May regulate the synthesis and function of lysosomes and of highly specialized organelles, such as melanosomes and platelet dense granules. Regulates intracellular vesicular trafficking in fibroblasts. May be involved in the regulation of general functions of integrins. Component of the biogenesis of lysosome-related organelles complex-2 (or BLOC2) composed of HPS3, HPS5 and HPS6. Interacts with HPS6 (PubMed:15030569, PubMed:25189619). Interacts with HPS3 (PubMed:15030569). May interact with all alpha-integrin chains that have an aromatic residue before the first lysine of the conserved KXGFFKR motif, including ITGA2, ITGA3, ITGA5 and ITGA6 (PubMed:10094488). Widely expressed. Isoform 1:Highly expressed in lungs and testis. Isoform 2:Highly expressed in placenta, kidney, testis ovary, lung and thymus. The disease is caused by variants affecting the gene represented in this entry. Belongs to the HPS5 family.