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A restricted set of apical proteins recycle through the trans‐Golgi network in MDCK cells.
Author(s) -
Brändli A.W.,
Simons K.
Publication year - 1989
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1989.tb08479.x
Subject(s) - biology , golgi apparatus , microbiology and biotechnology , set (abstract data type) , genetics , computational biology , endoplasmic reticulum , computer science , programming language
Sorting of newly synthesized proteins destined for the apical plasma membrane takes place in the trans‐Golgi network (TGN) in MDCK cells. This process is most likely receptor mediated and requires components that recycle between both compartments. We have developed an assay to detect apical proteins that recycle through the sialyltransferase‐containing TGN. Cell surface glycoproteins were exogalactosylated apically using a mutant cell line derived from MDCK, MDCKII‐RCAr. The mutant exhibits impaired galactosylation of glycoconjugates and thereby allows maximal incorporation of exogenously added galactose in the presence of galactosyltransferase. Upon reculture at 37 degrees C, a time‐dependent increase of sialylated apical surface glycoproteins was observed by lectin binding as well as by the sialic acid‐specific NaIO4/NaB[3H]4 labeling technique. This indicates that some galactosylated surface molecules had returned to the TGN. Recycling through the TGN was blocked, if exogalactosylated cells were incubated at 20 degrees C. Two‐dimensional gel electrophoresis identified three apical proteins which recycle through the TGN, suggesting that this pathway is selective for a subset of the apical surface proteins.