Detection of Brain-derived Neurotrophic Factor in a Vesicular Fraction of Brain Synaptosomes*
- James P. Fawcett,
- Raquel Aloyz‡,
- John H. McLean§,
- Sangeeta Pareek,
- Freda D. Miller¶,
- Peter S. McPherson∥** and
- Richard A. Murphy‡‡
- From the Centre for Neuronal Survival,
- ∥ Cell Biology of Excitable Tissue Group, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada and the
- § Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3V6, Canada
- ‡‡ To whom correspondence should be addressed. Tel.: 514-398-5359; Fax: 514-398-8248; E-mail: Director{at}MNI.Lan.McGill.Ca
Abstract
The mRNA encoding brain-derived neurotrophic factor (BDNF) is widely distributed in central nervous system neurons, including in hippocampus and cortex. However, little is known about the physiology of BDNF protein within neurons, including how it is processed or packaged and the mechanisms that control its release. In this study, we have used antibodies to monitor the subcellular distribution of BDNF in cortical extracts from adult rats treated with kainic acid. BDNF immunoreactivity is elevated in rat cortex 12 h after kainic acid treatment. The protein is enriched in a vesicular fraction isolated from lysed synaptosomes, its distribution being similar to that of synaptotagmin, which is associated with synaptic vesicles and large dense core vesicles at nerve terminals. The vesicular pool of BDNF is digested by proteinase K only in the presence of Triton X-100 suggesting localization of BDNF in membrane fractions. Immunocytochemistry detects diffuse and punctate BDNF staining within cell bodies and processes of cortical neurons from kainic acid-treated rats, as well as in mossy fiber terminals of rat hippocampus. Taken together, these data show that BDNF can accumulate axonally within a vesicular compartment of brain neurons. Results support the idea that endogenous BDNF may be transported anterogradely and released by regulated secretory mechanisms.
Footnotes
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↵‡ Postdoctoral Fellow and funded through the Network of Centers of Excellence, Canada.
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↵¶ Killam Scholar of the Montreal Neurological Institute.
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↵** Scholar of the Medical Research Council of Canada and an Alfred P. Sloan Research Fellow.
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↵* This work was supported in part by funds from the Medical Research Council of Canada (to R. A. M.). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- BDNF
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brain-derived neurotrophic factor
- hrBDNF
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human recombinant BDNF
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- Received November 15, 1996.
- Revision received January 30, 1997.
- © 1997 by The American Society for Biochemistry and Molecular Biology, Inc.
