Amphiregulin Explained

Amphiregulin, also known as AREG, is a protein synthesized as a transmembrane glycoprotein with 252 aminoacids and it is encoded by the AREG gene.^{[1] [2] [3]} in humans.^[4]

Function

The protein encoded by this gene is a member of the epidermal growth factor (EGF) family.

It is a critical autocrine growth factor as well as a mitogen for astrocytes, Schwann cells, and fibroblasts. It is ligand for epidermal growth factor (EGF) and it is related to transforming growth factor alpha (TGF-alpha). This protein interacts with the Epidermal growth factor receptor (EGFR) to promote the growth of normal epithelial cells.

Biological role

AREG is a critical factor in estrogen action and ductal development of the mammary glands.^{[5] [6] [7] [8] [9]} Amphiregulin has been found to be essential for mammary ductal development, as evidenced by absence of ductal growth in amphiregulin knockout mice. This is similar to the phenotypes of EGFR and ERα knockout mice, which also show absence of ductal growth. Amphiregulin is expressed in many parts of body such as ovaries, placenta, pancreas, breasts, lungs and spleen. Expression of amphiregulin can be induced by TGF-α, TNF-α, interleukin 1, and prostaglandins.^{[10] [11]}

Clinical significance

Role in tissue repair

Generally, amphiregulin is considered to be a part of type 2 mediated resistance and tolerance, the latter of which occurs by promoting the reestablishment of tissue integrity after damage that is due to acute or chronic inflammation. Its involvement in tissue repair can be explained by its dual role, as amphiregulin can induce mitogenic signals, but it can also lead to cell differentiation of epithelial cells.^[12]

While epithelial-derived amphiregulin can promote tissue repair, several immune cells are found to express it in cases of tissue damage, so amphiregulin is part of the crosstalk between immune and epithelial cells. ^[13]

A population of immune cells that is found to increase its amphiregulin expression after tissue damage, is the innate lymphoid cell 2 (ILC2) population. This has been observed in several organs, such as the lung, the intestine, and the skin. The expression of amphiregulin by ILC2s can be induced by interleukin 33 (IL-33).^[14] Also, in skin derived ILC2s, amphiregulin expression was regulated by the interaction of killer-cell lectin-like receptor G1 (KLRG1) with E-cadherin.^[15] After intestinal damage, activated intestinal ILC2s produce amphiregulin which enhances the production of mucin by epithelial cells, increases the expression of Claudin-1 and promotes the activity of goblet cells. These functions of amphiregulin lead to increased junction strength, as well as the strengthening of the mucus layer.

Tissue resident regulatory T cells (Tregs) can also express amphiregulin to promote tissue repair. In the skeletal muscle, the IL-33 receptor (ST2) expressing Tregs have a distinct T-cell receptor (TCR) repertoire,^[16] and TCR signals don’t seem to be required for amphiregulin production, but this process can be dependent on the IL-33/ST2 (or IL-33 receptor) pathway and the expression of interleukin 18 receptor (IL-18R) on tissue resident Tregs.^[17] Also, amphiregulin that is expressed from these Tregs can further enhance their function, forming an autocrine positive feedback loop.^[18] Amphiregulin-expressing tissue resident Tregs have been observed in the lung, where most of them are CD44^hiCD62L^lo and they express higher levels of CD103, programmed cell death protein 1 (PD-1), glucocorticoid-induced TNFR-related protein (GITR), cytotoxic T-lymphocyte antigen 4 (CTLA-4) and KLRG1. They have been found in injured muscles, where this population has been associated with eosinophil influx, and the production of amphiregulin could enhance the colony-forming efficiency and myogenic differentiation of skeletal muscle satellite cells in vitro, increasing muscle healing. In the inflamed colon, Gata3⁺Helios⁺ Tregs express high levels of amphiregulin too.^[19] Moreover, Tregs that express amphiregulin, along with keratinocyte growth factor (KGF), CD39 and CD73, act on parenchymal cells to promote tissue repair and regeneration.

Some unconventional T cells have been associated with the promotion of tissue repair by amphiregulin in a direct or in an indirect manner. After intestinal damage, mucosal-associated invariant T (MAIT) cells produce amphiregulin that leads to epithelial cell turnover and enhances the activity of goblet cells. Also, a pro-repair response by amphiregulin produced by ILC2s and Tregs, that is dependent on IL-33 signaling, is induced by gamma delta (γδ) T cells that produce interleukin 17A (IL-17A). This correlation between IL-17A-producing γδ T cells and amphiregulin has been observed in the lungs and in the oral mucosa.

