Although human MUC3 and rodent Muc3 are both membrane-associated intestinal mucins, the present study has explored the possibility that rodent Muc3 might exist in soluble as well as membrane forms. No evidence was obtained for the existence of soluble splice variants; however, experiments with heterologous cells transfected with cDNA encoding the 381-residue C-terminal domain of rodent Muc3 showed that a definitive proteolytic cleavage occurs during processing in the endoplasmic reticulum. The products consisted of a V5-tagged 30kDa extracellular glycopeptide and a Myc-tagged 49kDa membrane-associated glycopeptide. Throughout their cellular transport to the plasma membrane, the two fragments remained associated by non-covalent SDS-sensitive interactions. Site-specific mutagenesis pinpointed the need for glycine and serine residues in the cleavage sequence Leu-Ser-Lys-Gly-Ser-Ile-Val-Val, which is localized between the two epidermal-growth-factor-like motifs of the mucin. A similar cleavage sequence (Phe-Arg-Pro-Gly↓Ser-Val-Val-Val, where ↓ signifies the cleavage site) has been reported in human MUC1 and analogous sites are present in human MUC3, MUC12 and MUC17. Thus early proteolytic cleavage may be a conserved characteristic of many membrane-associated mucins, possibly as a prelude to later release of their large extracellular domains at cell surfaces.
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September 2002
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Research Article|
September 01 2002
C-terminal domain of rodent intestinal mucin Muc3 is proteolytically cleaved in the endoplasmic reticulum to generate extracellular and membrane components
Rongquan WANG;
Rongquan WANG
∗Research Institute, Department of Structural Biology and Biochemistry, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
†Department of Gastroenterology, Southwestern Hospital, Third Military Medical University, Chongqing 400038, People's Republic of China,
‡Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON, Canada M5S 1A8
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Ismat A. KHATRI;
Ismat A. KHATRI
∗Research Institute, Department of Structural Biology and Biochemistry, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
‡Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON, Canada M5S 1A8
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Janet F. FORSTNER
Janet F. FORSTNER
1
∗Research Institute, Department of Structural Biology and Biochemistry, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
†Department of Gastroenterology, Southwestern Hospital, Third Military Medical University, Chongqing 400038, People's Republic of China,
‡Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON, Canada M5S 1A8
1To whom correspondence should be addressed (e-mail jfforst@sickkids.on.ca).
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Publisher: Portland Press Ltd
Received:
February 19 2002
Revision Received:
May 09 2002
Accepted:
May 23 2002
Accepted Manuscript online:
May 23 2002
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London ©2002
2002
Biochem J (2002) 366 (2): 623–631.
Article history
Received:
February 19 2002
Revision Received:
May 09 2002
Accepted:
May 23 2002
Accepted Manuscript online:
May 23 2002
Citation
Rongquan WANG, Ismat A. KHATRI, Janet F. FORSTNER; C-terminal domain of rodent intestinal mucin Muc3 is proteolytically cleaved in the endoplasmic reticulum to generate extracellular and membrane components. Biochem J 1 September 2002; 366 (2): 623–631. doi: https://doi.org/10.1042/bj20020289
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