YAP1 

YAP1 (yes-associated protein 1), also known as YAP or YAP65, is a protein that acts as a transcription coregulator that promotes transcription of genes involved in cellular proliferation and suppressing apoptotic genes. YAP1 is a component in the hippo signaling pathway which regulates organ size, regeneration, and tumorigenesis. YAP1 was first identified by virtue of its ability to associate with the SH3 domain of Yes and Src protein tyrosine kinases.[5]YAP1 is a potent oncogene, which is amplified in various human cancers.[6][7]

Cloning of the YAP1 gene facilitated the identification of a modular protein domain, known as the WW domain.[8][9][10] Two splice isoforms of the YAP1 gene product were initially identified, named YAP1-1 and YAP1-2, which differed by the presence of an extra 38 amino acids that encoded the WW domain.[11][12] Apart from the WW domain, the modular structure of YAP1 contains a proline-rich region at the very amino terminus, which is followed by a TID (TEAD transcription factor interacting domain).[13] Next, following a single WW domain, which is present in the YAP1-1 isoform, and two WW domains, which are present in the YAP1-2 isoform, there is the SH3-BM (Src Homology 3 binding motif).[5][14] Following the SH3-BM is a TAD (transactivation domain) and a PDZ domain-binding motif (PDZ-BM) (Figure 1).[15][16]

Function

YAP1 is a transcriptional co-activator[17] and its proliferative and oncogenic activity is driven by its association with the TEAD family of transcription factors,[13] which up-regulate genes that promote cell growth and inhibit apoptosis.[18] Several other functional partners of YAP1 were identified, including RUNX,[17] SMADs,[19][20] p73,[21] ErbB4,[22][23] TP53BP2,[24] LATS1/2,[25] PTPN14,[26] AMOTs,[27][28][29][30] and ZO1/2.[31] YAP1 and its close paralog, TAZ (WWTR1), are the main effectors of the Hippo tumor suppressor pathway.[32] When the pathway is activated, YAP1 and TAZ are phosphorylated on a serine residue and sequestered in the cytoplasm by 14-3-3 proteins.[32] When the Hippo pathway is not activated, YAP1/TAZ enter the nucleus and regulate gene expression.[32]

It is reported that several genes are regulated by YAP1, including Birc2Birc5, connective tissue growth factor (CTGF), amphiregulin (AREG), Cyr61Hoxa1 and Hoxc13.

YAP/TAZ have also been shown to act as stiffness sensors, regulating mechanotransduction independently of the Hippo signalling cascade.[33]

As YAP and TAZ are transcriptional co-activators, they do not have DNA-binding domains. Instead, when inside the nucleus, they regulate gene expression through TEAD1-4 which are sequence-specific transcription factors that mediate the main transcriptional output of the Hippo pathway.[34] The YAP/TAZ and TEAD interaction competitively inhibits and actively dissociates the TEAD/VGLL4 interaction which functions as a transcriptional repressor.[35] Mouse models with YAP over-expression have been shown to exhibit up-regulation of the TEAD target gene expression which results in increased expansion of progenitor cells and tissue overgrowth.[36]

Regulation

Biochemical

At the biochemical level, YAP is part of and regulated by the Hippo signaling pathway where a kinase cascade results in its “inactivation”, along with that of TAZ.[37] In this signaling cascade, TAO kinases phosphorylate Ste20-like kinases, MST1/2, at their activation loops (Thr183 for MST1 and Thr180 for MST2).[38][39] Active MST1/2 then phosphorylate SAV1 and MOB1A/B which are scaffold proteins that assist in the recruitment and phosphorylation of LATS1/2.[40][41] LATS1/2 can also be phosphorylated by two groups of MAP4Ks.[42][43] LATS1/2 then phosphorylate YAP and TAZ which causes them to bind with 14-3-3, resulting in cytoplasmic sequestration of YAP and TAZ.[44] The result of the activation of this pathway is the restriction of YAP/TAZ from entering the cell nucleus.

