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: In our simulations, the kinetics of cross-link formation and breakage are described by two parameters: cross-linking range, rcrslnk, and spring constant, kcrslnk, which determines the depth of the interaction potential between cross-linked filament beads (for given rcrslnk). These parameters determine the rates of cross-link formation/breakage and reflect the type and concentration of cross-linker proteins in cells, with larger values representing stronger cross-linking. The simulated actin cable configurations at steady state vary depending on the values of rcrslnk and kcrslnk (Figure 4A and Supplemental Videos S2 and S3). We found that larger rcrslnk and kcrslnk promote actin filament bundling (Figure 4B). At kcrslnk = 2 pN/μm, the standard parameter, the actin filament bundled percentage increases from 2 to 77% as rcrslnk changes from 0.06 to 0.11 μm (Figure 4B). Conversely, the bundled percentage increases from 4 to 74% as kcrslnk increases from 0.1 to 5.0 pN/μm when rcrslnk = 0.09 μm (Figure 4B). Similar trends to Figure 4B are observed when measuring the number of filaments in the largest linked cable (Supplemental Figure S4A). Moreover, we show that rcrslnk and kcrslnk together regulate the number of cables (Figure 4C). For a given rcrslnk, there exists a k*crslnk value giving the maximum number of cables (the cables at the peak value have average three to six filaments each; see Supplemental Figure S4B). For kcrslnk < k*crslnk, the system has mostly unbundled filaments, and so the number of cables increases with increasing rcrslnk. For kcrslnk > k*crslnk, most filaments become bundled. In this range, the dependence of the number of cables on kcrslnk and rcrslnk is weak, reflecting the maximum filament bundling that can be achieved within the filament turnover time with the given geometry and polymerization rate.
Affiliation: Department of Physics, Lehigh University, Bethlehem, PA 18015.