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Gene Review

Gjb2  -  gap junction protein, beta 2

Rattus norvegicus

Synonyms: CXN-26, Connexin-26, Cx26, Cxn-26, Gap junction beta-2 protein
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Disease relevance of Gjb2


High impact information on Gjb2

  • RESULTS: Protein expression of connexin 43 was up-regulated in activated hepatic stellate cells in vivo and in vitro and was mainly localized on the cell surface, whereas connexin 26 was found intracellularly [6].
  • The mRNA and protein expression of alpha 1 (connexin 43), beta 1 (connexin 32), and beta 2 (connexin 26) gap junction genes were examined in the regenerating rat liver after 70% partial hepatectomy (PH) [7].
  • Subtractive hybridization, selecting for mRNAs expressed in normal human mammary epithelial cells (NMECs) but not in mammary tumor cell lines (TMECs), led to the cloning of the human gap junction gene connexin 26 (Cx26), identified by its sequence similarity to the rat gene [8].
  • Further analysis demonstrated that Cx26 is a cell-cycle regulated gene expressed at a moderate level during G1 and S, and strongly up-regulated in late S and G2, as shown with lovastatin-synchronized NMECs [8].
  • Northern blots indicate that Cx32 and Cx26 are typically coexpressed, messages for both having been identified in liver, kidney, intestine, lung, spleen, stomach, testes, and brain, but not heart and adult skeletal muscle [9].

Chemical compound and disease context of Gjb2


Biological context of Gjb2

  • Overall sequence homology with Cx32 and Cx43 (64 and 51% amino acid identities, respectively) and a similar predicted tertiary structure confirm that this protein forms part of the connexin family and is consequently referred to as Cx26 [9].
  • Sequence and tissue distribution of a second protein of hepatic gap junctions, Cx26, as deduced from its cDNA [9].
  • The Cx26 gene is present as a single copy per haploid genome in rat and, based on Southern blots, appears to contain at least one intron outside the open reading frame [9].
  • GJIC measured by propidium iodide, which indicated the function of Cx26, decreased from before the onset of the S phase and then increased slightly in the S/M phase [11].
  • During stimulation of DNA synthesis, both Cx26 and Cx32 messenger RNA (mRNAs) in hepatocytes transiently increased in the G1 phase and then markedly decreased before the onset of the S phase, while only Cx26 messenger RNA (mRNA) increased slightly in the S/M phase [11].

Anatomical context of Gjb2


Associations of Gjb2 with chemical compounds

  • Different changes in expression and function of connexin 26 and connexin 32 during DNA synthesis and redifferentiation in primary rat hepatocytes using a DMSO culture system [11].
  • Estrogen treatment of ovariectomized rats caused the appearance of both Cx26 and E-cadherin in centrilobular hepatocytes not only in the perfused liver but also in the non-perfused liver [14].
  • The appearance of Cx26 in the centrilobular hepatocytes was inhibited by treatment with cytoskeleton disruptors such as colchicine and cytochalasin B, and intracytoplasmic transport inhibitors such as brefeldin A [14].
  • Analysis of Triton X-100-solubilized connexons from co-expressing cells by centrifugation through sucrose gradients or by affinity purification using a Ni-NTA column showed no evidence of mixing of Cx26 and Cx43 [15].
  • Our results indicate that in the rat liver: (a) the localization of Cx26 can be modulated by a post-translational mechanism; (b) E-cadherin may play an important role in the formation of gap junctions composed of Cx26; and (c) the formation of gap junctions is regulated by female steroid hormones [14].

Co-localisations of Gjb2

  • Immunocytochemically, Cx26-positive spots were observed between most adjacent cells and were co-localized with the Cx32-positive spots [16].

Regulatory relationships of Gjb2

  • These findings indicate that alterations in Cx32 and Cx26 expression occur rapidly in hepatocytes stimulated to proliferate and that several nonparenchymal liver cell types upregulate Cx43 expression when induced to proliferate [17].
  • In the present study, we found that the addition of 10(-7) M glucagon into the culture medium could dramatically induce Cx26 mRNA and protein [16].

