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Actin cable distribution and dynamics arising from cross-linking, motor pulling, and filament turnover.

Tang H, Laporte D, Vavylonis D - Mol. Biol. Cell (2014)

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.

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Affiliation: Department of Physics, Lehigh University, Bethlehem, PA 18015.

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Actin cable morphology changes due to increasing Ain1p concentration in live cells. (A) Fluorescence microscopy shows GFP-CHD–labeled actin of both wild-type and 3nmt1Ain1 fission yeasts. CK666 is added to the cells to depolymerize actin patches (bottom). (B) Measurement of cable number in different cells. (C) Measurement of lateral cable movement per frame, 8 s for WT and 10 s for other cases (see Supplemental Figure S5). In B and C, black square dot indicates average value; boxes contain 50% of data; whiskers, 1.5 interquartile range. (D) Curvature of the actin cables in different cells. (E) Loop occurrence in difference cells. For non–CK666-treated cells, loops occur rarely and last 16–50 s before disappearing. For CK666-treated cells, loops are stable and last >80 s. (F) Predominant cable curvature as function of cross-linking range and spring constant (n = 3 simulations/square). Symbols show one possible mapping of simulation parameters to experiments (*WT; **3nmt1Ain1; †WT+CK666; ††3nmt1Ain1+CK666). Cables cannot be clearly distinguished in the blank area. (G) Cable curvature distribution for the corresponding parameter sets of F (n = 8 per parameter set) matches experiments of D. (H) Loop occurrences as a function of cross-linking range and spring constant for the same simulations as in F.
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Figure 6: Actin cable morphology changes due to increasing Ain1p concentration in live cells. (A) Fluorescence microscopy shows GFP-CHD–labeled actin of both wild-type and 3nmt1Ain1 fission yeasts. CK666 is added to the cells to depolymerize actin patches (bottom). (B) Measurement of cable number in different cells. (C) Measurement of lateral cable movement per frame, 8 s for WT and 10 s for other cases (see Supplemental Figure S5). In B and C, black square dot indicates average value; boxes contain 50% of data; whiskers, 1.5 interquartile range. (D) Curvature of the actin cables in different cells. (E) Loop occurrence in difference cells. For non–CK666-treated cells, loops occur rarely and last 16–50 s before disappearing. For CK666-treated cells, loops are stable and last >80 s. (F) Predominant cable curvature as function of cross-linking range and spring constant (n = 3 simulations/square). Symbols show one possible mapping of simulation parameters to experiments (*WT; **3nmt1Ain1; †WT+CK666; ††3nmt1Ain1+CK666). Cables cannot be clearly distinguished in the blank area. (G) Cable curvature distribution for the corresponding parameter sets of F (n = 8 per parameter set) matches experiments of D. (H) Loop occurrences as a function of cross-linking range and spring constant for the same simulations as in F.

Mentions: To further investigate the predicted effect of cross-linkers, we analyzed actin cables in wild-type cells and cells overexpressing α-actinin, using the 3nmt1Ain1 promoter (Figure 6A). We chose α-actinin because the effect of overexpression of the other cross-linker in fission yeast, fimbrin, is very drastic, with overexpression mutants having significantly modified cable morphologies (Wu et al., 2001; Laporte et al., 2012; Burke et al., 2014; see also Discussion). To better visualize actin cables, we also treated cells with CK666, an inhibitor of the Arp2/3 complex that depolymerizes actin patches (Nolen et al., 2009). This treatment causes an increase in the amount of actin in the cables, which also become longer and more curved (Burke et al., 2014). Treatment by CK666 may also release fimbrin from actin patches, resulting in an increase in cable cross-linking (Burke et al., 2014).


Actin cable distribution and dynamics arising from cross-linking, motor pulling, and filament turnover.

Tang H, Laporte D, Vavylonis D - Mol. Biol. Cell (2014)

Actin cable morphology changes due to increasing Ain1p concentration in live cells. (A) Fluorescence microscopy shows GFP-CHD–labeled actin of both wild-type and 3nmt1Ain1 fission yeasts. CK666 is added to the cells to depolymerize actin patches (bottom). (B) Measurement of cable number in different cells. (C) Measurement of lateral cable movement per frame, 8 s for WT and 10 s for other cases (see Supplemental Figure S5). In B and C, black square dot indicates average value; boxes contain 50% of data; whiskers, 1.5 interquartile range. (D) Curvature of the actin cables in different cells. (E) Loop occurrence in difference cells. For non–CK666-treated cells, loops occur rarely and last 16–50 s before disappearing. For CK666-treated cells, loops are stable and last >80 s. (F) Predominant cable curvature as function of cross-linking range and spring constant (n = 3 simulations/square). Symbols show one possible mapping of simulation parameters to experiments (*WT; **3nmt1Ain1; †WT+CK666; ††3nmt1Ain1+CK666). Cables cannot be clearly distinguished in the blank area. (G) Cable curvature distribution for the corresponding parameter sets of F (n = 8 per parameter set) matches experiments of D. (H) Loop occurrences as a function of cross-linking range and spring constant for the same simulations as in F.
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Figure 6: Actin cable morphology changes due to increasing Ain1p concentration in live cells. (A) Fluorescence microscopy shows GFP-CHD–labeled actin of both wild-type and 3nmt1Ain1 fission yeasts. CK666 is added to the cells to depolymerize actin patches (bottom). (B) Measurement of cable number in different cells. (C) Measurement of lateral cable movement per frame, 8 s for WT and 10 s for other cases (see Supplemental Figure S5). In B and C, black square dot indicates average value; boxes contain 50% of data; whiskers, 1.5 interquartile range. (D) Curvature of the actin cables in different cells. (E) Loop occurrence in difference cells. For non–CK666-treated cells, loops occur rarely and last 16–50 s before disappearing. For CK666-treated cells, loops are stable and last >80 s. (F) Predominant cable curvature as function of cross-linking range and spring constant (n = 3 simulations/square). Symbols show one possible mapping of simulation parameters to experiments (*WT; **3nmt1Ain1; †WT+CK666; ††3nmt1Ain1+CK666). Cables cannot be clearly distinguished in the blank area. (G) Cable curvature distribution for the corresponding parameter sets of F (n = 8 per parameter set) matches experiments of D. (H) Loop occurrences as a function of cross-linking range and spring constant for the same simulations as in F.
Mentions: To further investigate the predicted effect of cross-linkers, we analyzed actin cables in wild-type cells and cells overexpressing α-actinin, using the 3nmt1Ain1 promoter (Figure 6A). We chose α-actinin because the effect of overexpression of the other cross-linker in fission yeast, fimbrin, is very drastic, with overexpression mutants having significantly modified cable morphologies (Wu et al., 2001; Laporte et al., 2012; Burke et al., 2014; see also Discussion). To better visualize actin cables, we also treated cells with CK666, an inhibitor of the Arp2/3 complex that depolymerizes actin patches (Nolen et al., 2009). This treatment causes an increase in the amount of actin in the cables, which also become longer and more curved (Burke et al., 2014). Treatment by CK666 may also release fimbrin from actin patches, resulting in an increase in cable cross-linking (Burke et al., 2014).

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.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Lehigh University, Bethlehem, PA 18015.

Show MeSH
Related in: MedlinePlus