Possible involvement of phosphatidylinositol 3-kinase in regulated exocytosis: studies in chromaffin cells with inhibitor LY294002

J Neurochem. 1998 Jun;70(6):2347-56. doi: 10.1046/j.1471-4159.1998.70062347.x.


Several lines of evidence suggest that phosphorylated products of phosphatidylinositol play critical functions in the regulation of membrane trafficking along the secretory pathway. To probe the possible involvement of phosphatidylinositol 3-kinase (PI 3-kinase) in regulated exocytosis, we have examined its subcellular distribution in cultured chromaffin cells by immunoreplica analysis and confocal immunofluorescence. We found that the PI 3-kinase heterodimer consisting of the regulatory and catalytic subunits was associated essentially with the subplasmalemmal cytoskeleton in both resting and nicotine-stimulated chromaffin cells. Attempts to immunoprecipitate PI 3-kinase with anti-phosphotyrosine antibodies failed, suggesting that the activity of PI 3-kinase was not modulated by tyrosine phosphorylation and/or physical interaction with SH2-containing proteins in stimulated chromaffin cells. LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], a potent inhibitor of PI 3-kinase, produced a dose-dependent inhibition of catecholamine secretion evoked by various secretagogues. Furthermore, cytochemical experiments with rhodamine-labeled phalloidin revealed that LY294002 blocked the disassembly of cortical actin in chromaffin cells stimulated by a depolarizing concentration of potassium. Our results suggest that PI 3-kinase may be one of the important regulatory exocytotic components involved in the signaling cascade controlling actin rearrangements required for catecholamine secretion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / ultrastructure
  • Adrenal Glands / drug effects
  • Adrenal Glands / enzymology
  • Adrenal Glands / metabolism
  • Adrenal Glands / ultrastructure
  • Animals
  • Calcium / metabolism
  • Cattle
  • Cell Fractionation
  • Chromaffin Cells / drug effects*
  • Chromaffin Cells / enzymology
  • Chromaffin Cells / metabolism
  • Chromaffin Cells / ultrastructure
  • Chromones / pharmacology*
  • Cytoskeleton / drug effects
  • Cytoskeleton / enzymology
  • Enzyme Inhibitors / pharmacology*
  • Exocytosis / drug effects*
  • Immunohistochemistry
  • In Vitro Techniques
  • Microscopy, Confocal
  • Morpholines / pharmacology*
  • Norepinephrine / metabolism
  • Phosphatidylinositol 3-Kinases / ultrastructure
  • Phosphoinositide-3 Kinase Inhibitors*


  • Actins
  • Chromones
  • Enzyme Inhibitors
  • Morpholines
  • Phosphoinositide-3 Kinase Inhibitors
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Calcium
  • Norepinephrine