Cells continuously take up nutrients and signaling molecules. Internalized proteins destined for degradation are routed from the plasma membrane through early endosomes, multivesicular bodies (MVBs), and finally to lysosomes. In specialized metazoan cells, endosomes also serve as intermediates in protein trafficking to lysosome-related organelles including melanosomes in the skin and eye, lamellar bodies in type II lung cells, dense granules in platelets, and lytic granules in cytotoxic T-cells. Genetic defects that interfere with trafficking in this pathway are the underlying causes of several disorders including Chediak-Higashi and Hermansky-Pudlak syndrome (HPS). The Drosophila compound eye is an excellent model system for a genetic analysis of endocytic trafficking. Mutations in many genes necessary for this process have been identified as eye color mutations because they interfere with the delivery of biosynthetic cargo to pigment granules. In the developing eye, the ligands Boss and Delta provide direct assays to analyze the contribution of genes to endocytic trafficking in vivo. This proposal is aimed at exploiting the features of the Drosophila eye for a genetic dissection of endocytic trafficking in multicellular organisms.
In Aim 1, we plan to dissect the specific roles each of two alternative Vps-C complexes have in regulating endocytic trafficking, and the biogenesis of lysosome-related organelles. For this purpose, we will use loss-of-function models of the two pairs of alternative subunits Car/dVps33A, dVps16A, dVpsSSB, and dVps16B.
In Aim 2, we will determine the specific step in endocytic trafficking that requires red, one of the genes discovered in a large-scale screen for HPS-related mutations.
In Aim 3, we will dissect how the dual functions of Drosophila Acinus in membrane trafficking and chromatin condensation are regulated.
In Aim 4, we will analyze the function of dPallidin in the delivery of cargo to lysosome-related organelles. We have generated a dpallidin null allele to test two alternative models that suggest that Pallidin may regulate early endosomal fusion or exit from MVBs.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Biology and Diseases of the Posterior Eye Study Section (BDPE)
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Mariani, Andrew P
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University of Texas Sw Medical Center Dallas
Schools of Medicine
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Casey, Amanda K; Moehlman, Andrew T; Zhang, Junmei et al. (2017) Fic-mediated deAMPylation is not dependent on homodimerization and rescues toxic AMPylation in flies. J Biol Chem 292:21193-21204
Tracy, Charles; Krämer, Helmut (2017) Escherichia coli Infection of Drosophila. Bio Protoc 7:
Nandi, Nilay; Tyra, Lauren K; Stenesen, Drew et al. (2017) Stress-induced Cdk5 activity enhances cytoprotective basal autophagy in Drosophila melanogaster by phosphorylating acinus at serine437. Elife 6:
Tracy, Charles; Krämer, Helmut (2017) Isolation and Infection of Drosophila Primary Hemocytes. Bio Protoc 7:
Klionsky, Daniel J (see original citation for additional authors) (2016) Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12:1-222
Akbar, Mohammed Ali; Mandraju, Rajakumar; Tracy, Charles et al. (2016) ARC Syndrome-Linked Vps33B Protein Is Required for Inflammatory Endosomal Maturation and Signal Termination. Immunity 45:267-79
Stenesen, Drew; Moehlman, Andrew T; Krämer, Helmut (2015) The carcinine transporter CarT is required in Drosophila photoreceptor neurons to sustain histamine recycling. Elife 4:e10972
Nandi, Nilay; Tyra, Lauren K; Krämer, Helmut (2015) Activated Acinus boosts basal autophagy. Mol Cell Oncol 2:e995043
Vokoun, Corinne R; Huang, Xin; Jackson, Meyer B et al. (2014) Response normalization in the superficial layers of the superior colliculus as a possible mechanism for saccadic averaging. J Neurosci 34:7976-87
Takáts, Szabolcs; Pircs, Karolina; Nagy, Péter et al. (2014) Interaction of the HOPS complex with Syntaxin 17 mediates autophagosome clearance in Drosophila. Mol Biol Cell 25:1338-54

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