Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Caco-2 cell line is derived from a human colon adenocarcinoma and differentiates in vitro into small-intestinal enterocyte-like cells, expressing the hydrolases lactase and sucrase-isomaltase. We cultured Caco-2 cells on permeable supports from 0 to 37 days after plating to study endogenous lactase and sucrase-isomaltase gene expression in relation to cell differentiation. Profiles of lactase and sucrase-isomaltase mRNA, protein and enzyme activity were analysed on a per-cell basis, using immunocytochemistry, RNase protection assays, metabolic polypeptide labelling and enzyme activity assays. Tight-junction formation was complete 6 days after plating. Immunocytochemistry of Caco-2 cross-sections showed lactase and sucrase-isomaltase predominantly in the microvillar membrane of polarized cells. mRNA, protein and enzyme activity of lactase appeared consecutively, reaching maximum levels 8-11 days after plating. Whereas lactase mRNA and protein biosynthesis showed a sharp decline after peak levels, lactase activity remained high until 37 days after plating. In contrast, mRNA and protein biosynthesis and activity of sucrase-isomaltase peaked successively 11-21 days after plating, and exhibited comparable levels throughout the entire experiment. The following conclusions were reached. (1) In Caco-2 cells, biosynthesis of lactase and sucrase-isomaltase is regulated by the amount of their mRNAs, indicating transcriptional control. (2) Sucrase-isomaltase activity is most probably transcriptionally controlled at all time points. (3) In contrast, lactase activity is initially regulated by its level of biosynthesis. After its peak at 8 days, the slow decline in activity compared with its biosynthesis indicates high stability. (4) Different mRNA profiles for lactase and sucrase-isomaltase indicate different mechanisms of transcriptional regulation of these genes.
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PMID:Lactase and sucrase-isomaltase gene expression during Caco-2 cell differentiation. 894 31

We have previously shown that fetal exposure to ethanol in rats produces both structural and biochemical abnormalities in absorptive enterocytes. Among the indicators of injury are derangements in the expression of lactase-phlorizin hydrolase (LPH), which is an essential enzyme for the assimilation of milk. In an animal model of fetal alcohol syndrome, unsuckled newborn rats prenatally exposed to maternal ethanol revealed a 10- to 15-fold increase in the number of LPH mRNA molecules per absorptive enterocyte, compared with controls (Estrada et al., Alcohol. Clin. Exp. Res. 20:1662-1668, 1996). However, lactase activity per cell was similar in both groups. The aim of this study was to characterize the effect of prenatal exposure to ethanol on the processing of LPH mRNA and protein. RNase protection assays using 3'- and 5'-directed antisense RNA probes revealed that the LPH mRNA from ethanol-exposed pups is full length. However, metabolic labeling, followed by immunoprecipitation using an anti-LPH monoclonal antibody, demonstrated a significant alteration in LPH protein processing. Intestinal explants from 21-day ethanol-exposed fetuses that were chased 30 min after a [35S]methionine pulse showed greater amounts of newly synthesized LPH precursors (205 and 220 kDa) and low molecular weight degradation products than controls. However, despite the increases in LPH precursor, the amount of 130 kDa mature LPH was similar in ethanol-exposed and control explants. These data suggest an increase in intracellular degradation of LPH precursor in rats prenatally exposed to ethanol, which occurs before its insertion into the microvillus membrane. Biosynthesis of LPH appears to be upregulated at the transcriptional level, which overcomes the degradation of LPH precursor during processing.
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PMID:Defective intracellular processing of lactase-phlorizin hydrolase protein in rats prenatally exposed to ethanol. 972 93

Numerous genes expressed by intestinal epithelial cells are developmentally regulated, and the influence that adaptive (AI) and passive (PI) immunity have in controlling their expression has not been evaluated. In this study, we tested the hypothesis that both PI and AI influenced enterocyte gene expression by developing a breeding scheme that used T and B cell-deficient recombination-activating gene (RAG) mice. RNA was isolated from the liver and proximal/distal small intestine at various ages, and the steady-state levels of six different transcripts were evaluated by RNase protection assay. In wild-type (WT) pups, all transcripts [Fc receptor of the neonate (FcRn), polymeric IgA receptor (pIgR), GLUT5, lactase-phlorizin hydrolase (lactase), apical sodium-dependent bile acid transporter (ASBT), and Na+/glucose cotransporter (SGLT1)] studied were developmentally regulated at the time of weaning, and all transcripts except ASBT had the highest levels of expression in the proximal small intestine. In WT suckling pups reared in the absence of PI, pIgR mRNA levels were increased 100% during the early phase of development. In mice lacking AI, the expression of pIgR and lactase were significantly attenuated, whereas FcRn and GLUT5 levels were higher compared with WT mice. Finally, in the absence of both passive and active immunity, expression levels of pIgR and lactase were significantly lower than similarly aged WT mice. In summary, we report that the adaptive and passive immune status of mice influences steady-state mRNA levels of several important, developmentally regulated enterocyte genes during the suckling and weaning periods of life.
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PMID:Role of passive and adaptive immunity in influencing enterocyte-specific gene expression. 1296 28

Mice lacking the mesenchymal winged helix transcription factor Foxl1 exhibit markedly abnormal small intestinal epithelia and postnatal growth retardation. We investigated whether defects in intestinal nutrient uptake and specific transport processes exist in mice homozygous for a Foxl1 null allele (Foxl1-/-). Foxl1-/- mice and controls on a defined genetic background were weighed regularly and killed at 2, 4, and 12 wk of age. Intestinal uptake studies, quantitative real-time PCR, RNase protection assays, and Western blot analyses were performed. Foxl1-/- mice have dysmorphic small intestinal epithelia and postnatal growth retardation. Foxl1-/- mice demonstrate decreased small intestinal uptake of D-glucose in all age groups studied. Intestinal uptake of D-fructose and two amino acids, L-proline and L-leucine, is not altered. Consistent with these findings, Foxl1-/- mice show decreased levels of the intestinal D-glucose transporter SGLT1. Expression of sucrase-isomaltase, lactase, GLUT2, and Na+-K+ ATPase are not changed. Foxl1-/- mice demonstrate markedly abnormal intestinal epithelia, postnatal growth retardation, and decreased intestinal uptake of D-glucose. The specific effect of Foxl1 on intestinal d-glucose uptake is due to decreased production of SGLT1 protein in the small intestine. Thus we identified, for the first time, a link between a mesenchymal factor, Foxl1, and the regulation of a specific epithelial transport process.
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PMID:Foxl1 null mice have abnormal intestinal epithelia, postnatal growth retardation, and defective intestinal glucose uptake. 1515 78