Other interactions of Gjb2


Analytical, diagnostic and therapeutic context of Gjb2


  1. Connexin-26 and connexin-43 are differentially expressed and regulated in the rat myometrium throughout late pregnancy and with the onset of labor. Orsino, A., Taylor, C.V., Lye, S.J. Endocrinology (1996) [Pubmed]
  2. Responsiveness of endometrial genes Connexin26, Connexin43, C3 and clusterin to primary estrogen, selective estrogen receptor modulators, phyto- and xenoestrogens. Heikaus, S., Winterhager, E., Traub, O., Grümmer, R. J. Mol. Endocrinol. (2002) [Pubmed]
  3. A novel connexin 26 mutation associated with autosomal recessive sensorineural deafness. Frei, K., Lucas, T., Ramsebner, R., Schöfer, C., Baumgartner, W.D., Weipoltshammer, K., Erginel-Unaltuna, N., Wachtler, F.J., Kirschhofer, K. Audiol. Neurootol. (2004) [Pubmed]
  4. Differential changes in expression of gap junction proteins connexin 26 and 32 during hepatocarcinogenesis in rats. Sakamoto, H., Oyamada, M., Enomoto, K., Mori, M. Jpn. J. Cancer Res. (1992) [Pubmed]
  5. Functional domain mapping and selective trans-dominant effects exhibited by Cx26 disease-causing mutations. Thomas, T., Telford, D., Laird, D.W. J. Biol. Chem. (2004) [Pubmed]
  6. Intercellular communication via gap junctions in activated rat hepatic stellate cells. Fischer, R., Reinehr, R., Lu, T.P., Schönicke, A., Warskulat, U., Dienes, H.P., Häussinger, D. Gastroenterology (2005) [Pubmed]
  7. Differential regulation of multiple gap junction transcripts and proteins during rat liver regeneration. Kren, B.T., Kumar, N.M., Wang, S.Q., Gilula, N.B., Steer, C.J. J. Cell Biol. (1993) [Pubmed]
  8. Transcriptional downregulation of gap-junction proteins blocks junctional communication in human mammary tumor cell lines. Lee, S.W., Tomasetto, C., Paul, D., Keyomarsi, K., Sager, R. J. Cell Biol. (1992) [Pubmed]
  9. Sequence and tissue distribution of a second protein of hepatic gap junctions, Cx26, as deduced from its cDNA. Zhang, J.T., Nicholson, B.J. J. Cell Biol. (1989) [Pubmed]
  10. Reduced expression of the Connexin26 gene and its aberrant DNA methylation in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine. Shimizu, K., Shimoichi, Y., Hinotsume, D., Itsuzaki, Y., Fujii, H., Honoki, K., Tsujiuchi, T. Mol. Carcinog. (2006) [Pubmed]
  11. Different changes in expression and function of connexin 26 and connexin 32 during DNA synthesis and redifferentiation in primary rat hepatocytes using a DMSO culture system. Kojima, T., Yamamoto, M., Mochizuki, C., Mitaka, T., Sawada, N., Mochizuki, Y. Hepatology (1997) [Pubmed]
  12. Expression of multiple connexins in the rat epididymis indicates a complex regulation of gap junctional communication. Dufresne, J., Finnson, K.W., Gregory, M., Cyr, D.G. Am. J. Physiol., Cell Physiol. (2003) [Pubmed]
  13. Identification of cells expressing Cx43, Cx30, Cx26, Cx32 and Cx36 in gap junctions of rat brain and spinal cord. Rash, J.E., Yasumura, T., Davidson, K.G., Furman, C.S., Dudek, F.E., Nagy, J.I. Cell Commun. Adhes. (2001) [Pubmed]
  14. Rapid appearance of connexin 26-positive gap junctions in centrilobular hepatocytes without induction of mRNA and protein synthesis in isolated perfused liver of female rat. Kojima, T., Sawada, N., Oyamada, M., Chiba, H., Isomura, H., Mori, M. J. Cell. Sci. (1994) [Pubmed]
  15. Connexin43 and connexin26 form gap junctions, but not heteromeric channels in co-expressing cells. Gemel, J., Valiunas, V., Brink, P.R., Beyer, E.C. J. Cell. Sci. (2004) [Pubmed]
  16. Induction and regulation of connexin26 by glucagon in primary cultures of adult rat hepatocytes. Kojima, T., Mitaka, T., Shibata, Y., Mochizuki, Y. J. Cell. Sci. (1995) [Pubmed]
  17. Proliferation-associated differences in the spatial and temporal expression of gap junction genes in rat liver. Neveu, M.J., Hully, J.R., Babcock, K.L., Vaughan, J., Hertzberg, E.L., Nicholson, B.J., Paul, D.L., Pitot, H.C. Hepatology (1995) [Pubmed]
  18. Connexin expression by alveolar epithelial cells is regulated by extracellular matrix. Guo, Y., Martinez-Williams, C., Yellowley, C.E., Donahue, H.J., Rannels, D.E. Am. J. Physiol. Lung Cell Mol. Physiol. (2001) [Pubmed]
  19. Differential expression of gap junction proteins connexin26, 32, and 43 in normal and crush-injured rat sciatic nerves. Close relationship between connexin43 and occludin in the perineurium. Nagaoka, T., Oyamada, M., Okajima, S., Takamatsu, T. J. Histochem. Cytochem. (1999) [Pubmed]
  20. Changes in cellular distribution of connexins 32 and 26 during formation of gap junctions in primary cultures of rat hepatocytes. Kojima, T., Yamamoto, M., Tobioka, H., Mizuguchi, T., Mitaka, T., Mochizuki, Y. Exp. Cell Res. (1996) [Pubmed]
  21. Cellular expression of connexins in the rat brain: neuronal localization, effects of kainate-induced seizures and expression in apoptotic neuronal cells. Condorelli, D.F., Trovato-Salinaro, A., Mudò, G., Mirone, M.B., Belluardo, N. Eur. J. Neurosci. (2003) [Pubmed]
  22. Differential expression of major gap junction proteins, connexins 26 and 32, in rat mammary glands during pregnancy and lactation. Yamanaka, I., Kuraoka, A., Inai, T., Ishibashi, T., Shibata, Y. Histochem. Cell Biol. (2001) [Pubmed]
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