AP-3 complex sorts preferential cargo to govern dense core vesicle function in neuroendocrine cells

Area of Science:

• Cell Biology
• Neuroscience
• Molecular Biology

Background:

• Dense-core vesicles (DCVs) are essential for regulated secretion of neurotransmitters and neuropeptides.
• The adaptor protein-3 (AP-3) complex's role in DCV biogenesis and function remains incompletely understood.

Purpose of the Study:

• To elucidate the multifaceted roles of the AP-3 complex in DCV function, including sorting, maturation, and exocytosis.
• To investigate the consequences of AP-3 depletion on DCV characteristics and protein content.

Main Methods:

• Biochemical analysis of PC12 cells with AP-3 depletion.
• Golgi and RUSH assays to assess DCV sorting.
• Proteomics and bioinformatics to identify protein changes and interactions.
• Proximity ligation assays to confirm protein interactions.

Main Results:

• AP-3 depletion impairs DCV exocytosis and alters vesicle size and positioning.
• AP-3 is essential for correct trans-Golgi sorting of DCVs, with defects leading to lysosomal misrouting.
• Loss of specific DCV proteins and impaired granule maturation, release, and neurotransmitter mobilization were observed.

Conclusions:

• The AP-3 complex plays a critical, multifaceted role in DCV biogenesis, trafficking, and function.
• Understanding AP-3's role is key to comprehending neurotransmitter and neuropeptide release mechanisms.
• Defects in AP-3 function lead to significant disruptions in DCV-mediated secretion.