. It contains a tensin-like domain as well as a catalytic domain similar to that of the dual specificity protein tyrosine phosphatases. Unlike most of the protein tyrosine phosphatases, this protein preferentially dephosphorylates phosphoinositide substrates. It negatively regulates intracellular levels of phosphatidylinositol-3,4,5-trisphosphate in cells and functions as a tumor suppressor by negatively regulating the Akt/PKB signaling pathway.[5]

Function

PTEN protein acts as a phosphatase to dephosphorylate phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5)P3 or PIP3). PTEN specifically catalyses the dephosphorylation of the 3` phosphate of the inositol ring in PIP3, resulting in the biphosphate product PIP2 (PtdIns(4,5)P2). This dephosphorylation is important because it results in inhibition of the Akt signaling pathway, which plays an important role in regulating cellular behaviors such as cell growth, survival, and migration.

PTEN also has weak protein phosphatase activity, but this activity is also crucial for its role as a tumor suppressor. PTEN's protein phosphatase activity may be involved in the regulation of the cell cycle, preventing cells from growing and dividing too rapidly.[4] There have been numerous reported protein substrates for PTEN, including IRS1[6] and Dishevelled.[7]

PTEN is one of the targets for drug candidates such as the oncomiR, MIRN21.

Structure

The structure of the core of PTEN (solved by X-ray crystallography, see figure to the upper right[1]) reveals that it consists primarily of a phosphatase domain, and a C2 domain: the phosphatase domain contains the active site, which carries out the enzymatic function of the protein, while the C2 domain binds the phospholipid membrane. Thus PTEN binds the membrane through both its phosphatase and C2 domains, bringing the active site to the membrane-bound PIP3 to dephosphorylate it.

The two domains of PTEN, a protein tyrosine phosphatase domain and a C2 domain, are inherited together as a single unit and thus constitute a superdomain, not only in PTEN but also in various other proteins in fungi, plants and animals, for example, tensin proteins and auxilin.[8]

The active site of PTEN consists of three loops, the TI Loop, the P Loop, and the WPD Loop, all named following the PTPB1 nomenclature.[1] Together they form an unusually deep and wide pocket which allows PTEN to accommodate the bulky phosphatidylinositol 3,4,5-trisphosphate substrate. The dephosphorylation reaction mechanism of PTEN is thought to proceed through a phosphoenzyme intermediate, with the formation of a phosphodiester bond on the active site cysteine, C124.

Not present in the crystal structure of PTEN is a short 10-amino-acid unstructured region N-terminal of the phosphatase domain (from residues 6 to 15), known variously as the PIP2 Binding Domain (PBD) or PIP2 Binding Motif (PBM)[9][10][11] This region increases PTEN's affinity for the plasma membrane by binding to Phosphatidylinositol 4,5-bisphosphate, or possibly any anionic lipid.

Also not present in the crystal structure is the intrinsically disordered C-terminal region (CTR) (spanning residues 353–403). The CTR is constitutively phosphorylated at various positions that effect various aspects of PTEN, including its ability to bind to lipid membranes, and also act as either a protein or lipid phosphatase.[12][13]

Additionally, PTEN can also be expressed as PTEN-L[14] (known as PTEN-Long, or PTEN-α[15]), a leucine initiator alternative start site variant, which adds an additional 173 amino acids to the N-terminus of PTEN. The exact role of this 173-amino acid extension is not yet known, either causing PTEN to be secreted from the cell, or to interact with the mitochondria. The N-terminal extension has been predicted to be largely disordered,[16] although there is evidence that there is some structure in the last twenty amino acids of the extension (most proximal to the start methionine of PTEN).[13]

Clinical significance

Cancer

PTEN is one of the most commonly lost tumor suppressors in human cancer; in fact, up to 70% of men with prostate cancer are estimated to have lost a copy of the PTEN gene at the time of diagnosis.[17] A number of studies have found increased frequency of PTEN loss in tumours which are more highly visible on diagnostic scans such as mpMRI, potentially reflecting increased proliferation and cell density in these tumours.[18]

During tumor development, mutations and deletions of PTEN occur that inactivate its enzymatic activity leading to increased cell proliferation and reduced cell death. Frequent genetic inactivation of PTEN occurs in glioblastoma, endometrial cancer, and prostate cancer; and reduced expression is found in many other tumor types such as lung and breast cancer. Furthermore, PTEN mutation also causes a variety of inherited predispositions to cancer.

