Neurotrophins Induce Sphingomyelin Hydrolysis

doi:10.1074/jbc.270.38.22135

Neurotrophins Induce Sphingomyelin Hydrolysis

MODULATION BY CO-EXPRESSION OF p75 WITH Trk RECEPTORS (*)

From the Departments of Medicine and Cell Biology, Duke University Medical Center, Durham, North Carolina 27710

^§ To whom correspondence should be addressed:
Dept. of Pharmacology and Toxicology, 5064 Malott Hall, University of Kansas, Lawrence, KS 66045-2505.

Abstract

We examined neurotrophin-induced sphingomyelin hydrolysis in cells expressing solely the low affinity neurotrophin receptor, p75, and in PC12 cells that co-express p75 and Trk receptors. Nerve growth factor (NGF), brain-derived neurotrophic factor, neurotrophin-3 (NT-3), and NT-5 stimulated sphingomyelin hydrolysis with similar kinetics in p75-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 p75-NIH-3T3 cells. NT-3 did not induce sphingomyelin hydrolysis in Trk C-NIH-3T3 cells nor in cells expressing a mutated p75 containing a 57-amino acid cytoplasmic deletion, thus demonstrating the role of p75 in this signal transduction pathway. In p75-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 p75, 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 p75-NIH-3T3 cells. However, in the presence of NGF, NT-3 was unable to induce sphingomyelin hydrolysis, raising the possibility that Trk was modulating p75-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 p75 serves as a common signaling receptor for neurotrophins through induction of sphingomyelin hydrolysis and that cross-talk pathways exist between Trk and p75-dependent signaling pathways.

Footnotes

↵* This work was supported in part by National Institutes of Health Grant GM43825 (to Y. A. H.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

NGF

nerve growth factor

p75

low affinity neurotrophin receptor

BDNF

brain-derived neurotrophic factor

NT-3

neurotrophin-3

DMEM

Dulbecco's modified Eagle's medium

PBS

phosphate-buffered saline

RP-HPLC

reverse phase high performance liquid chromotography

EGF

epidermal growth factor.
↵²R. T. Dobrowsky, unpublished results.
- Received April 27, 1995.
- Revision received June 28, 1995.