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Gangliosides activate Trk receptors by inducing the release of neurotrophins
Author(s) -
Mocchetti I.,
Bachis A.,
Rabin S. J.
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.81.s1.32_5.x
Subject(s) - trk receptor , tropomyosin receptor kinase b , tropomyosin receptor kinase a , tropomyosin receptor kinase c , neurotrophin , low affinity nerve growth factor receptor , receptor , tyrosine phosphorylation , biology , ganglioside , phosphorylation , microbiology and biotechnology , endocrinology , chemistry , medicine , neurotrophic factors , biochemistry , platelet derived growth factor receptor , growth factor
We used NIH‐3T3 fibroblasts expressing the different Trk receptors to examine whether GM1 ganglioside and its semisynthetic derivative LIGA20 activate various neurotrophin receptors. GM1 elicited a rapid activation of TrkC and TrkA, but not TrkB, tyrosine phosphorylation. In contrast, LIGA20 activated TrkB tyrosine phosphorylation only. These data suggest that gangliosides may act as ligands for specific Trk receptors similar to the neurotrophins. To test this hypothesis, we performed Scatchard analysis to determine if GM1 binds to the TrkC receptor. GM1 failed to displace neurotrophin‐3 (NT‐3) binding suggesting that gangliosides are not ligands for the Trk receptors. Moreover, GM1 did not activate a TNF/Trk chimeric receptor. We next determined whether gangliosides induce the release of neurotrophins. NIH‐3T3 cells and cerebellar granule neurons were exposed to GM1 or LIGA20 for 5 min and the levels of brain‐derived neurotrophic factor (BDNF) and NT‐3 measured in the medium. GM1 induced a significant increase in the amount of NT‐3, but not BDNF. In contrast, LIGA20 increased the secretion of BDNF, suggesting that gangliosides differentially affect the release of neurotrophins, which, in turn, activate Trk receptors. Therefore, Trk tyrosine phosphorylation was determined in the presence of Trk‐IgG receptor bodies. TrkB‐IgG, but not TrkC‐IgG, inhibited LIGA20‐mediated induction of TrkB tyrosine phosphorylation, while TrkC‐IgG, but not TrkB‐IgG, inhibited GM1‐mediated activation of TrkC, further suggesting that gangliosides activate Trk receptors by inducing the release of endogenous neurotrophins.