Adaptor Related Protein Complex 3 Beta 2 (AP3b2)

Adaptor protein-3 (AP3) is a heterotetrameric vesicle-coat protein complex. Some AP3 subunits are ubiquitously expressed, whereas others are expressed exclusively in neurons. The neuron-specific AP3 complex, which includes AP3B2, is thought to serve neuron-specific functions such as neurotransmitter release.

Overexpression of neuronal AP3 subunits, including Ap3b2, in mouse chromaffin cells produced a large number of small-volume vesicles that released relatively small amounts of neurotransmitter. In contrast, depleting AP3 produced large-diameter vesicles that released large amounts of neurotransmitter. The authors concluded that interaction of neuronal AP3 with vesicles regulates vesicle neurotransmitter content.