Myosin II Filament Dynamics in Actin Networks Revealed with Interferometric Scattering Microscopy

Area of Science:

• Cell Biology
• Biophysics
• Molecular Motors

Background:

• The plasma membrane and cytoskeletal cortex are crucial for cellular functions.
• Acto-myosin network remodeling influences membrane organization, but molecular mechanisms remain unclear due to experimental limitations.

Purpose of the Study:

• To investigate the dynamics of a minimal acto-myosin network interacting with a lipid bilayer membrane.
• To elucidate the role of ATP concentration in acto-myosin network behavior and membrane organization.

Main Methods:

• Utilized interferometric scattering microscopy to image individual actin and myosin II filaments.
• Measured molecular mass via interferometric contrast and tracked filament dynamics at fast acquisition rates.
• Quantified myosin II filament dwell times and processivity as a function of ATP concentration.

Main Results:

• Successfully detected and imaged individual membrane-associated actin filaments and myosin II filaments.
• Provided experimental evidence for predicted myosin head domain ensemble behavior.
• Demonstrated that reduced ATP concentration increases myosin II filament dwell times and promotes a transition from network remodeling to contraction.

Conclusions:

• ATP concentration is a critical regulator of acto-myosin network dynamics at the cell membrane.
• Myosin II filament behavior, including dwell time and processivity, is directly influenced by ATP levels.
• The findings offer molecular insights into how acto-myosin networks control membrane organization and cellular processes.