Use of Transgenic Mice to Study the Routing of Secretory Proteins in Intestinal Epithelial Cells: Analysis of Human Growth Hormone Compartmentalization as A Function of Cell Type and Differentiation

• Published in: The Journal of cell biology Vol. 109; no. 6; pp. 3231 - 3242
• Main Authors: Trahair, Jeffrey F., Neutra, Marian R., Gordon, Jeffrey I.
• Format: Journal Article
• Language: English
• Published: New York, NY Rockefeller University Press 01-12-1989; The Rockefeller University Press
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Base Sequence; Biological and medical sciences; Biological Transport; Carrier Proteins - genetics; Cell lines; Cells; Cloning, Molecular; Cytoplasmic Granules - metabolism; Cytoplasmic Granules - ultrastructure; DNA; Endocrine cells; Epithelial cells; epithelium; Epithelium - metabolism; Epithelium - ultrastructure; Exocrine cells; Fatty Acid-Binding Protein 7; Fatty Acid-Binding Proteins; Fundamental and applied biological sciences. Psychology; Goblets; growth hormone; Growth Hormone - genetics; Growth Hormone - metabolism; Immunoenzyme Techniques; Intestinal Mucosa - metabolism; Intestinal Mucosa - ultrastructure; Intestines; Male; Mice; Mice, Transgenic; Molecular Sequence Data; Neoplasm Proteins; Nerve Tissue Proteins; Protein hormones. Growth factors. Cytokines; Proteins; Secretory cells; Stem cells; Transgenic animals; Human; Immunogold technique; Immunocytochemistry; STH; Rodentia; Gut; Transgenic animal; Electron microscopy; Protein hormone; Vertebrata; Optical microscopy; Mammalia; Endocrine cell; Adenohypophyseal hormone; Mouse; Secretory protein; Epithelial cell; Localization
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.109.6.3231

The intestinal epithelium is a heterogeneous cell monolayer that undergoes continuous renewal and differentiation along the crypt-villus axis. We have used transgenic mice to examine the compartmentalization of a regulated endocrine secretory protein, human growth hormone (hGH), in the four exocrine cells of the mouse intestinal epithelium (Paneth cells, intermediate cells, typical goblet cells, and granular goblet cells), as well as in its enteroendocrine and absorptive (enterocyte) cell populations. Nucleotides -596 to +21 of the rat liver fatty acid binding protein gene, when linked to the hGH gene (beginning at nucleotide +3) direct efficient synthesis of hGH in the gastrointestinal epithelium of transgenic animals (Sweetser, D. A., D. W. McKeel, E. F. Birkenmeier, P. C. Hoppe, and J. I. Gordon. 1988. Genes & Dev. 2:1318-1332). This provides a powerful in vivo model for analyzing protein sorting in diverse, differentiating, and polarized epithelial cells. Using EM immunocytochemical techniques, we demonstrated that this foreign polypeptide hormone entered the regulated basal granules of enteroendocrine cells as well as the apical secretory granules of exocrine Paneth cells, intermediate cells, and granular goblet cells. This suggests that common signals are recognized by the "sorting mechanisms" in regulated endocrine and exocrine cells. hGH was targeted to the electron-dense cores of secretory granules in granular goblet and intermediate cells, along with endogenous cell products. Thus, this polypeptide hormone contains domains that promote its segregation within certain exocrine granules. No expression of hGH was noted in typical goblet cells, suggesting that differences exist in the regulatory environments of granular and typical goblet cells. In enterocytes, hGH accumulated in dense-core granules located near apical and lateral cell surfaces, raising the possibility that these cells, which are known to conduct constitutive vesicular transport toward both apical and basolateral surfaces, also contain a previously unrecognized regulated pathway. Together our studies indicate that transgenic mice represent a valuable system for analyzing trafficking pathways and sorting mechanisms of secretory proteins in vivo.