Open AccessPulling-force generation by ensembles of polymerizing actin filaments
Author(s) -
Fowad Motahari,
Anders Carlsson
Publication year - 2019
Publication title -
physical biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.137
H-Index - 68
eISSN - 1478-3975
pISSN - 1478-3967
DOI - 10.1088/1478-3975/ab59bd
Subject(s) - protein filament , polymerization , membrane , actin , flexural rigidity , rigidity (electromagnetism) , chemistry , elasticity (physics) , biophysics , materials science , chemical physics , polymer , composite material , biochemistry , biology
The process by which actin polymerization generates pulling forces in cellular processes such as endocytosis is less well understood than pushing-force generation. To clarify the basic mechanisms of pulling-force generation, we perform stochastic polymerization simulations for a square array of polymerizing semiflexible actin filaments, having different interactions with the membrane. The filaments near the array center have a strong attractive component. Filament bending and actin-network elasticity are treated explicitly. We find that the outer filaments push on the membrane and the inner filaments pull, with a net balance of forces. The total calculated pulling force is maximized when the central filaments have a very deep potential well, and the outer filaments have no well. The steady-state force is unaffected by the gel rigidity, but equilibration takes longer for softer gels. The force distributions are flat over the pulling and pushing regions. Actin polymerization is enhanced by softening the gel or reducing the filament binding to the membrane. Filament-membrane detachment can occur for softer gels, even if the total binding energy of the filaments to the membrane is 100 or more. It propagates via a stress-concentration mechanism similar to that of a brittle crack in a solid, and the breaking stress is determined by a criterion similar to that of the ‘Griffith’ theory of crack propagation.