Transcriptional Regulation of Tlr11 Gene Expression in Epithelial Cells

Abstract

As sensors of invading microorganisms, Toll-like receptors (TLRs) are expressed not only on macrophages and dendritic cells (DCs) but also on epithelial cells. In the TLR family, Tlr11 appears to have the unique feature in that it is expressed primarily on epithelial cells, although it is also expressed on DCs and macrophages. Here, we demonstrate that transcription of the Tlr11 gene is regulated through two cis-acting elements, one Ets-binding site and one interferon regulatory factor (IRF)-binding site. The Ets element interacts with the epithelium-specific transcription factors, ESE-1 and ESE-3, and the IRF motif interacts with IRF-8. Thus, Tlr11 expression on epithelial cells is regulated by the transcription factors that are presumably distinct from transcription factors that regulate the expression of TLRs in innate immune cells such as macrophages and DCs. Our results imply that the distinctive transcription regulatory machinery for TLRs on epithelium may represent a promising new avenue for the development of epithelia-specific therapeutic interventions. As sensors of invading microorganisms, Toll-like receptors (TLRs) are expressed not only on macrophages and dendritic cells (DCs) but also on epithelial cells. In the TLR family, Tlr11 appears to have the unique feature in that it is expressed primarily on epithelial cells, although it is also expressed on DCs and macrophages. Here, we demonstrate that transcription of the Tlr11 gene is regulated through two cis-acting elements, one Ets-binding site and one interferon regulatory factor (IRF)-binding site. The Ets element interacts with the epithelium-specific transcription factors, ESE-1 and ESE-3, and the IRF motif interacts with IRF-8. Thus, Tlr11 expression on epithelial cells is regulated by the transcription factors that are presumably distinct from transcription factors that regulate the expression of TLRs in innate immune cells such as macrophages and DCs. Our results imply that the distinctive transcription regulatory machinery for TLRs on epithelium may represent a promising new avenue for the development of epithelia-specific therapeutic interventions. introductionThe expression and function of Toll-like receptor (TLR) 2The abbreviations used are: TLRToll-like receptorLPSlipopolysaccharideDCdendritic cellEMSAelectrophoretic mobility shift assayIFNinterferonIRFinterferon regulatory factorRACErapid amplification of cDNA endsChIPchromatin immunoprecipitationRTreverse transcriptionsiRNAsmall interfering RNA. genes in innate immune cells have been studied extensively (1.Akira S. Uematsu S. Takeuchi O. Cell. 2006; 124: 783-801Abstract Full Text Full Text PDF PubMed Scopus (8543) Google Scholar, 2.Medzhitov R. Nature. 2007; 449: 819-826Crossref PubMed Scopus (1962) Google Scholar, 3.Beutler B. Jiang Z. Georgel P. Crozat K. Croker B. Rutschmann S. Du X. Hoebe K. Annu. Rev. Immunol. 2006; 24: 353-389Crossref PubMed Scopus (658) Google Scholar), and the mechanisms that regulate TLR expression in these cells have been well defined (4.Medzhitov R. Nat. Rev. Immunol. 2001; 1: 135-145Crossref PubMed Scopus (3192) Google Scholar, 5.Rehli M. Trends Immunol. 2002; 23: 375-378Abstract Full Text Full Text PDF PubMed Scopus (247) Google Scholar). For instance, TLR2 can be up-regulated by LPS, peptidoglycan, and mycobacteria in macrophages and DCs, and the induction of TLR2 is mainly controlled by NF-κB and Sp1 transcriptional factors (6.Liu Y. Wang Y. Yamakuchi M. Isowaki S. Nagata E. Kanmura Y. Kitajima I. Maruyama I. Infect. Immun. 