The protein encoded by this gene is the medium subunit of
AP-3, which is an adaptor-related protein complex associated with
the Golgi region as well as more peripheral intracellular
structures. AP-3 facilitates the budding of vesicles from the Golgi
membrane and may be directly involved in protein sorting to the
endosomal/lysosomal system. AP-3 is a heterotetrameric protein
complex composed of two large subunits (delta and beta3), a medium
subunit (mu3), and a small subunit (sigma 3). Mutations in one of
the large subunits of AP-3 have been associated with the
Hermansky-Pudlak syndrome, a genetic disorder characterized by
defective lysosome-related organelles. Alternatively spliced
transcript variants encoding the same protein have been observed.
