Phosphoinositide 3-kinase regulates phospholipase Cgamma-mediated calcium signaling.
It has been demonstrated that the lipid products of the phosphoinositide 3-kinase (PI3K) can associate with the Src homology 2 (SH2) domains of specific signaling molecules and modify their actions. In the current experiments, phosphatidylinositol 3,4, 5-trisphosphate (PtdIns-3,4,5-P3) was found to bind to the C-terminal SH2 domain of phospholipase Cgamma (PLCgamma) with an apparent Kd of 2.4 microM and to displace the C-terminal SH2 domain from the activated platelet-derived growth factor receptor (PDGFR). To investigate the in vivo relevance of this observation, intracellular inositol trisphosphate (IP3) generation and calcium release were examined in HepG2 cells expressing a series of PDGFR mutants that activate PLCgamma with or without receptor association with PI3K. Coactivation of PLCgamma and PI3K resulted in an approximately 40% increase in both intracellular IP3 generation and intracellular calcium release as compared with selective activation of PLCgamma. Similarly, the addition of wortmannin or LY294002 to cells expressing the wild-type PDGFR inhibited the release of intracellular calcium. Thus, generation of PtdIns-3,4,5-P3 by receptor-associated PI3K causes an increase in IP3 production and intracellular calcium release, potentially via enhanced PtdIns-4, 5-P2 substrate availability due to PtdIns-3,4,5-P3-mediated recruitment of PLCgamma to the lipid bilayer.
Rameh
L E
LE
Division of Signal Transduction, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Rhee
S G
SG
Spokes
K
K
Kazlauskas
A
A
Cantley
L C
LC
Cantley
L G
LG
D000730:Androstadienes / Q000494:pharmacology; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D051966:Phospholipase C gamma; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology / Q000502:physiology; D017479:Receptors, Platelet-Derived Growth Factor / Q000096:biosynthesis / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism*; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009025:Morpholines; D018129:Phosphatidylinositol Phosphates; D010982:Platelet-Derived Growth Factor; D011993:Recombinant Fusion Proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium; D000077191:Wortmannin