A novel role for villin in intestinal epithelial cell survival and homeostasis

Apoptosis is a key regulator for the normal turnover of the intestinal mucosa, and abnormalities associated with this function have been linked to inflammatory bowel disease and colorectal cancer. Despite this, little is known about the mechanism(s) mediating intestinal epithelial cell apoptosis. Villin is an actin regulatory protein that is expressed in every cell of the intestinal epithelium as well as in exocrine glands associated with the gastrointestinal tract. In this study we demonstrate for the first time that villin is an epithelial cell-specific anti-apoptotic protein. Absence of villin predisposes mice to dextran sodium sulfate-induced colitis by promoting apoptosis. To better understand the cellular and molecular mechanisms of the anti-apoptotic function of villin, we overexpressed villin in the Madin-Darby canine kidney Tet-Off epithelial cell line to demonstrate that expression of villin protects cells from apoptosis by maintaining mitochondrial integrity thus inhibiting the activation of caspase-9 and caspase-3. Furthermore, we report that the anti-apoptotic response of villin depends on activation of the pro-survival proteins, phosphatidylinositol 3-kinase and phosphorylated Akt. The results of our studies shed new light on the previously unrecognized function of villin in the regulation of apoptosis in the gastrointestinal epithelium.     

Modulation of enzymatic activities by n-3 polyunsaturated fatty acids to support cardiovascular health

Epidemiological evidence from Greenland Eskimos and Japanese fishing villages suggests that eating fish oil and marine animals can prevent coronary heart disease. Dietary studies from various laboratories have similarly indicated that regular fish oil intake affects several humoral and cellular factors involved in atherogenesis and may prevent atherosclerosis, arrhythmia, thrombosis, cardiac hypertrophy and sudden cardiac death. The beneficial effects of fish oil are attributed to their n-3 polyunsaturated fatty acid (PUFA; also known as omega-3 fatty acids) content, particularly eicosapentaenoic acid (EPA; 20:5, n-3) and docosahexaenoic acid (DHA; 22:6, n-3). Dietary supplementation of DHA and EPA influences the fatty acid composition of plasma phospholipids that, in turn, may affect cardiac cell functions in vivo. Recent studies have demonstrated that long-chain omega-3 fatty acids may exert beneficial effects by affecting a wide variety of cellular signaling mechanisms. Pathways involved in calcium homeostasis in the heart may be of particular importance. L-type calcium channels, the Na+-Ca2+ exchanger and mobilization of calcium from intracellular stores are the most obvious key signaling pathways affecting the cardiovascular system; however, recent studies now suggest that other signaling pathways involving activation of phospholipases, synthesis of eicosanoids, regulation of receptor-associated enzymes and protein kinases also play very important roles in mediating n-3 PUFA effects on cardiovascular health. This review is therefore focused on the molecular targets and signaling pathways that are regulated by n-3 PUFAs in relation to their cardioprotective effects.     

Melatonin and Gibberellic Acid Promote Growth and Chlorophyll Biosynthesis by Regulating Antioxidant and Methylglyoxal Detoxification System in Tomato Seedlings Under Salinity

Journal of Plant Growth Regulation - The beneficial roles of melatonin (Mel) and gibberellic acid (GA3) in the biosynthesis of photosynthetic pigments, osmoregulation, and methylglyoxal (MG)...     

Structure-function analysis of the rat prolactin promoter: phasing requirements of proximal cell-specific elements

Expression of PRL, a member of the GH family of genes, is restricted to the lactotroph cells of the anterior pituitary. The proximal promoter of the rat PRL (rPRL) gene contains four factor-binding sites. Three nonadjacent elements, footprints (FP) I, III, and IV, are separated by an integral number of helical turns and bind a pituitary-specific factor, LSF-1. FP II binds another factor present in pituitary and nonpituitary cells. The mechanisms by which DNA-bound proteins influence RNA polymerase-II activity over large distances are not fully understood, but protein-protein interactions, with looping of intervening DNA, may bring distant sites into close proximity. Here, we demonstrate, using protein titration studies, that LSF-1 binds to the most proximal FP I element with the highest affinity, whereas it binds the more distal elements, FP III and FP IV, with progressively lower affinities. Time-course and salt-sensitivity studies reveal that binding of LSF-1 to all three pituitary-specific rPRL promoter sites occurs rapidly (less than or equal to 1 min) and requires fairly high salt concentrations (greater than or equal to 300 mM KCl) to destabilize protein-DNA interactions. Moreover, once bound, the pituitary nuclear factor(s) induces a conformational change in rPRL DNA structure with greatly delayed kinetics (greater than 15 min) and at a different salt concentration than are required for simply factor binding. Taken together, these data suggest a model in which LSF-1 initially binds fairly rapidly to multiple nonadjacent elements and then interacts with itself or other DNA-bound proteins much more slowly, possibly looping or bending the rPRL promoter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in in vivo levels of charged transfer RNA species during development of the posterior silkgland of Bombyx mori

The changes in the in vivo levels of acylated tRNA specific for the amino acids that make the bulk of silf-fibroin were examined during the distinct physiological phases, the growth phase and the silk-fibroin production phase, of the developing posterior silkgland of Bombyx mori. The levels of tRNA acylated with glycine and alanine, the major amino acid components of silk-fibroin, increased about 30-fold during the transition from growth stage to fibroin production stage in each gland, whereas the increments in the levels of other aminoacylated tRNA's were substantially low. An analysis of the iso-accepting species of tRNA^Gly, the most abundant tRNA in silkgland, on benzoylated DEAE-cellulose columns showed that the levels of acylated tRNA^Gly species increased differentially during the same stages of development. These results suggested that the quantitative alterations in aminoacylated tRNA population were closely associated with the changes in protein synthesis during the terminal differentiation of silkgland.