Relationship between N-linked oligosaccharides in SEA module and proteolytic cleavage within C-terminal domain of rodent Muc3 / 第三军医大学学报

Objective The C-terminal domain of rodent Muc3 is proteolytically cleaved.This study is to explore the relationship between N-linked oligosaccharides in SEA module and the proteolytic cleavage within C-terminal domain of rodent Muc3.Methods Truncated rodent Muc3 C-terminal domains with complete SEA module(p20SEA) were produced by site-directed mutagenesis to insert a stop code in the required place.Proteins were detected by pulse/chase and immunoprecipitation method,or SDS/PAGE and Western blot.Inhibition of glycosylation of the expressed protein was performed by using tunicamycin.Results Muc3 C-terminal domain was posttranslationally cleaved to produce a V5-tagged 30 000 extracellular glycopeptide and a Myc-tagged 49 000 membrane-associated glycopeptide.Treatment with tunicamycin to transfected COS-1 cells led to the abundant production of 60 000 uncleaved and whole-length Muc3 C-terminal domain,the 30 000 N-terminal fragment shifted to 22 000 and 49 000 C-terminal fragment shifted to 41 000 after deglycosylation.The truncated Muc3 C-terminal domain containing complete SEA module but without the following residues led to production of 36 000 uncleaved and whole-length protein,and 30 000 cleaved product shifted to 22 000 after deglycosylation.Conclusion Proteolytic cleavage in both complete rodent C-terminal domain and complete SEA module without the following residues were partially inhibited by tunicamycin.

Relationship between the integrity of SEA module and the proteolytic digestion within C-terminal domain of rodent Muc3 / 解放军医学杂志

Objective It has been known that the C-terminal domain of rodent Muc3 underwent proteolytic digestion.G/S within the motif of cleavage,LSKGSIVV,was one of the important pivots for digestion.The present investigation was aiming at exploring the unknown relationship between the integrity of SEA module and the proteolytic digestion.Method Truncated rodent Muc3 C-terminal domains(p20t and p20SEA) were produced by site-directed mutagenesis to insert a stop code in the required place.Proteins were detected by SDS/PAGE and Western blotting.Deglycosylation of the expressed protein was performed by digestion using N-glycosidase F.Results Muc3 C-terminal domain was posttranslationally cleaved to produce a V5-tagged 30kDa extracellular glycopeptide and a Myc-tagged 49kDa membrane-associated glycopeptide.The 30kDa N-terminal fragment shifted to 22kDa after deglycosylation.The truncated rodent Muc3 C-terminal domain containing complete SEA module,but without the following residues after SEA module,was 30kDa Mw as detected with anti-V5 antibody,and it was shifted to 22kDa after deglycosylation.But the truncated rodent Muc3 C-terminal domain containing incomplete SEA module(p20t) of 26-30kDa Mw was shifted to 26kDa after deglycosylation.Conclusion There was proteolytic digestion in both complete rodent C-terminal domain and complete SEA module without residues after SEA module.But proteolytic digestion does not occur in the incomplete SEA module of rodent Muc3.So it may be concluded that the integrity of SEA module of rodent Muc3 was also a crucial condition for its proteolytic digestion.