Psoriasis

Mutations in this encoded protein are associated with a psoriasis-like skin phenotype.^[20] Higher circulating levels of amphiregulin are associated with AGVHD progression.^{[21] [22] [23]}

Cancer

Overexpression of amphiregulin is connected with cancer of the breast, prostate, colon, pancreas, lung, spleen, and bladder.^{[24] [25] [8]}

Rheumatoid arthritis

It seems that expression of AREG is connected with proliferation of fibroblasts and production of proinflammatory cytokines interleukin 8 and vascular endothelial growth factor (VEGF).^[26]

Fibrosis

Chronic elevation of amphiregulin levels has been associated with fibrosis in several organs. ILC2s are drivers of liver, skin, and pulmonary fibrosis, and their expression of interleukin 13 (IL-13) and amphiregulin is implicated in this process. Pathogenic memory Th2 cells that express amphiregulin are also involved in pulmonary fibrosis. Exposure to house dust mite leads to the increase of amphiregulin-expressing pathogenic memory Th2 cells. This increase might be related to the IL-33/ST2 signaling, as blocking this pathway causes less production of amphiregulin. The function of amphiregulin in airway fibrosis is related to eosinophils that express EGFR, in which amphiregulin binds to, resulting in the upregulation of inflammatory genes, including Spp1 that encodes osteopontin. The expression of osteopontin by eosinophils shapes the pathogenesis of pulmonary fibrosis.^[27] Moreover, macrophage-derived amphiregulin is involved in the transforming growth factor beta (TGF-β)-induced fibrosis too, as it has been found to activate latent TGF-β through the activation of integrin-α_V complex. ^{[28] [29]} In the liver, ongoing necrosis leads to the activation of hepatic ILC2s which release amphiregulin along with IL-13. The release of them activates the hepatic stellate cells that transform into myofibroblasts, and ultimately promotes liver fibrosis.

Inflammation

Amphiregulin is part of cellular response type 2.^[30] It was found that the cell source of amphiregulin is innate lymphoid cells 2 (ILC2) which are dependent on interleukin 33. ILC2 expressed amphiregulin after tissue damage of the intestines and activation by IL-33. Moreover, endogenous AREG with IL-33 decreased the intestinal inflammation in mice with normal count of T-lymphocytes and in deficient mice.^[31]

