A tango for coats and membranes: New insights into ER-to-Golgi traffic

The realization that the meticulous organization of cellular organelles is not required for the reconstitution of select intracellular traffic steps has revolutionized cell biology. It transformed the discipline from a morphological one into a molecular one. It helped in defining the activities of COPII and COPI vesicle coats in secretion. The work established the principles of the vesicular traffic model as envisioned by George Palade 50 years ago. However, in recent years, numerous advances in cellular and imaging technologies afforded an unprecedented molecular resolution that sheds new light on COPII activities and biosynthetic traffic between the ER and the Golgi. In the following review, I summarize this new information and attempt to provide a unified physical-molecular-morphological description of this traffic step. This information expands on the simplistic principles of vesicular traffic and provides novel frameworks to examine and explain physiological secretion.