Adaptive changes in protein synthesis in gastrointestinal mucosa

The small intestinal mucosa of mammals is a complex structure with the enterocyte as its major cell type. The enterocyte is capable of responding to various signals by altering cell content along the vertical (crypt/villus) axis, or along the longitudinal (duodenum-ileum) axis. Proteins can be expressed uniformly or in a mosaic pattern, a phenomenon also found in mucosa lining other gastrointestinal organs. Alterations in level of expression of proteins can occur over days, as in postnatal development or following intestinal resection, or they can be short-term, as in the few hours after a meal. Adaptations can involve cellular or secreted proteins, or a recently described secreted protein/lipid particle. These adaptations may lead to alterations in the function of the cell by modifying the protein content of the enterocyte itself, or in the permeability of the mucosa, by altering the intercellular region between the cells. The relative importance of these complex interactions is not clear, but it is clear that the enterocyte-containing mucosa is much more than a simple epithelial layer used for transport.