BLOC1S1 encodes a subunit of both the BLOC-1 and BORC complexes that regulate endolysosomal processes and lysosome-related organelle biogenesis 1. The protein functions as a protein acetyltransferase, negatively regulating aerobic respiration through mitochondrial protein lysine-acetylation and counteracting SIRT3 deacetylase activity 2. BLOC1S1 is essential for anterograde lysosome transport and autophagy function in both non-neuronal cells and neurons 1. The protein also modulates hepatic lysosomal content and lysosomal lipolysis, influencing cellular lipid storage independent of autophagy pathways 3. Structurally, BLOC1S1 contributes to BLOC-1's hetero-octameric architecture as part of the BLOC1S1/3/4/6 hemicomplex that forms the characteristic arc-shaped complex 4. Loss-of-function mutations in BLOC1S1 cause a neurological disorder characterized by early psychomotor delay, hypotonia, spasticity, epileptic encephalopathy, and leuko-axonopathy with hypomyelination, establishing BORCopathies as a distinct disease entity 1. Some patients also exhibit hypopigmentation features similar to Hermansky-Pudlak syndrome, though typically milder 1. These findings demonstrate BLOC1S1's critical role in multiple cellular processes including mitochondrial metabolism, lysosomal function, and neurological development.