Further reading

• Culouscou JM, Remacle-Bonnet M, Carlton GW, Plowman GD, Shoyab M . Colorectum cell-derived growth factor (CRDGF) is homologous to amphiregulin, a member of the epidermal growth factor family . Growth Factors . 7 . 3 . 195–205 . 1993 . 1333777 . 10.3109/08977199209046924 .
• Cook PW, Mattox PA, Keeble WW, Pittelkow MR, Plowman GD, Shoyab M, Adelman JP, Shipley GD . A heparin sulfate-regulated human keratinocyte autocrine factor is similar or identical to amphiregulin . Molecular and Cellular Biology . 11 . 5 . 2547–2557 . May 1991 . 2017164 . 360024 . 10.1128/MCB.11.5.2547 .
• Kimura H, Fischer WH, Schubert D . Structure, expression and function of a schwannoma-derived growth factor . Nature . 348 . 6298 . 257–260 . November 1990 . 2234093 . 10.1038/348257a0 . 4275004 . 1990Natur.348..257K .
• Plowman GD, Green JM, McDonald VL, Neubauer MG, Disteche CM, Todaro GJ, Shoyab M . The amphiregulin gene encodes a novel epidermal growth factor-related protein with tumor-inhibitory activity . Molecular and Cellular Biology . 10 . 5 . 1969–1981 . May 1990 . 2325643 . 360543 . 10.1128/MCB.10.5.1969 .
• Shoyab M, Plowman GD, McDonald VL, Bradley JG, Todaro GJ . Structure and function of human amphiregulin: a member of the epidermal growth factor family . Science . 243 . 4894 Pt 1 . 1074–1076 . February 1989 . 2466334 . 10.1126/science.2466334 . 1989Sci...243.1074S .
• Shoyab M, McDonald VL, Bradley JG, Todaro GJ . Amphiregulin: a bifunctional growth-modulating glycoprotein produced by the phorbol 12-myristate 13-acetate-treated human breast adenocarcinoma cell line MCF-7 . Proceedings of the National Academy of Sciences of the United States of America . 85 . 17 . 6528–6532 . September 1988 . 3413110 . 282006 . 10.1073/pnas.85.17.6528 . free . 1988PNAS...85.6528S .
• Chen CS, Bejcek BE, Kersey JH . A mapping study of 13 genes on human chromosome bands 4q11→q25 . Cytogenetics and Cell Genetics . 69 . 3–4 . 260–265 . 1995 . 7698025 . 10.1159/000133976 .
• Cook PW, Piepkorn M, Clegg CH, Plowman GD, DeMay JM, Brown JR, Pittelkow MR . Transgenic expression of the human amphiregulin gene induces a psoriasis-like phenotype . The Journal of Clinical Investigation . 100 . 9 . 2286–2294 . November 1997 . 9410906 . 508424 . 10.1172/JCI119766 .
• Wong L, Deb TB, Thompson SA, Wells A, Johnson GR . A differential requirement for the COOH-terminal region of the epidermal growth factor (EGF) receptor in amphiregulin and EGF mitogenic signaling . The Journal of Biological Chemistry . 274 . 13 . 8900–8909 . March 1999 . 10085134 . 10.1074/jbc.274.13.8900 . free .
• Reddy KB, Krueger JS, Kondapaka SB, Diglio CA . Mitogen-activated protein kinase (MAPK) regulates the expression of progelatinase B (MMP-9) in breast epithelial cells . International Journal of Cancer . 82 . 2 . 268–273 . July 1999 . 10389762 . 10.1002/(SICI)1097-0215(19990719)82:2<268::AID-IJC18>3.0.CO;2-4 . 22627041 .
• Fernandes AM, Hamburger AW, Gerwin BI . Production of epidermal growth factor related ligands in tumorigenic and benign human lung epithelial cells . Cancer Letters . 142 . 1 . 55–63 . July 1999 . 10424781 . 10.1016/S0304-3835(99)00166-4 .
• Lee SB, Huang K, Palmer R, Truong VB, Herzlinger D, Kolquist KA, Wong J, Paulding C, Yoon SK, Gerald W, Oliner JD, Haber DA . The Wilms tumor suppressor WT1 encodes a transcriptional activator of amphiregulin . Cell . 98 . 5 . 663–673 . September 1999 . 10490105 . 10.1016/S0092-8674(00)80053-7 . 14607182 . free .
• Tokumaru S, Higashiyama S, Endo T, Nakagawa T, Miyagawa JI, Yamamori K, Hanakawa Y, Ohmoto H, Yoshino K, Shirakata Y, Matsuzawa Y, Hashimoto K, Taniguchi N . Ectodomain shedding of epidermal growth factor receptor ligands is required for keratinocyte migration in cutaneous wound healing . The Journal of Cell Biology . 151 . 2 . 209–220 . October 2000 . 11038170 . 2192647 . 10.1083/jcb.151.2.209 .
• Ebert MP, Hernberg S, Fei G, Sokolowski A, Schulz HU, Lippert H, Malfertheiner P . Induction and expression of cyclin D3 in human pancreatic cancer . Journal of Cancer Research and Clinical Oncology . 127 . 7 . 449–454 . July 2001 . 11469683 . 10.1007/s004320100235 . 33146049 .
• Berquin IM, Dziubinski ML, Nolan GP, Ethier SP . A functional screen for genes inducing epidermal growth factor autonomy of human mammary epithelial cells confirms the role of amphiregulin . Oncogene . 20 . 30 . 4019–4028 . July 2001 . 11494130 . 10.1038/sj.onc.1204537 . free .
• Thøgersen VB, Sørensen BS, Poulsen SS, Orntoft TF, Wolf H, Nexo E . A subclass of HER1 ligands are prognostic markers for survival in bladder cancer patients . Cancer Research . 61 . 16 . 6227–6233 . August 2001 . 11507076 .
• Wolfgang CD, Essand M, Lee B, Pastan I . T-cell receptor gamma chain alternate reading frame protein (TARP) expression in prostate cancer cells leads to an increased growth rate and induction of caveolins and amphiregulin . Cancer Research . 61 . 22 . 8122–8126 . November 2001 . 11719440 .
• Schiemann U, Konturek J, Assert R, Rembiasz K, Domschke W, Konturek S, Pfeiffer A . mRNA expression of EGF receptor ligands in atrophic gastritis before and after Helicobacter pylori eradication . Medical Science Monitor . 8 . 2 . CR53–CR58 . February 2002 . 11859273 .
• Tørring N, Møller-Ernst Jensen K, Lund L, Nielsen JE, Djurhuus JC, Poulsen SS, Nexø E . Possible autocrine loop of the epidermal growth factor system in patients with benign prostatic hyperplasia treated with finasteride: a placebo-controlled randomized study . BJU International . 89 . 6 . 583–590 . April 2002 . 11942969 . 10.1046/j.1464-410X.2002.02665.x . 42241168 . free .
• Hurbin A, Dubrez L, Coll JL, Favrot MC . Inhibition of apoptosis by amphiregulin via an insulin-like growth factor-1 receptor-dependent pathway in non-small cell lung cancer cell lines . The Journal of Biological Chemistry . 277 . 51 . 49127–49133 . December 2002 . 12356750 . 10.1074/jbc.M207584200 . free .

