Influence of proteolytic cleavage blockage and N-linked oligosaccharide inhibition on the membrane targeting of rodent Muc3 C-terminal domain / 解放军医学杂志

ABSTRACT

Objective To explore the correlation between membrane targeting of rodent Muc3 C-terminal domain and proteolytic cleavage blockage within its SEA module and N-linked oligosaccharides inhibition.Methods COS-1 cells were transfected with three different expression vectors containing rodent Muc3 C-terminal domain,namely p20,p20t and p20s/a by lipofectAMINE reagent.Inhibition of N-glycosylation of the expressed protein was performed by using tunicamycin.The transfected COS-1 cells(fixed or unfixed) were detected by immunolocalization experiments(anti-V5 and anti-Myc antibody) for the protein expression.Results In fixed COS-1 cells,the expressed product of p20 transfectant detected using both anti-Myc and anti-V5 antibodies was found to localize in perinuclear position and on the plasma membrane.While in the unfixed cells,immunostaining was only confined on cell surface using anti-V5 antibody.The expressed product of p20t transfectant was detected by anti-V5 antibody to localize only in perinuclear region,as observed in a few fixed cells.The distribution of p20s/a fluorescence resembled that of p20 transfectant.Plasma membrane targeting of the non-glycosylated products due to tunicamycin treatment still occurred in transfected COS-1 cells and resembled the glycosylated products.Conclusions The blockage of proteolytic cleavage within C-terminal domain of rodent Muc3 and its inhibition of N-linked oligosaccharides in SEA module cannot affect its membrane targeting.The only apparent requirement for membrane targeting is the transmembrane and/or cytoplasmic tail segments which exist in the C-terminal domains of rMuc3.