Fast-evolving cofactors regulate the role of HEATR5 complexes in intra-Golgi trafficking

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Interactions

Background:

• HEATR5 proteins are conserved and crucial for membrane traffic, particularly involving adaptor protein complex-1 (AP1).
• HEATR5 proteins interact with rapidly evolving cofactors to bind AP1, but the precise interaction mechanisms remain unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms by which HEATR5 proteins interact with their cofactors.
• To investigate the distinct functional roles of the budding yeast HEATR5 protein, Laa1, and its binding partners.

Main Methods:

• Biochemical analysis of Laa1 in distinct protein complexes.
• Structure prediction to analyze binding mechanisms between Laa1, Laa2, and Lft1.
• Functional assays to assess roles in intra-Golgi recycling and AP1 localization.

Main Results:

• Budding yeast Laa1 operates in two separate complexes, mediated by mutually exclusive binding partners Laa2 and Lft1.
• Lft1 and Laa2 share structurally similar binding mechanisms to Laa1, despite low sequence similarity.
• Both Laa1 complexes are involved in intra-Golgi recycling, but only the Laa2-Laa1 complex interacts with AP1.

Conclusions:

• Laa1 utilizes structurally conserved mechanisms to bind distinct cofactors, providing insight into HEATR5 protein interactions.
• Laa1 has functions independent of AP1 recruitment, expanding our understanding of its cellular roles.
• The findings suggest conserved cofactor binding mechanisms for HEATR5 proteins across species, including humans.