High-speed depolymerization at actin filament ends jointly catalysed by Twinfilin and Srv2/CAP

Area of Science:

• Cell Biology
• Biochemistry

Background:

• Cytosolic conditions favor actin assembly, making rapid actin filament turnover in vivo poorly understood.
• Actin filament severing by factors like Cofilin is insufficient to explain observed depolymerization rates.

Purpose of the Study:

• To elucidate the mechanism by which Twinfilin and Cyclase-associated protein accelerate actin filament depolymerization.
• To investigate the in vivo relevance of this accelerated depolymerization mechanism.

Main Methods:

• Reconstitution and direct visualization of individual actin filaments.
• In vivo studies using specific mutations in Twinfilin.

Main Results:

• Twinfilin and Cyclase-associated protein accelerate barbed-end depolymerization by 3-fold and pointed-end depolymerization by 17-fold.
• This accelerated depolymerization occurs under assembly-favoring conditions.
• Mutations affecting this activity demonstrate its in vivo importance for Twinfilin function.

Conclusions:

• Twinfilin and Cyclase-associated protein provide a mechanism for rapid actin filament disassembly, even under assembly conditions.
• This finding addresses a significant gap in understanding cellular actin disassembly.
• The study suggests separate or combined deployment of depolymerization and severing to control actin network dynamics.