Mechanotransductive

Additionally, YAP is regulated by mechanical cues such as extracellular matrix (ECM) rigidity, strain, shear stress, or adhesive area, processes that are reliant on cytoskeletal integrity.[45] These mechanically induced localization phenomena are thought to be the result of nuclear flattening induced pore size change, mechanosensitive nuclear membrane ion channels, mechanical protein stability, or a variety of other factors.[45] These mechanical factors have also been linked to certain cancer cells via nuclear softening and higher ECM stiffnesses.[46][47][48] Under this framework, the nuclear softening phenotype of cancer cells would promote nuclear flattening in response to a force, causing YAP localization, which could explain its over-expression and promoted proliferation in oncogenic cells.[49] Additionally, the higher ECM stiffness phenotype commonly seen in tumors due to enhanced integrin signaling[48] could flatten the cell and nucleus, once again causing higher YAP nuclear localization. Likewise, the opposite effect of nuclear stiffening as a result of a variety of stimuli such as an over-expression of lamin A, has been shown to decrease nuclear YAP localization.[50][51]

Clinical significance

Cancer

Dysregulation of YAP/TAZ-mediated transcriptional activity is implicated in the development of abnormal cell growth and hyperactivation of YAP and TAZ has been observed amongst many cancers.[49][52][53] Hence YAP1 represents a potential target for the treatment of cancer.[54]

While YAP has been identified as a proto-oncogene, it can also act as a tumor suppressor depending on cellular context.[55]

As a drug target

The YAP1 oncogene serves as a target for the development of new cancer drugs.[56] Small compounds have been identified that disrupt the YAP1-TEAD complex or block the binding function of WW domains.[57][58] These small molecules represent lead compounds for the development of therapies for cancer patients, who harbor amplified or overexpressed YAP oncogene.

Neuroprotection

The Hippo/YAP signaling pathway may exert neuroprotective effects through mitigating blood–brain barrier disruption after cerebral ischemia/reperfusion injury.[59]

Mutations

Heterozygous loss-of-function mutations in the YAP1 gene have been identified in two families with major eye malformations with or without extra-ocular features such as hearing loss, cleft lip, intellectual disability and renal disease.[60]

External links

  • Overview of all the structural information available in the PDB for UniProtP46937 (Human Transcriptional coactivator YAP1) at the PDBe-KB.
  • Overview of all the structural information available in the PDB for UniProtP46938 (Mouse Transcriptional coactivator YAP1) at the PDBe-KB.

