Efficient use of a translation start codon in BDNF exon I

Area of Science:

• Molecular Biology
• Neuroscience

Background:

• The brain-derived neurotrophic factor (BDNF) gene exhibits complex alternative splicing of its 5' untranslated regions.
• BDNF protein is typically synthesized from transcripts originating from a common 3' exon (exon IX), which contains the primary translation start site.

Purpose of the Study:

• To investigate the translational efficiency of an alternative start site located within exon I of the BDNF gene.
• To determine if the use of the exon I start site influences BDNF protein levels and secretion.

Main Methods:

• Analysis of BDNF mRNA and protein synthesis in PC12 cells and cultured cortical neurons.
• Comparison of translation initiation efficiency between the exon I and exon IX start sites.
• Assessment of BDNF protein degradation and secretion rates.

Main Results:

• The in-frame AUG start codon within BDNF exon I is efficiently utilized for translation initiation in neuronal cells.
• Translation initiation using the exon I start site results in higher BDNF protein levels compared to the exon IX start site due to increased translation rates.
• No significant differences were observed in protein degradation or secretion between BDNF isoforms with alternative 5' termini.

Conclusions:

• The alternative translation start site in BDNF exon I facilitates more efficient protein synthesis.
• This mechanism, coupled with the activity-dependent regulation of the BDNF exon I promoter, suggests a role in rapid, stimulus-induced BDNF production.