AP-3 complex subunit mu-2

AP-3 complex subunit mu-2 (AP3M2) is a component of the AP-3 adaptor complex, which mediates vesicle budding from the Golgi and trafficking to lysosomes (UniProt: P53677). In neurons, AP-3 works with the BLOC-1 complex to direct cargo into vesicles at the cell body for transport into neurites and synaptic terminals, making it critical for neuronal protein delivery and synaptic function.

AP3M2 is consistently downregulated in Alzheimer's disease brain tissue compared to age-matched controls, with a mean log2 fold-change of −1.35 in post-mortem human brain proteomics (Chaparral AD proteomics). This reduction was observed across the examined subcellular fractions in a TMT-labeled mass spectrometry experiment. The decreased abundance of this trafficking component suggests impaired vesicular transport and lysosomal targeting pathways in AD pathology, potentially contributing to protein accumulation and neuronal dysfunction characteristic of the disease.