References

  1. Jump up to:a b c GRCh38: Ensembl release 89: ENSG00000137693 – Ensembl, May 2017
  2. Jump up to:a b c GRCm38: Ensembl release 89: ENSMUSG00000053110 – Ensembl, May 2017
  3. ^ “Human PubMed Reference:”National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ “Mouse PubMed Reference:”National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. Jump up to:a b Sudol M (August 1994). “Yes-associated protein (YAP65) is a proline-rich phosphoprotein that binds to the SH3 domain of the Yes proto-oncogene product”. Oncogene9 (8): 2145–52. PMID 8035999.
  6. ^ Huang J, Wu S, Barrera J, Matthews K, Pan D (August 2005). “The Hippo signaling pathway coordinately regulates cell proliferation and apoptosis by inactivating Yorkie, the Drosophila Homolog of YAP”Cell122 (3): 421–34. doi:10.1016/j.cell.2005.06.007PMID 16096061S2CID 14139806.
  7. ^ Overholtzer M, Zhang J, Smolen GA, Muir B, Li W, Sgroi DC, et al. (August 2006). “Transforming properties of YAP, a candidate oncogene on the chromosome 11q22 amplicon”Proceedings of the National Academy of Sciences of the United States of America103 (33): 12405–10. Bibcode:2006PNAS..10312405Odoi:10.1073/pnas.0605579103PMC 1533802PMID 16894141.
  8. ^ Bork P, Sudol M (December 1994). “The WW domain: a signalling site in dystrophin?”. Trends in Biochemical Sciences19 (12): 531–3. doi:10.1016/0968-0004(94)90053-1PMID 7846762.
  9. ^ André B, Springael JY (December 1994). “WWP, a new amino acid motif present in single or multiple copies in various proteins including dystrophin and the SH3-binding Yes-associated protein YAP65”. Biochemical and Biophysical Research Communications205 (2): 1201–5. doi:10.1006/bbrc.1994.2793PMID 7802651.
  10. ^ Hofmann K, Bucher P (January 1995). “The rsp5-domain is shared by proteins of diverse functions”FEBS Letters358 (2): 153–7. doi:10.1016/0014-5793(94)01415-WPMID 7828727S2CID 23110605.
  11. ^ Sudol M, Bork P, Einbond A, Kastury K, Druck T, Negrini M, et al. (June 1995). “Characterization of the mammalian YAP (Yes-associated protein) gene and its role in defining a novel protein module, the WW domain”The Journal of Biological Chemistry270 (24): 14733–41. doi:10.1074/jbc.270.24.14733PMID 7782338.
  12. ^ Gaffney CJ, Oka T, Mazack V, Hilman D, Gat U, Muramatsu T, et al. (November 2012). “Identification, basic characterization and evolutionary analysis of differentially spliced mRNA isoforms of human YAP1 gene”Gene509 (2): 215–22. doi:10.1016/j.gene.2012.08.025PMC 3455135PMID 22939869.
  13. Jump up to:a b Vassilev A, Kaneko KJ, Shu H, Zhao Y, DePamphilis ML (May 2001). “TEAD/TEF transcription factors utilize the activation domain of YAP65, a Src/Yes-associated protein localized in the cytoplasm”Genes & Development15 (10): 1229–41. doi:10.1101/gad.888601PMC 313800PMID 11358867.
  14. ^ Ren R, Mayer BJ, Cicchetti P, Baltimore D (February 1993). “Identification of a ten-amino acid proline-rich SH3 binding site”. Science259 (5098): 1157–61. Bibcode:1993Sci…259.1157Rdoi:10.1126/science.8438166PMID 8438166.
  15. ^ Wang S, Raab RW, Schatz PJ, Guggino WB, Li M (May 1998). “Peptide binding consensus of the NHE-RF-PDZ1 domain matches the C-terminal sequence of cystic fibrosis transmembrane conductance regulator (CFTR)”FEBS Letters427 (1): 103–8. doi:10.1016/S0014-5793(98)00402-5PMID 9613608S2CID 20803242.
  16. ^ Mohler PJ, Kreda SM, Boucher RC, Sudol M, Stutts MJ, Milgram SL (November 1999). “Yes-associated protein 65 localizes p62(c-Yes) to the apical compartment of airway epithelia by association with EBP50”The Journal of Cell Biology147 (4): 879–90. doi:10.1083/jcb.147.4.879PMC 2156157PMID 10562288.
