Our results support the second possibility. First, we found that Rab32 is localized in autophagosomes, but not lipid droplets. Its location appears to be important for Rab32 function, since the DN form of Rab32 is mainly present in the cytosol. Second, it is known that autophagy affects lipid storage. The autophagosome is a special lysosome-related organelle. Lipid storage is reduced in the adipocytes of mice autophagy mutants. Third, levels of the autophagy activity marker GFP-huLC3 are reduced in Rab32 and ca mutants, suggesting that Rab32 and ca mutants have impaired autophagy. Therefore, Rab32 may execute its functions in lipid storage by affecting autophagy. Lastly, in mice, Rab32 and Rab38, which is very closely related to Rab32, have different expression patterns and function redundantly in the biogenesis of the melanosome, which is also a lysosome-related organelle. In cultured cells, human Rab32 affects the formation of autophagic vacuoles. These results suggest that the functions of Rab32 are likely evolutionarily conserved. What is the relationship between autophagy and lipid storage? Previously, several studies reported that autophagy can regulate lipid metabolism. For example, inhibition of autophagy in cultured hepatocytes by Atg5 RNAi or 3-methyladenine, an autophagy inhibitor, leads to increased TAG storage in lipid droplets. In addition, hepatocyte-specific knockout ATG7 results in elevated hepatic lipids. Interestingly, in contrast, knockdown of ATG5 or ATG7 in the pre-adipocyte cell line 3T3-L1 leads to decreased TAG accumulation, affecting adipocyte Ellipticine differentiation. In vivo, adipocyte-specific knockout ATG7 mice are lean and have greatly reduced white adipocyte mass, but increased brown adipocyte mass. Mutant white adipocytes exhibit features resembling brown adipocytes, such as an increased rate of fatty acid b-oxidation, suggesting that autophagy may affect adipocyte differentiation. Therefore, autophagy may affect lipid Columbianadin metabolism in a tissue-specific manner. Our results also support the involvement of autophagy in lipid metabolism. During the wandering third instar larvae to pupae transition, animals do not feed and are in a state resembling starvation or nutrient-deprivation. Programmed autophagy of fat bodies and other tissues is important for providing energy and other nutrients for development. Mutations in or tissue-specific knockdown of autophagy components lead to reduced lipid storage.