Claudin-2 (E1H9O) Rabbit mAb

Tight junctions, or zonula occludens, form a continuous barrier to fluids across the epithelium and endothelium. They function in regulation of paracellular permeability and in the maintenance of cell polarity, blocking the movement of transmembrane proteins between the apical and the basolateral cell surfaces. Tight junctions are composed of claudin and occludin proteins, which join the junctions to the cytoskeleton (1,2). The claudin family is composed of 23 integral membrane proteins, and their expression, which varies among tissue types, may determine both the strength and properties of the epithelial barrier. Alteration in claudin protein expression pattern is associated with several types of cancer (2,3). Claudin-1 is expressed primarily in keratinocytes (4) and normal mammary epithelial cells, but is absent or reduced in breast carcinomas and breast cancer cell lines (5,6).Claudin-2 is expressed primarily in the proximal tubule of the normal mammalian kidney, where it regulates transepithelial ion (e.g., Na+, Cl-) reabsorption (7). Increased expression of Claudin-2 has been reported in some cancer cell lines (8), including A549 lung adenocarcinoma cells, where its nuclear distribution was positively associated with enhanced proliferation (9). 1.Shin, K. et al. (2006) Annu Rev Cell Dev Biol 22, 207-35. 2.Oliveira, S.S. and Morgado-Díaz, J.A. (2007) Cell Mol Life Sci 64, 17-28. 3.Hewitt, K.J. et al. (2006) BMC Cancer 6, 186. 4.Brandner, J.M. et al. (2002) Eur J Cell Biol 81, 253-63. 5.Krämer, F. et al. (2000) Hum Genet 107, 249-56. 6.Swisshelm, K. et al. (1999) Gene 226, 285-95. 7.Muto, S. et al. (2010) Proc Natl Acad Sci U S A 107, 8011-6. 8.Ikari, A. et al. (2012) Biochim Biophys Acta 1823, 1110-8. 9.Ikari, A. et al. (2014) Biochim Biophys Acta 1843, 2079-88.