Regulation of glycosylphosphatidylinositol-specific phospholipase D secretion from beta TC3 cells.
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.
Deeg
M A
MA
Department of Medicine, Indiana University School of Medicine, Indianapolis 46202, USA. deeg.mark@indianapolis.va.gov
Verchere
C B
CB
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D004763:Glucagon-Like Peptides; D005947:Glucose / Q000494:pharmacology; D007150:Immunohistochemistry; D007328:Insulin / Q000032:analysis / Q000378:metabolism; D000078790:Insulin Secretion; D007340:Insulinoma / Q000201:enzymology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D051379:Mice; D010190:Pancreatic Neoplasms / Q000201:enzymology*; D010446:Peptide Fragments / Q000494:pharmacology; D010739:Phospholipase D / Q000032:analysis / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D007328:Insulin; D010446:Peptide Fragments; C055453:glucagon-like peptide 1 (7-36)amide; D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D002217:Carbachol; D005934:Glucagon; D003513:Cycloheximide; D010739:Phospholipase D; C065017:glycoprotein phospholipase D; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate; D015056:1-Methyl-3-isobutylxanthine