Occludin protein

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... 

Guo X, Rao JN, Liu L, Zou T, Keledjian KM, Boneva D, Marasa BS, Wang JY (2005) Polyamines are necessary for synthesis and stability of occludin protein in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 288(6) G1159-G1169 Igarashi K, Kashiwagi K (2010) Modulation of cellular function by polyamines. Int J Biochem Cell Biol 42(1) 39-51... 

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.

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, 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... 

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... 

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... 

Tight junctions form selective barriers that regulate paracellular transport across epithelia and endothelia. Tight junctions are composed of transmembrane proteins (occludin, claudins, and JAMs) linked to the actin cytoskeleton through cytoplasmic ZO proteins, whereas adherence junctions are composed of the nectin-afadin system and the E-cadhcrin catenin system [143]. These cell cell adhesion proteins create the barrier and regulate electrical resistance, size, and ionic charge selectivity [144], Several experimental procedures have... 

Mitic LL, van Itallie CM (2001) Occludin and claudins transmembrane proteins of the tight junction. In Cereijido M, Anderson JM (eds) Tight Junctions (2nd edn.). CRC, Boca Raton, pp 213-230... 

The TJPs form an intricate complex of transmembrane (occludin, claudins, junctional adhesion molecule-1) and cytoplasmic (zona occludens-1 and -2, cingulin, AF-6, and 7H6) proteins linked to the cytoskeleton (Hawkins and Davis, 2005) (Fig. 1). Occludin was the first TJP discovered. It is a 60- to 65-kDa protein with four transmembrane domains and two extracellular loops that span the cleft between adjacent endothelial cells (Furuse et al., 1993 Hirase et al., 1997 Hawkins and Davis, 2005). Occludin is highly expressed in cerebral endothelium (Fig. 2) and sparsely distributed in nonneural endothelia (Hirase et al., 1997). The phosphorylation state of occludin regulates its association with the cell membrane (Hirase et al., 2001). In experimental autoimmune encephalomyelitis, a model of multiple sclerosis, occludin dephosphorylation precedes the neurological deterioration and increased leakage of plasma proteins across the BBB (Morgan et al., 2007). The C-terminal cytoplasmic domain of occludin is involved in its association with the cytoskeleton via accessory proteins such as zona occludens ZO-1 and ZO-2 (Furuse et al, 1993). 

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