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What is BDNF?

This gene encodes a member of the nerve growth factor family of proteins. Alternative splicing results in multiple transcript variants, at least one of which encodes a preproprotein that is proteolytically processed to generate the mature protein. Binding of this protein to its cognate receptor promotes neuronal survival in the adult brain. Expression of this gene is reduced in Alzheimer's, Parkinson's, and Huntington's disease patients. This gene may play a role in the regulation of the stress response and in the biology of mood disorders. [provided by RefSeq, Nov 2015]

https://www.ncbi.nlm.nih.gov/gene/627


BDNF and Sigma 1

Prog Neurobiol. 2013 Jan;100:15-29. doi: 10.1016/j.pneurobio.2012.09.001. Epub 2012 Oct 5.
Sigma-1 receptor chaperone and brain-derived neurotrophic factor: emerging links between cardiovascular disease and depression.
Hashimoto K1.
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Abstract
Epidemiological studies have demonstrated a close relationship between depression and cardiovascular disease (CVD). Although it is known that the central nervous system (CNS) contributes to this relationship, the detailed mechanisms involved in this process remain unclear. Recent studies suggest that the endoplasmic reticulum (ER) molecular chaperone sigma-1 receptor and brain-derived neurotrophic factor (BDNF) play a role in the pathophysiology of CVD and depression. Several meta-analysis studies have showed that levels of BDNF in the blood of patients with major depressive disorder (MDD) are lower than normal controls, indicating that blood BDNF might be a biomarker for depression. Furthermore, blood levels of BDNF in patients with CVD are also lower than normal controls. A recent study using conditional BDNF knock-out mice in animal models of myocardial infarction highlighted the role of CNS-mediated mechanisms in the cardioprotective effects of BDNF. In addition, a recent study shows that decreased levels of sigma-1 receptor in the mouse brain contribute to the association between heart failure and depression. Moreover, sigma-1 receptor agonists, including the endogenous neurosteroid dehydroepiandosterone (DHEA) and the selective serotonin reuptake inhibitor (SSRI) fluvoxamine, show potent cardioprotective and antidepressive effects in rodents, via sigma-1 receptor stimulation. Interestingly, agonist activation of sigma-1 receptors increased the secretion of mature BDNF from its precursor proBDNF via chaperone activity in the ER. Given the role of ER stress in the pathophysiology of CVD and MDD, the author will discuss the potential link between sigma-1 receptors and BDNF-TrkB pathway in the pathophysiology of these two diseases. Finally, the author will make a case for potent sigma-1 receptor agonists and TrkB agonists as new potential therapeutic drugs for depressive patients with CVD.

https://www.ncbi.nlm.nih.gov/pubmed/23044468

Sigma-1 receptor chaperones regulate the secretion of brain-derived neurotrophic factor
Michiko Fujimoto,1,3,5 Teruo Hayashi,1,3,* Roman Urfer,2,4 Shiro Mita,2,4 and Tsung-Ping Su1,3,*
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Abstract
The sigma-1 receptor (Sig-1R) is a novel endoplasmic reticulum (ER) molecular chaperone that regulates protein folding and degradation. The Sig-1R activation by agonists is known to improve memory, promote cell survival, and exert an antidepressant-like action in animals. Cutamesine (SA4503), a selective Sig-1R ligand, was shown to increase BDNF in the hippocampus of rats. How exactly the intracellular chaperone Sig-1R or associated ligand causes the increase of BDNF or any other neurotrophins is unknown. We examined here whether the action of Sig-1Rs may relate to the post-translational processing and release of BDNF in neuroblastoma cell lines. We used in vitro assays and confirmed that cutamesine possesses the bona fide Sig-1R agonist property by causing the dissociation of BiP from Sig-1Rs. The C-terminus of Sig-1Rs exerted robust chaperone activity by completely blocking the aggregation of BDNF and GDNF in vitro. Chronic treatment with cutamesine in rat B104 neuroblastoma caused a time- and dose-dependent potentiation of the secretion of BDNF without affecting the mRNA level of BDNF. Cutamesine decreased the intracellular level of pro-BDNF and mature BDNF whereas increased the extracellular level of mature BDNF. The pulse-chase experiment indicated that the knockdown of Sig-1Rs decreased the secreted mature BDNF in B104 cells without affecting the synthesis of BDNF. Our findings indicate that, in contrast to clinically used antidepressants that promote the transcriptional upregulation of BDNF, the Sig-1R agonist cutamesine potentiates the post-translational processing of neurotrophins. This unique pharmacological profile may provide a novel therapeutic opportunity for the treatment of neuropsychiatric disorders.

Keywords: sigma-1 receptor, sigma receptor, BDNF, GDNF, cutamesine, SA4503, antidepressant, depression, cleavage, secretion, neuroprotection

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3824965/