Lipid raft organization and function in the small intestinal brush border

ABSTRACT

The enterocyte brush border of the small intestine is a highly specialized membranedesigned to function both as a high capacity digestive/absorptive surface ofdietary nutrients and a permeability barrier towards lumenal pathogens. It is characterizedby an unusually high content of glycolipids (~30% of the total microvillarmembrane lipid), enabling the formation of liquid ordered microdomains, betterknown as lipid rafts. The glycolipid rafts are stabilized by galectin-4, a 36 kDa divalentlectin that cross-links galactosyl (and other carbohydrate) residues present onmembrane lipids and several brush border proteins, including some of the majorhydrolases. These supramolecular complexes are further stabilized by intelectin, a 35kDa trimeric lectin that also functions as an intestinal lactoferrin receptor. As a result,brush border hydrolases, otherwise sensitive to pancreatic proteinases, are protectedfrom untimely release into the gut lumen. Finally, anti-glycosyl antibodies, synthesizedby plasma cells locally in the gut, are deposited on the brush border glycolipidrafts, protecting the epithelium from lumenal pathogens that exploit lipid rafts asportals for entry to the organism (AU)

RESUMEN

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