Structural Studies Of GRASP65and Fstll

The Golgi apparatus play crucial roles in processing and glycosylation of proteins and lipids. It is also responsible for protein sorting and transportation. In mammalian cells, the Golgi apparatus consists of many stacks of cisternae, which are laternally linked by tubules forming the Golgi ribbon.The GRASP65(Golgi ReAssembly Stacking Protein65) is found at cis-golgi and cis-golgi network. As a scaffold protein, GRASP65together with other proteins, participates in laternally linking of stacks.GRASP65phosphorylation leads to trans-oligomer disassembly, and eventurally results in Golgi ribbon unlinking and fragmentation. The fragmentation of Golgi apparatus is crucial for cell-cycle and mitosis progression. In addition, The Golgi apparatus is involved in the formation of spindle, apoptosis and unconventional secretion in the cell.The crystal structure of GRASP65GRASP domain was determined. It is the first high resolution structure reported for GRASP65. The difference between GRASP65and its homologous proteins were analyzed based on their crystal structures. Critical residues involved in protein polymerization were identified, and roles of these residues on dimerization and oligomerization were analyzed by series of mutations. To verify the significance of these mutations, the mutant proteins were overexpressed within the Hela cell, and their effect on Golgi stacking were checked by confocal microscopy. Overall, from molecular structure to cell level, our research provides a basis for understanding the stacking mechanism of this cis-golgi stacking protein.Moreover, the secretory glycoprotein follistatin-likel (Fstl1) have been successfully expressed in Drosophila S2cell. Fstll play important roles in mediating many developmental processes, such as lung development, ureter development and skeleton development. Different ligand binding and function exist between Fstll and its homologous proteins. The crystal structure of Fstll FOLN-KAZAL domain was determined. The difference between Fstll FOLN-KAZAL domain and that of homologous proteins were compared. The crystal structure of Fstll FOLN-KAZAL domain is helpful in illustrating the different function of these proteins, and may provide clues for the prevention and treatment of Fstll-related diseases.