Non-cancerous neoplasia

Researchers have identified more than 70 mutations in the PTEN gene in people with Cowden syndrome.[citation needed] These mutations can be changes in a small number of base pairs or, in some cases, deletions of a large number of base pairs.[citation needed] Most of these mutations cause the PTEN gene to make a protein that does not function properly or does not work at all. The defective protein is unable to stop cell division or signal abnormal cells to die, which can lead to tumor growth, particularly in the breast, thyroid, or uterus.[19]

Mutations in the PTEN gene cause several other disorders that, like Cowden syndrome, are characterized by the development of non-cancerous tumors called hamartomas. These disorders include Bannayan–Riley–Ruvalcaba syndrome and Proteus-like syndrome. Together, the disorders caused by PTEN mutations are called PTEN hamartoma tumor syndromes, or PHTS. Mutations responsible for these syndromes cause the resulting protein to be non-functional or absent. The defective protein allows the cell to divide in an uncontrolled way and prevents damaged cells from dying, which can lead to the growth of tumors.[19]

Brain function and autism

Defects of the PTEN gene have been cited to be a potential cause of autism spectrum disorders.[20]

When defective, PTEN protein interacts with the protein of a second gene known as Tp53 to dampen energy production in neurons. This severe stress leads to a spike in harmful mitochondrial DNA changes and abnormal levels of energy production in the cerebellum and hippocampus, brain regions critical for social behavior and cognition. When PTEN protein is insufficient, its interaction with p53 triggers deficiencies and defects in other proteins that also have been found in patients with learning disabilities including autism.[20] People with autism and PTEN mutations may have macrocephaly (unusually large heads).[21]

Patients with defective PTEN can develop cerebellar mass lesions called dysplastic gangliocytomas or Lhermitte–Duclos disease.[19]

Cell regeneration

PTEN's strong link to cell growth inhibition is being studied as a possible therapeutic target in tissues that do not traditionally regenerate in mature animals, such as central neurons. PTEN deletion mutants have recently[22] been shown to allow nerve regeneration in mice.[23][24]

As a drug target

PTEN inhibitors

Bisperoxovanadium compounds may have a neuroprotective effect after CNS injury.[25] PTEN is inhibited by sarcopoterium.[26]

Cell lines

Cell lines with known PTEN mutations include:

  • prostate: LNCaP, PC-3
  • kidney: 786-O
  • glioblastoma: U87MG[27]
  • breast : MB-MDA-468, BT549[27]
  • bladder: J82, UMUC-3

Interactions

PTEN (gene) has been shown to interact with:


