Related Experiment Video
Updated: Aug 1, 2026

Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis
Published on: January 26, 2015
Polarized secretion of the regulated secretory protein chromogranin A
1Department of Molecular, Cellular, and Craniofacial Biology, University of Louisville, Louisville, Kentucky 40292, USA.
Abstract:
Bovine chromogranin A (CgA), together with secreted alkaline phosphatase (SEAP) as an external control for apical secretion were expressed in MDCK cells to test if CgA contains sorting signals for polarized secretion. CgA, SEAP, and the endogenous apical marker GP80 were secreted 75-80% apically. Basolateral secretion of SEAP was inhibited 40% by ammonium chloride. Sulfate labeling and digestion with chondroitinase ABC revealed a 120 kDa proteoglycan-CgA and 75 kDa CgA. Inhibition of proteoglycan synthesis did not affect apical secretion of CgA. As CgA is not N-glycosylated, we used tunicamycin to test if cellular N-glycosylation is required for apical sorting. Tunicamycin reversed the polarity of secretion of CgA to the basolateral side. These results suggest that CgA contains dominant apical and recessive basolateral sorting information.
Related Concept Videos
Hormonal Regulation
Hormonal Regulation
Overview of Secretory Vesicles
Various proteins regulate the aggregation of molecules inside the secretory vesicles. Chromogranins...
Insulin Secretory Vesicles
Regulation of Hormone Secretion
Humoral stimuli,...
Hormones Secreted by the Stomach
Each of these hormones secreted by different enteroendocrine cells plays a unique role in digestion. Here are a few examples:

