Volume 272, Number 38,
Issue of September 19, 1997
pp. 23547-23551
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.
Brain-derived Neurotrophic Factor Binding to the p75 Neurotrophin
Receptor Reduces TrkA Signaling While Increasing Serine Phosphorylation
in the TrkA Intracellular Domain
(Received for publication, June 27, 1997)
Ian J.
MacPhee
and
Philip A.
Barker
From the Center for Neuronal Survival, Montreal Neurological
Institute, McGill University, 3801 University Avenue, Montreal,
Quebec H3A 2B4, Canada
We have examined whether the low affinity
neurotrophin receptor p75NTR modulates TrkA function by intracellular
signaling. Using ligands that selectively bind p75NTR or TrkA, we found
that a p75NTR-derived signal reduces TrkA activation. Short term
treatment of PC12 cells with ceramide analogues also resulted in
reduced NGF-stimulated TrkA activation, suggesting that p75-mediated
increases in sphingomyelinase activity may contribute to this
modulatory effect. Phosphoamino acid analysis was performed to
determine if brain-derived neurotrophic factor- or ceramide-mediated
phosphorylation of the TrkA intracellular domain correlated with a
reduction in its ligand-induced activation. A specific increase in TrkA
phosphoserine content was observed in response to both
C2-ceramide and brain-derived neurotrophic factor.
These results suggest that ligand binding of p75NTR can activate a
signaling cascade that results in reduced TrkA activity through
phosphorylation of its intracellular domain.