Roland Kolbeck

Biosynthesis and processing of endogenous BDNF: CNS neurons store and secrete BDNF, not pro-BDNF

Pro- and mature BDNF activate very different receptors and intracellular pathways, potentially leading to either neuronal death or survival. Here we examined the biochemistry of endogenous BDNF in mouse neurons using sensitive reagents and found that pro-BDNF is rapidly converted intracellularly to mature BDNF, the latter being stored and released by excitatory input.

Are There Differences Between the Secretion Characteristics of NGF and BDNF? Implications for the Modulatory Role of Neurotrophins in Activity-Dependent Neuronal Plasticity

In previous experiments the activity‐dependent secretion of nerve growth factor (NGF) from native hippocampal slices and from NGF‐cDNA transfected hippocampal neurons showed unusual characteristics [Blöchl and Thoenen (1995) Eur J Neurosci 7:1220–1228; (1996) Mol Cell Neurosci 7:173–190]. In both hippocampal slices and cultured hippocampal neurons the activity‐dependent secretion proved to be independent of extracellular calcium, but dependent on the release of calcium from intracellular stores. Under different experimental conditions, Goodman et al. [(1996) Mol Cell Neurosci 7:222–238] reported that the high potassium‐mediated secretion of brain‐derived neurotrophic factor (BDNF) from hippocampal cultures was dependent on extracellular calcium. Mowla et al. [(1997) Proc 27th Annu Meet Soc Neurosci New Orleans 875.10] reported on even further‐reaching differences between NGF and BDNF secretion, namely, that in hippocampal neurons and in pituitary cell lines NGF was secreted exclusively according to the constitutive pathway, whereas BDNF was exclusively sorted according to the activity‐dependent regulated pathway. In view of the crucial importance of such potential differences between the processing, sorting, and secretory mechanisms of different neurotrophins for their modulatory roles in activity‐dependent neuronal plasticity, a thorough analysis under comparable experimental conditions was mandatory. We demonstrate that in native hippocampal slices and adenoviral‐transduced hippocampal neurons there are no differences between NGF and BDNF with respect to the subcellular distribution and mechanism of secretion; that the activity‐dependent secretion of both NGF and BDNF is dependent on intact intracellular calcium stores; and that the differences between our own observations and those of Goodman et al. (ibid.) regarding the dependence on extracellular calcium do not reflect differences between NGF and BDNF sorting and secretion, but reflect the differing experimental conditions used. Microsc. Res. Tech. 45:262–275, 1999.

Brain-derived neurotrophic factor levels in the nervous system of wild-type and neurotrophin gene mutant mice

Abstract: Although brain‐derived neurotrophic factor is the most abundant and widely distributed neurotrophin in the nervous system, reproducible determinations of its levels have been hampered by difficulties in raising suitable monoclonal antibodies. Following immunization of mice with recombinant fish and mammalian brain‐derived neurotrophic factor, monoclonal antibodies were generated and used in an immunoassay based on the recognition of two different epitopes. Neither antibody cross‐reacts with neurotrophin homodimers other than brain‐derived neurotrophic factor, although reactivity was detected with brain‐derived neurotrophic factor/neurotrophin‐3 heterodimers. As both nerve growth factor and neurotrophin‐3 are known to affect the development of a variety of neurons expressing the brain‐derived neurotrophic factor (bdnf) gene, this assay was used to determine levels in tissues isolated from newborn mice carrying a null mutation in the nerve growth factor (ngf) or the neurotrophin‐3 (nt3) gene. Marked differences were observed between mutants and wild‐type littermates in the PNS, but not in the CNS, suggesting that neither nerve growth factor nor neurotrophin‐3 is a unique regulator of brain‐derived neurotrophic factor levels in the newborn mouse CNS.