The Study Of The Mechanism Of 3?-hydroxysteroid-?24reductase(DHCR24) Against Endoplasmic Reticulum(ER) Stress In The Nervous System

3?-Hydroxysteroid-?24 reductase(DHCR24)is a multifunctional enzyme that possesses anti-apoptotic and cholesterol-synthesizing activities.It was demonstrated that DHCR24 could protect mouse embryonic fibroblasts by ER stress(ERS)through eliminating intracellular ROS produced by ERS.Accumulating evidence suggests that ERS involved in the pathogenesis of neurodegeneration disease,contributing to neuronal cell apoptosis.To investigate whether DHCR24 could protect neuronal cells from apoptosis induced by ERS,we cultured neuroblastoma cell line N2A cells,infected by adenovirus expressing DHCR24 tagged with myc(Ad-DHCR24-myc)and used the adenovirus expressing lacZ(Ad-lacZ)as the control.Tunicamycin(TM)was used as the ERS inducer.We found that Ad-DHCR24-myc infected cells were resistant to TM-induced apoptosis,if compared to the control.The similar results were observed when using the Amyloid ?(A?)as the ERS inducer.Immunocytochemical results showed that caspase 3 and caspase 12 was much stronger activated by TM in control.Bip/Grp78 and CHOP are ERS markers,which are upregulated under ERS.Western blot analysis showed that the inductions of Bip/Grp78 and CHOP were weaker in Ad-DHCR24-myc cells than that in Ad-lacZ infected cells,which was consistant with the immunocytochemical results,suggesting that the overexpression of DHCR24 could suppress ERS induced by TM in N2A cells.We further studied the activation of PERK,JNK and p3 8 in the ERS-associated signaling pathway by western blot and found that compared to the Ad-lacZ cells,their phosphorylations were delayed,along with the decreasing of the phosphorylation level,implying that DHCR24 could protect the neuronal cells from ERS-induced apoptosis through multiple pathways.Using the H2DCFHDA as the ROS probe,we detected that the intracellular ROS under ERS was diminished through the overexpression of DHCR24 mediated by the adenovirus,demonstrating a ROS-scavenging activity of DHCR24 in neuronal cells.DHCR24 is the enzyme in the final step of cholesterol biosynthesis and we found that the intracellular cholesterol level was increased in the Ad-DHCR24-myc infected cells.Meanwhile the dual immunocytochemistry results revealed that the overexpression of DHCR24 promoted the colocalization of caveolin-1 and insulin-like growth factor 1(IGF-1)receptor.These demonstrated that DHCR24 functions as an anti-apoptosis protein maybe through the increasing the production of the intracellular cholesterol,the stronger activation and maintaining of cell survival signaling associated with caveolae.In conclusion,the present study demonstrated for the first time that DHCR24 can protect neuronal cells from apoptosis induced by ERS.