EXPRESSION OF SULFATED GP300 AND CHANGES IN GLYCOSYLATION DURING PANCREATIC DEVELOPMENT

The pancreatic zymogen granule membrane protein gp300 is the major sul fated glycoprotein of the mouse acinar cell and has been proposed to b e an important structural component of the zymogen granule membrane. A prediction of ths proposed function is that gp300 expression should b e coordinately regulated with the digestive enzymes and apperance of z ymogen granules during differentiation of acinar cells in fetal develo pment. By Western blots and immunolocalization with a polyclonal antis erum to gp300, we found that gp300 protein expression paralleled expre ssion of amylase and the appearance of zymogen granules in differentia ting acinar cells. Lectin blots were performed to assess the glycoconj ugate composition of gp300 during development. Using the fucose bindin g lectin Ulex europaeus I, we found that gp300 acquires this carbohydr ate only postnatally, temporally correlated with weaning. In addition, gp300 showed complex changes during postnatal development in reactivi ty with the galactose binding lectin peanut agglutinin (PNA) and the s ialic acid binding lectin Maackia amutesis (MAA). Levels of reactivity of PNA and MAA were reciprocal suggesting that sialylation of galacto se (which can block peanut agglutinin binding) was not constant on gp3 00 during development.