Journal of Cell Science 116, e205-e205 (2003)
Copyright © 2003 The Company of Biologists Limited
Budding without COPII
Transport of proteins from the ER to the Golgi is relatively well
understood: vesicle budding, for example, is known to require the ordered
assembly of COPII coat proteins, and the SNARE proteins syntaxin 5 and BET1
are implicated in vesicle targeting. By contrast, almost nothing is known
about ER-to-Golgi trafficking of the pre-chylomicron transport vesicles
(PCTVs) that transport lipid. Charles Mansbach, II and co-workers have
therefore developed an in vitro system for analysing PCTV trafficking, using
ER isolated from labelled small intestinal mucosal cells (see
p. 415). They demonstrate that
PCTVs, although distinct from protein-transport vesicles, nevertheless contain
COPII proteins and the two SNAREs. Surprisingly, the authors find that
antibodies to the COPII protein Sar1, which block budding of protein-transport
vesicles, actually stimulate PCTV budding (addition of recombinant Sar1
reverses this effect). However, they show that PCTVs that are formed in the
absence of Sar1, which lack the other COPII proteins, cannot fuse with the
Golgi. Mansbach and co-workers therefore suggest that, in contrast to the
protein-transport vesicles, PCTVs do not require COPII proteins for budding
but instead require them for fusion with the Golgi.

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Related articles in JCS:
- COPII proteins are required for Golgi fusion but not for endoplasmic reticulum budding of the pre-chylomicron transport vesicle
- Shadab A. Siddiqi, Fred S. Gorelick, James T. Mahan, and Charles M. Mansbach, II
JCS 2003 116: 415-427.
[Abstract]
[Full Text]