Dendritic nucleation model

This is a model for molecular mechanisms contolling actin filament dynamics in nonmuscle cells (Fig. CM11B)."/>
Fig. CM11B. The dendritic nucleation model (From Pollard et al., with permission from the Annual Review of Biphysics and Biomolecular Sructure. vol. 29, 2000, by Annual Reviews,

There are 10 steps in the figure. In the first step all the ATP-actin monomers are bound to profilin, there are no free barbed ends; the actin cytoskeletal components are held in a metastable state, poised for assembly. Activation of WASp family proteins (Step 2) leads to activation of the Arp2/3 complex and this creates new barbed ends and subsequently new filaments (Step 3). These filaments grow rapidly (Step 4) and push the membrane forward (Step 5). After a short while, growth of the barbed ends is terminated by capping (Step 6). ATP hydrolysis and Pi dissociation (Step 7) triggers severing and depolymerization of actin filaments by ADF/cofilins (Step 8). LIM kinase inhibits ADF/cofilins (Step 9). Nucleotide exchange catalyzed by profilin recycles ADP-actin to ATP-actin monomer in the pool (Step 10).

Accordingly, the molecular mechanism of motion in nonmuscle cells is a very complex cycle that converts the energy of the hydrolysis of actin-bound ATP into mechanical force through the polymerization and depolymerization of actin filaments ( treadmilling of actin filaments). In a continuously moving cell, assembly and dysassembly of actin filaments are balanced.

Reviews of Pollard et al. (2000), Higgs and Pollard (2001), and Pantaloni et al. (2001) are recommended for a further understanding of the molecular mechanism of motion in nonmuscle cells.

Was this article helpful?

0 0

Post a comment