NT5E explained

5′-nucleotidase (5′-NT), also known as ecto-5′-nucleotidase or CD73 (cluster of differentiation 73), is an enzyme that in humans is encoded by the NT5E gene. CD73 commonly serves to convert AMP to adenosine.

Transcription factor binding sites

NT5E contains binding sites for transcription factors AP-2, SMAD proteins, SP-1 and elements responsive to c-AMP, which can be found in c-AMP promoter parts. SMADs 2, 3, 4 and 5 and SP-1 are binding to the NT5E promoter in rats, as was proven in chromatin immunoprecipitation assays. Due to the fact, that the human and rat NT5E transcripts are 89% identical, human NT5E could be also regulated by SMAD proteins.^[1]

Function

Ecto-5-prime-nucleotidase (5-prime-ribonucleotide phosphohydrolase; EC 3.1.3.5) catalyzes the conversion at neutral pH of purine 5-prime mononucleotides to nucleosides, the preferred substrate being AMP. The enzyme consists of a dimer of 2 identical 70-kD subunits bound by a glycosyl phosphatidyl inositol linkage to the external face of the plasma membrane. The enzyme is used as a marker of lymphocyte differentiation. Consequently, a deficiency of NT5 occurs in a variety of immunodeficiency diseases (e.g., see MIM 102700, MIM 300300). Other forms of 5-prime nucleotidase exist in the cytoplasm and lysosomes and can be distinguished from ecto-NT5 by their substrate affinities, requirement for divalent magnesium ion, activation by ATP, and inhibition by inorganic phosphate. Rare allelic variants are associated with a syndrome of adult-onset calcification of joints and arteries (CALJA) affecting the iliac, femoral, and tibial arteries reducing circulation in the legs and the joints of the hands and feet causing pain.

Immunosuppression

NT5E (CD73) is a surface enzyme which is expressed on multiple cells. This enzyme mediates the gradual hydrolysis of the autocrine and paracrine danger signals of ATP and ADP to anti-inflammatory adenosine. Immune suppression mediated by adenosinergic pathways is very important for maintaining immune system homeostasis. Immune suppressive functions of T regulatory cells are also dependent on CD73 expression. Treg's generally suppress the immune response. They affect proliferation and function of T cell.^[2] CD73 also occurs on anergic CD4 + T cells, thereby maintaining self tolerance to healthy tissues as well as protecting the fetus from the mother's immune system during pregnancy. Also described was adenosine generated by NT5E, which limits the inflammatory immune response by negative feedback in neutrophil which express the adenosine receptor.^[3]

As a drug target

Some tumours have upregulation and overexpression of CD73 so it has been proposed as a drug target for cancer therapy.^{[4] [5] [6]}

An anti-CD73 antibody CPI-006 has started early stage clinical trials as a treatment for advanced cancers.^[7]

Systemic lupus erythematosus

Specialized immune cells such as myeloid-derived suppressor cells and regulatory T cells also mediate their effects via adenosine generated by local ectonucleotidase. In some cases of lupus patients, adequate T cell expression of CD73 is missing, which shows an impaired regulatory function of T cells.^[8]

Cancer

NT5E can act as an immune inhibitory control molecule. Free adenosine generated by NT5E inhibits cellular immune responses and thereby promotes immune escape of tumor cells.^[3] Due to enzymatic and non-enzymatic properties, CD73 is involved in cancer-related processes and is upregulated in many cancers such as leukemia, glioblastoma, melanoma, oesophageal, prostate, ovarian and breast cancer. It is an important key molecule in cancer regulation and development and is involved in tumor progression. In addition, NT5E functions as an adhesion and signaling molecule and can regulate cellular signaling with extracellular matrix components such as fibronectin and laminin. This can mediate the metastatic and invasive properties of cancer.^[9] In mouse breast and prostate cancer tumor models as well as in breast cancer xenograft model, NT5E was confirmed to support tumor angiogenesis. His expression promotes invasion and metastasis of murine and human melanoma cells and human breast cancer cells. Tumor infiltration by cells which express NT5E such as myeloid derived suppressor cells (MDSC), Treg's, dendritic cells (DC) leads to accumulation of adenosine. Subsequently, cAMP signaling is triggered in T cell that express the adenosine A2A receptor.^[10] Adenosine receptor are also expressed on macrophage, DCs, MDSC and natural killer cell(NK). Thus, adenosine may inhibit the function of these immune cells. In addition, the tumor cells may also express adenosine A1 and A3 receptors associated with Gαi proteins, promoting both the migration and proliferation of tumor cells.^{[3] [9] [11]} Especially due to its beneficial effects in mouse tumor model, anti-CD73 therapy is now a promising approach to cancer treatment in the future. CD73 inhibitor are currently being tested in clinical trials for the cancer treatment.^[9]

miRNA

MicroRNA are small non-coding RNA molecules which regulate gene expression at posttranscriptional level via binding to mRNA. This leads to degradation of the target mRNA molecule or translational repression. In tumor cells the miRNA expression pattern often change and therefore affect the surface NT5E, which as result interfere the anti-tumor immune response.^{[12] [13]} For example, studies confirm the role of the miR30 family in NT5E regulation. Upon miR-30a-5p expression, NT5E expression was decreased.^[3]