See also

References

  1. ↑ 1.0 1.1 1.2 "Crystal structure of the PTEN tumor suppressor: implications for its phosphoinositide phosphatase activity and membrane association". Cell 99 (3): 323–334. October 1999. doi:10.1016/S0092-8674(00)81663-3. PMID 10555148. 
  2. ↑ "Identification of a candidate tumour suppressor gene, MMAC1, at chromosome 10q23.3 that is mutated in multiple advanced cancers". Nature Genetics 15 (4): 356–362. April 1997. doi:10.1038/ng0497-356. PMID 9090379. 
  3. ↑ "OrthoMaM phylogenetic marker: PTEN coding sequence". http://www.orthomam.univ-montp2.fr/orthomam/data/cds/detailMarkers/ENSG00000171862_PTEN.xml. 
  4. ↑ 4.0 4.1 "PTEN regulatory functions in tumor suppression and cell biology". Medical Science Monitor 10 (10): RA235–RA241. October 2004. PMID 15448614. http://www.medscimonit.com/fulltxt.php?ICID=11797. 
  5. ↑ "Entrez Gene: PTEN phosphatase and tensin homolog (mutated in multiple advanced cancers 1)". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=5728. 
  6. ↑ "PTEN is a protein tyrosine phosphatase for IRS1". Nature Structural & Molecular Biology 21 (6): 522–527. June 2014. doi:10.1038/nsmb.2828. PMID 24814346. 
  7. ↑ "PTEN regulates cilia through Dishevelled". Nature Communications 6: 8388. September 2015. doi:10.1038/ncomms9388. PMID 26399523. Bibcode: 2015NatCo...6.8388S. 
  8. ↑ "Superdomains in the protein structure hierarchy: The case of PTP-C2". Protein Science 24 (5): 874–882. May 2015. doi:10.1002/pro.2664. PMID 25694109. 
  9. ↑ "Allosteric activation of PTEN phosphatase by phosphatidylinositol 4,5-bisphosphate". The Journal of Biological Chemistry 278 (36): 33617–33620. September 2003. doi:10.1074/jbc.C300296200. PMID 12857747. 
  10. ↑ "Novel mechanism of PTEN regulation by its phosphatidylinositol 4,5-bisphosphate binding motif is critical for chemotaxis". The Journal of Biological Chemistry 279 (16): 16606–16613. April 2004. doi:10.1074/jbc.M312098200. PMID 14764604. 
  11. ↑ "Interfacial kinetic analysis of the tumour suppressor phosphatase, PTEN: evidence for activation by anionic phospholipids". The Biochemical Journal 371 (Pt 3): 947–955. May 2003. doi:10.1042/BJ20021848. PMID 12534371. 
  12. ↑ "A phosphorylation-dependent intramolecular interaction regulates the membrane association and activity of the tumor suppressor PTEN". Proceedings of the National Academy of Sciences of the United States of America 106 (2): 480–485. January 2009. doi:10.1073/pnas.0811212106. PMID 19114656. Bibcode: 2009PNAS..106..480R. 
  13. ↑ 13.0 13.1 "The intrinsically disordered tails of PTEN and PTEN-L have distinct roles in regulating substrate specificity and membrane activity". The Biochemical Journal 473 (2): 135–144. January 2016. doi:10.1042/BJ20150931. PMID 26527737. 
  14. ↑ "A secreted PTEN phosphatase that enters cells to alter signaling and survival". Science 341 (6144): 399–402. July 2013. doi:10.1126/science.1234907. PMID 23744781. Bibcode: 2013Sci...341..399H. 
  15. ↑ "PTENα, a PTEN isoform translated through alternative initiation, regulates mitochondrial function and energy metabolism". Cell Metabolism 19 (5): 836–848. May 2014. doi:10.1016/j.cmet.2014.03.023. PMID 24768297. 
  16. ↑ "The PTEN Long N-tail is intrinsically disordered: increased viability for PTEN therapy". Molecular BioSystems 9 (11): 2877–2888. November 2013. doi:10.1039/c3mb70267g. PMID 24056727. 
  17. ↑ "Crucial role of p53-dependent cellular senescence in suppression of Pten-deficient tumorigenesis". Nature 436 (7051): 725–730. August 2005. doi:10.1038/nature03918. PMID 16079851. Bibcode: 2005Natur.436..725C. 
  18. ↑ "Genetic Landscape of Prostate Cancer Conspicuity on Multiparametric Magnetic Resonance Imaging: A Systematic Review and Bioinformatic Analysis". European Urology Open Science 20: 37–47. July 2020. doi:10.1016/j.euros.2020.06.006. PMID 33000006. 
