A Translocation Pathway for Vesicle-Mediated Unconventional Protein Secretion

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Secretion

Background:

• Leaderless proteins are secreted via unconventional pathways, often involving vesicles.
• The mechanism of leaderless cargo entry into vesicles remains poorly understood.
• Vesicle trafficking is a key process in cellular secretion.

Purpose of the Study:

• To elucidate the mechanism by which leaderless cargoes enter vesicles for secretion.
• To identify the molecular players involved in regulating leaderless cargo vesicle entry.
• To understand the role of protein channels in unconventional protein secretion.

Main Methods:

• In vitro reconstitution assays using liposomes.
• Cellular localization studies of TMED10.
• Analysis of protein-cargo interactions and oligomerization.
• Investigating the role of HSP90 in cargo translocation.

Main Results:

• TMED10 identified as a protein channel mediating leaderless cargo vesicle entry.
• TMED10 C-terminal region interacts with a cargo motif for selective release.
• TMED10 directly translocates leaderless cargoes into liposomes in vitro.
• Translocation is protein unfolding-dependent and HSP90-enhanced.
• TMED10 localizes to the ER-Golgi intermediate compartment, directing cargo entry.
• Cargo binding induces TMED10 homo-oligomerization, potentially forming a translocation channel.

Conclusions:

• TMED10 is a critical component of the translocation pathway for leaderless cargo secretion.
• The TMED10-cargo interaction dictates selective protein release.
• TMED10 functions as a channel, possibly as homo-oligomers, for vesicle entry.
• This discovery sheds light on a fundamental mechanism of unconventional protein secretion.