Epithelial cell function

The mechanisms whereby mast cells enhance host protection to H. polygyms and T. spiralis (and whether these are related to the leak-lesion hypothesis) have not yet been fully defined. Certainly, mast cells contribute to intestinal inflammation during infection through the secretion of a range of cytokines (Gordon et al., 1990) and vasoactive substances (see above). In addition, the release of mast cell proteases are known to increase enterocyte permeability to macromolecules in the rat intestine (Scudamore et al., 1995) and regulate epithelial cell functions at other mucosal sites (Cairns and Walls, 1996). 

The number of channels synthesized, processed, and trafficked to the apical membrane and rate of CFTR internalization at the apical membrane determine the cell surface density. Mutations in CFTR that alter one or more of these parameters decrease total CFTR-mediated anion flux and impair epithelial cell function. 

Rennard SI, Romberger DJ, Sisson JH, Von Essen SG, Rubinstein I, Robbins RA, Spurzem JR (1994) Airway epithelial cells Functional roles in airway disease. Am J Respir Crit Care Med 150(5 Pt 2) S27-S30. 

Sharif NA, Wiernas TK, Howe WE, Griffin BW, Offord EA, Pfeifer AM. Human corneal epithelial cell functional responses to inflammatory agents and their antagonists. Invest Ophthalmol Vis Sci 39 2562-2571 (1998). 

B. Kirchhof, N. Sorgente, Pathogenesis of proliferative vitreoretinopathy. Modulation of retinal pigment epithelial cell functions by vitreous and macrophages. Dev. Ophthalmol. 16 (1989) 1-53. 

The highly enriched expression of S-HTjc receptors on epithelial cells of the choroid plexus suggest a role in conveying serotonergic innervation to epithelial cell function. 

F. Proteolytically Active Allergens and Epithelial Cell Function... 

Cilia are thin cylindrical hair-like structures with a cross-sectional radius of 0.1 gm projecting from the apical epithelial surface of ciliated columnar cells. Ciliary length is thought to correspond to periciliary fluid depth and range from approximately 7 gm in proximal airways to roughly 5 gm in more distal airways.- Each ciliated epithelial cell supports approximately 200 cilia at a density of eight cilia/gm. Short microvilli, possibly associated with secretory functions, are interspersed among the cilia. 

ENaC is located in the apical membrane of polarized epithelial cells where it mediates Na+ transport across tight epithelia [3], The most important tight epithelia expressing ENaC include the distal nephron of the kidney, the respiratory epithelium, and the distal colon. The basic function of ENaC in polarized epithelial cells is to allow vectorial transcellular transport of Na+ ions. This transepithelial Na+ transport through a cell involves... 

The membrane cytoskeleton (inclusive of the submembranous actin-spec-trin network) may function in the establishment and maintenance of restricted domains of specific proteins on the plasma membrane of polarized epithelial cells (Rodriguez-Boulan and Nelson, 1989 Mays et al., 1994). 

Mays, R.W., Beck, K.A.. Nelson, W.J. (1994). Organization and function of the cytoskeleton in polarized epithelial cells a component of the protein sorting machinery. Curr. Opin. Cell Biol. 6, 16-24. 

Taub, M. Sato, G. (1980). Growth of functional primary cultures of kidney epithelial cells in defined medium. J. Cell. Physiol. 105, 369-378. 

Next, Reilly et al. [65] localized the Na /H exchanger gene product in renal epithelial cells where the distributions of the kinetic isoforms was well-established. The strategy was based on the observation that the resistant- and sensitive-types are restricted to the apical and basolateral membranes, respectively, in confluent LLC-PK]/Clone 4 cells [8]. Thus, if proteins encoded by the cloned cDNAs localized to the apical membrane this would indicate that they represent the resistant-type. Localization to the basolateral membrane would prove they were the sensitive-type and presence on both membranes would suggest that the two functional isoforms had identical primary structures. Na exchanger proteins were localized by... 

Plasminogen activator inhibitors have been shown to be present in a large variety of different cells and tissues. These inhibitors are thought to play an important role in regulating tissue fibrinolysis. One of these inhibitors has been purified from cultured bovine aortic epithelial cells. This inhibitor has been shown to be a serine protease inhibitor and inhibits the function of two proteolytic enzymes urokinase and tissue plasminogen activator, both of which cleave and activate plasminogen. The mechanism by which this inhibitor functions is very similar to that described above with a-l-PI. Thus, the inhibitor forms a binary complex with the proteolytic enzyme and thereby inhibits its activity. Again in a situation comparable to that with a-l-PI, it was found that when the purified bovine aortic epithelial inhibitor was exposed to Al-chlorosuccinimide,... 

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