Based on limited published evidence, BLOC1S4 is a component of the BLOC-1 complex required for biogenesis of lysosome-related organelles including melanosomes and platelet dense granules. It functions in protein trafficking and vesicle targeting in concert with the AP-3 complex, directing membrane cargo into vesicles for neuronal delivery 1. BLOC1S4 participates in anterograde axonal and synaptic vesicle transport, neurite extension, and melanosome organization. Disruption of BLOC-1-mediated protein trafficking pathways can modulate melanoma chemotherapy sensitivity by altering melanosome formation and drug sequestration 2.