Early Uncoating of COPII from ER Exit Sites Membranes During Cargo Accumulation and Membrane Fission
28 Pages Posted: 18 May 2019 Sneak Peek Status: Review CompleteMore...
COPII and COPI are considered to be analogous sets of vesicle coat protein hretrocomplexes. Coupled to cargo selection, they mediate the formation of membrane vesicles translocating in opposite directions to different destinations within the secretory pathway. Here, live cell and electron microscopy provided evidence for a different localization and mode of function of the COPII coat during protein export from the endoplasmic reticulum (ER). Pharmaceutical and genetic perturbations of ER-Golgi transport were used to demonstrate that COPII is recruited to membranes defining the boundary of ER-ER Exit Sites (ERES) where it facilitates Golgi-bound selective cargo concentration. Uncoating of COPII membranes precedes cargo accumulation and fission of Golgi-bound carriers. Moreover, we show that anterograde carriers are positive with the COPI complex. These findings change our understanding of the role of coat proteins in ER to Golgi transport.
Keywords: COPII, ER export, ER exit sites, Secretory pathway, ER-Golgi transport
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