Cargo can modulate COPII vesicle formation from the endoplasmic reticulum

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Transport

Background:

• The COPII (coat protein complex II) coat complex is essential for selecting cargo and forming vesicles from the endoplasmic reticulum (ER).
• The precise mechanisms by which cargo molecules themselves influence COPII coat assembly and vesicle budding remain incompletely understood.

Purpose of the Study:

• To investigate the role of biosynthetic cargo in modulating COPII coat assembly and vesicle budding from the ER.
• To determine how the accumulation or export of specific cargo proteins affects general COPII vesicle formation.

Main Methods:

• Studied the effects of accumulating vesicular stomatitis glycoprotein (VSV-G) and PiZ alpha1-antitrypsin in the ER on COPII vesicle formation in vivo.
• Utilized ER-derived microsomes to examine the impact of VSV-G export blockade and synchronized export on COPII vesicle budding in vitro.
• Investigated the association of retained VSV-G with COPII components in pre-budding complexes.

Main Results:

• ER accumulation of VSV-G or PiZ significantly reduced general COPII vesicle formation in vivo.
• Preventing VSV-G export inhibited COPII vesicle budding from ER microsomes and the export of p58 protein in vitro.
• Synchronized VSV-G export enhanced COPII vesicle budding both in vivo and in vitro.
• Retained VSV-G was found in pre-budding complexes with COPII components.

Conclusions:

• The export of biosynthetic cargo is tightly integrated with ER protein folding and oligomerization processes.
• Biosynthetic cargo can actively regulate COPII vesicle budding, either by preventing or enhancing ER export.
• Interactions between cargo and the COPII machinery are critical for the formation of ER-derived vesicles.