Targeting pathways of C-tail-anchored proteins

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Biochemistry

Background:

• Tail-anchored (TA) proteins possess a unique membrane topology with a cytosolic N-terminus and a C-terminal transmembrane anchor.
• These proteins are targeted post-translationally to various cellular membranes, including the ER, as their C-terminal anchor is exposed only after ribosomal release.

Purpose of the Study:

• To review the diverse biogenetic pathways for TA protein insertion into membranes.
• To emphasize the roles of cytosolic chaperones and membrane receptors in TA protein targeting.
• To discuss the recently identified Guided Entry of Tail-anchored Proteins (Get) system and Transmembrane Recognition Complex (TRC) pathways.

Main Methods:

• Literature review of current research on TA protein biogenesis.
• Comparative analysis of different TA protein insertion mechanisms.
• Focus on the Get/TRC systems in yeast and mammals.

Main Results:

• TA proteins utilize distinct insertion pathways, some independent of accessory factors and others requiring cytosolic chaperones and membrane receptors.
• The Get system (yeast) and TRC (mammals) are crucial chaperone systems for ER targeting of TA proteins.
• The final insertion step may not require membrane proteins, with chaperones ensuring target specificity.

Conclusions:

• Multiple pathways govern TA protein insertion, reflecting their functional diversity.
• Chaperone systems play a critical role in ensuring precise delivery of TA proteins to their correct cellular destinations.
• Understanding these pathways is key to comprehending membrane protein biogenesis and cellular organization.