Reassembly of contractile actin cortex in cell blebs

Area of Science:

• Cell Biology
• Biochemistry
• Biophysics

Background:

• The contractile actin cortex is vital for cell functions like morphogenesis and movement.
• Its organization and assembly mechanisms remain incompletely understood.
• Cell blebbing involves membrane detachment and subsequent cortex reassembly for retraction.

Purpose of the Study:

• To elucidate the temporal sequence of protein recruitment during actin cortex reassembly in cell blebs.
• To investigate the dependency relationships between proteins during cortex assembly.
• To explore the role of ezrin and the Rho pathway in bleb retraction.

Main Methods:

• Utilized the cell blebbing cycle to observe and measure protein recruitment dynamics.
• Employed Cytochalasin D to investigate the role of actin polymerization.
• Assessed the impact of protein depletions or pathway inhibition on cortex assembly.

Main Results:

• Actin-free expanding blebs recruited submembranous cytoskeleton proteins.
• Upon cessation of expansion, ezrin was recruited first, followed by actin and associated proteins.
• Complete cortex assembly, forming a mesh-like structure, occurred in approximately 30 seconds.
• Cytochalasin D inhibited actin and alpha-actinin recruitment but not membrane association of ankyrin B and ezrin.
• Ezrin was essential for membrane-cortex tethering but not actin nucleation.
• The Rho pathway significantly contributed to cortex assembly in blebs.

Conclusions:

• Ezrin acts as a crucial linker between the cell membrane and the reassembling actin cortex.
• The Rho pathway is a key regulator of contractile cortex assembly during bleb retraction.
• Understanding these dynamics provides insights into fundamental cell mechanics and morphogenesis.