Researchers from INSERM report on findings in rotavirus
2007 NOV 20 -- "Lactase-phlorizin hydrolase (LPH, EC 3.2.1.23-62) is a brush border membrane (BBM)-associated enzyme in intestinal cells that hydrolyse lactose, the most important sugar in milk. Impairing in lactase activity during rotavirus infection has been described in diseased infants but the mechanism by which the functional lesion occurs remains unknown," scientists in Chatenay-Malabry, France report. "We undertook a study to elucidate whether rotavirus impairs the lactase enzymatic activity in BBM of human enterocyte cells. In this study we use cultured human intestinal fully differentiated enterocyte-like Caco-2 cells to demonstrate how the lactase enzymatic activity at BBM is significantly decreased in rhesus monkey rotavirus (RRV)-infected cells. We found that the decrease in enzyme activity is not dependent of the Ca2+- and cAMP-dependent signalling events triggered by the virus. The LPH biosynthesis, stability, and expression of the protein at the BBM of infected cells were not modified. We provide evidence that in RRV-infected cells the kinetic of lactase enzymatic activity present at the BBM was modified. Both BBMcontrol and BBMRRV have identical K-m values, but hydrolyse the substrate at different rates. Thus, the BBMRRV exhibits almost a 1.5-fold decreased V-max than that of BBMcontrol and is therefore enzymatically less active than the latter," wrote I. Beau and colleagues, INSERM. The researchers concluded: "Our study demonstrate conclusively that the impairment of lactase enzymatic activity at the BBM of the enterocyte-like Caco-2 cells observed during rotavirus infection results from an inhibitory action of the secreted non-structural rotavirus protein NSP4." Beau and colleagues published their study in Cellular Microbiology (An NSP4-dependant mechanism by which rotavirus impairs lactase enzymatic activity in brush border of human enterocyte-like Caco-2 cells. Cellular Microbiology, 2007;9(9):2254-2266). For more information, contact A.L. Servin, INSERM, UMR 756, Chatenay Malabry, France. Publisher contact information for the journal Cellular Microbiology is: Blackwell Publishing, 9600 Garsington Rd., Oxford OX4 2DQ, Oxon, England. Keywords: France, Chatenay-Malabry, Immunization, Rotavirus Vaccine, Vaccination, INSERM. This article was prepared by Virus Weekly editors from staff and other reports. Copyright 2007, Virus Weekly via NewsRx.com.
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