  17. Jump up to:a b Yagi R, Chen LF, Shigesada K, Murakami Y, Ito Y (May 1999). “A WW domain-containing yes-associated protein (YAP) is a novel transcriptional co-activator”The EMBO Journal18 (9): 2551–62. doi:10.1093/emboj/18.9.2551PMC 1171336PMID 10228168.
  18. ^ Zhao B, Kim J, Ye X, Lai ZC, Guan KL (February 2009). “Both TEAD-binding and WW domains are required for the growth stimulation and oncogenic transformation activity of yes-associated protein”Cancer Research69 (3): 1089–98. doi:10.1158/0008-5472.CAN-08-2997PMID 19141641.
  19. ^ Ferrigno O, Lallemand F, Verrecchia F, L’Hoste S, Camonis J, Atfi A, Mauviel A (July 2002). “Yes-associated protein (YAP65) interacts with Smad7 and potentiates its inhibitory activity against TGF-beta/Smad signaling”Oncogene21 (32): 4879–84. doi:10.1038/sj.onc.1205623PMID 12118366.
  20. ^ Aragón E, Goerner N, Xi Q, Gomes T, Gao S, Massagué J, Macias MJ (October 2012). “Structural basis for the versatile interactions of Smad7 with regulator WW domains in TGF-β Pathways”Structure20 (10): 1726–36. doi:10.1016/j.str.2012.07.014PMC 3472128PMID 22921829.
  21. ^ Strano S, Munarriz E, Rossi M, Castagnoli L, Shaul Y, Sacchi A, et al. (May 2001). “Physical interaction with Yes-associated protein enhances p73 transcriptional activity”The Journal of Biological Chemistry276 (18): 15164–73. doi:10.1074/jbc.M010484200PMID 11278685.
  22. ^ Komuro A, Nagai M, Navin NE, Sudol M (August 2003). “WW domain-containing protein YAP associates with ErbB-4 and acts as a co-transcriptional activator for the carboxyl-terminal fragment of ErbB-4 that translocates to the nucleus”The Journal of Biological Chemistry278 (35): 33334–41. doi:10.1074/jbc.M305597200PMID 12807903.
  23. ^ Omerovic J, Puggioni EM, Napoletano S, Visco V, Fraioli R, Frati L, et al. (April 2004). “Ligand-regulated association of ErbB-4 to the transcriptional co-activator YAP65 controls transcription at the nuclear level”. Experimental Cell Research294 (2): 469–79. doi:10.1016/j.yexcr.2003.12.002PMID 15023535.
  24. ^ Espanel X, Sudol M (April 2001). “Yes-associated protein and p53-binding protein-2 interact through their WW and SH3 domains”The Journal of Biological Chemistry276 (17): 14514–23. doi:10.1074/jbc.M008568200PMID 11278422.
  25. ^ Oka T, Mazack V, Sudol M (October 2008). “Mst2 and Lats kinases regulate apoptotic function of Yes kinase-associated protein (YAP)”The Journal of Biological Chemistry283 (41): 27534–46. doi:10.1074/jbc.M804380200PMID 18640976.
  26. ^ Liu X, Yang N, Figel SA, Wilson KE, Morrison CD, Gelman IH, Zhang J (March 2013). “PTPN14 interacts with and negatively regulates the oncogenic function of YAP”Oncogene32 (10): 1266–73. doi:10.1038/onc.2012.147PMC 4402938PMID 22525271.
  27. ^ Wang W, Huang J, Chen J (February 2011). “Angiomotin-like proteins associate with and negatively regulate YAP1”The Journal of Biological Chemistry286 (6): 4364–70. doi:10.1074/jbc.C110.205401PMC 3039387PMID 21187284.
  28. ^ Chan SW, Lim CJ, Chong YF, Pobbati AV, Huang C, Hong W (March 2011). “Hippo pathway-independent restriction of TAZ and YAP by angiomotin”The Journal of Biological Chemistry286 (9): 7018–26. doi:10.1074/jbc.C110.212621PMC 3044958PMID 21224387.
  29. ^ Zhao B, Li L, Lu Q, Wang LH, Liu CY, Lei Q, Guan KL (January 2011). “Angiomotin is a novel Hippo pathway component that inhibits YAP oncoprotein”Genes & Development25 (1): 51–63. doi:10.1101/gad.2000111PMC 3012936PMID 21205866.
  30. ^ Oka T, Schmitt AP, Sudol M (January 2012). “Opposing roles of angiomotin-like-1 and zona occludens-2 on pro-apoptotic function of YAP”Oncogene31 (1): 128–34. doi:10.1038/onc.2011.216PMID 21685940.
  31. ^ Oka T, Remue E, Meerschaert K, Vanloo B, Boucherie C, Gfeller D, et al. (December 2010). “Functional complexes between YAP2 and ZO-2 are PDZ domain-dependent, and regulate YAP2 nuclear localization and signalling”The Biochemical Journal (Submitted manuscript). 432 (3): 461–72. doi:10.1042/BJ20100870hdl:1854/LU-1256657PMID 20868367.