See also

• Cluster of differentiation
• Arterial calcification due to CD73 deficiency

Further reading

• Resta R, Thompson LF . T cell signalling through CD73 . Cellular Signalling . 9 . 2 . 131–9 . February 1997 . 9113412 . 10.1016/S0898-6568(96)00132-5 .
• Kirchhoff C, Hale G . Cell-to-cell transfer of glycosylphosphatidylinositol-anchored membrane proteins during sperm maturation . Molecular Human Reproduction . 2 . 3 . 177–84 . March 1996 . 9238677 . 10.1093/molehr/2.3.177 . free .
• Resta R, Yamashita Y, Thompson LF . Ecto-enzyme and signaling functions of lymphocyte CD73 . Immunological Reviews . 161 . 95–109 . February 1998 . 9553767 . 10.1111/j.1600-065X.1998.tb01574.x . 29930691 .
• Rosi F, Carlucci F, Marinello E, Tabucchi A . Ecto-5'-nucleotidase in B-cell chronic lymphocytic leukemia . Biomedicine & Pharmacotherapy . 56 . 2 . 100–4 . March 2002 . 12000134 . 10.1016/S0753-3322(01)00072-5 .
• Babiychuk EB, Draeger A . Regulation of ecto-5'-nucleotidase activity via Ca2+-dependent, annexin 2-mediated membrane rearrangement? . Biochemical Society Transactions . 34 . Pt 3 . 374–6 . June 2006 . 16709165 . 10.1042/BST0340374 . 8728207 .
• Stefanovic V, Mandel P, Rosenberg A . Ecto-5'-nucleotidase of intact cultured C6 rat glioma cells . The Journal of Biological Chemistry . 251 . 13 . 3900–5 . July 1976 . 10.1016/S0021-9258(17)33333-1 . 819433 . free .
• Thomson LF, Ruedi JM, Glass A, Moldenhauer G, Moller P, Low MG, Klemens MR, Massaia M, Lucas AH . Production and characterization of monoclonal antibodies to the glycosyl phosphatidylinositol-anchored lymphocyte differentiation antigen ecto-5'-nucleotidase (CD73) . Tissue Antigens . 35 . 1 . 9–19 . January 1990 . 2137649 . 10.1111/j.1399-0039.1990.tb01750.x .
• Klemens MR, Sherman WR, Holmberg NJ, Ruedi JM, Low MG, Thompson LF . Characterization of soluble vs membrane-bound human placental 5'-nucleotidase . Biochemical and Biophysical Research Communications . 172 . 3 . 1371–7 . November 1990 . 2173922 . 10.1016/0006-291X(90)91601-N .
• Boyle JM, Hey Y, Guerts van Kessel A, Fox M . Assignment of ecto-5'-nucleotidase to human chromosome 6 . Human Genetics . 81 . 1 . 88–92 . December 1988 . 2848759 . 10.1007/BF00283737 . 22488106 .
• Vlahović P, Stefanović V . Effect of dopamine on ecto-5'-nucleotidase expression in human glomerular mesangial cells . Archives Internationales de Physiologie, de Biochimie et de Biophysique . 102 . 3 . 171–3 . 1995 . 8000038 . 10.3109/13813459409007533 .
• Hansen KR, Resta R, Webb CF, Thompson LF . Isolation and characterization of the promoter of the human 5'-nucleotidase (CD73)-encoding gene . Gene . 167 . 1–2 . 307–12 . December 1995 . 8566797 . 10.1016/0378-1119(95)00574-9 .
• Airas L, Jalkanen S . CD73 mediates adhesion of B cells to follicular dendritic cells . Blood . 88 . 5 . 1755–64 . September 1996 . 8781432 . 10.1182/blood.V88.5.1755.1755 . free .
• Airas L, Niemelä J, Salmi M, Puurunen T, Smith DJ, Jalkanen S . Differential regulation and function of CD73, a glycosyl-phosphatidylinositol-linked 70-kD adhesion molecule, on lymphocytes and endothelial cells . The Journal of Cell Biology . 136 . 2 . 421–31 . January 1997 . 9015312 . 2134816 . 10.1083/jcb.136.2.421 .
• Strohmeier GR, Lencer WI, Patapoff TW, Thompson LF, Carlson SL, Moe SJ, Carnes DK, Mrsny RJ, Madara JL . Surface expression, polarization, and functional significance of CD73 in human intestinal epithelia . The Journal of Clinical Investigation . 99 . 11 . 2588–601 . June 1997 . 9169488 . 508104 . 10.1172/JCI119447 .
• Book: Aumüller G, Renneberg H, Schiemann PJ, Wilhelm B, Seitz J, Konrad L, Wennemuth G . The Role of Apocrine Released Proteins in the Post-Testicular Regulation of Human Sperm Function . Advances in Experimental Medicine and Biology . 1997 . The Fate of the Male Germ Cell . 424 . 193–219 . 9361795 . 10.1007/978-1-4615-5913-9_39 . 978-1-4613-7711-5 .
• Rosi F, Agostinho AB, Carlucci F, Zanoni L, Porcelli B, Marinello E, Galieni P, Tabucchi A . Behaviour of human lymphocytic isoenzymes of 5'-nucleotidase . Life Sciences . 62 . 25 . 2257–66 . 1998 . 9651114 . 10.1016/S0024-3205(98)00206-9 .

