Research On The Mechanism Of UBIAD1 Inhibiting The Proliferation Of Bladder Cancer Cells

UbiA prenyltransferase domain-containing protein 1(UBIAD1),a nine-cross membrane protein,participates in vitamin K and coenzyme Q10(CoQ10)synthesis using geranligeranli diphosphate(GGPP).UBIAD1 synthesizes vitamin K(MK-4)in mitochondria,regulates the electron transport chain(ETC),stables mitochondria membrane potential and synthesizes ATP.Lack of UBIAD1 causes mitochondria dysfunction and induces Parkinson’s disease.UBIAD1 participates in non-mitochondria CoQ10 synthesis in the Golgi apparatus and regulates the endothelial nitric oxide synthase activity(eNOS).The deficiency of UBIAD1 or the lowing of CoQ10 uncouples eNOS,causing consequently reactive oxygen species(ROS)overload leading to cellular oxidative damage in the cardio vascular tissues.UBIAD1 regulates the cholesterol metabolism by interacting with HMG-CoA reductase.The mutation of UBIAD1,which cannot use GGPP,protects HMG-CoA reductase from degradation and generates cholesterol.This process causes lipid accumulation in eyes and induces Schneider crystallized corneal dystrophy.Moreover,UBIAD1 is low expressed or absent in the bladder cancer,prostate cancer and kidney cancer.Ectopic expression of UBIAD1 inhibites the growth of cancer cells.Our previous study shows that UBIAD1 knockdown activates ERK signal.However,the mechanism by which UBIAD1 could be involved in tumorigenesis remains ambiguous.To this end,we explored the mechanism of UBIAD1 regulating Ras/MAPK signaling pathway in this thesis.Here,we found that ectopic expression of UBIAD1 inhibited Ras/MAPK signaling and cell proliferation of bladder cancer T24 cells.Slencing UBIAD1 activated Ras/MAPK signal in normal HEK293 T cells.Using different inhibitors in Ras/MAPK signal pathway,we found that UBIAD1 functioned on Ras.UBIAD1 retained Ras in the Golgi and Ras transported to the plasmid membrane in the lack of UBIAD1.Thought FRET,BIFC and Co-IP,we found that UBIAD1 interacted with H-Ras.In addition,the truncated experiment suggested that the C-terminus of H-Ras could interact with UBIAD1.To further study the mechanism between UBIAD1 and H-Ras,we used statins and si-GGPPS to decrease the GGPP level in the cells.It was found that lowing GGPP abolished UBIAD1 function(UBIAD1 interacted with H-Ras;UBIAD1 retained H-Ras in the Golgi;UBIAD1 inhibited Ras/ERK signal and UBIAD1 decreased T24 cell viability)and supplementary GGPP rescued this phenomenon.Moreover,we found that eNOS interacted with UBIAD1 and H-Ras.Dysfunction of eNOS blocked the function of UBIAD1 in Ras/MAPK signal pathway.To verify the function of UBIAD1 in vivo,we used the Drosophila as animal model to study it.We found that the Ras/MAPK signal activated and the melanoma appeared in heix mutant larvae.Less traces of melanoma were detected in the heix mutants under the Ras/MAPK signal inhibitor or Ras inhibitors treatment.In addition,statins and eNOS inhibitors,which blocked heix function,could induce melanoma in wild-type larvae by different mechanism.The result in vivo was consistent to that in cell.Taken together,UBIAD1 bound with eNOS and H-Ras in the Golgi,retained H-Ras in the Golgi,inhibited Ras/MAPK signal and supressed cell proliferation.When UBIAD1 was absent,Ras transported to plasmid membrane and activated Ras/MAPK signal.Moreover,lack of UBIAD1 uncoupled eNOS and generated ROS.Ethier Ras signal or ROS production induced cell proliferation.Thus,our study not only suggest the function of UBIAD1 as a tumor suppressor in cancer but also tentatively reveals the formation of melanoma in Drosophila.