Vesicle trafficking from the endoplasmic reticulum (ER) is a vital cellular process in all eukaryotes responsible for moving secretory cargoes from the ER to the Golgi apparatus. To accomplish this feat, the cell employs a set of conserved cytoplasmic coat proteins - the coat protein II (COPII) complex - that recruit cargo into nascent buds and deform the ER membrane to drive vesicle formation. While our understanding of COPII coat mechanics has developed substantially since its discovery, we have only recently begun to appreciate the factors that regulate this complex and, in turn, ER-to-Golgi trafficking. Here, we describe these factors and their influences on COPII vesicle formation. Properties intrinsic to the GTP cycle of the coat, as well as coat structure, have critical implications for COPII vesicle trafficking. Extrinsic factors in the cytosol can modulate COPII activity through direct interaction with the coat or with scaffolding components, or by changing composition of the ER membrane. Further, lumenal and membrane-bound cargoes and cargo receptors can influence COPII-mediated trafficking in equally profound ways. Together, these factors work in concert to ensure proper cargo movement in this first step of the secretory pathway. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
Keywords: CLSD; COPII; Cargo export; Cargo receptor; ER; ER exit sites; ERES; ERK; Endoplasmic reticulum; GAP; GEF; GPI-AP; GST; GTPase activating protein; MAPK; PH; PtdIns4P; TANGO1; TFG-1; TRK-fused gene 1; VSVG; Vesicle; bst; bypass-of-sec-thirteen; cTAGE5; coat protein II complex; cranio–lentinculo–sutural dysplasia; cutaneous T-cell lymphoma-associated antigen 5; endoplasmic reticulum; extracellular signal-regulated kinase; glutathione S-transferase; glycosylphophatidylinositol-anchored protein; guanine nucleotide exchange factor; mitogen activated protein kinase; phosphatidylinositol 4-phosphate; pleckstrin homology; transport and Golgi organization 1; vesicular stomatitis virus G protein.
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