  32. Jump up to:a b c Pan D (October 2010). “The hippo signaling pathway in development and cancer”Developmental Cell19 (4): 491–505. doi:10.1016/j.devcel.2010.09.011PMC 3124840PMID 20951342.
  33. ^ McMurray RJ, Dalby MJ, Tsimbouri PM (May 2015). “Using biomaterials to study stem cell mechanotransduction, growth and differentiation” (PDF). Journal of Tissue Engineering and Regenerative Medicine9 (5): 528–39. doi:10.1002/term.1957PMID 25370612S2CID 39642567.
  34. ^ Zhao B, Ye X, Yu J, Li L, Li W, Li S, et al. (July 2008). “TEAD mediates YAP-dependent gene induction and growth control”Genes & Development22 (14): 1962–71. doi:10.1101/gad.1664408PMC 2492741PMID 18579750.
  35. ^ Koontz LM, Liu-Chittenden Y, Yin F, Zheng Y, Yu J, Huang B, et al. (May 2013). “The Hippo effector Yorkie controls normal tissue growth by antagonizing scalloped-mediated default repression”Developmental Cell25 (4): 388–401. doi:10.1016/j.devcel.2013.04.021PMC 3705890PMID 23725764.
  36. ^ Chen Q, Zhang N, Xie R, Wang W, Cai J, Choi KS, et al. (June 2015). “Homeostatic control of Hippo signaling activity revealed by an endogenous activating mutation in YAP”Genes & Development29 (12): 1285–97. doi:10.1101/gad.264234.115PMC 4495399PMID 26109051.
  37. ^ Meng Z, Moroishi T, Guan KL (January 2016). “Mechanisms of Hippo pathway regulation”Genes & Development30 (1): 1–17. doi:10.1101/gad.274027.115PMC 4701972PMID 26728553.
  38. ^ Boggiano JC, Vanderzalm PJ, Fehon RG (November 2011). “Tao-1 phosphorylates Hippo/MST kinases to regulate the Hippo-Salvador-Warts tumor suppressor pathway”Developmental Cell21 (5): 888–95. doi:10.1016/j.devcel.2011.08.028PMC 3217187PMID 22075147.
  39. ^ Poon CL, Lin JI, Zhang X, Harvey KF (November 2011). “The sterile 20-like kinase Tao-1 controls tissue growth by regulating the Salvador-Warts-Hippo pathway”Developmental Cell21 (5): 896–906. doi:10.1016/j.devcel.2011.09.012PMID 22075148.
  40. ^ Callus BA, Verhagen AM, Vaux DL (September 2006). “Association of mammalian sterile twenty kinases, Mst1 and Mst2, with hSalvador via C-terminal coiled-coil domains, leads to its stabilization and phosphorylation”The FEBS Journal273 (18): 4264–76. doi:10.1111/j.1742-4658.2006.05427.xPMID 16930133S2CID 8261982.
  41. ^ Praskova M, Xia F, Avruch J (March 2008). “MOBKL1A/MOBKL1B phosphorylation by MST1 and MST2 inhibits cell proliferation”Current Biology18 (5): 311–21. doi:10.1016/j.cub.2008.02.006PMC 4682548PMID 18328708.
  42. ^ Meng Z, Moroishi T, Mottier-Pavie V, Plouffe SW, Hansen CG, Hong AW, et al. (October 2015). “MAP4K family kinases act in parallel to MST1/2 to activate LATS1/2 in the Hippo pathway”Nature Communications6: 8357. Bibcode:2015NatCo…6.8357Mdoi:10.1038/ncomms9357PMC 4600732PMID 26437443.
  43. ^ Zheng Y, Wang W, Liu B, Deng H, Uster E, Pan D (September 2015). “Identification of Happyhour/MAP4K as Alternative Hpo/Mst-like Kinases in the Hippo Kinase Cascade”Developmental Cell34 (6): 642–55. doi:10.1016/j.devcel.2015.08.014PMC 4589524PMID 26364751.
  44. ^ Zhao B, Wei X, Li W, Udan RS, Yang Q, Kim J, et al. (November 2007). “Inactivation of YAP oncoprotein by the Hippo pathway is involved in cell contact inhibition and tissue growth control”Genes & Development21 (21): 2747–61. doi:10.1101/gad.1602907PMC 2045129PMID 17974916.
  45. Jump up to:a b Elosegui-Artola A, Andreu I, Beedle AE, Lezamiz A, Uroz M, Kosmalska AJ, et al. (November 2017). “Force Triggers YAP Nuclear Entry by Regulating Transport across Nuclear Pores”Cell171 (6): 1397–1410.e14. doi:10.1016/j.cell.2017.10.008PMID 29107331.
  46. ^ Cross SE, Jin YS, Rao J, Gimzewski JK (December 2007). “Nanomechanical analysis of cells from cancer patients”. Nature Nanotechnology2 (12): 780–3. Bibcode:2007NatNa…2..780Cdoi:10.1038/nnano.2007.388PMID 18654431.