Notes and References

1. Kordaß T, Osen W, Eichmüller SB . Controlling the Immune Suppressor: Transcription Factors and MicroRNAs Regulating CD73/NT5E . en . Frontiers in Immunology . 9 . 813 . 2018 . 29720980 . 5915482 . 10.3389/fimmu.2018.00813 . free .
2. Dong K, Gao ZW, Zhang HZ . The role of adenosinergic pathway in human autoimmune diseases . Immunologic Research . 64 . 5–6 . 1133–1141 . December 2016 . 27665459 . 5126201 . 10.1007/s12026-016-8870-2 .
3. Kordaß T, Osen W, Eichmüller SB . Controlling the Immune Suppressor: Transcription Factors and MicroRNAs Regulating CD73/NT5E . Frontiers in Immunology . 9 . 813 . 2018-04-18 . 29720980 . 5915482 . 10.3389/fimmu.2018.00813 . free .
4. https://jitc.biomedcentral.com/articles/10.1186/s40425-018-0360-8 Targeting adenosine for cancer immunotherapy 2018
5. https://www.cell.com/trends/cancer/pdf/S2405-8033(16)00004-2.pdf Anti-CD73 in Cancer Immunotherapy: Awakening New Opportunities 2016
6. 30556751 . 10.1080/14728222.2019.1559829 . 23 . CD73 as a potential opportunity for cancer immunotherapy . 2019 . Expert Opin Ther Targets . 127–142 . Ghalamfarsa G, Kazemi MH, Raoofi Mohseni S, Masjedi A, Hojjat-Farsangi M, Azizi G, Yousefi M, Jadidi-Niaragh F. 2 . 58767911 .
7. https://www.healio.com/hematology-oncology/gastrointestinal-cancer/news/online/%7B4d2d76bf-104b-4780-a831-91ebae610347%7D/anti-cd73-antibody-agent-appears-safe-shows-promise-in-advanced-cancers Anti-CD73 antibody agent appears safe, shows promise in advanced cancers
8. Knight JS, Mazza LF, Yalavarthi S, Sule G, Ali RA, Hodgin JB, Kanthi Y, Pinsky DJ . Ectonucleotidase-Mediated Suppression of Lupus Autoimmunity and Vascular Dysfunction . en . Frontiers in Immunology . 9 . 1322 . 2018 . 29942314 . 6004379 . 10.3389/fimmu.2018.01322 . free .
9. Zhu J, Zeng Y, Li W, Qin H, Lei Z, Shen D, Gu D, Huang JA, Liu Z . CD73/NT5E is a target of miR-30a-5p and plays an important role in the pathogenesis of non-small cell lung cancer . Molecular Cancer . 16 . 1 . 34 . February 2017 . 28158983 . 5291990 . 10.1186/s12943-017-0591-1 . free .
10. Yu M, Guo G, Huang L, Deng L, Chang CS, Achyut BR, Canning M, Xu N, Arbab AS, Bollag RJ, Rodriguez PC, Mellor AL, Shi H, Munn DH, Cui Y . 2B-mediated feedforward circuit enforces an immune checkpoint . Nature Communications . 11 . 1 . 515 . January 2020 . 31980601 . 6981126 . 10.1038/s41467-019-14060-x .
11. Tripathi. Abhishek. Lin. Edwin. Nussenzveig. Roberto. Yandell. Mark. Pal. Sumanta K.. Agarwal. Neeraj. 2019-05-20. NT5E expression and the immune landscape of prostate cancer (PC): An analysis from The Cancer Genome Atlas database.. Journal of Clinical Oncology. 37. 15_suppl. e16591. 10.1200/JCO.2019.37.15_suppl.e16591. 190909472 . 0732-183X.
12. Bazhin AV, Amedei A, Karakhanova S . Editorial: Immune Checkpoint Molecules and Cancer Immunotherapy . en . Frontiers in Immunology . 9 . 2878 . 2018 . 30568661 . 6290335 . 10.3389/fimmu.2018.02878 . free .
13. Zhang F, Luo Y, Shao Z, Xu L, Liu X, Niu Y, Shi J, Sun X, Liu Y, Ding Y, Zhao L . MicroRNA-187, a downstream effector of TGFβ pathway, suppresses Smad-mediated epithelial-mesenchymal transition in colorectal cancer . Cancer Letters . 373 . 2 . 203–13 . April 2016 . 26820227 . 10.1016/j.canlet.2016.01.037 .