Technical Data
Claudin 4 (CLDN4)
Initially only transmembrane protein known to be associated with tight junctions was occludin, an ~65kD 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. A closer examination of isolated tight junctions uncovered two related ~22kD, four-transmembrane domain proteins, claudin 1 and claudin 2, with no similarity to occludin. 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. The overexpression of Claudin-4 was found to decrease paracellular electrical conductance due to a selective decrease in Na+ permeability, with no significant change for Cl-. Claudin-4 is the first to confer ionic selectivity to paracellular transport, leading to the prediction that the combination of different claudins defines the overall selectivity of different junctions. Thus, Claudin-4 forms channels through the tight junctions that discriminate against Na+ ions and are indifferent to Cl- ions.

Suitable for use in Immunofluorescence, Western Blot and Immunohistochemistry. Other applications have not been tested.

Recommended Dilutions:
Western Blot: 1-3ug/ml
Immunofluorescence: 2.5-10ug/ml
Immunohistochemistry: 2-3ug/ml; For best results in immunohistochemistry with formalin-fixed, paraffin-embedded (FFPE) tissues, heat induced epitope retrieval (HIER) with citrate buffer, pH 6.0, is required prior to staining.
Optimal dilutions to be determined by the researcher.

Storage and Stability:
May be stored at 4C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20C. Aliquots are stable for 12 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.
MabIgG16A43Affinity Purified
100ug-20CBlue IceHumanMouse
Synthetic peptide corresponding to a 22 amino acid sequence derived from the C-terminal region of human Claudin 4.
Purified by Protein A affinity chromatography.
Supplied as a liquid in PBS, pH 7.4, 0.09% sodium azide.
Recognizes the human ~22kD Claudin 4 protein and does not crossreact with the protein at 55kD. Species Crossreactivity: rat ileum homogenates and canine MDCK cell lysates by Western Blot and Immunofluorescence. Reactivity has also been confirmed with formalin-fixed, paraffin-embedded (FFPE) human normal colon and colon cancer tissues by Immunohistochemistry.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.
1. Saitou, M., et al., J. Cell Biol. 141: 397-408 (1998). 2. Furuse, M., et al., J. Cell Biol. 143: 391-401 (1998). 3. Tsukita, S. & Furuse, M., Genes Cells 3: 569-573 (1998). 4. Morita, K., et al., PNAS 96: 511-516 (1999). 5. Van Itallie, C.M., et al., J. Clin. Invest. 107(10): 1319-1327 (2001).