Study On The Function Of Glycosyltransferase β4GalT1 In Bladder Cancer

β1,4-galactosyltransferase 1(β1,4-galactosyltransferase 1,β4GalT1),one member of β-1,4-galactosyltransferase family,is the key glycosyltransferase to synthesize Galβ1-4GlcNAc structure on glycoproteins.In this study,we investigated the functional role of β4GalT1 in the human bladder normal epithelial cell HCV29 and invasive bladder cancer cell YTS1.Firstly,Cy3 labeled Erythrina cristagalli lectin was used to detect the contents of N-acetyl lactose.Our data showed that the expression of N-acetyl lactose.in YTS1 cells was significantly higher than that in HCV29.Furthermore,the protein level of β4GalT1,catalyzed Galβ1-4GlcNAc structure,was significantly higher in HCV29 than in YTS1 cells.In addition,the immunohistochemistry data of bladder cancer tissue sections showed that higher expression of β4GalT1 in cancer cells than in control cells.We then treated the normal cell HCV29 with transforming growth factor beta(TGF-β),a factor can induce the epithelial-mesenchymal transition(EMT)process,and found elongated morphology of HCV29 cells from epithelial cells to mesenchymal cells.Meanwhile,the expression of terminal lactosamine and β4GalT1 were remarkably increased in HCV29 cells after treated with TGF-β.It is known that β4GalT1 is a type II transmembrane protein,and has long and short forms.We then cloned the long and short form β4GalT1 from YTS1 cells and ligated into eukaryotic expression vector pLVX to construct the HCV29 cells stabely expressing long form(HCV29/B4-L)or short form β4GalT1(HCV29/B4-S).We found different distribution of long form and short form β4GalT1 in HCV29 cells via cellular immunofluorescence staining.Short form β4GalT1 was mainly localized on the Golgi apparatus in HCV29 cells.In contrast,long form β4GalT1 was distributed partly on the surface of the cell membrane and partly on the Golgi apparatus in HCV29 cells,hinting the different biological functions of these two forms of β4GalT1.Our results showed that HCV29 cells expressing long form β4GalT promoted cell proliferation,and HCV29 cells expressing short form β4GalT1 inhibited cell proliferation.Cells expressing short form β4GalT1 was blocked in the S phase,which is likely to result in the inhibition of cell proliferation.There was no significant effect on cell apoptosis of HCV29 cells expressing both long form and short from β4GalT1.However,the apoptotic rates in HCV29/B4-L and HCV29/B4-S cells were quite different after camptothecin treatment.HCV29 cells expressing long form β4GalT1 promoted cell apoptosis and HCV29 cells expressing short form β4GalT1 inhibited cell apoptosis after treated by camptothecin.Moreover it was found that HCV29 cells expressing both long form and short form β4GalT1 could enhance cell migration.Taken together,our data indicated the different roles of long form and short form β4GalT1 in modulating cell behaviors and further studies are needed to investigate the molecular mechenisms in regulating those two forms of β4GalT1 in cancer cells.