2001; 69: 2788-2796Crossref PubMed Scopus (93) Google Scholar, 7.Wang T. Lafuse W.P. Zwilling B.S. J. Immunol. 2001; 167: 6924-6932Crossref PubMed Scopus (78) Google Scholar, 8.Johnson C.M. Tapping R.I. J. Biol. Chem. 2007; 282: 31197-31205Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar). The murine Tlr4 gene is highly expressed on macrophages, and the expression is regulated by the myeloid-specific Ets transcription factor PU.1 (9.Roger T. Miconnet I. Schiesser A.L. Kai H. Miyake K. Calandra T. Biochem. J. 2005; 387: 355-365Crossref PubMed Scopus (74) Google Scholar). TLR9 is predominantly expressed by DCs and macrophages (10.Kadowaki N. Ho S. Antonenko S. Malefyt R.W. Kastelein R.A. Bazan F. Liu Y.J. J. Exp. Med. 2001; 194: 863-869Crossref PubMed Scopus (1669) Google Scholar, 11.Edwards A.D. Diebold S.S. Slack E.M. Tomizawa H. Hemmi H. Kaisho T. Akira S. Reis e Sousa C. Eur. J. Immunol. 2003; 33: 827-833Crossref PubMed Scopus (458) Google Scholar) and can be induced by type I interferons (IFNs), signal transducers and activators of transcription 1, and two IFN regulatory factors. IRF-1 and IRF-2 up-regulate Tlr9 through directly binding to IFN regulatory factor element (IRF-E) within the TLR9 promoter (12.Guo Z. Garg S. Hill K.M. Jayashankar L. Mooney M.R. Hoelscher M. Katz J.M. Boss J.M. Sambhara S. J. Immunol. 2005; 175: 7407-7418Crossref PubMed Scopus (28) Google Scholar). Collectively, these studies reveal the critical role of transcription factors in the regulation of TLR expression and function in cells of the innate immune system.Epithelial cells not only provide the first physical barrier to infection, but they also contribute actively to innate immunity against invading microbes through pattern recognition receptors that recognize conserved molecular patterns present in microorganisms (13.Bals R. Hiemstra P.S. Eur. Respir. J. 2004; 23: 327-333Crossref PubMed Scopus (427) Google Scholar, 14.Iwamura C. Nakayama T. Curr. Allergy Asthma Rep. 2008; 8: 7-13Crossref PubMed Scopus (65) Google Scholar). It is clear that epithelial cells express functional TLRs; however, these epithelial TLRs display different sensitivity to their cognate ligands from the TLRs expressed on DCs and macrophages (15.Uehara A. Fujimoto Y. Fukase K. Takada H. Mol. Immunol. 2007; 44: 3100-3111Crossref PubMed Scopus (252) Google Scholar, 16.Gribar S.C. Anand R.J. Sodhi C.P. Hackam D.J. J. Leukocyte Biol. 2008; 83: 493-498Crossref PubMed Scopus (157) Google Scholar, 17.Song J. Duncan M.J. Li G. Chan C. Grady R. Stapleton A. Abraham S.N. PLoS Pathog. 2007; 3: e60Crossref PubMed Scopus (124) Google Scholar). This difference in sensitivity is poorly understood (18.Cario E. Gerken G. Podolsky D.K. Gastroenterology. 2007; 132: 1359-1374Abstract Full Text Full Text PDF PubMed Scopus (524) Google Scholar, 19.Hornef M.W. Frisan T. Vandewalle A. Normark S. Richter-Dahlfors A. J. Exp. Med. 2002; 195: 559-570Crossref PubMed Scopus (351) Google Scholar, 20.Lee J. Mo J.H. Katakura K. Alkalay I. Rucker A.N. Liu Y.T. Lee H.K. Shen C. Cojocaru G. Shenouda S. Kagnoff M. Eckmann L. Ben-Neriah Y. Raz E. Nat. Cell Biol. 2006; 8: 1327-1336Crossref PubMed Scopus (476) Google Scholar). Still, one clearly recognizable difference is the varied expression levels of TLRs, which might be controlled by distinct transcriptional regulators of individual cell types.We previously demonstrated that Tlr11, which is different from other TLRs, is primarily expressed in urinary tract epithelial cells (21.Zhang D. Zhang G. Hayden M.S. Greenblatt M.B. Bussey C. Flavell R.A. Ghosh S. Science. 