Insulin-like growth factor binding protein profile secreted by human intestinal epithelial cells varies with polarity.
The actions of insulin-like growth factors (IGFs) are modulated by interaction with a family of secreted binding proteins (IGFBPs). We have now demonstrated in intestinal epithelial cells (Caco-2) that the secretion of different members of this family depends on the cell surface secreting them. Polarized monolayers of cells secreted IGFBP-3 mainly into the medium adjacent to the apical surface, while IGFBP-2 was secreted predominantly through the basolateral surface. The secretion of IGFBP-1 and -4 was equivalent from both surfaces. However, administration of epidermal growth factor (EGF) induced polarized secretion of IGFBP-4 by increasing secretion from the apical surface more than from the basolateral aspect. It did not affect the polarity of the other IGFBPs. We believe that this is the first evidence that epithelial cells can interact with extrinsic agents in a polarized fashion at sites other than the membrane surface.
Oguchi
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Developmental Gastroenterology Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
Walker
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Sanderson
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D000230:Adenocarcinoma; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D003110:Colonic Neoplasms; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D018969:Insulin-Like Growth Factor Binding Proteins; D011994:Recombinant Proteins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I