Sec16 influences transitional ER sites by regulating rather than organizing COPII

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Dynamics

Background:

• Sec16 is hypothesized to regulate coat protein complex II (COPII) vesicle budding from the endoplasmic reticulum.
• Proposed roles for Sec16 include negative regulation of COPII turnover and organization of COPII assembly at transitional ER (tER) sites.

Purpose of the Study:

• To investigate the distinct roles of Sec16 in COPII vesicle budding.
• To determine whether Sec16 negatively regulates COPII turnover or organizes COPII assembly.

Main Methods:

• Utilized the yeast Pichia pastoris model system.
• Examined the effects of Sec16 redistribution on tER dynamics.
• Dissected functional regions of Sec16 to assess their roles in COPII organization.

Main Results:

• Relocating Sec16 to the cytosol accelerated tER dynamics, supporting its negative regulatory role.
• The central conserved domain of Sec16 is dispensable for tER structure.
• COPII components recruit Sec16 to tER sites via its upstream conserved region (UCR), rather than Sec16 organizing COPII.

Conclusions:

• Sec16's primary function is the negative regulation of COPII turnover.
• Sec16 does not organize COPII assembly; COPII components recruit Sec16.
• Regulation of COPII turnover adequately explains Sec16's influence on tER sites.