2004; 303: 1522-1526Crossref PubMed Scopus (874) Google Scholar). We hypothesize that the specific expression pattern of Tlr11 might be controlled and regulated by different transcriptional factors that differ from those that regulate other TLRs in myeloid innate immune cells. Therefore, we cloned the murine Tlr11 promoter and analyzed transcriptional regulation of the Tlr11 gene. We found that the epithelium-specific Ets factors, ESE-1 and ESE-3, along with IRF8, control and regulate Tlr11 expression in epithelial cells.DISCUSSIONTlr11 appears to be predominantly expressed in epithelial cells (21.Zhang D. Zhang G. Hayden M.S. Greenblatt M.B. Bussey C. Flavell R.A. Ghosh S. Science. 2004; 303: 1522-1526Crossref PubMed Scopus (874) Google Scholar). Our present studies of the transcriptional regulation of Tlr11 demonstrate that two cis-acting elements within the murine Tlr11 promoter, one Ets-binding site and one IRF-binding site, are required for maximal transcription of the murine Tlr11 gene. The epithelium-specific Ets transcription factors, ESE-1 and ESE-3, along with IRF-8 appear to regulate the expression of Tlr11 transcription in murine epithelial cells, implicating a distinct transcription regulatory machinery for TLRs that is unique to epithelial cells and may control infections therein.Epithelial cells express several functional TLRs through which invading pathogens are identified and immune responses are elicited (15.Uehara A. Fujimoto Y. Fukase K. Takada H. Mol. Immunol. 2007; 44: 3100-3111Crossref PubMed Scopus (252) Google Scholar, 23.Diamond G. Legarda D. Ryan L.K. Immunol. Rev. 2000; 173: 27-38Crossref PubMed Scopus (349) Google Scholar, 24.Medzhitov R. Janeway Jr., C.A. Cell. 1997; 91: 295-298Abstract Full Text Full Text PDF PubMed Scopus (1951) Google Scholar). For instance, the subcellular localization of TLR4 in lung and intestinal epithelial cells is intracellular; this expression pattern is different from that found on macrophages and DCs (19.Hornef M.W. Frisan T. Vandewalle A. Normark S. Richter-Dahlfors A. J. Exp. Med. 2002; 195: 559-570Crossref PubMed Scopus (351) Google Scholar, 25.Guillot L. Medjane S. Le-Barillec K. Balloy V. Danel C. Chignard M. Si-Tahar M. J. Biol. Chem. 2004; 279: 2712-2718Abstract Full Text Full Text PDF PubMed Scopus (310) Google Scholar). In addition, TLR9 activation through apical and basolateral surfaces in intestinal epithelial cells promotes distinct immune responses. Basolateral TLR9 activation invokes inflammatory responses, whereas apical TLR9 simulation inhibits inflammation and induces tolerance, which proved to be important for the maintenance of colonic homeostasis and the regulation of inflammation (20.Lee J. Mo J.H. Katakura K. Alkalay I. Rucker A.N. Liu Y.T. Lee H.K. Shen C. Cojocaru G. Shenouda S. Kagnoff M. Eckmann L. Ben-Neriah Y. Raz E. Nat. Cell Biol. 2006; 8: 1327-1336Crossref PubMed Scopus (476) Google Scholar). Tlr5, a well known cell surface TLR, seems to be restricted only to the basolateral membrane in epithelial cells (26.Rhee S.H. Im E. Riegler M. Kokkotou E. O'brien M. Pothoulakis C. Proc. Natl. Acad. Sci. U.S.A. 2005; 102: 13610-13615Crossref PubMed Scopus (176) Google Scholar).Moreover, transcriptional regulation plays a key role in the control of the TLR expression level, which may be a factor in the unique features of