Study On The Function And Mechanism Of Ubiquitin Carboxyl-terminal Hydrolase Isozyme L5 In The Development Of Gliomas

As the major protein degradation pathway in cells,Ubiquitin Proteasome System(UPS)includs 26S proteasome,Deubiquitinase(DUBs),ubiquitin molecule,ubiquitin activating enzyme E1,ubiquitin conjugating enzyme E2 and ubiquitin ligase E3.DUBs is a group of proteinases being able to hydrolyze peptide bond,ester bond and isopeptide bond in ubiquitin carboxy terminal and removing ubiquitin from proteins.Ubiquitin C-terminal Hydrolase-L5(UCH-L5/UCH37),a member of the deubiquitinases(DUBs),removes ubiquitins from the distal subunit of the polyubiquitin chain.UCH-L5 has double functions in the regulation of protein degradation.On the one hand,UCH-L5 suppresses protein degradation via removing ubiquitin from proteins.On the other hand,UCH-L5 promotes protein degeneration through trimming polyubiquitin chain helping proteins form a proper conformation to enter into proteasome for degradation.The activity of UCH-L5 is enhanced when UCH-L5 combines with proteasome 19S regulatory subunit by Rpn13/Admrl receptor and inhibited when UCH-L5 interacts with NFRKB,a subunit of INO80 complex.But the role of UCH-L5 in gliomas remains unknown.In this study,analysis of 19 frozen and 51 paraffin-embedded clinic pathological cases showed that UCH-L5 expression in glioma tissues was lower than normal brain tissues.In vitro,we found that UCH-L5 inhibits migration and invasion of U87MG and U251 cells.It has been reported that the expression of SNRPN,SNRPF,and CKLF are abnormal in gliomas or other tumors,and then we chose them as candidate targeting genes.We found that knockdown of SNRPF,SNRPN and CKLF inhibit migration and invasion of U87MG cells.And knockdown of UCH-L5 expression improved both mRNA expression and protein level of SNRPF in U87MG cells.The relationship between UCH-L5 and SNRPF was further confirmed in 293T cells.Our study showed that UCH-L5 could inhibit migration and invasion of glioma cells via downregulating SNRPF.We also found that UCH-L5 could regulate the mRNA level of Sm family.And the above findings suggest that UCH-L5 may inhibit occurrence and metastasis of gliomas.The activity of UCH-L5 is inhibited by NFRKB,and in U87MG and U251 cells,we found that knockdown of NFRKB downregulated the mRNA levels of SNRPF,so the expression of mRNA regulation of SNRPF by UCH-L5 might be regulated by NFRKB.At present,the specific role and regulatory mechanism of UCH-L5 in glioma have not been fully elucidated;therefore,further researches on the biological function of UCH-L5 would provide new ideas for the treatment of related diseases in clinic.