The A2 chain of cholera toxin (CTX) contains a COOH-terminal Lys-Asp-Glu-Leu (KDEL) sequence. We have, therefore, analyzed by immunofluorescence and by subcellular fractionation in Vero cells whether CTX can used to demonstrate a retrograde transport of KDEL proteins from the Golgi to the ER. Immunofluorescence studies reveal that after a pulse treatment with CTX, the CTX-A and B subunits (CTX-A and CTX-B) reach Golgi-like structures after 15-20 min (maximum after 30 min). Between 30 and 90 min, CTX-A (but not CTX-B) appear in the intermediate compartment and in the ER, whereas the CTX-B are translocated to the lysosomes. Subcellular fractionation studies confirm these results: after CTX uptake for 15 min, CTX-A is associated only with endosomal and Golgi compartments. After 30 min, a small amount of CTX-A appears in the ER in a trypsin-resistant form, and after 60 min, a significant amount appears. CTX-A seems to be transported mainly in its oxidized form (CTX-A1-S-S-CTX-A2) from the Golgi to the ER, where it becomes slowly reduced to form free CTX A1 and CTX-A2, as indicated by experiments in which cells were homogenized 30 and 90 min after the onset of CTX uptake in the presence of N-ethylmaleimide. Nocodazol applied after accumulation of CTX in Golgi inhibits the appearance of CTX-A in the ER and delays the increase of 3',5'cAMP, indicating the participation of microtubules in the retrograde Golgi-ER transport.
Article|
May 15 1996
Transport of an external Lys-Asp-Glu-Leu (KDEL) protein from the plasma membrane to the endoplasmic reticulum: studies with cholera toxin in Vero cells.
I V Majoul,
I V Majoul
Abteilung Klinische Biochemie, Universität Göttingen, Germany.
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P I Bastiaens,
P I Bastiaens
Abteilung Klinische Biochemie, Universität Göttingen, Germany.
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H D Söling
H D Söling
Abteilung Klinische Biochemie, Universität Göttingen, Germany.
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I V Majoul
Abteilung Klinische Biochemie, Universität Göttingen, Germany.
P I Bastiaens
Abteilung Klinische Biochemie, Universität Göttingen, Germany.
H D Söling
Abteilung Klinische Biochemie, Universität Göttingen, Germany.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1996) 133 (4): 777–789.
Citation
I V Majoul, P I Bastiaens, H D Söling; Transport of an external Lys-Asp-Glu-Leu (KDEL) protein from the plasma membrane to the endoplasmic reticulum: studies with cholera toxin in Vero cells.. J Cell Biol 15 May 1996; 133 (4): 777–789. doi: https://doi.org/10.1083/jcb.133.4.777
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