Component of the BLOC-1 complex, a complex that is required for normal biogenesis of lysosome-related organelles (LRO), such as platelet dense granules and melanosomes. In concert with the AP-3 complex, the BLOC-1 complex is required to target membrane protein cargos into vesicles assembled at cell bodies for delivery into neurites and nerve terminals. The BLOC-1 complex, in association with SNARE proteins, is also proposed to be involved in neurite extension. Associates with the BLOC-2 complex to facilitate the transport of TYRP1 independent of AP-3 function. Plays a role in synaptic vesicle trafficking and in neurotransmitter release. Plays a role in the regulation of cell surface exposure of DRD2. May play a role in actin cytoskeleton reorganization and neurite outgrowth. May modulate MAPK8 phosphorylation. Appears to promote neuronal transmission and viability through regulating the expression of SNAP25 and SYN1, modulating PI3-kinase-Akt signaling and influencing glutamatergic release. Regulates the expression of SYN1 through binding to its promoter. Modulates prefrontal cortical activity via the dopamine/D2 pathway (By similarity). Interacts (via its coiled coil domain) with KXD1. Interacts with CMYA5, PI4K2 and RNF151 (By similarity). Component of the biogenesis of lysosome-related organelles complex 1 (BLOC-1) composed of at least BLOC1S1, BLOC1S2, BLOC1S3, BLOC1S4, BLOC1S5, BLOC1S6, DTNBP1/BLOC1S7 and SNAPIN/BLOC1S8. Interacts directly in the complex with BLOC1S5, BLOC1S6 and SNAPIN/BLOC1S8. The BLOC-1 complex associates with the AP-3 protein complex and membrane protein cargos. This BLOC-1 complex also associates with the BLOC-2 complex in endosomes. Binds to DTNA and DTNB but may not be a physiological binding partner. Interacts with the DNA-dependent protein kinase complex DNA-PK; the interaction phosphorylates DTNBP1 in vitro. Interacts directly in this complex with XRCC5 and XRCC6. Interacts with AP3M1, AP3B2 and TRIM32. Interacts with XPO1; the interaction exports DTNBP1 out of the nucleus (By similarity). Mainly cytoplasmic but shuttles between the cytoplasm and nucleus. Exported out of the nucleus via its NES in a XPO1-dependent manner. Nuclear localization is required for regulation of the expression of genes such as SYN1 (By similarity). Detected in neuron cell bodies, axons and dendrites. Detected at synapses, at postsynaptic density, at presynaptic vesicle membranes and microtubules. Detected at tubulovesicular elements in the vicinity of the Golgi apparatus and of melanosomes. Occasionally detected at the membrane of pigmented melanosomes in cultured melanoma cells. The BLOC-1 complex associates with the BLOC-2 complex in early endosome-associated tubules. Associated with the AP-3 complex at presynaptic terminals (By similarity). Ubiquitinated by TRIM32. Ubiquitination leads to DTNBP1 degradation. Belongs to the dysbindin family.