Lysosome-related organelles in intestinal cells are a zinc storage site in C. elegans

Zinc is an essential trace element involved in many biological processes and human diseases. Because zinc deficiency and excess are deleterious, animals require homeostatic mechanisms to maintain zinc levels in response to dietary fluctuations. Here, we demonstrate that lysosome-related organelles in intestinal cells of C. elegans, called gut granules, function as the major site of zinc storage. Zinc storage in gut granules promotes detoxification and subsequent mobilization, linking cellular and organismal zinc metabolism. The cation diffusion facilitator protein CDF-2 plays a critical role in this process by transporting zinc into gut granules. In response to high dietary zinc, gut granules displayed structural changes characterized by a bilobed morphology with asymmetric distributions of zinc and molecular markers. We defined a genetic pathway that mediates the formation of bilobed morphology. These findings elucidate mechanisms of zinc storage, detoxification, and mobilization in C. elegans and may be relevant to other animals.