Structure and dynamics of actin filament solutions in the presence of latrunculin A

Abstract

We study the polymerization kinetics and linear rheology of actin filaments in the absence and in the presence of latrunculin A. Filamentous actin is a semiflexible polymer, and latrunculin A is an organic, actin-binding molecule. Using diffusing wave spectroscopy (DWS), we monitor the thermally excited motion of monodisperse polystyrene microspheres in semidilute solutions of actin filaments. From these measurements, we extract the microspheres mean-square displacement, which is related to the viscoelastic nature of the actin solutions. These optical measurements, along with mechanical measurements, suggest that despite its depolymerizing effect, latrunculin A promotes the strengthening of actin networks. DWS shows that while the scaling nature of the viscoelastic properties of actin filaments is essentially unmodified in the presence of latrunculin A at small time scales, the elasticity of actin solutions becomes enhanced for increasing latrunculin concentrations at large time scales. Complementary electron-microscopy measurements help uncover the structural origin of this enhanced elasticity at small time scales.

Live cell imaging: a computational perspective

“…The other common analyses include modeling of cell motion using techniques of correlated random walks (Alt 1980; Dunn and Brown 1987; Shenderov and Sheetz 1997). Typically, once motion analysis is performed, averaged mean-square displacements (MSD) can be computed Palmer [59,60,97], from which time-lag-dependent MSD distributions were generated. These distributions could be normalized by the timelag-averaged, ensemble-averaged MSD, and subsequently analyzed by computing median, standard deviation, and skewness, statistical parameters that describe the heterogeneity of the networks.…”

Live cell imaging: a computational perspective

“…The other common analyses include modeling of cell motion using techniques of correlated random walks (Alt 1980; Dunn and Brown 1987; Shenderov and Sheetz 1997). Typically, once motion analysis is performed, averaged mean-square displacements (MSD) can be computed Palmer [59,60,97], from which time-lag-dependent MSD distributions were generated. These distributions could be normalized by the timelag-averaged, ensemble-averaged MSD, and subsequently analyzed by computing median, standard deviation, and skewness, statistical parameters that describe the heterogeneity of the networks.…”

Micromechanics and ultrastructure of actin filament networks crosslinked by human fascin: A comparison with α-actinin

“…64,65 Fascin also localizes in the lamellipodia of adherent cells; using laser-de¯ection particle-tracking microrheology, we recently found that the cytoskeleton of the lamellipodia of COS7 cells exhibited an elasticity of G H 820(AE520) dyne/cm 2 (at 1 rad/ second). 30 That study also showed that polymerized actin is necessary, but not suf®cient, to generate these levels of elasticity as cells treated with the actin-depolymerizing drug latrunculin A 66 and reconstituted F-actin networks 29 both exhibited much lower elasticity. Therefore, the formation and stabilization of lamellipodia requires the action of structural proteins that organize F-actin into assemblies compatible with the large stresses associated with these cellular structures.…”

An endothelial cell model containing cytoskeletal components: Suspension and adherent states

“…Actins are about 5 -8 nm in diameter with an elastic modulus of 2.2 GPa. These elements sustain extension of mechanical forces [12,13]. In microtubules α-and βtubulin creates a tube like link with a natural resistance to both compression and torsion.…”

“…The amounts of cross section and Young module used in this work are shown in Table 1. These values are obtained by considering the following references: [11][12][13]15].…”

Live cell imaging: a computational perspective

“…The other common analyses include modeling of cell motion using techniques of correlated random walks (Alt 1980; Dunn and Brown 1987; Shenderov and Sheetz 1997). Typically, once motion analysis is performed, averaged mean-square displacements (MSD) can be computed Palmer [59,60,97], from which time-lag-dependent MSD distributions were generated. These distributions could be normalized by the timelag-averaged, ensemble-averaged MSD, and subsequently analyzed by computing median, standard deviation, and skewness, statistical parameters that describe the heterogeneity of the networks.…”

Micromechanics and ultrastructure of actin filament networks crosslinked by human fascin: A comparison with α-actinin

“…64,65 Fascin also localizes in the lamellipodia of adherent cells; using laser-de¯ection particle-tracking microrheology, we recently found that the cytoskeleton of the lamellipodia of COS7 cells exhibited an elasticity of G H 820(AE520) dyne/cm 2 (at 1 rad/ second). 30 That study also showed that polymerized actin is necessary, but not suf®cient, to generate these levels of elasticity as cells treated with the actin-depolymerizing drug latrunculin A 66 and reconstituted F-actin networks 29 both exhibited much lower elasticity. Therefore, the formation and stabilization of lamellipodia requires the action of structural proteins that organize F-actin into assemblies compatible with the large stresses associated with these cellular structures.…”

An endothelial cell model containing cytoskeletal components: Suspension and adherent states

“…Actins are about 5 -8 nm in diameter with an elastic modulus of 2.2 GPa. These elements sustain extension of mechanical forces [12,13]. In microtubules α-and βtubulin creates a tube like link with a natural resistance to both compression and torsion.…”

“…The amounts of cross section and Young module used in this work are shown in Table 1. These values are obtained by considering the following references: [11][12][13]15].…”

Live cell imaging: a computational perspective

“…The other common analyses include modeling of cell motion using techniques of correlated random walks (Alt 1980; Dunn and Brown 1987; Shenderov and Sheetz 1997). Typically, once motion analysis is performed, averaged mean-square displacements (MSD) can be computed Palmer [59,60,97], from which time-lag-dependent MSD distributions were generated. These distributions could be normalized by the timelag-averaged, ensemble-averaged MSD, and subsequently analyzed by computing median, standard deviation, and skewness, statistical parameters that describe the heterogeneity of the networks.…”

Micromechanics and ultrastructure of actin filament networks crosslinked by human fascin: A comparison with α-actinin

“…64,65 Fascin also localizes in the lamellipodia of adherent cells; using laser-de¯ection particle-tracking microrheology, we recently found that the cytoskeleton of the lamellipodia of COS7 cells exhibited an elasticity of G H 820(AE520) dyne/cm 2 (at 1 rad/ second). 30 That study also showed that polymerized actin is necessary, but not suf®cient, to generate these levels of elasticity as cells treated with the actin-depolymerizing drug latrunculin A 66 and reconstituted F-actin networks 29 both exhibited much lower elasticity. Therefore, the formation and stabilization of lamellipodia requires the action of structural proteins that organize F-actin into assemblies compatible with the large stresses associated with these cellular structures.…”

An endothelial cell model containing cytoskeletal components: Suspension and adherent states

“…Actins are about 5 -8 nm in diameter with an elastic modulus of 2.2 GPa. These elements sustain extension of mechanical forces [12,13]. In microtubules α-and βtubulin creates a tube like link with a natural resistance to both compression and torsion.…”

“…The amounts of cross section and Young module used in this work are shown in Table 1. These values are obtained by considering the following references: [11][12][13]15].…”