The effect of Golgi depletion on exocytic transport

Here we evaluate the idea that the Golgi is in dynamic equilibrium with the endoplasmic reticulum (ER). In cytoplasts that lack the Golgi apparatus, no regrowth of the Golgi is observed, nor is any transport from the ER to the cell surface detected. However, introduction of the smallest measurable amount of Golgi (equivalent to a few per cent per cell) yields significant exocytic transport. Our results indicate that the steady-state levels of Golgi in the ER are far smaller than the 30% that has been postulated, and that the Golgi may be an independent organelle and not simply an extension of the ER.