COPII gets in shape: Lessons derived from morphological aspects of early secretion

Our view of the secretory pathway has evolved from a morphological one to one that includes molecular mechanistic understanding of basic traffic components. These components include coat complexes involved in cargo sorting and budding and proteins that mediate targeting, tethering and fusion. The expanding repertoire of regulators that control basic traffic activities begins to paint a unified morphological-molecular view of secretion. The emerging picture provides key insights into the coupling of secretion with physiology. This review examines aspects of morphological-molecular relations that are derived from studies on traffic from the endoplasmic reticulum carried by the coat protein complex II.