  19. ↑ 19.0 19.1 19.2 "Will the real Cowden syndrome please stand up (again)? Expanding mutational and clinical spectra of the PTEN hamartoma tumour syndrome". Journal of Medical Genetics 41 (5): 323–326. May 2004. doi:10.1136/jmg.2004.018036. PMID 15121767. 
  20. ↑ 20.0 20.1 "Mitochondrial dysfunction in Pten haplo-insufficient mice with social deficits and repetitive behavior: interplay between Pten and p53". PLOS ONE 7 (8): e42504. 2012. doi:10.1371/journal.pone.0042504. PMID 22900024. Bibcode: 2012PLoSO...742504N. 
  21. ↑ Charney, Dennis S.; Sklar, Pamela B.; Nestler, Eric J.; Buxbaum, Joseph D. (2018) (in en). Charney & Nestler's Neurobiology of Mental Illness. Oxford University Press. pp. 846. ISBN 9780190681425. https://books.google.com/books?id=y8M9DwAAQBAJ&pg=PA846. 
  22. ↑ "Rodent of the Week: Nerves regenerated after spinal cord injury". The Los Angeles Times. August 13, 2010. http://www.latimes.com/health/boostershots/la-heb-rodent-20100813,0,5830521.story. 
  23. ↑ "PTEN deletion enhances the regenerative ability of adult corticospinal neurons". Nature Neuroscience 13 (9): 1075–1081. September 2010. doi:10.1038/nn.2603. PMID 20694004. 
  24. ↑ "GSK3-CRMP2 signaling mediates axonal regeneration induced by Pten knockout". Communications Biology 2: 318. 2019. doi:10.1038/s42003-019-0524-1. PMID 31453382. 
  25. ↑ "Systemic bisperoxovanadium activates Akt/mTOR, reduces autophagy, and enhances recovery following cervical spinal cord injury". PLOS ONE 7 (1): e30012. 2012. doi:10.1371/journal.pone.0030012. PMID 22253859. Bibcode: 2012PLoSO...730012W. 
  26. ↑ "Insulin-sensitizing and insulin-mimetic activities of Sarcopoterium spinosum extract". Journal of Ethnopharmacology 155 (1): 362–372. August 2014. doi:10.1016/j.jep.2014.05.030. PMID 24882728. 
  27. ↑ 27.0 27.1 "PTEN, a putative protein tyrosine phosphatase gene mutated in human brain, breast, and prostate cancer". Science 275 (5308): 1943–1947. March 1997. doi:10.1126/science.275.5308.1943. PMID 9072974. 
  28. ↑ 28.0 28.1 "Direct identification of PTEN phosphorylation sites". FEBS Letters 528 (1–3): 145–153. September 2002. doi:10.1016/S0014-5793(02)03274-X. PMID 12297295. 
  29. ↑ "Interaction of the tumor suppressor PTEN/MMAC with a PDZ domain of MAGI3, a novel membrane-associated guanylate kinase". The Journal of Biological Chemistry 275 (28): 21477–21485. July 2000. doi:10.1074/jbc.M909741199. PMID 10748157. 
  30. ↑ "PTEN associates with the vault particles in HeLa cells". The Journal of Biological Chemistry 277 (43): 40247–40252. October 2002. doi:10.1074/jbc.M207608200. PMID 12177006. 
  31. ↑ "Crucial role of the C-terminus of PTEN in antagonizing NEDD4-1-mediated PTEN ubiquitination and degradation". The Biochemical Journal 414 (2): 221–229. September 2008. doi:10.1042/BJ20080674. PMID 18498243. 
  32. ↑ "Regulation of androgen receptor signaling by PTEN (phosphatase and tensin homolog deleted on chromosome 10) tumor suppressor through distinct mechanisms in prostate cancer cells". Molecular Endocrinology 18 (10): 2409–2423. October 2004. doi:10.1210/me.2004-0117. PMID 15205473. 
  33. ↑ "PTEN tumor suppressor regulates p53 protein levels and activity through phosphatase-dependent and -independent mechanisms". Cancer Cell 3 (2): 117–130. February 2003. doi:10.1016/S1535-6108(03)00021-7. PMID 12620407. 
  34. ↑ "PTEN interactions with focal adhesion kinase and suppression of the extracellular matrix-dependent phosphatidylinositol 3-kinase/Akt cell survival pathway". The Journal of Biological Chemistry 274 (29): 20693–20703. July 1999. doi:10.1074/jbc.274.29.20693. PMID 10400703. 
  35. ↑ "PTEN regulates tumor cell adhesion of colon carcinoma cells under dynamic conditions of fluid flow". Oncogene 21 (9): 1450–1460. February 2002. doi:10.1038/sj.onc.1205213. PMID 11857088. 

Further reading

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.



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