Stochastic severing of actin filaments by ADF/cofilin controls the emergence of a steady dynamical regime. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Biophysical Journal Année : 2008

Stochastic severing of actin filaments by ADF/cofilin controls the emergence of a steady dynamical regime.

Jeremy Roland
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Julien Berro
  • Fonction : Auteur
Jean-Louis Martiel
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Résumé

Actin dynamics (ie: polymerization/depolymerization) powers a large number of cellular processes. However, a great deal remains to be learned in order to explain the rapid actin filament turnover observed in vivo. Here, we developed a minimal kinetic model that describes key details of actin filament dynamics in the presence of ADF/cofilin. We limited the molecular mechanism to (1) the spontaneous growth of filaments by polymerization of actin monomers, (2) the ageing of actin subunits in filaments, (3) the cooperative binding of ADF/cofilin to actin filament subunits, and (4) filament severing by ADF/cofilin. First, from numerical simulations and mathematical analysis, we find that the average filament length, < L >, is controlled by the concentration of actin monomers (power law: 5/6) and ADF/cofilin (power law: -2/3). We also showed that the average subunit residence time inside the filament, < T >, depends on the actin monomer (power law: -1/6) and ADF/cofilin (power law: -2/3) concentrations. In addition, filament length fluctuations are ~ 20% of the average filament length. Moreover, ADF/cofilin fragmentation while modulating filament length keeps filaments in a high molar ratio of ATP- or ADP-Pi- versus ADP-bound subunits. This latter property has a protecting effect against a too high severing activity of ADF/cofilin. We propose that the activity of ADF/cofilin in vivo is under the control of an affinity gradient that builds up dynamically along growing actin filaments. Our analysis shows that ADF/cofilin regulation maintains actin filaments in a highly dynamical state compatible with the cytoskeleton dynamics observed in vivo.

Dates et versions

hal-00198384 , version 1 (17-12-2007)

Identifiants

Citer

Jeremy Roland, Julien Berro, Alphee Michelot, Laurent Blanchoin, Jean-Louis Martiel. Stochastic severing of actin filaments by ADF/cofilin controls the emergence of a steady dynamical regime.. Biophysical Journal, 2008, 94, pp.2082-2094. ⟨10.1529/biophysj.107.121988⟩. ⟨hal-00198384⟩
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