epithelial TLRs (22.Rehli M. Poltorak A. Schwarzfischer L. Krause S.W. Andreesen R. Beutler B. J. Biol. Chem. 2000; 275: 9773-9781Abstract Full Text Full Text PDF PubMed Scopus (211) Google Scholar). The transcriptional regulation of TLRs in myeloid innate immune cells has been extensively studied and determined. TLR expression is generally regulated by NF-κB, Sp1, and PU.1 (a myeloid-specific transcription factor in the Ets family). The Ets transcription factor family consists of more than 30 members that have a diverse range of functions (27.Sharrocks A.D. Nat. Rev. Mol. Cell Biol. 2001; 2: 827-837Crossref PubMed Scopus (810) Google Scholar). The Ets transcription factors share a conserved Ets domain that binds to purine-rich DNA sequences with a central GGAA/T core consensus, and they function as activators or repressors based on promoter context, cell type, or growth cycle. In this family, the myeloid-specific member PU.1 has been reported to play a role in regulating the expression of TLRs, including TLR1, TLR4, and TLR9 (22.Rehli M. Poltorak A. Schwarzfischer L. Krause S.W. Andreesen R. Beutler B. J. Biol. Chem. 2000; 275: 9773-9781Abstract Full Text Full Text PDF PubMed Scopus (211) Google Scholar, 33.Schroder K. Lichtinger M. Irvine K.M. Brion K. Trieu A. Ross I.L. Ravasi T. Stacey K.J. Rehli M. Hume D.A. Sweet M.J. J. Leukocyte Biol. 2007; 81: 1577-1590Crossref PubMed Scopus (40) Google Scholar). Although we found an Ets-binding site within the crucial region of the Tlr11 promoter, we failed to detect PU.1 binding to the Tlr11 promoter. Also, overexpression of PU.1 did not affect Tlr11 promoter activity.Considering that Tlr11 is predominantly expressed in epithelial cells, we pursued the theory that epithelium-specific transcription factors in the Ets family control and regulate Tlr11 promoter activity. ESE-1, ESE-2, and ESE-3 are the epithelium-specific Ets members (28.Kas K. Finger E. Grall F. Gu X. Akbarali Y. Boltax J. Weiss A. Oettgen P. Kapeller R. Libermann T.A. J. Biol. Chem. 2000; 275: 2986-2998Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar). More importantly, ESE-1 was reported as a transcription mediator of inflammation that interacts with NF-κB to regulate the inducible nitric-oxide synthetase gene (29.Rudders S. Gaspar J. Madore R. Voland C. Grall F. Patel A. Pellacani A. Perrella M.A. Libermann T.A. Oettgen P. J. Biol. Chem. 2001; 276: 3302-3309Abstract Full Text Full Text PDF PubMed Scopus (80) Google Scholar, 30.Grall F.T. Prall W.C. Wei W. Gu X. Cho J.Y. Choy B.K. Zerbini L.F. Inan M.S. Goldring S.R. Gravallese E.M. Goldring M.B. Oettgen P. Libermann T.A. FEBS J. 2005; 272: 1676-1687Crossref PubMed Scopus (51) Google Scholar). Our analysis of these epithelium-specific Ets transcription factors revealed that ESE-1 and ESE-3 bound specifically to the Ets cis-element in the Tlr11 promoter region. However, we cannot exclude that other factors or members of the Ets family can bind to this site, because multiple complex formations were also detected with our EMSA protocol. The ChIP assay further confirmed the interaction between these epithelium-specific Ets transcription factors and the Tlr11 promoter in vivo.Additionally, overexpression of ESE-1 and ESE-3 in MLE15 cells can up-regulate the promoter activity of Tlr11. The siRNA knockdown assay further demonstrated the essential role of ESE-1 and ESE-3 in the expression of Tlr11 in MLE15 cells. It is known that ESE-1 basal expression is restricted in epithelial cells but not in resting