A dual function for Deep orange in programmed autophagy in the Drosophila melanogaster fat body
- Department of Biochemistry, Norwegian Radium Hospital, Montebello, N-0310 Oslo (Norway)
- Cellular Neurobiology Lab (CNB), Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037-1099 (United States)
Lysosomal degradation of cytoplasm by way of autophagy is essential for cellular amino acid homeostasis and for tissue remodeling. In insects such as Drosophila, autophagy is developmentally upregulated in the larval fat body prior to metamorphosis. Here, autophagy is induced by the hormone ecdysone through down-regulation of the autophagy-suppressive phosphoinositide 3-kinase (PI3K) signaling pathway. In yeast, Vps18 and other members of the HOPS complex have been found essential for autophagic degradation. In Drosophila, the Vps18 homologue Deep orange (Dor) has previously been shown to mediate fusion of multivesicular endosomes with lysosomes. A requirement of Dor for ecdysone-mediated chromosome puffing has also been reported. In the present report, we have tested the hypothesis that Dor may control programmed autophagy at the level of ecdysone signaling as well as by mediating autophagosome-to-lysosome fusion. We show that dor mutants are defective in programmed autophagy and provide evidence that autophagy is blocked at two levels. First, PI3K activity was not down-regulated correctly in dor larvae, which correlated with a decrease in ecdysone reporter activity. The down-regulation of PI3K activity was restored by feeding ecdysone to the mutant larvae. Second, neither exogenous ecdysone nor overexpression of PTEN, a silencer of PI3K signaling, restored fusion of autophagosomes with lysosomes in the fat body of dor mutants. These results indicate that Dor controls autophagy indirectly, via ecdysone signaling, as well as directly, via autolysosomal fusion.
- OSTI ID:
- 20857993
- Journal Information:
- Experimental Cell Research, Vol. 312, Issue 11; Other Information: DOI: 10.1016/j.yexcr.2006.03.002; PII: S0014-4827(06)00088-7; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0014-4827
- Country of Publication:
- United States
- Language:
- English
Similar Records
Tetrandrine induces lipid accumulation through blockade of autophagy in a hepatic stellate cell line
Hepatic steatosis inhibits autophagic proteolysis via impairment of autophagosomal acidification and cathepsin expression