Actin Waves and Dynamic Patterning of the Plasma Membrane

Area of Science:

• Cell biology
• Biophysics
• Molecular dynamics

Background:

• The plasma membrane and actin cytoskeleton form a functional unit capable of generating dynamic patterns through non-linear interactions.
• Cellular processes like motility and chemotaxis involve polarization, forming distinct protruding fronts and retracting tails.

Purpose of the Study:

• To investigate dynamic patterns formed on planar substrate surfaces, accessible via optical recording.
• To understand the molecular mechanisms underlying the interconversion of membrane and actin cortex territories driven by circular actin waves.

Main Methods:

• Observation of dynamic patterns on planar substrates using optical recording.
• Analysis of molecular markers (PIP3, Ras activity, PTEN) in distinct cellular territories.
• Investigation of actin dynamics and protein associations within the actin cortex.
• Experimental manipulation including actin depolymerization and observation of wave collisions.

Main Results:

• Circular actin waves delineate two distinct territories: an inner area with high PIP3 and Ras activity, and an outer area with PTEN.
• Actin waves are associated with myosin IB and can form under conditions of increasing or decreasing Ras activity.
• Wave collisions typically result in mutual extinction, accompanied by coronin accumulation.
• Pattern generation is dependent on the presence of residual actin filaments.

Conclusions:

• The interplay between the plasma membrane and actin cortex generates dynamic patterns essential for cellular functions.
• Findings in Dictyostelium provide insights into human cell behaviors, including macropinocytosis, tumor suppressor mutations (PTEN), frustrated phagocytosis, and the role of coronin in immune cells and neurons.