Regulation of glycosylphosphatidylinositol-specific phospholipase D secretion from βTC3 cells

• Published in: Endocrinology (Philadelphia) 1997-02, Vol.138 (2), p.819-826
• Main Authors: DEEG, M. A, VERCHERE, C. B
• Format: Article
• Language: English
• Subjects: 1-Methyl-3-isobutylxanthine - pharmacology; Animals; Biological and medical sciences; Carbachol - pharmacology; Cell physiology; Cycloheximide - pharmacology; Fundamental and applied biological sciences. Psychology; Glucagon; Glucagon-Like Peptide 1; Glucagon-Like Peptides; Glucose - pharmacology; Immunohistochemistry; Insulin - analysis; Insulin - metabolism; Insulin Secretion; Insulinoma - enzymology; Islets of Langerhans - drug effects; Islets of Langerhans - enzymology; Kinetics; Mice; Molecular and cellular biology; Pancreatic Neoplasms - enzymology; Peptide Fragments - pharmacology; Phospholipase D - analysis; Phospholipase D - metabolism; Secretion. Exocytosis; Tetradecanoylphorbol Acetate - pharmacology; Tumor Cells, Cultured
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.138.2.819

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abundant in mammalian serum, but the source of the circulating enzyme is unknown. Pancreatic islets have been reported to contain and secrete GPI-PLD. In this report we examined the regulation of GPI-PLD secretion from beta TC3 cells, a mouse insulinoma cell line. In the absence of glucose, phorbol myristic acid (0.1 microM) stimulated insulin secretion by 2.5-fold and GPI-PLD secretion by 2-fold. Carbachol (5 microM), glucagon-like peptide I-(7-36) amide (0.1 microM), and isobutylmethylxanthine (0.1 mM) had no significant effect on insulin or GPI-PLD secretion in the absence of glucose. Glucose (16.7 mM) stimulated both GPI-PLD and insulin secretion from beta TC3 cells by 55% and 235%, respectively. In addition, glucose potentiated the secretagogue effect of isobutylmethylxanthine, phorbol myristic acid, and glucagon-like peptide I on both insulin and GPI-PLD secretion. By immunohistochemistry and confocal microscopy, beta TC3 cells contain both insulin and GPI-PLD, which generally colocalized intracellularly. However, GPI-PLD secretion differed from insulin secretion by a higher rate of basal release (2.8% vs. 0.23%/h), a lower magnitude of response to secretagogues, and a more prolonged period of increased secretion. These results demonstrate that beta TC3 cells secrete GPI-PLD in response to insulin secretagogues and suggest that GPI-PLD may be secreted via the regulated pathway in these cells.