Visualizing dynamic actin cross-linking processes driven by the actin-binding protein anillin.

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Dynamics

Background:

• Anillin is a crucial actin filament cross-linking protein involved in stabilizing the contractile ring during cell division (cytokinesis).
• Understanding the molecular interactions between anillin and actin filaments is key to elucidating its role in cytokinesis.

Purpose of the Study:

• To investigate the intermolecular interactions between actin filaments and anillin at the single-molecule level.
• To visualize and characterize the dynamics of actin filament cross-linking mediated by anillin.

Main Methods:

• Total Internal Reflection Fluorescence Microscopy (TIRFM) for single-molecule imaging of anillin.
• High-Speed Atomic Force Microscopy (Hs-AFM) for real-time imaging of actin filament cross-linking dynamics.

Main Results:

• TIRFM revealed anillin exists as monomers with low binding affinity for actin filaments.
• Hs-AFM demonstrated anillin monomers cross-link actin filaments at an 8 nm distance.
• Anillin cross-links actin filaments with both parallel and antiparallel polarity.

Conclusions:

• Anillin's cross-linking mechanism supports its role in the actin ring transition during cytokinesis.
• Anillin may contribute to the thinning of ring-shaped apolar actin bundles in vivo.