macrophages; however, ESE-1 can be induced by LPS in macrophages and can up-regulate murine Tlr4 transcriptional activity (9.Roger T. Miconnet I. Schiesser A.L. Kai H. Miyake K. Calandra T. Biochem. J. 2005; 387: 355-365Crossref PubMed Scopus (74) Google Scholar). Therefore, the role played by ESE-1 may be limited to activated macrophages. Here, we ascertained that the epithelium-specific Ets members, ESE-1 and ESE-3, control and regulate Tlr11 expression in epithelial cells.Elsewhere, ESE-3 was proposed as a candidate gene related to asthma susceptibility (31.Wu J. Duan R. Cao H. Field D. Newnham C.M. Koehler D.R. Zamel N. Pritchard M.A. Hertzog P. Post M. Tanswell A.K. Hu J. Cell Res. 2008; 18: 649-663Crossref PubMed Scopus (50) Google Scholar). Our previous report demonstrated that Tlr11 recognizes a profilin-like protein in parasites (32.Yarovinsky F. Zhang D. Andersen J.F. Bannenberg G.L. Serhan C.N. Hayden M.S. Hieny S. Sutterwala F.S. Flavell R.A. Ghosh S. Sher A. Science. 2005; 308: 1626-1629Crossref PubMed Scopus (780) Google Scholar). Because more than 100 allergens such as various pollens possess profilin-like domains, these profilin-like allergens may function via a TLR such as Tlr11. If so, this TLR could be regulated by ESE-3 and act to control sensitivity to asthma.The IRF family of transcription factors, which also regulate TLR expression, has the capacity for direct mediation of the action of TLR through IRF-binding sites in TLR promoters (22.Rehli M. Poltorak A. Schwarzfischer L. Krause S.W. Andreesen R. Beutler B. J. Biol. Chem. 2000; 275: 9773-9781Abstract Full Text Full Text PDF PubMed Scopus (211) Google Scholar, 33.Schroder K. Lichtinger M. Irvine K.M. Brion K. Trieu A. Ross I.L. Ravasi T. Stacey K.J. Rehli M. Hume D.A. Sweet M.J. J. Leukocyte Biol. 2007; 81: 1577-1590Crossref PubMed Scopus (40) Google Scholar, 34.Heinz S. Haehnel V. Karaghiosoff M. Schwarzfischer L. Müller M. Krause S.W. Rehli M. J. Biol. Chem. 2003; 278: 21502-21509Abstract Full Text Full Text PDF PubMed Scopus (164) Google Scholar). For instance, both TLR3 and TLR9 can be induced by IFN-β via constitutively bound IRF-2 and recruitment of IRF-1 to the promoters (12.Guo Z. Garg S. Hill K.M. Jayashankar L. Mooney M.R. Hoelscher M. Katz J.M. Boss J.M. Sambhara S. J. Immunol. 2005; 175: 7407-7418Crossref PubMed Scopus (28) Google Scholar, 34.Heinz S. Haehnel V. Karaghiosoff M. Schwarzfischer L. Müller M. Krause S.W. Rehli M. J. Biol. Chem. 2003; 278: 21502-21509Abstract Full Text Full Text PDF PubMed Scopus (164) Google Scholar). IFN-β and poly(I-C) can induce TLR7 expression that relies on IRF-1 binding to the TLR7 promoter (35.Severa M. Remoli M.E. Giacomini E. Annibali V. Gafa V. Lande R. Tomai M. Salvetti M. Coccia E.M. J. Immunol. 2007; 178: 6208-6216Crossref PubMed Scopus (40) Google Scholar). Not surprisingly, all these TLRs (TLR3, TLR7, and TLR9) regulated by IFRs play a role in the recognition of viral infection (1.Akira S. Uematsu S. Takeuchi O. Cell. 2006; 124: 783-801Abstract Full Text Full Text PDF PubMed Scopus (8543) Google Scholar).In this study, we found an IRF-binding site within the crucial region of the Tlr11 promoter and then tested multiple IRFs in that context. However, only IRF-8 was identified with direct binding to the Tlr11 promoter. IRF-8 is one of the transcription factors that regulate gene expression in response to pathogen-derived danger signals (36.Tamura T. Yanai H. Savitsky D. T. Annu. Rev. Immunol. 