title: Neurotrophins induce sphingomyelin hydrolysis. Modulation by co-expression of p75NTR with Trk receptors.
abstract: We examined neurotrophin-induced sphingomyelin hydrolysis in cells expressing solely the low affinity neurotrophin receptor, p75NTR, and in PC12 cells that co-express p75NTR and Trk receptors. Nerve growth factor (NGF), brain-derived neurotrophic factor, neurotrophin-3 (NT-3), and NT-5 stimulated sphinomyelin hydrolysis with similar kinetics in p75NTR-NIH-3T3 cells. Although brain-derived neurotrophic factor (10 ng/ml) was slightly more potent than NGF at inducing sphingomyelin hydrolysis, NT-3 and NT-5 induced significant hydrolysis (30-35%) at 0.1 to 1 ng/ml in p75NTR-NIH-3T3 cells. NT-3 did not induce sphingomyelin hydrolysis in Trk C-NIH-3T3 cells nor in cells expressing a mutated p75NTR containing a 57-amino acid cytoplasmic deletion, thus demonstrating the role of p75NTR in this signal transduction pathway. In p75NTR-NIH-3T3 cells, neurotrophin-induced sphingomyelin hydrolysis 1) localized to an internal pool of sphingomyelin, 2) was not a consequence of receptor internalization, and 3) showed no specificity with respect to the molecular species of sphingomyelin hydrolyzed. In contrast to cells expressing solely p75NTR, NGF (100 ng/ml) did not induce sphingomyelin hydrolysis in PC12 cells. Interestingly, NT-3 (10 ng/ml) induced the same extent of sphingomyelin hydrolysis in PC12 cells as was apparent in p75NTR-NIH-3T3 cells. However, in the presence of NGF, NT-3 was unable to induce sphingomyelin hydrolysis, raising the possibility that Trk was modulating p75NTR-dependent sphingomyelin hydrolysis. Inhibition of Trk tyrosine kinase activity with 200 nM K252a enabled both NGF and NT-3 in the presence of NGF to induce sphingomyelin hydrolysis. These data support that p75NTR serves as a common signaling receptor for neurotrophins through induction of sphingomyelin hydrolysis and that crosstalk pathways exist between Trk and p75NTR-dependent signaling pathways.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: R T
authors.initials: RT
authors.lastname: Dobrowsky
authors.forename: G M
authors.initials: GM
authors.lastname: Jenkins
authors.forename: Y A
authors.initials: YA
authors.lastname: Hannun
mesh_terms: D016475:3T3 Cells; D000818:Animals; D066246:ErbB Receptors / Q000502:physiology; D006801:Humans; D051379:Mice; D009414:Nerve Growth Factors / Q000494:pharmacology*; D020933:Neurotrophin 3; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D020800:Receptor, Nerve Growth Factor; D020917:Receptor, trkA; D020812:Receptor, trkC; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism*; D018013:Receptors, Neuropeptide / Q000737:chemistry / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000502:physiology; D013109:Sphingomyelins / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D009414:Nerve Growth Factors; D020933:Neurotrophin 3; D011518:Proto-Oncogene Proteins; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor; D018013:Receptors, Neuropeptide; D013109:Sphingomyelins; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA; D020812:Receptor, trkC; D017479:Receptors, Platelet-Derived Growth Factor