Effects of ZNRF1, UCHL1 and Oleuropein on Ubiquitin-Proteasome System and Mitochondrial Functions

• Main Authors: Zih-TingHuang, 黃紫婷
• Other Authors: Lu-Shiun Her
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/bc2h44

碩士 === 國立成功大學 === 生命科學系 === 103 === UPS is highly regulated process usually involving many proteins. The presence of mutant huntingtin impairs UPS and leads to aggregates formation. This study attempted to study the UPS-related regulatory proteins in wild-type STHdhQ7/Q7and mutant STHdhQ111/Q111 striatal cells. Western blot assays showed that there is a significant decrease in levels of UCHL1 and ZNRF1 in STHdhQ111/Q111 cells. UCHL1 and ZNRF1 are deubiquitinating enzyme and E3 ubiquitin-protein ligase, respectively. Our results indicated that UCHL1 did not affect UPS functions. On the other hand, depletion of ZNRF1 in STHdhQ7/Q7 cells showed an increase in the UPS degradation activity. Earlier study found that reduced UCHL1 level in cells lowers the level of glutathione (GSH), which leads to increased oxidative stress followed by mitochondria dysfunction. Moreover, it is discovered that an abnormal expression of parkin, an E3 ubiquitin-protein ligase similar to ZNRF1, results in mitochondria dysfunction. Therefore, our study also examined the effects of UCHL1 and ZNRF1 on mitochondrial function. It is found that mitochondria morphology changes when ZNRF1 is down-regulated in STHdhQ7/Q7 cells. DRP1 is a pro-fission protein inducing mitochondrial fragmentation whereas Mfn1 is a mitochondrial fusion-promoting protein. Western blot assays showed that there is an increase in DRP1 level and a decrease in Mfn1 level after depletion of ZNRF1. Evidences indicated that poly-Q diseases are due to the mutated poly-Q chains impairs UPS and leads to aggregates accumulation. As previous study has shown that Oleuropein is able to enhance proteasomal activities, we also found that Oleuropein has improves on the UPS function. Increment of cellular ATP concentration however, is not the factor that provides more energy for proteasome pathway to take place.