Thrombin receptors modulate insulin-stimulated phosphatidylinositol 3,4,5-trisphosphate accumulation in 1321N1 astrocytoma cells.

Abstract

Thrombin and insulin receptor signaling via phosphoinositide (PI)-specific phospholipase C (PLC) and PI 3-kinase was studied in [3H]inositol-labelled 1321N1 cells. Thrombin stimulated a dramatic, transient activation of PLC which is probably mediated via receptors of the 'tethered-ligand' type, since it was both reproduced by, and abolished following, pretreatment of cells with a synthetic peptide (SFLLRN) corresponding to the ligand domain of the human thrombin receptor. However, neither thrombin nor SFLLRN stimulated PI 3-kinase. By contrast, insulin did not influence [3H]InsP3 concentration but stimulated accumulation of [3H]PtdIns(3,4,5)P3 and [3H]PtdIns(3,4)P2, the relative steady-state concentrations of which may indicate degradation of [3H]PtdIns(3,4,5)P3 by 5- and 3-phosphatases. The independent coupling of thrombin and insulin receptors to PLC and PI 3-kinase respectively in 1321N1 cells allowed interactions between these systems to be examined. Thus insulin-stimulated [3H]PtdIns(3,4,5)P3 accumulation was attenuated on co-stimulation of the thrombin receptor, whereas concentrations of [3H]PtdIns(3,4)P2 were transiently enhanced but then reduced. These results indicate that thrombin receptors in 1321N1 cells do not activate PI 3-kinase, but can modulate signalling by this enzyme.

• Authors: I H Batty, C P Downes
• Journal: The Biochemical journal (Biochem J) Vol. 317 ( Pt 2) Pg. 347-51 (Jul 15 1996) ISSN: 0264-6021 [Print] England
• PMID: 8713057 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Insulin
• Peptide Fragments
• Phosphatidylinositol Phosphates
• Receptors, Thrombin
• phosphatidylinositol 3,4,5-triphosphate
• phosphatidylinositol 3,4-diphosphate
• thrombin receptor peptide (42-47)
• Phosphatidylinositol 3-Kinases
• Phosphotransferases (Alcohol Group Acceptor)
• Type C Phospholipases
• Thrombin

Topics

• Amino Acid Sequence
• Astrocytoma
• Enzyme Activation (drug effects)
• Humans
• Insulin (pharmacology)
• Molecular Sequence Data
• Peptide Fragments (pharmacology)
• Phosphatidylinositol 3-Kinases
• Phosphatidylinositol Phosphates (biosynthesis)
• Phosphotransferases (Alcohol Group Acceptor) (metabolism)
• Receptors, Thrombin (metabolism)
• Signal Transduction (drug effects)
• Thrombin (pharmacology)
• Tumor Cells, Cultured
• Type C Phospholipases (metabolism)