Neurotrophin-3 Sorts to the Constitutive Secretory Pathway of Hippocampal Neurons and Is Diverted to the Regulated Secretory Pathway by Coexpression with Brain-Derived Neurotrophic Factor

Hippocampal neurons release nerve growth factor (NGF) through the constitutive secretory pathway, thus allowing the protein to be continuously available for promoting nerve cell survival. In contrast, hippocampal neurons use the regulated secretory pathway to process brain-derived neurotrophic facto...

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Bibliographic Details
Published in:The Journal of neuroscience 2000-06, Vol.20 (11), p.4059-4068
Main Authors: Farhadi, Hooman F, Mowla, S. Javad, Petrecca, Kevin, Morris, Stephen J, Seidah, Nabil G, Murphy, Richard A
Format: Article
Language:English
Subjects:
alpha 1-Antitrypsin - pharmacology
Animals
Brain-Derived Neurotrophic Factor - biosynthesis
Cell Survival - physiology
Cells, Cultured
COS Cells
Hippocampus - cytology
Hippocampus - metabolism
Hippocampus - physiology
Immunohistochemistry
Mice
Microscopy, Confocal
Neurons - metabolism
Neurons - physiology
Neurons - ultrastructure
Neurotrophin 3 - biosynthesis
Neurotrophin 3 - genetics
Neurotrophin 3 - physiology
Precipitin Tests
Transfection - genetics
Vaccinia virus - genetics
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Summary:Hippocampal neurons release nerve growth factor (NGF) through the constitutive secretory pathway, thus allowing the protein to be continuously available for promoting nerve cell survival. In contrast, hippocampal neurons use the regulated secretory pathway to process brain-derived neurotrophic factor (BDNF), which alters synaptic activity when released acutely from dense-core vesicles. Thus, understanding how neurons sort and deliver neurotrophins may provide clues to their functions in brain. In this study, we monitored the processing and delivery of neurotrophin-3 (NT-3). Pulse-chase studies, immunocytochemistry, and secretagogue-induced release experiments were performed on cultured hippocampal neurons and AtT-20 cells infected with vaccinia viruses encoding the NT-3 precursor (pro-NT-3). Results show that most newly synthesized NT-3 is released through the constitutive secretory pathway as a result of furin-mediated endoproteolytic cleavage of pro-NT-3 in the trans-Golgi network. Pro-NT-3 can also be diverted into the regulated secretory pathway when cells are treated with alpha1-PDX, a selective inhibitor of furin-like enzymes, or when pro-NT-3 expression is increased by transient transfection methods. In cells coinfected with viruses coding for pro-NT-3 and pro-BDNF, NT-3 is sorted into the regulated pathway, stored in secretory granules, and released in response to extracellular cues together with BDNF, apparently as a result of heterodimerization, as suggested by coimmunoprecipitation data. Taken together, these data show that sorting of the NT-3 precursor can occur in both the constitutive and regulated secretory pathways, which is consistent with NT-3 having both survival-promoting and synapse-altering functions.
ISSN:0270-6474
1529-2401
DOI:10.1523/jneurosci.20-11-04059.2000