Phosphoinositide 3-kinase regulates crosstalk between Trk A tyrosine kinase and p75(NTR)-dependent sphingolipid signaling pathways.
The mechanism of crosstalk between signaling pathways coupled to the Trk A and p75(NTR) neurotrophin receptors in PC12 cells was examined. In response to nerve growth factor (NGF), Trk A activation inhibited p75(NTR)-dependent sphingomyelin (SM) hydrolysis. The phosphoinositide 3-kinase (PI 3-kinase) inhibitor, LY294002, reversed this inhibition suggesting that Trk A activation of PI 3-kinase is necessary to inhibit sphingolipid signaling by p75(NTR). In contrast, SM hydrolysis induced by neurotrophin-3 (NT-3), which did not activate PI-3 kinase, was uneffected by LY294002. However, transient expression of a constituitively active PI 3-kinase inhibited p75(NTR)-dependent SM hydrolysis by both NGF and NT-3. Intriguingly, NGF induced an association of activated PI 3-kinase with acid sphingomyelinase (SMase). This interaction localized to caveolae-related domains and correlated with a 50% decrease in immunoprecipitated acid SMase activity. NGF-stimulated PI 3-kinase activity was necessary for inhibition of acid SMase but was not required for ligand-induced association of the p85 subunit of PI 3-kinase with the phospholipase. Finally, this interaction was specific for NGF since EGF did not induce an association of PI 3-kinase with acid SMase. In summary, our data suggest that PI 3-kinase regulates the inhibitory crosstalk between Trk A tyrosine kinase and p75(NTR)-dependent sphingolipid signaling pathways and that this interaction localizes to caveolae-related domains.
Department of Pharmacology and Toxicology, University of Kansas, Lawrence, Kansas, USA.
T R
TR
Bilderback
V R
VR
Gazula
R T
RT
Dobrowsky
D000818:Animals; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D009025:Morpholines / Q000494:pharmacology; D020932:Nerve Growth Factor / Q000494:pharmacology; D020933:Neurotrophin 3 / Q000494:pharmacology; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011335:Proadifen / Q000494:pharmacology; D051381:Rats; D020239:Receptor Cross-Talk / Q000502:physiology*; D020800:Receptor, Nerve Growth Factor; D020917:Receptor, trkA / Q000502:physiology*; D017475:Receptors, Nerve Growth Factor / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D020933:Neurotrophin 3; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor; D011994:Recombinant Proteins; D013107:Sphingolipids; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D020932:Nerve Growth Factor; D011335:Proadifen; D019869:Phosphatidylinositol 3-Kinases; D020917:Receptor, trkA; D013108:Sphingomyelin Phosphodiesterase