Multiple functions of precursor BDNF to CNS neurons: negative regulation of neurite growth, spine formation and cell survival.
BACKGROUND
Proneurotrophins and mature neurotrophins elicit opposite effects via the p75 neurotrophin receptor (p75(NTR)) and Trk tyrosine kinase receptors, respectively; however the molecular roles of proneurotrophins in the CNS are not fully understood.


RESULTS
Based on two rare single nucleotide polymorphisms (SNPs) of the human brain-derived neurotrophic factor (BDNF) gene, we generated R125M-, R127L- and R125M/R127L-BDNF, which have amino acid substitution(s) near the cleavage site between the pro- and mature-domain of BDNF. Western blot analyses demonstrated that these BDNF variants are poorly cleaved and result in the predominant secretion of proBDNF. Using these cleavage-resistant proBDNF (CR-proBDNF) variants, the molecular and cellular roles of proBDNF on the CNS neurons were examined. First, CR-proBDNF showed normal intracellular distribution and secretion in cultured hippocampal neurons, suggesting that inhibition of proBDNF cleavage does not affect intracellular transportation and secretion of BDNF. Second, we purified recombinant CR-proBDNF and tested its biological effects using cultured CNS neurons. Treatment with CR-proBDNF elicited apoptosis of cultured cerebellar granule neurons (CGNs), while treatment with mature BDNF (matBDNF) promoted cell survival. Third, we examined the effects of CR-proBDNF on neuronal morphology using more than 2-week cultures of basal forebrain cholinergic neurons (BFCNs) and hippocampal neurons. Interestingly, in marked contrast to the action of matBDNF, which increased the number of cholinergic fibers and hippocampal dendritic spines, CR-proBDNF dramatically reduced the number of cholinergic fibers and hippocampal dendritic spines, without affecting the survival of these neurons.


CONCLUSIONS
These results suggest that proBDNF has distinct functions in different populations of CNS neurons and might be responsible for specific physiological cellular processes in the brain.
Koshimizu
Hisatsugu
H
National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, 563-8577 Japan. koshimih@mail.nih.gov
Kiyosue
Kazuyuki
K
Hara
Tomoko
T
Hazama
Shunsuke
S
Suzuki
Shingo
S
Uegaki
Koichi
K
Nagappan
Guhan
G
Zaitsev
Eugene
E
Hirokawa
Takatsugu
T
Tatsu
Yoshiro
Y
Ogura
Akihiko
A
Lu
Bai
B
Kojima
Masami
M
D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D000918:Antibody Specificity / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D019208:Brain-Derived Neurotrophic Factor / Q000737:chemistry / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002490:Central Nervous System / Q000166:cytology* / Q000378:metabolism; D019295:Computational Biology; D003470:Culture Media; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D016501:Neurites / Q000187:drug effects / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011188:Potassium / Q000494:pharmacology; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017433:Protein Structure, Secondary; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology
D019208:Brain-Derived Neurotrophic Factor; D003470:Culture Media; D050505:Mutant Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; C426674:brain-derived neurotrophic factor precursor; D011188:Potassium
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