Claudin 2 Polyclonal Antibody, Invitrogen™

Description

• Immunogen sequence: WKTSSYVGAS IVTAVGFSKG LWMECATHST GITQCDIYST LLGLPADIQA AQAMMVTSSA ISSLACIISV VGMRCTVFCQ ESRAKDRVAV AGGVFFILGG LLGFIPVAWN LHGILRDFYS PLVPDSMKFE IGEALYLGII SSLFSLIAGI ILCFSCSSQR NRSNYYDAYQ AQPLATRSSP RPGQPPKVKS EFNSYSLTGY V Tight junctions are specialized regions of cell-cell contact that are particularly abundant in luminal epithelial cell sheets
• In freeze-fracture electron micrographs, tight junctions are visualized as belt-like bands of anastomosing sealing strands (TJ strands) that completely encircle the lateral surfaces of each cell
• TJ strands on adjacent cells are presumed to interact with each other to form a sort of &quotemolecular gasket&quote that prevents ions, water and other molecules from leaking between cells and thus, from one side of the sheet to the other
• In addition to this so-called &quotebarrier&quote function, the &quotefence&quote function of tight junctions plays an important role in maintaining epithelial cell-polarity by blocking the diffusion of membrane proteins between apical (luminal) and basolateral cell surfaces
• Confinement of, for example, the glucose symport to apical surfaces allows glucose to be transported vectorially from the lumen, through the cell, and into the bloodstream
• Several peripheral membrane proteins are associated with tight junctions including ZO-1, ZO-2, ZO-3 (members of membrane-associated guanylate-kinase family), cingulin, the 7H6 antigen, Rab-3b, symplekin
• While their precise functions are not known, roles for these proteins have been suggested in tight junction assembly and maintenance; signal transduction; and the regulation of tight junction permeability
• Furthermore, a growing body of evidence suggests that actin filaments play a major role in regulating tight junction permeability
• Until recently, the only transmembrane protein known to be associated with tight junctions was occludin, an ∽65 kDa protein with four transmembrane domains
• Despite widespread expectation, a critical structural role for occludin in TJ strands was ruled out by the observation of apparently normal tight junctions formed between cells disrupted at both occludin alleles
• Fortunately, a closer examination of isolated tight junctions uncovered two related ∽22 kDa, four-transmembrane domain proteins, claudin-1 and claudin-2, with no similarity to occludin
• In contrast to occludin, which induces only a small number of short strands at cell-cell contact sites when introduced into fibroblasts lacking tight junctions, claudin-1 and -2 induce networks of strands characteristic of true tight junctions
• Though inconclusive, these findings suggest that claudin-1 and -2 are major structural components of TJ strands and that occludin plays some other accessory role
• Excitement in the tight junction field continues to rise following the recent discovery of claudins -3, -4, -5, -6, -7, and -8 and experiments suggesting that tight junctions in different tissues are comprised of different sets of claudin family proteins
• Claudin-1 and claudin-2 connect to the actin cytoskeleton through ZO-1; Claudin-2 functions as a paracellular channel with cation (Na+) selectivity at tight junctions
• The expression of claudin-2 is restricted to the liver and kidney, with small amounts also found in the brain.