The Fuction Of CIDEc In Lipid-droplet Formation

Cell death-inducing dFF45-like effector c (CIDEc),also known as Fat-specific protein of27kD (Fsp27) in mus, plays an important role in the process of energy metabolism and fat accumulation.Recent reports indicate that Fsp27binds to the surface of lipid droplets and promotes cellular triglyceride accumulation. The expression level research revealed that Fsp27specifically expressed in brown and white adipose tissue, no expression was detected in other tissues. Moreover, Fsp27only express in matured adipocyte in vitro. Further study show abundant presence of Fsp27in lipid droplets and high expression of Fsp27were found in the fatty liver. The latest research shows that, Fsp27promotes energy reservesion, inhibits lipolysis, and participates in the balance and regulation of the whole body energy. Inhibition or knockout of Fsp27result in the increaseing of lipolysis as well as the development of small lipid droplets. These studies suggest that, Fsp27expression level can impact the number and the form of lipid droplets in adipocytes. This may be the an important mechanism of molecular switch between the form and the number of lipid droplets in adipocyte. Therefore. Fsp27may become a potential target for the treatment of obesity and related metabolic disorders. However, how does Fsp27control the formation of lipid droplets? What signaling pathways are involved in the process of fat deposition? How does Lipid droplets identify signals of Fsp27? These key issues are still unclear.In this study, sus CIDEc was choosen as the target gene, using over-expression, RT-PCR, Western blotting, the function of different sus CIDEc domains and the mechanism of lipid droplet fusion were explored. The results are as follow.1, Full-length CDS sequences of sus CIDEc and homo CIDEc were successfully cloned. The length of ORF of both genes are717bp, both sus CIDEc and homo CIDEc gene encode238amino acids; The full-length amino acid sequence similarity between sus CIDEc and homo CIDEc is83.6%.2, Through amino acid homology comparison with Perilipin, different fractions of CIDEc CDS sequences were amplified and constructed into the eukaryotic expression vector. Location analysis showed that1-105aa and1-173aa can be located in the lipid droplets,1-105aa positioning capability is weak. Further experiments show that lipid droplets positioning need1-105aa and106-173aa. 3, HepG2cells as a model, CIDEc located in the fat droplets when high fat diet, however, CIDEc located in the endoplasmic reticulum when low fat diet. Endoplasmic reticulum localization sequence is106-173aa.4, Some reports confirm that CIDEc promote the fusion of lipid droplet, CIDEc were constructed into non-fusion vector of eukaryotic expression, and transfected into cells, results reveal that the fraction of174-238aa increase the size of lipid droplet but reduce the number of lipid droplet. That is to say, fraction of174-238aa promote the formation of single-chamber large lipid droplets which indicat that this amino acid fraction promote lipid droplet fusion.5, In order to study the mechanism of lipid droplets fusion, the specific surface area (surface area/volume) of lipid droplets was measured after transfection with CIDEc, Results show an decreasing of lipid droplets SSA but an increasing of triglyceride accumulation. We speculate that it’s the decreasing of lipid droplet SSA that result in the diminish of binding sites of lipolysis-related enzymes, the dropping of lipolysis, and the increasing of the glycerol content.