Kinetically distinct sorting pathways through the Golgi exhibit different requirements for Arf1.

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Trafficking

Background:

• Transmembrane protein trafficking through the Golgi apparatus is crucial for cellular function.
• Cytoplasmic sequences play a key role in directing protein sorting and transport.
• The precise mechanisms by which cytoplasmic tails influence Golgi transit remain incompletely understood.

Purpose of the Study:

• To investigate the role of cytoplasmic sequences in directing transmembrane protein trafficking through the Golgi.
• To compare the Golgi transport kinetics and regulatory mechanisms of VSV G protein with its native tail versus an AE1-4 anion exchanger tail.

Main Methods:

• Analysis of VSV tsO45 G protein fusions with native G cytoplasmic domain (G) or chicken AE1-4 anion exchanger cytoplasmic tail (G(AE)).
• Assessment of protein folding, ER accumulation, and transport through the Golgi upon temperature shift.
• Investigation of Arf1 and COPI dependency in proximal Golgi transport and TGN exit.

Main Results:

• Both G and G(AE) proteins folded and transited the Golgi, but exhibited distinct trafficking kinetics and did not form hetero-oligomers.
• Transport of G through the proximal Golgi was Arf1 and COPI-dependent.
• G(AE) protein progression through the proximal Golgi was Arf1 and COPI-independent, but Arf1 regulated its exit from the TGN, similar to native AE1-4.

Conclusions:

• Cytoplasmic sequences significantly influence transmembrane protein trafficking rates and regulatory pathways within the Golgi.
• Differential recognition of cytosolic signals by Arf1-dependent machinery affects cargo progression through the Golgi.
• This highlights a mechanism by which distinct protein tails can modulate their own transport dynamics.