title: A protein targeting signal that functions in polarized epithelial cells in vivo.
abstract: Eukaryotic membrane-associated polypeptides often contain a glycosylphosphatidylinositol (GPI) anchor that signals the attachment of GPI lipids to these proteins. The GPI anchor can function as a basolateral or apical targeting signal in mammalian cells cultured in vitro, although the function of the GPI anchor in vivo remains to be elucidated. In this study we have evaluated the effect of fusing a GPI anchor sequence to a prokaryotic reporter protein on the cellular location of the polypeptide in polarized epithelial cells of transgenic mice. The bacterial enzyme, when fused to a eukaryotic signal peptide, was secreted through the basolateral membrane of small-intestinal enterocytes; however, when the enzyme was lined to the GPI anchor sequence the polypeptide was redirected to the apical surface of the epithelial cells. These data provide the first direct evidence that the GPI anchor functions as an apical membrane protein sorting signal in polarized epithelial cells in vivo.
authors.affiliation: Department of Biological and Nutritional Sciences, University of Newcastle upon Tyne, U.K.
authors.forename: S
authors.initials: S
authors.lastname: Ali
authors.forename: J
authors.initials: J
authors.lastname: Hall
authors.forename: G P
authors.initials: GP
authors.lastname: Hazlewood
authors.forename: B H
authors.initials: BH
authors.lastname: Hirst
authors.forename: H J
authors.initials: HJ
authors.lastname: Gilbert
mesh_terms: D000818:Animals; D016764:Cell Polarity / Q000502:physiology*; D002480:Cellulase / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D007150:Immunohistochemistry; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008854:Microscopy, Electron; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D002480:Cellulase