TANGO1 marshals the early secretory pathway for cargo export.

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Function

Background:

• The endoplasmic reticulum (ER) exports proteins and lipids via transport vesicles.
• Large cargoes exceeding standard vesicle capacity pose a challenge for ER export.
• The TANGO1 protein is known to be involved in the ER export pathway.

Purpose of the Study:

• To elucidate the mechanism by which TANGO1 facilitates the export of large ER cargoes.
• To understand how TANGO1 bypasses conventional vesicular transport.
• To investigate the role of TANGO1 in differentiating yeast and animal secretory pathways.

Main Methods:

• Structural analysis of TANGO1 assembly at the ER membrane.
• Investigating the interaction of TANGO1 with COPII and COPI coat proteins.
• Studying the formation of a direct tunnel for cargo transfer.

Main Results:

• TANGO1 assembles into a ring structure at the ER membrane, creating a specialized export domain.
• The lumenal part of TANGO1 collects and sorts folded cargoes.
• Cytoplasmic domains of TANGO1 recruit COPII coats and COPI-coated membranes, facilitating fusion and tunnel formation for cargo export.
• This process enables the direct transfer of large cargoes, bypassing vesicular intermediates.

Conclusions:

• TANGO1 provides a non-vesicular mechanism for exporting large and abundant cargoes from the ER.
• The unique TANGO1-mediated export pathway is crucial for handling bulky cargo.
• The evolution and function of TANGO1 highlight key differences between yeast and animal early secretory pathways.