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. (C) 2000 Academic Press.
|Original language||English (US)|
|Number of pages||6|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Apr 13 2000|
Bibliographical noteFunding Information:
We thank Drs. Darrin J. Cowley, Renu K. Jain, and William W. Young, Jr. for helpful discussions. This work was supported by NIH Grants R01 DK 53367 and R01 DE 12205.
- Canine kidney cells
- Chromogranin A
- Secretion polarity