Zinc storage granules in the Malpighian tubules of Drosophila melanogaster

Membrane transporters and sequestration mechanisms concentrate metal ions differentially into discrete subcellular microenvironments for usage in protein cofactors, signaling, storage, or excretion. Here we identify zinc storage granules as the insects major zinc reservoir in primary Malpighian tubule epithelial cells of Drosophila melanogaster. The concerted action of Adaptor Protein-3, Rab32, HOPS and BLOC complexes as well as of the white-scarlet (ABCG2-like) and ZnT35C transporters is required for zinc storage granule biogenesis. Due to similar lysosome related organelle defects, patients with Hermansky-Pudlak syndrome may lack zinc granules in beta pancreatic cells, intestinal paneth cells and presynaptic vesicles of hippocampal mossy fibers.