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Expression of sulfated gp300 and changes in glycosylation during pancreatic development
1Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City 66160, USA.
Abstract:
The pancreatic zymogen granule membrane protein gp300 is the major sulfated glycoprotein of the mouse acinar cell and has been proposed to be an important structural component of the zymogen granule membrane. A prediction of this proposed function is that gp300 expression should be coordinately regulated with the digestive enzymes and appearance of zymogen granules during differentiation of acinar cells in fetal development. By Western blots and immunolocalization with a polyclonal antiserum to gp300, we found that gp300 protein expression paralleled expression of amylase and the appearance of zymogen granules in differentiating acinar cells. Lectin blots were performed to assess the glycoconjugate composition of gp300 during development. Using the fucose binding lectin Ulex europaeus I, we found that gp300 acquires this carbohydrate only postnatally, temporally correlated with weaning. In addition, gp300 showed complex changes during postnatal development in reactivity with the galactose binding lectin peanut agglutinin (PNA) and the sialic acid binding lectin Maackia amuresis (MAA). Levels of reactivity of PNA and MAA were reciprocal, suggesting that sialylation of galactose (which can block peanut agglutinin binding) was not constant on gp300 during development.
Insights
Pancreatic zymogen granule membrane protein gp300 expression aligns with digestive enzyme development in mouse acinar cells. This major sulfated glycoprotein acquires specific carbohydrates postnatally, indicating developmental regulation.
Area of Science:
- Cell Biology
- Glycobiology
- Developmental Biology
Background:
- The pancreatic zymogen granule membrane protein gp300 is a major sulfated glycoprotein in mouse acinar cells.
- It is hypothesized to be a key structural component of the zymogen granule membrane.
Purpose of the Study:
- To investigate the developmental regulation of gp300 expression in mouse acinar cells.
- To characterize the changes in gp300's glycoconjugate composition during postnatal development.
Main Methods:
- Western blotting and immunolocalization using anti-gp300 antiserum.
- Lectin blotting with fucose, galactose, and sialic acid binding lectins (Ulex europaeus I, peanut agglutinin, Maackia amuresis).
Main Results:
- gp300 protein expression paralleled amylase expression and zymogen granule appearance during fetal acinar cell differentiation.
- gp300 acquired fucose residues postnatally, coinciding with weaning.
- Reciprocal changes in peanut agglutinin and Maackia amuresis binding indicated dynamic sialylation of galactose residues during postnatal development.
Conclusions:
- gp300 expression is coordinately regulated with digestive enzyme production during acinar cell differentiation.
- The glycosylation pattern of gp300 undergoes significant, regulated changes during postnatal development, particularly around weaning.
- These findings support gp300's role as a structural component whose composition is modulated during cellular maturation.