2008; PubMed Scopus Google Scholar). Although IRF-8 was to regulate (36.Tamura T. Yanai H. Savitsky D. T. Annu. Rev. Immunol. 2008; PubMed Scopus Google Scholar), to the of infection is but might that of Tlr11, which recognizes for this is that IRF-8 and TLR4 expression, which can recognize LPS (22.Rehli M. Poltorak A. Schwarzfischer L. Krause S.W. Andreesen R. Beutler B. J. Biol. Chem. 2000; 275: 9773-9781Abstract Full Text Full Text PDF PubMed Scopus (211) Google Scholar). a of IRF-8 protein is expression in cells, and (36.Tamura T. Yanai H. Savitsky D. T. Annu. Rev. Immunol. 2008; PubMed Scopus Google Scholar). we detected IRF-8 expression in MLE15 lung epithelial cells not generally not bind to DNA by but can with other transcription factors of the IRF family, including and A.D. J. K. S.N. J. Immunol. Google Scholar). between IRF-8 and other IRF family members results in an binding to IRF-binding However, because we did not these of IRF-8 and as regulators of Tlr11 expression in epithelial cells, IRF-8 may distinct mechanisms in different cell our results that the epithelium-specific Ets transcription factors, ESE-1 and ESE-3, along with IRF-8 appear to regulate the expression of Tlr11 transcription in murine lung epithelial cells. This the of a transcription regulatory machinery for TLRs in epithelial cells different from that for innate immune cells. of this to the could provide new for regulating TLR expression as a of and C.M. D. R. E. R. M.J. J. Respir. Med. 2008; PubMed Scopus Google Scholar, D. J. A.K. G. G. M. Y. M.J. J. Respir. Cell Mol. Biol. Google Scholar). introductionThe expression and function of Toll-like receptor (TLR) 2The abbreviations used are: TLRToll-like receptorLPSlipopolysaccharideDCdendritic cellEMSAelectrophoretic mobility shift assayIFNinterferonIRFinterferon regulatory factorRACErapid amplification of cDNA endsChIPchromatin immunoprecipitationRTreverse transcriptionsiRNAsmall interfering RNA. genes in innate immune cells have been studied extensively (1.Akira S. Uematsu S. Takeuchi O. Cell. 2006; 124: 783-801Abstract Full Text Full Text PDF PubMed Scopus (8543) Google Scholar, 2.Medzhitov R. Nature. 2007; 449: 819-826Crossref PubMed Scopus (1962) Google Scholar, 3.Beutler B. Jiang Z. Georgel P. Crozat K. Croker B. Rutschmann S. Du X. Hoebe K. Annu. Rev. Immunol. 2006; 24: 353-389Crossref PubMed Scopus (658) Google Scholar), and the mechanisms that regulate TLR expression in these cells have been well defined (4.Medzhitov R. Nat. Rev. Immunol. 2001; 1: 135-145Crossref PubMed Scopus (3192) Google Scholar, 5.Rehli M. Trends Immunol. 2002; 23: 375-378Abstract Full Text Full Text PDF PubMed Scopus (247) Google Scholar). For instance, TLR2 can be up-regulated by LPS, peptidoglycan, and mycobacteria in macrophages and DCs, and the induction of TLR2 is mainly controlled by NF-κB and Sp1 transcriptional factors (6.Liu Y. Wang Y. Yamakuchi M. Isowaki S. Nagata E. Kanmura Y. Kitajima I. Maruyama I. Infect. Immun. 2001; 69: 2788-2796Crossref PubMed Scopus (93) Google Scholar, 7.Wang T. Lafuse W.P. Zwilling B.S. J. Immunol. 2001; 167: 6924-6932Crossref PubMed Scopus (78) Google Scholar, 8.Johnson C.M. Tapping R.I. J. Biol. Chem. 2007; 282: 31197-31205Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar). The murine Tlr4 gene is highly expressed on macrophages, and the expression is regulated by the myeloid-specific Ets transcription factor PU.1 (9.Roger T. Miconnet I. Schiesser A.L. Kai H. Miyake K. Calandra T. Biochem. J. 2005; 387: 355-365Crossref PubMed Scopus (74) Google Scholar). TLR9 is predominantly expressed by DCs and macrophages (10.Kadowaki N. Ho S. Antonenko S. Malefyt R.W. Kastelein R.A. Bazan F. Liu Y.J. J. Exp. Med. 2001; 194: 863-869Crossref PubMed Scopus (1669) Google Scholar, 11.Edwards A.D. Diebold S.S. Slack E.M. Tomizawa H. Hemmi H. Kaisho T. Akira S. Reis e Sousa C. Eur. J. Immunol. 