Notes and References

1. Web site: Entrez Gene: AREG amphiregulin (schwannoma-derived growth factor).
2. Shoyab M, Plowman GD, McDonald VL, Bradley JG, Todaro GJ . Structure and function of human amphiregulin: a member of the epidermal growth factor family . Science . 243 . 4894 Pt 1 . 1074–1076 . February 1989 . 2466334 . 10.1126/science.2466334 . 1989Sci...243.1074S .
3. Plowman GD, Green JM, McDonald VL, Neubauer MG, Disteche CM, Todaro GJ, Shoyab M . The amphiregulin gene encodes a novel epidermal growth factor-related protein with tumor-inhibitory activity . Molecular and Cellular Biology . 10 . 5 . 1969–1981 . May 1990 . 2325643 . 360543 . 10.1128/MCB.10.5.1969 .
4. Web site: AREG (amphiregulin (schwannoma-derived growth factor)). atlasgeneticsoncology.org. 2019-08-27. 2019-08-27. https://web.archive.org/web/20190827181624/http://atlasgeneticsoncology.org/Genes/GC_AREG.html. dead.
5. Aupperlee MD, Leipprandt JR, Bennett JM, Schwartz RC, Haslam SZ . Amphiregulin mediates progesterone-induced mammary ductal development during puberty . Breast Cancer Research . 15 . 3 . R44 . May 2013 . 23705924 . 3738150 . 10.1186/bcr3431 . free .
6. Jeffrey M. Rosen . LaMarca HL, Rosen JM . Estrogen regulation of mammary gland development and breast cancer: amphiregulin takes center stage . Breast Cancer Research . 9 . 4 . 304 . 2007 . 17659070 . 2206713 . 10.1186/bcr1740 . free .
7. Kariagina A, Xie J, Leipprandt JR, Haslam SZ . Amphiregulin mediates estrogen, progesterone, and EGFR signaling in the normal rat mammary gland and in hormone-dependent rat mammary cancers . Hormones & Cancer . 1 . 5 . 229–244 . October 2010 . 21258428 . 3000471 . 10.1007/s12672-010-0048-0 .
8. McBryan J, Howlin J, Napoletano S, Martin F . Amphiregulin: role in mammary gland development and breast cancer . Journal of Mammary Gland Biology and Neoplasia . 13 . 2 . 159–169 . June 2008 . 18398673 . 10.1007/s10911-008-9075-7 . 13229645 .
9. Sternlicht MD, Sunnarborg SW . The ADAM17-amphiregulin-EGFR axis in mammary development and cancer . Journal of Mammary Gland Biology and Neoplasia . 13 . 2 . 181–194 . June 2008 . 18470483 . 2723838 . 10.1007/s10911-008-9084-6 .
10. Web site: AREG (amphiregulin (schwannoma-derived growth factor)). atlasgeneticsoncology.org. 2019-08-27. 2019-08-27. https://web.archive.org/web/20190827181624/http://atlasgeneticsoncology.org/Genes/GC_AREG.html. dead.
11. Busser B, Sancey L, Brambilla E, Coll JL, Hurbin A . The multiple roles of amphiregulin in human cancer . Biochimica et Biophysica Acta (BBA) - Reviews on Cancer . 1816 . 2 . 119–131 . December 2011 . 21658434 . 10.1016/j.bbcan.2011.05.003 .
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21. Bhagavathula N, Nerusu KC, Fisher GJ, Liu G, Thakur AB, Gemmell L, Kumar S, Xu ZH, Hinton P, Tsurushita N, Landolfi NF, Voorhees JJ, Varani J . Amphiregulin and epidermal hyperplasia: amphiregulin is required to maintain the psoriatic phenotype of human skin grafts on severe combined immunodeficient mice . The American Journal of Pathology . 166 . 4 . 1009–1016 . April 2005 . 15793282 . 1780140 . 10.1016/S0002-9440(10)62322-X .
