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Keratocytes pull with similar forces on their dorsal and ventral surfaces.

Galbraith CG, Sheetz MP - J. Cell Biol. (1999)

Bottom Line: Borisy. 1997.Cell Biol. 139:397-415).Similar forces were generated on both the ventral (0.2 nN/microm(2)) and the dorsal (0.4 nN/microm(2)) surfaces of the lamella, suggesting that dorsal matrix contacts are as effectively linked to the force-generating cytoskeleton as ventral contacts.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.

ABSTRACT
As cells move forward, they pull rearward against extracellular matrices (ECMs), exerting traction forces. However, no rearward forces have been seen in the fish keratocyte. To address this discrepancy, we have measured the propulsive forces generated by the keratocyte lamella on both the ventral and the dorsal surfaces. On the ventral surface, a micromachined device revealed that traction forces were small and rearward directed under the lamella, changed direction in front of the nucleus, and became larger under the cell body. On the dorsal surface of the lamella, an optical gradient trap measured rearward forces generated against fibronectin-coated beads. The retrograde force exerted by the cell on the bead increased in the thickened region of the lamella where myosin condensation has been observed (Svitkina, T.M., A.B. Verkhovsky, K.M. McQuade, and G. G. Borisy. 1997. J. Cell Biol. 139:397-415). Similar forces were generated on both the ventral (0.2 nN/microm(2)) and the dorsal (0.4 nN/microm(2)) surfaces of the lamella, suggesting that dorsal matrix contacts are as effectively linked to the force-generating cytoskeleton as ventral contacts. The correlation between the level of traction force and the density of myosin suggests a model for keratocyte movement in which myosin condensation in the perinuclear region generates rearward forces in the lamella and forward forces in the cell rear.

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Density of F-actin in the keratocyte lamella. a, A line intensity histogram of a phalloidin-labeled keratocyte shows that the density of the F-actin network decreases away from the leading edge. The density increases again to ∼75% of its maximal value in the perinuclear region. b, Oregon green phalloidin-labeled keratocyte. Bar, 10 μm.
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Figure 9: Density of F-actin in the keratocyte lamella. a, A line intensity histogram of a phalloidin-labeled keratocyte shows that the density of the F-actin network decreases away from the leading edge. The density increases again to ∼75% of its maximal value in the perinuclear region. b, Oregon green phalloidin-labeled keratocyte. Bar, 10 μm.

Mentions: To determine if this positional reinforcement could be due to an increase in cytoskeletal density rather than an enhancement of the linkage, keratocytes were labeled with Oregon green phalloidin, and the intensity of fluorescence from the leading edge to the perinuclear region was determined (Fig. 9). Similar to the results shown by others (Small et al. 1995), we observed a decrease in fluorescence between the front and the perinuclear region of the lamella, with the fluorescence intensity in the perinuclear region being ∼75% of the intensity at the leading edge. Since we were able to recapture beads located above the region where the actin cytoskeleton is the densest, the positional reinforcement is probably not completely due to entanglement with the underlying cytoskeleton, but rather an enhanced integrin–cytoskeletal linkage.


Keratocytes pull with similar forces on their dorsal and ventral surfaces.

Galbraith CG, Sheetz MP - J. Cell Biol. (1999)

Density of F-actin in the keratocyte lamella. a, A line intensity histogram of a phalloidin-labeled keratocyte shows that the density of the F-actin network decreases away from the leading edge. The density increases again to ∼75% of its maximal value in the perinuclear region. b, Oregon green phalloidin-labeled keratocyte. Bar, 10 μm.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2168090&req=5

Figure 9: Density of F-actin in the keratocyte lamella. a, A line intensity histogram of a phalloidin-labeled keratocyte shows that the density of the F-actin network decreases away from the leading edge. The density increases again to ∼75% of its maximal value in the perinuclear region. b, Oregon green phalloidin-labeled keratocyte. Bar, 10 μm.
Mentions: To determine if this positional reinforcement could be due to an increase in cytoskeletal density rather than an enhancement of the linkage, keratocytes were labeled with Oregon green phalloidin, and the intensity of fluorescence from the leading edge to the perinuclear region was determined (Fig. 9). Similar to the results shown by others (Small et al. 1995), we observed a decrease in fluorescence between the front and the perinuclear region of the lamella, with the fluorescence intensity in the perinuclear region being ∼75% of the intensity at the leading edge. Since we were able to recapture beads located above the region where the actin cytoskeleton is the densest, the positional reinforcement is probably not completely due to entanglement with the underlying cytoskeleton, but rather an enhanced integrin–cytoskeletal linkage.

Bottom Line: Borisy. 1997.Cell Biol. 139:397-415).Similar forces were generated on both the ventral (0.2 nN/microm(2)) and the dorsal (0.4 nN/microm(2)) surfaces of the lamella, suggesting that dorsal matrix contacts are as effectively linked to the force-generating cytoskeleton as ventral contacts.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.

ABSTRACT
As cells move forward, they pull rearward against extracellular matrices (ECMs), exerting traction forces. However, no rearward forces have been seen in the fish keratocyte. To address this discrepancy, we have measured the propulsive forces generated by the keratocyte lamella on both the ventral and the dorsal surfaces. On the ventral surface, a micromachined device revealed that traction forces were small and rearward directed under the lamella, changed direction in front of the nucleus, and became larger under the cell body. On the dorsal surface of the lamella, an optical gradient trap measured rearward forces generated against fibronectin-coated beads. The retrograde force exerted by the cell on the bead increased in the thickened region of the lamella where myosin condensation has been observed (Svitkina, T.M., A.B. Verkhovsky, K.M. McQuade, and G. G. Borisy. 1997. J. Cell Biol. 139:397-415). Similar forces were generated on both the ventral (0.2 nN/microm(2)) and the dorsal (0.4 nN/microm(2)) surfaces of the lamella, suggesting that dorsal matrix contacts are as effectively linked to the force-generating cytoskeleton as ventral contacts. The correlation between the level of traction force and the density of myosin suggests a model for keratocyte movement in which myosin condensation in the perinuclear region generates rearward forces in the lamella and forward forces in the cell rear.

Show MeSH
Related in: MedlinePlus