Polarized Secretion of the Regulated Secretory Protein Chromogranin A

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. Ba...

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Bibliographic Details
Published in:Biochemical and biophysical research communications 2000-04, Vol.270 (2), p.631-636
Main Authors: Kühn, Ulrike, Cohn, David V., Gorr, Sven-Ulrik
Format: Article
Language:English
Subjects:
Animals
Carbohydrate Metabolism
Cattle
Cell Line
Chondroitin Sulfates - metabolism
Chromogranin A
Chromogranins - secretion
Dogs
Endocytosis
Glycosylation
Hydrogen-Ion Concentration
Kidney - cytology
Kidney - metabolism
Kidney - secretion
Madin-Darby canine kidney cells
N-glycosylation
secretion polarity
sorting
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Summary: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.
ISSN:0006-291X
1090-2104
DOI:10.1006/bbrc.2000.2469