Regulation of AP1 adaptor assembly by the bi-handed chaperone MEA1

Area of Science:

• Cellular Biology
• Molecular Biology
• Protein Trafficking

Background:

• Bidirectional trafficking between the trans-Golgi network (TGN) and endolysosomal compartments is vital for cellular pathways.
• Adaptor protein complex 1 (AP1) is central to this trafficking, mediating cargo recognition and vesicle budding.

Purpose of the Study:

• To identify novel regulators of AP1 function.
• To elucidate the mechanism by which AP1 assembly is controlled.

Main Methods:

• Protein identification and characterization.
• Analysis of AP1 subunit stability and localization.
• Investigation of cargo trafficking in MEA1-deficient cells.

Main Results:

• Male-Enhanced Antigen 1 (MEA1) was identified as a critical regulator of AP1.
• Loss of MEA1 leads to AP1 subunit depletion and impaired AP1-dependent cargo trafficking.
• MEA1 functions as a chaperone, stabilizing AP1 subunits before assembly via a dual chaperone collision mechanism with AAGAB.

Conclusions:

• MEA1 is essential for AP1 stability and function.
• A novel dual chaperone collision mechanism governs AP1 heterotetramer formation.
• This mechanism may be broadly applicable to the assembly of other multi-subunit protein complexes.