Effect of ATP depletion and DTT on the transport of membrane proteins from the endoplasmic reticulum and the intermediate compartment to the Golgi complex.

Newly synthesized membrane proteins are exported from the endoplasmic reticulum to the Golgi complex through an intermediate compartment. Incubation st low temperature (15 degrees C) arrests the proteins in the intermediate compartment and prevents the entry into the Golgi complex. We have studied, in living cells, the effect of dithiothreitol (DTT) and ATP depletion on the transport to the Golgi complex of proteins accumulated either in the endoplasmic reticulum or in the intermediate compartment after a temperature block. The morphological results obtained with vesicular stomatitis virus ts-O45 G glycoprotein and the biochemical analysis performed with human CD8 protein, an O-glycosylated protein, showed that: i) ATP depletion blocks the export to the Golgi complex of proteins located either in the endoplasmic reticulum or in the intermediate compartment and ii) DTT interferes with the folding and export of proteins located in the endoplasmic reticulum, but it does not prevent the transfer from the intermediate compartment to the Golgi complex.