The elementary events underlying force generation in neuronal lamellipodia

Area of Science:

• Cell Biology
• Biophysics
• Neuroscience

Background:

• Neuronal lamellipodia are crucial for cell migration and neurite outgrowth.
• Understanding the molecular mechanisms of force generation in lamellipodia is essential for neuroscience and cell biology.
• Previous studies have suggested complex actin-myosin interactions, but elementary events remain elusive.

Purpose of the Study:

• To identify and characterize the elementary events responsible for force generation in neuronal lamellipodia.
• To investigate the roles of actin dynamics and myosin II in these elementary force-generating events.

Main Methods:

• Utilized optical tweezers to trap beads on the lamellipodium membrane.
• Analyzed Brownian fluctuations and bead velocities to detect elementary events.
• Investigated the effects of Jasplakinolide (inhibiting actin turnover) and Blebbistatin (inhibiting myosin II) on force generation.

Main Results:

• Observed distinct, discrete jumps (elementary events) in bead velocity with amplitudes up to 20 nm and durations of 0.1-0.2 ms.
• Reduced jump frequency and amplitude upon inhibiting actin turnover with Jasplakinolide.
• Observed a reduction in jump frequency, but less pronounced than with Jasplakinolide, when inhibiting myosin II with Blebbistatin.
• These jumps represent the fundamental units of force generation.

Conclusions:

• Identified discrete molecular events, characterized by rapid jumps, as the elementary units of force generation in neuronal lamellipodia.
• Demonstrated that both actin turnover and myosin II activity contribute to these force-generating events.
• Provided new insights into the biophysical mechanisms underlying neuronal cell motility and development.