An extended interaction site determines binding between AP180 and AP2 in clathrin mediated endocytosis

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Clathrin-mediated endocytosis involves complex protein interactions mediated by clathrin-associated sorting proteins (CLASPs).
• These CLASPs, including neuronal protein AP180, possess intrinsically disordered regions (IDRs) whose functions are not fully understood.
• AP180's specific role and interaction with other key proteins like AP2 remain partially elusive.

Purpose of the Study:

• To investigate the interaction between the intrinsically disordered region of neuronal AP180 and the major adaptor protein AP2.
• To determine the binding dynamics and functional significance of this interaction at atomic resolution.
• To elucidate the role of AP180-AP2 interactions in the early stages of clathrin-mediated endocytosis.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study the interaction between AP180 and AP2.
• Atomic resolution details of the binding interface and dynamics were analyzed.
• Binding affinities and the contribution of different interaction sites were characterized.

Main Results:

• An extended and strong interaction site (approximately 70 residues) within AP180's IDR was identified, significantly determining AP180-AP2 interaction.
• The interaction exists in a dynamic equilibrium between bound and unbound states.
• Weaker binding sites contribute to overall affinity at higher AP2 concentrations.

Conclusions:

• The identified 70-residue interaction site on AP180 plays a central role in recruiting adaptors to clathrin-coated pits.
• Transient and promiscuous interactions facilitate network reshaping during cargo uptake.
• Understanding these dynamics provides insights into the precise molecular mechanisms of endocytosis.