Single-molecule imaging of a three-component ordered actin disassembly mechanism

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Actin filament destabilization and disassembly mechanisms are not fully understood.
• Coronin, Cofilin, and AIP1 are proteins previously implicated in actin filament regulation.

Purpose of the Study:

• To elucidate the precise mechanisms and temporal order by which Coronin, Cofilin, and AIP1 cooperate to disassemble actin filaments.
• To visualize the dynamic interplay of these proteins during actin filament severing and disassembly.

Main Methods:

• Multi-wavelength single-molecule fluorescence imaging was employed.
• Reconstitution assays were performed to observe protein interactions and filament dynamics in vitro.

Main Results:

• A temporally ordered pathway was identified: Cor1B binds first, accelerating Cof1 binding, which then recruits AIP1.
• AIP1 triggers rapid filament severing and remains bound to newly formed barbed ends, blocking further polymerization.
• The combined action of Cor1B, Cof1, and AIP1 leads to efficient actin filament disassembly and prevents growth from barbed ends.

Conclusions:

• Mammalian Cor1B, Cof1, and AIP1 function in a coordinated manner to achieve rapid and efficient actin filament severing and disassembly.
• This pathway involves sequential protein binding and activity, culminating in blocked barbed-end polymerization and pointed-end disassembly.
• The findings provide a detailed mechanistic understanding of actin network regulation by these key proteins.