G. Miesenbock et Je. Rothman, THE CAPACITY TO RETRIEVE ESCAPED ER PROTEINS EXTENDS TO THE TRANS-MOST CISTERNA OF THE GOLGI STACK, The Journal of cell biology, 129(2), 1995, pp. 309-319
To explore how far into the Golgi stack the capacity to retrieve KDEL
proteins extends, we have introduced an exogenous probe (the peptide Y
HPNSTCSEKDEL) into the TGN of living cells. For this purpose, a CHO ce
ll line expressing a c-myc-tagged version of the transmembrane protein
TGN38-which cycles between the TGN and the cell surface-was generated
. The cells internalized peptides that were disulfide bonded to anti-m
yc antibodies and accumulated the peptide-antibody complexes in the TG
N. Peptides released from these complexes under-went retrograde transp
ort to the ER, as evidenced by the transfer of N-linked carbohydrate t
o their acceptor site. The KDEL-tagged glycopeptides (similar to 10% o
f the endocytosed load) behaved like endogenous ER residents: they sta
yed intracellular, and their oligosaccharide side chains remained sens
itive to endoglycosidase H. An option thus exists to extract ER reside
nts even at the most distant pole of the Golgi stack, suggesting that
sorting of resident from exported ER proteins may occur in a multistag
e process akin to fractional distillation.