Occludins

Many structural components of the tight junctions (TJs) have been defined since 1992 [85-97]. Lutz and Siahaan [95] reviewed the protein structural components of the TJ. Figure 2.7 depicts the occludin protein complex that makes the water pores so restrictive. Freeze-fracture electronmicrographs of the constrictive region of the TJ show net-like arrays of strands (made partly of the cytoskeleton) circumscribing the cell, forming a division between the apical and the basolateral... 

Ohtake K, Maeno T, Ueda H, Ogihara M, Natsume H, Morimoto Y (2003) Poly-L-arginine enhances paracellular permeability via serine/threonine phosphorylation of ZO-1 and tyrosine dephosphorylation of occludin in rabbit nasal epithelium. Pharm Res 20 1838-1845. 

Alveolar epithelial cells (AECs) are connected with each other by various epithelial cell-cell contacts (i.e., tight junctions, adherens junctions and others). These contacts comprise several groups of proteins, such as occludin, zonula occludens (ZO-1, -2, -3), claudins, tricellulin, E-cadherin and intercellular adhesion molecule-1 (ICAM-1) [13-15], Their regulation and interplay, which has influence on epithelial barrier properties, however, is largely unknown to date. 

Figure 11.2 Morphological differences between human alveolar epithelial cells in primary culture (A and C) and the A549 cell line (B and D). Cells are visualised by light microscopy (A and B) and immunofluorescence microscopy (C and D) using an antibody against a tight junctional protein, occludin.

In human vaginal-cervical epithelia, occludin appears to play a significant role in the regulation of 7 tj- In the vaginal-cervical epithelia, occludin is present in two forms the full length 65-kDa isoform and a truncated 50-kDa isoform [35,43], A shift from 65 kDa to 50 kDa dominance is associated with abrogation of [35,43], suggesting that in low-resistance epithelia, occludin plays an important role in 7 tj-... 

Recent studies using vaginal-cervical cells suggest yet another mechanism for the early stage of tight junctional disassembly, namely, the breakdown of occludin 65-kDa isoform to the lesser functional 50-kDa isoform. Occludin appears to constitutively undergo calpain-mediated proteolysis, increasing the amount of non-functional 50-kDa isoform [35, 43], As described above,... 

Zeng R, Li X, and Gorodeski GI [2004] Estrogen abrogates transcervical tight junctional resistance by acceleration of Occludin modulation. J Clin Endocrinol Metab 89 5145-5155... 

Zhu L, Li X, Zeng R, and Gorodeski GI [2006] Changes in tight junctional resistance of the cervical epithelium are associated with modulation of content and phosphorylation of occludin 65 kDa and 50 kDa forms. Endocrinology... 

Furuse M, Fujita K, Hiiragi T, Fujimoto K, and Tsukita S [1998] Claudin-1 and -2 Novel integral membrane proteins localizing at tight junctions with no sequence similarity to occludin. J Cell Biol 141 1539-1550... 

Furuse M, Sasaki H, Fujimoto K, and Tsukita S [1998] A single gene product, claudin-1 or -2, reconstitutes tight junction strands and recruits occludin in fibroblasts. J Cell Biol 143 391—401... 

Furuse M, Hirase T, Itoh M, Nagafuchi A, Yonemura S, Tsukita S, and Tsukita S [1993] Occludin a novel integral membrane protein localizing at tight junctions. J Cell Biol 123 1777-1788... 

Ando-Akatsuka Y, Saitou M, Hirase T, Kishi M, Sakakibara A, Itoh M, Yonemura S, Furuse M, and Tsukita S [1996] Interspecies diversity of the occludin sequence cDNA cloning of human, mouse, dog and ratkangaroo homologues. J Cell Biol 133 43 17... 

Nusrat A, Brown GT, Tom J, Drake A, Bui TTT, Quan C, and Mrsny RJ [2005] Multiple protein interactions involving proposed extracellular loop domains of the tight junction protein occludin. Mol Biol Cell 16 1725-1734... 

Saitou M, Fujimoto K, Doi Y, Itoh M, Fujimoto T, Furuse M, Takano H, Noda T, and Tsukita S [1998] Occludin-deficient embryonic stem cells can differentiate into polarized epithelial cells bearing tight junctions. J Cell Biol 141 397-408... 

Baida MS, Flores-Maldonado C, Cereijido M, and Matter K [2000] Multiple domains of occludin are involved in the regulation of paracellular permeability. J Cell Biochem 78 85-96... 

Huber D, Baida MS, and Matter K [2000] Occludin modulates transepithelial migration of neutrophils. J Biol Chem 275 5773-5778... 

Saitou M, ando-Akatsuka Y, Itoh M, Furuse M, Inazawa J, Fujimoto K, and Tsukita, S [1997] Mammalian occludin in epithelial cells its expression and subcellular distribution. Eur J Cell Biol 73 222-231... 

Furuse M, Fujimoto K, Sato N, Hirase T, Tsukita S, and Tsukita S [1996] Overexpression of occludin, a tight junction-associated integral membrane protein, induces the formation of intracellular multilamellar bodies bearing tight junction-like structures. J Cell Sci 109 429-435... 

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