Usakin L.A., Romanova O.A., Tverye E.A., Klein O.I., Sysoeva A.P., Paltsev M.A., Panteleyev A.A.

ntroduction. Agr2protein belongs to the family of disulfide isomerases of the endoplasmic reticulum and contains active cysteine domains involved in the formation of disulfide bonds with mucins. It is expressed in goblet cells of the intestinal epithelium and plays a key role in controlling the secretion of mucin 2, the main component responsible for the viscosity of mucus and performing many other regulatory functions in the intestinal tract epithelium. The role of Agr family genes in the development and functioning of other mucin-producing epithelial tissues has been poorly studied. The aim of the study was to identify the role of Agr2 in the development of mammalian respiratory epithelium and in the control of its functions, in particular, in the secretion of mucins. Methods. As an experimental model, a transgenic line of mice with knockout of the Agr2 gene (Agr2tm1.2Erle) was used. Immunohistochemical and standard histological and molecular biology techniques were used as methods of analysis.Results. Our data have shown for the first time the key role of Agr2 in the production of mucus in the tracheal mammalian epithelium. At the middle stages of embryonic development (E16 – E18), the active expression of the Agr2 protein precisely coincided (both spatially and temporally) with the onset of secretion of mucin 2 and mucin 5 – the main components of tracheal mucus responsible for performing the evacuation function of the tracheal epithelium. Unlike in the intestinal epithelium, the knockout of Agr2 does not lead to the total disappearance of mucins in the respiratory epithelium, both in embryos and in adult mice. However, we found that in adult mutant mice the full-fledged processing of mucin was disrupted, which remains inside the cells of the respiratory epithelium (in the endoplasmic reticulum), and not secreted in the mucus. Thus, the protein Agr2 is one of the main factors controlling the secretion process and, consequently, the evacuation function of the tracheal epithelium. Conclusion. The pharmacological or genetic manipulation of the Agr2 protein activity may be a promising approach to the modulation of the secretory function of the tracheal epithelium both in tissue equivalents in vitro and in the trachea in situunder various clinical circumstances, including tracheal transplantation or application of tracheal tissue equivalents.
Agr2, epithelium, trachea, respiratory system

Список литературы: 
  1. Aberger F., Weidinger G., Grunz H. & Richter K. Anterior specification of embryonic ectoderm: the role of the Xenopus cement gland-specific gene XAG-2. Mechanisms of development. 1998; 72: 115–30.
  2. Kumar A., Godwin J. W., Gates P. B., Garza-Garcia A. A. & Brockes J. P. Molecular basis for the nerve dependence of limb regeneration in an adult vertebrate. Science. 2007; 318: 772–7.
  3. Ivanova A.S., Tereshina M.B., Ermakova G.V., Belousov V.V., Zaraisky A.G. Agr genes, missing in amniotes, are involved in the body appendages regeneration in frog tadpoles. Scientific reports. 2013; 3: 1279.
  4. Park S., Zhena G.,Verhaeghea C., Nakagamia Y., Nguyenvua L.T., Barczaka A.J., Killeend N., Erl D. The protein disulfide isomerase AGR2 is essential for production of intestinal mucus. PNAS. 2009; 106 (17): 6950–5.
  5. Shih L.J., Lu Y.F., Chen Y.H., Lin C.C., Hwang S.P. Characterization of the agr2 gene, a homologue of X.laevis anterior gradient 2, from the zebrafish, Danio rerio. Gene Expres. Patterns. 2007; 7: 225–30.
  6. Thompson D.A., Weigel R.J. HAG-2, the human homologue of the Xenopus laevis cement gland gene XAG-2, is coexpressed with estrogen receptor in breast cancer cell lines. Biochem. Biophys. Res. Commun. 1998; 251: 111–6.
  7. Zheng, W., Rosenstiel, P., Huse, K., Sina, C., Valentonyte, R., Mah, N., Zeitlmann, L.,Grosse, J., Ruf, N., Nurnberg, P., Costello, C.M., Onnie, C., Mathew, C., Platzer, M.,Schreiber, S., Hampe, J. Evaluation of AGR2 and AGR3 as candidate genes for inflammatory bowel disease. Genes Immun. 2006; 7: 11–5.
  8. Brychtova V., Vojtesek B., Hrstka R. Anterior gradient 2: A novel player in tumor cell biology. Cancer Letters. 2011; 304: 1–7.
  9. Komiya T., Tanigawa Y., Hirohashi S. Cloning of the gene gob-4, which is expressed in intestinal goblet cells in mice. Biochim. Biophys. Acta. 1999; 1444: 434–8.
  10. Schroeder B.W.,Verhaeghe C., Park S.W., Nguyenvu L.T., Huang X., Zhen G., et al. AGR2 is induced in asthma and promotes allergen-induced mucin overproduction. Am. J. Respir.Cell Mol. Biol. 2012; 47: 178–85.
  11. Wang Z., Hao Y., Lowe A.W. The adenocarcinoma-associated antigen, AGR2, promotes tumor growth, cell migration, and cellular transformation. Cancer Res. 2008; 68: 492–7.
  12. Zhao F., Edwards R., Dizon D., Afrasiabi K., Mastroianni J.R., Geyfman M., Ouellette A.J., Andersen B., Lipkin S.M. Disruption of paneth and goblet cell homeostasis and increased endoplasmic reticulum stress in Agr2 -/- mice. Dev. Biol. 2010; 338 (2): 270–9.
  13. Ambort D., Johansson M.E., Gustafsson J.K., Ermund A., Hansson G.C. Perspectives on mucus properties and formation – lessons from the biochemical world. Cold Spring Harb. Perspect. Med. 2012; 2 (11): a014149.
  14. Roy M.G., Rahmani M., Hernandez J.R., Alexander S.N., Ehre C., Ho S.B., Evans C.M. Mucin Production during Prenatal and Postnatal Murine Lung Development. Am. J. Respir. Cell Mol. Biol. 2011; 44: 755–60.
  15. Fahy J.V., Dickey B.F. Airway mucus function and dysfunction. N. Engl. J. Med. 2010; 363: 2233–47.
  16. Adler K.B., Tuvim M.J., Dickey B.F. Regulated mucin secretion from airway epithelial cells. Frontiersin Endocrinology, Neuroendocrine Science. 2013; 4 (129): 1–9.