Actin cable distribution and dynamics arising from cross-linking, motor pulling, and filament turnover.
Bottom Line: Our simulations reproduce the particular actin cable structures in myoVΔ cells and predict the effect of increased myosin V pulling.Increasing cross-linking parameters generates thicker actin cables.It also leads to antiparallel and parallel phases with straight or curved cables, consistent with observations of cells overexpressing α-actinin.
Affiliation: Department of Physics, Lehigh University, Bethlehem, PA 18015.Show MeSH
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Mentions: Figure 5A shows enlarged snapshots of cells at steady state in the strong antiparallel (left) and strong parallel (right) regimes. In the standard condition (kcrslnk = 2 pN/μm), actin filaments that grow out of the opposite tips form mostly cables with antiparallel filaments (solid arrowheads) and a few with parallel filaments (hollow arrowheads). In this condition, cross-linking is sufficiently weak to allow filaments polymerizing from opposite tips to slide past one another when they meet by end-to-end encounter or by lateral fluctuations, leading to steady cables with minor undulations (Figure 5, B and C, and Supplemental Video S4). In the high-cross-linking condition (kcrslnk = 5 pN/μm), we find mostly cables with parallel filaments and only few with antiparallel filaments. In this condition, cross-links are long lived, which induces buckling and bulging of filaments that meet by end-to-end encounter or lateral fluctuations (Figure 5, B and C, Supplemental Video S4). This results in formation of junctions at which filaments change direction to bundle in parallel (Figure 5A, c–e). The outcome of end-to-end encounters also depends on the angle of encounter, with a higher probability of parallel bundle formation for larger angle, similar to prior in vitro experiments (Reymann et al., 2010). These results further highlight how cross-linking dynamics combines with actin filament mechanics and nucleation geometry to regulate the polarity of actin filaments in bundles (Reymann et al., 2010).
Affiliation: Department of Physics, Lehigh University, Bethlehem, PA 18015.