22. Holtan SG, DeFor TE, Panoskaltsis-Mortari A, Khera N, Levine JE, Flowers ME, Lee SJ, Inamoto Y, Chen GL, Mayer S, Arora M, Palmer J, Cutler CS, Arai S, Lazaryan A, Newell LF, Jagasia MH, Pusic I, Wood WA, Renteria AS, Yanik G, Hogan WJ, Hexner E, Ayuk F, Holler E, Bunworasate U, Efebera YA, Ferrara JL, Pidala J, Howard A, Wu J, Bolaños-Meade J, Ho V, Alousi A, Blazar BR, Weisdorf DJ, MacMillan ML . Amphiregulin modifies the Minnesota Acute Graft-versus-Host Disease Risk Score: results from BMT CTN 0302/0802 . Blood Advances . 2 . 15 . 1882–1888 . August 2018 . 30087106 . 6093743 . 10.1182/bloodadvances.2018017343 .
23. Piepkorn M . Overexpression of amphiregulin, a major autocrine growth factor for cultured human keratinocytes, in hyperproliferative skin diseases . The American Journal of Dermatopathology . 18 . 2 . 165–171 . April 1996 . 8739992 . 10.1097/00000372-199604000-00010 .
24. Busser B, Sancey L, Brambilla E, Coll JL, Hurbin A . The multiple roles of amphiregulin in human cancer . Biochimica et Biophysica Acta (BBA) - Reviews on Cancer . 1816 . 2 . 119–131 . December 2011 . 21658434 . 10.1016/j.bbcan.2011.05.003 .
25. Web site: AREG (amphiregulin (schwannoma-derived growth factor)). atlasgeneticsoncology.org. 2019-08-27. 2019-08-27. https://web.archive.org/web/20190827181624/http://atlasgeneticsoncology.org/Genes/GC_AREG.html. dead.
26. Yamane S, Ishida S, Hanamoto Y, Kumagai K, Masuda R, Tanaka K, Shiobara N, Yamane N, Mori T, Juji T, Fukui N, Itoh T, Ochi T, Suzuki R . Proinflammatory role of amphiregulin, an epidermal growth factor family member whose expression is augmented in rheumatoid arthritis patients . Journal of Inflammation . 5 . 5 . April 2008 . 18439312 . 2396620 . 10.1186/1476-9255-5-5 . free .
27. Hirahara K, Aoki A, Morimoto Y, Kiuchi M, Okano M, Nakayama T . The immunopathology of lung fibrosis: amphiregulin-producing pathogenic memory T helper-2 cells control the airway fibrotic responses by inducing eosinophils to secrete osteopontin . Seminars in Immunopathology . 41 . 3 . 339–348 . May 2019 . 30968186 . 10.1007/s00281-019-00735-6 . 106409455 .
28. Huang H, Yin K, Tang H . Macrophage amphiregulin-pericyte TGF-β axis: a novel mechanism of the immune system that contributes to wound repair . Acta Biochimica et Biophysica Sinica . 52 . 4 . 463–465 . April 2020 . 32147698 . 10.1093/abbs/gmaa001 . free .
29. Zaiss DM, Minutti CM, Knipper JA . Immune- and non-immune-mediated roles of regulatory T-cells during wound healing . Immunology . 157 . 3 . 190–197 . July 2019 . 30866049 . 6600083 . 10.1111/imm.13057 .
30. Zaiss DM, Yang L, Shah PR, Kobie JJ, Urban JF, Mosmann TR . Amphiregulin, a TH2 cytokine enhancing resistance to nematodes . Science . 314 . 5806 . 1746 . December 2006 . 17170297 . 10.1126/science.1133715 . 27808704 . 2006Sci...314.1746Z .
31. Monticelli LA, Osborne LC, Noti M, Tran SV, Zaiss DM, Artis D . IL-33 promotes an innate immune pathway of intestinal tissue protection dependent on amphiregulin-EGFR interactions . Proceedings of the National Academy of Sciences of the United States of America . 112 . 34 . 10762–10767 . August 2015 . 26243875 . 4553775 . 10.1073/pnas.1509070112 . free . 2015PNAS..11210762M .