2003; 33: 827-833Crossref PubMed Scopus (458) Google Scholar) and can be induced by type I interferons (IFNs), signal transducers and activators of transcription 1, and two IFN regulatory factors. IRF-1 and IRF-2 up-regulate Tlr9 through directly binding to IFN regulatory factor element (IRF-E) within the TLR9 promoter (12.Guo Z. Garg S. Hill K.M. Jayashankar L. Mooney M.R. Hoelscher M. Katz J.M. Boss J.M. Sambhara S. J. Immunol. 2005; 175: 7407-7418Crossref PubMed Scopus (28) Google Scholar). Collectively, these studies reveal the critical role of transcription factors in the regulation of TLR expression and function in cells of the innate immune system.Epithelial cells not only provide the first physical barrier to infection, but they also contribute actively to innate immunity against invading microbes through pattern recognition receptors that recognize conserved molecular patterns present in microorganisms (13.Bals R. Hiemstra P.S. Eur. Respir. J. 2004; 23: 327-333Crossref PubMed Scopus (427) Google Scholar, 14.Iwamura C. Nakayama T. Curr. Allergy Asthma Rep. 2008; 8: 7-13Crossref PubMed Scopus (65) Google Scholar). It is clear that epithelial cells express functional TLRs; however, these epithelial TLRs display different sensitivity to their cognate ligands from the TLRs expressed on DCs and macrophages (15.Uehara A. Fujimoto Y. Fukase K. Takada H. Mol. Immunol. 2007; 44: 3100-3111Crossref PubMed Scopus (252) Google Scholar, 16.Gribar S.C. Anand R.J. Sodhi C.P. Hackam D.J. J. Leukocyte Biol. 2008; 83: 493-498Crossref PubMed Scopus (157) Google Scholar, 17.Song J. Duncan M.J. Li G. Chan C. Grady R. Stapleton A. Abraham S.N. PLoS Pathog. 2007; 3: e60Crossref PubMed Scopus (124) Google Scholar). This difference in sensitivity is poorly understood (18.Cario E. Gerken G. Podolsky D.K. Gastroenterology. 2007; 132: 1359-1374Abstract Full Text Full Text PDF PubMed Scopus (524) Google Scholar, 19.Hornef M.W. Frisan T. Vandewalle A. Normark S. Richter-Dahlfors A. J. Exp. Med. 2002; 195: 559-570Crossref PubMed Scopus (351) Google Scholar, 20.Lee J. Mo J.H. Katakura K. Alkalay I. Rucker A.N. Liu Y.T. Lee H.K. Shen C. Cojocaru G. Shenouda S. Kagnoff M. Eckmann L. Ben-Neriah Y. Raz E. Nat. Cell Biol. 2006; 8: 1327-1336Crossref PubMed Scopus (476) Google Scholar). Still, one clearly recognizable difference is the varied expression levels of TLRs, which might be controlled by distinct transcriptional regulators of individual cell types.We previously demonstrated that Tlr11, which is different from other TLRs, is primarily expressed in urinary tract epithelial cells (21.Zhang D. Zhang G. Hayden M.S. Greenblatt M.B. Bussey C. Flavell R.A. Ghosh S. Science. 2004; 303: 1522-1526Crossref PubMed Scopus (874) Google Scholar). We hypothesize that the specific expression pattern of Tlr11 might be controlled and regulated by different transcriptional factors that differ from those that regulate other TLRs in myeloid innate immune cells. Therefore, we cloned the murine Tlr11 promoter and analyzed transcriptional regulation of the Tlr11 gene. We found that the epithelium-specific Ets factors, ESE-1 and ESE-3, along with IRF8, control and regulate Tlr11 expression in epithelial cells.