The Molecular Mechanism of Ctp Synthase Filament Assembly and Compartmentalization.

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

Project Details


The importance of subcellular compartments for metabolic pathways is evident in recent studies, and is essential for certain cellular functions in response to environments. Purinosome organizes multiple enzymes in purine synthesis pathway in responding to purine depletion. The glycolytic enzymes are localized to the leading edge during directional migration. Cytidine triphosphate synthase (CTPsyn) controls CTP production, which is crucial for DNA, RNA, and phospholipid synthesis. CTPsyn forms a unique and conserved cytoplasmic filamentous structure in many cell types and organisms. The formation and biological function of this structure seem to be various under different physiological conditions. Our previous publication showed that the naturally existing filaments in Drosophila follicle cells are required for endocycles by promoting S phase in endoreplication. Cbl, an E3 ligase is required for the filament maintenance. We then discovered that histidine supply during starvation could induce filament formation in human cancer cells. Histidine promotes one carbon metabolism to increase protein methylation which participates in filament formation. Interestingly, ubiquitination is required for filament formation in both systems independent of the protein level of CTPsyn. To understand what components involved in the filament assembly induced by histidine, we performed APEX in vivo labeling then subjected to streptavidin pull-down for proteomic analysis. Among these candidates, interactions between vesicle trafficking, cytoskeleton associated proteins were validated by knockdown assays. Our preliminary results showed this vesicle trafficking is autophagy-independent. In addition, common factors were identified in Drosophila germline cells by APEX approach. Starvation in Drosophila females also increased the length of CTPsyn filaments. These results suggest that vesicle trafficking beside autophagy might be an important stress response to nutrition deprivation. Moreover, we found CTPsyn filament is in the close compartment with enzyme in de novo purine synthesis pathway in Drosophila germline cells, suggesting these compartments may play a crucial role in regulation of metabolism. We propose here to address three major questions related to above findings in Drosophila and human cells. I. To study the CTP synthase filament assembled in human cancer cells. II. To study the assembly process and methylation dependent regulation of CTPS filament assembly in Drosophila. III. To study the biological function of CTPsyn and Ade3 co-compartmentalization in Drosophila germ cells.

Project IDs

Project ID:PA10708-1006
External Project ID:MOST107-2311-B182-003
Effective start/end date01/08/1831/07/19


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