ApoE isoforms differentially regulates cleavage and secretion of BDNF

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Apolipoprotein E4 (ApoE4) is a major genetic risk factor for Alzheimer's disease (AD).
• Brain-derived neurotrophic factor (BDNF) levels are reduced in AD patients.
• The differential regulation of BDNF by ApoE isoforms in AD is not well understood.

Purpose of the Study:

• To investigate the impact of different Apolipoprotein E (ApoE) isoforms on Brain-Derived Neurotrophic Factor (BDNF) regulation.
• To examine the relationship between ApoE isoforms, BDNF processing, and Alzheimer's disease (AD) pathophysiology.

Main Methods:

• Analysis of prepro-BDNF and pro-BDNF expression in hippocampal regions of AD patients and age-matched controls.
• In vitro study of ApoE isoform effects (ApoE2, ApoE3, ApoE4) on BDNF maturation and secretion from primary human astrocytes.
• Quantification of intracellular and secreted BDNF forms following ApoE isoform treatment.

Main Results:

• AD patient hippocampi showed decreased prepro-BDNF (40%) and pro-BDNF (60%) compared to controls.
• ApoE2 and ApoE3 isoforms differentially regulated BDNF secretion, with ApoE2 promoting mature BDNF and ApoE3 promoting pro-BDNF.
• ApoE4 treatment resulted in negligible secretion of mature and pro-BDNF and reduced intracellular pre-pro BDNF levels.

Conclusions:

• ApoE2 and ApoE3 isoforms may offer neuroprotection through positive BDNF regulation.
• ApoE4-associated defects in BDNF processing are implicated in Alzheimer's disease (AD) pathogenesis.
• Interactions between ApoE isoforms and BDNF provide insights into AD risk associated with the ApoE4 allele.