Molecular Mechanism of Compartmentalization of Nucleotide Synthesis Enzymes under Stress Response in Drosophila

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details


Accumulating evidence demonstrated that subcellular compartments for metabolic pathways is crucial in response to environmental stresses and various physiological conditions. Under purine depletion, purinosome assembles multiple enzymes in purine synthesis pathway. Cytidine triphosphate synthase (CTPsyn) functions at the rate-limiting step of CTP production which is crucial for DNA, RNA, and phospholipid synthesis. CTPsyn forms conserved cytoplasmic filamentous structures in many cell types and organisms. However, the regulation and biological function of these structures are not fully understood. Our previous publication demonstrated that ubiquitination is required for naturally existed CTPsyn filament in Drosophila follicle cells and is required for endoreplication. Indeed, ubiquitination is essential for CTPsyn filament formation in human cancer cells induced by glutamine deprivation. Our recent publication demonstrated that histidine-mediated methylation is crucial for filament formation under glutamine deprivation in human cancer cells, and filament formation preserves CTPsyn protein for a growth advantage after the relief of nutrient stress. Therefore, post-translational modifications play central roles in CTPsyn filament formation and control stress responses. To understand how glutamine deprivation promotes histidine influx to induce filament formation, we used APEX in vivo labeling to identify components involved in the filament assembly. We found that intermediate filament-cytokeratin, serves as a compartment for CTPsyn filament assembly. In addition, annexin A11 and inosine monophosphate dehydrogenase (IMPDH2) were found to co-locate with CTPsyn filaments. Starvation in Drosophila females also increased the length of CTPsyn filaments in germ cells, indicating that CTPsyn filament assembly is regulated by nutrient stress in fly. Moreover, we found CTPsyn and ade3, an enzyme in de novo purine synthesis pathway, form filaments together in Drosophila germline cells, suggesting these compartments may play a crucial role in regulation of metabolism. In summary, we demonstrated that CTPsyn filament is a subcellular compartment important for regulating metabolism under different physiological conditions. Since nutrient supply and fertility is highly correlated, we apply the fly egg system to understand starvation response on nucleotide synthesis through compartmentalization of enzymes. We propose here to address three major aims. I. To identify proteins located in the CTP synthase filament compartment during starvation in Drosophila germ cells II. To reveal the regulation of CTP synthase compartment formation in Drosophila germ cells III. To study the effects of CTPsyn compartmentalization on metabolism in Drosophila germ cells during starvation

Project IDs

Project ID:PA10901-0556
External Project ID:MOST108-2311-B182-004-MY3
Effective start/end date01/08/2031/07/21


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