  47. ^ Guck J, Schinkinger S, Lincoln B, Wottawah F, Ebert S, Romeyke M, et al. (May 2005). “Optical deformability as an inherent cell marker for testing malignant transformation and metastatic competence”Biophysical Journal88 (5): 3689–98. Bibcode:2005BpJ….88.3689Gdoi:10.1529/biophysj.104.045476PMC 1305515PMID 15722433.
  48. Jump up to:a b Friedl P, Alexander S (November 2011). “Cancer invasion and the microenvironment: plasticity and reciprocity”Cell147 (5): 992–1009. doi:10.1016/j.cell.2011.11.016PMID 22118458.
  49. Jump up to:a b Shimomura T, Miyamura N, Hata S, Miura R, Hirayama J, Nishina H (January 2014). “The PDZ-binding motif of Yes-associated protein is required for its co-activation of TEAD-mediated CTGF transcription and oncogenic cell transforming activity”. Biochemical and Biophysical Research Communications443 (3): 917–23. doi:10.1016/j.bbrc.2013.12.100PMID 24380865.
  50. ^ Swift J, Ivanovska IL, Buxboim A, Harada T, Dingal PC, Pinter J, et al. (August 2013). “Nuclear lamin-A scales with tissue stiffness and enhances matrix-directed differentiation”Science341 (6149): 1240104. doi:10.1126/science.1240104PMC 3976548PMID 23990565.
  51. ^ Gjorevski N, Sachs N, Manfrin A, Giger S, Bragina ME, Ordóñez-Morán P, et al. (November 2016). “Designer matrices for intestinal stem cell and organoid culture”. Nature539 (7630): 560–564. doi:10.1038/nature20168PMID 27851739S2CID 4470849.
  52. ^ Harvey KF, Zhang X, Thomas DM (April 2013). “The Hippo pathway and human cancer”. Nature Reviews. Cancer13 (4): 246–57. doi:10.1038/nrc3458PMID 23467301S2CID 2008641.
  53. ^ Johnson R, Halder G (January 2014). “The two faces of Hippo: targeting the Hippo pathway for regenerative medicine and cancer treatment”Nature Reviews. Drug Discovery13 (1): 63–79. doi:10.1038/nrd4161PMC 4167640PMID 24336504.
  54. ^ Moroishi T, Hansen CG, Guan KL (February 2015). “The emerging roles of YAP and TAZ in cancer”Nature Reviews. Cancer15 (2): 73–79. doi:10.1038/nrc3876PMC 4562315PMID 25592648.
  55. ^ Jho E (November 2018). “Dual role of YAP: oncoprotein and tumor suppressor”Journal of Thoracic Disease10 (Suppl 33): S3895–S3898. doi:10.21037/jtd.2018.10.70PMC 6297531PMID 30631509.
  56. ^ Sudol M, Shields DC, Farooq A (September 2012). “Structures of YAP protein domains reveal promising targets for development of new cancer drugs”Seminars in Cell & Developmental Biology23 (7): 827–33. doi:10.1016/j.semcdb.2012.05.002PMC 3427467PMID 22609812.
  57. ^ Liu-Chittenden Y, Huang B, Shim JS, Chen Q, Lee SJ, Anders RA, et al. (June 2012). “Genetic and pharmacological disruption of the TEAD-YAP complex suppresses the oncogenic activity of YAP”Genes & Development26 (12): 1300–5. doi:10.1101/gad.192856.112PMC 3387657PMID 22677547.
  58. ^ Kang SG, Huynh T, Zhou R (2012). “Non-destructive inhibition of metallofullerenol Gd@C(82)(OH)(22) on WW domain: implication on signal transduction pathway”Scientific Reports2: 957. Bibcode:2012NatSR…2E.957Kdoi:10.1038/srep00957PMC 3518810PMID 23233876.
  59. ^ Gong P, Zhang Z, Zou C, Tian Q, Chen X, Hong M, et al. (January 2019). “Hippo/YAP signaling pathway mitigates blood–brain barrier disruption after cerebral ischemia/reperfusion injury”Behavioural Brain Research356: 8–17. doi:10.1016/j.bbr.2018.08.003PMC 6193462PMID 30092249.
  60. ^ Williamson KA, Rainger J, Floyd JA, Ansari M, Meynert A, Aldridge KV, et al. (February 2014). “Heterozygous loss-of-function mutations in YAP1 cause both isolated and syndromic optic fissure closure defects”American Journal of Human Genetics94 (2): 295–302. doi:10.1016/j.ajhg.2014.01.001PMC 3928658PMID 24462371.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.