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. 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 (PubMed:16980328). Interacts (isoform 1 and isoform 2 only) 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. 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. Detected in neuron cell bodies, axons and dendrites. Mainly located to the postsynaptic density. 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. 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. Mainly expressed in the dendritic spine. Predominantly a synaptic vesicle isoform but also highly expressed in the nucleus. The BLOC-1 complex associates with the BLOC-2 complex in early endosome-associated tubules. Associated with the AP-3 complex at presynaptic terminals. Exclusivley cytoplasmic. Predominantly found in the postsynaptic density (PSD). Little association with synaptic vesicles. The BLOC-1 complex associates with the BLOC-2 complex in early endosome-associated tubules. Associated with the AP-3 complex at presynaptic terminals. Detected in brain, in neurons and in neuropil. Isoform 1 is expressed in the cerebral cortex, and hippocampal frontal (HF). Specific expression in the posterior half of the superior temporal gyrus (pSTG). Higher expression of isoform 2 and 3 in the HF than in the pSTG while isoform 1 shows no difference in expression in these areas. In the HF, detected in dentate gyrus (DG) and in pyramidal cells of hippocampus CA2 and CA3 (at protein level). Expressed in all principal neuronal populations of the HF, namely pyramidal neurons in the subiculum and CA1-3, granule cells in the dense cell layer of the DG (DGg), and polymorph cells in the hilus of the DG (DGh). Maximal levels in CA2, CA3, and DGh. Isoform 2 not expressed in the cerebral cortex. Ubiquitinated by TRIM32. Ubiquitination leads to DTNBP1 degradation. Isoforms 1 and 2 highly phosphorylated by PRKDC in vitro. Isoform 3 only weakly phosphorylated by PRKDC in vitro. The disease is caused by variants affecting the gene represented in this entry. Defects in DTNBP1 are associated with susceptibility to schizophrenia, a mental disorder characterized by a breakdown of thought processes and by poor emotional responsiveness. Genetic mutations lead to alterations in the glutamatergic transmission in the brain and modified Akt signaling (PubMed:15345706). Protein levels and expression are reduced in nerve terminals of the hippocampus and there is an increased release of glutamate in schizophrenic patients (PubMed:15124027). Levels of isoform 1 are reduced in the pSTG, but not in HF, by about 48% in 92% of schizophrenic patients. In the HF, there is an average of 33% reduction in synaptic expression of isoform 2 in 67% of cases, and of isoform 3, an average reduction of 35% in 80% of cases. In the dorsolateral prefrontal cortex (DLPFC), significant reductions in levels of isoform 3 are observed about 71% of schizophrenic patients showed an average reduction of this isoform of about 60% (PubMed:19617633). Major isoform. May be due to intron retention. Belongs to the dysbindin family. Truncated N-terminus.