Post-translational interaction of two fragments cleaved by protease within carboxyl-terminal domain of intestinal mucin Muc3 / 第三军医大学学报

ABSTRACT

Objective To explore the existing molecular pattern of rodent Muc3 carboxyl-terminal domain. Methods Muc3 carboxyl-terminal domain was expressed by a transient expression system and detected with SDS/PAGE and Western blotting. Identification of interaction between two proteolytically cleaved fragments was carried out by using both metabolic labeling and immunoprecipitation of expressed proteins and affinity purification of His-tagged proteins. Results Experiments with heterologous cells transfected with cDNA encoding the 381-residue C-terminal domain of rodent Muc3 showed that a definitive proteolytic cleavage occurred during the process in the endoplasmic reticulum. The products consisted of a V5-tagged 30 000 extracellular peptide, a Myc-tagged 49 000 membrane-associated peptide and non-cleaved 55 000 of whole-length protein. Two fragments remained associated by non-covalent SDS-sensitive interactions. Conclusion The proteolytic cleavage may be a prelude to later release of the large extracellular domains at cell surfaces. But the interaction between two cleaved fragments may be an important factor to interfere with the later release of the extracellular domain.