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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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Lamella of keratocytes generate a small rearward traction force against the micromachined substratum. Bar, 5 μm. Once the lamella of a keratocyte is over the measurement pad (t = 30 s), it generates a traction force of ∼5 nN (t = 45 s) in the direction opposite that of migration, indicated as a negative force. The direction of the force changes and the magnitude increases as the thickened region of the lamella crosses the pad (t = 50 s).
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Figure 3: Lamella of keratocytes generate a small rearward traction force against the micromachined substratum. Bar, 5 μm. Once the lamella of a keratocyte is over the measurement pad (t = 30 s), it generates a traction force of ∼5 nN (t = 45 s) in the direction opposite that of migration, indicated as a negative force. The direction of the force changes and the magnitude increases as the thickened region of the lamella crosses the pad (t = 50 s).

Mentions: With the micromachined substratum, we were able to measure traction forces in the front region of the lamella. An example of a typical experiment is shown in Fig. 3. Initially, the lamella generated a small force directed opposite to the direction of motion; this is consistent with the forward movement of lamella fragments (Euteneuer and Schliwa 1984). This force was not detectable by our measurement device until the majority of the lamella was over the pad (Fig. 3, time [t] = 30), and then the force was only two- to threefold greater than our measurement noise. The force increased in magnitude from the front of the cell toward the perinuclear region. As the perinuclear region of the cell crossed the pad (Fig. 3t = 45) the force changed direction, and it was now oriented in the direction of motion. The maximal rearward forces were ∼4.5 nN, or 0.2 nN/μm2. This was similar to the traction forces generated by fibroblast lamella (Galbraith and Sheetz 1997), and was ∼75% less than the smallest force measured with deformable substrata (Lee et al. 1994). Thus, keratocytes, like fibroblasts, pull rearward under their lamella, change traction force direction near the nucleus (Galbraith and Sheetz 1997; Dembo and Wang 1999), and pull forward under the nucleus (data not shown).


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

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

Lamella of keratocytes generate a small rearward traction force against the micromachined substratum. Bar, 5 μm. Once the lamella of a keratocyte is over the measurement pad (t = 30 s), it generates a traction force of ∼5 nN (t = 45 s) in the direction opposite that of migration, indicated as a negative force. The direction of the force changes and the magnitude increases as the thickened region of the lamella crosses the pad (t = 50 s).
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Lamella of keratocytes generate a small rearward traction force against the micromachined substratum. Bar, 5 μm. Once the lamella of a keratocyte is over the measurement pad (t = 30 s), it generates a traction force of ∼5 nN (t = 45 s) in the direction opposite that of migration, indicated as a negative force. The direction of the force changes and the magnitude increases as the thickened region of the lamella crosses the pad (t = 50 s).
Mentions: With the micromachined substratum, we were able to measure traction forces in the front region of the lamella. An example of a typical experiment is shown in Fig. 3. Initially, the lamella generated a small force directed opposite to the direction of motion; this is consistent with the forward movement of lamella fragments (Euteneuer and Schliwa 1984). This force was not detectable by our measurement device until the majority of the lamella was over the pad (Fig. 3, time [t] = 30), and then the force was only two- to threefold greater than our measurement noise. The force increased in magnitude from the front of the cell toward the perinuclear region. As the perinuclear region of the cell crossed the pad (Fig. 3t = 45) the force changed direction, and it was now oriented in the direction of motion. The maximal rearward forces were ∼4.5 nN, or 0.2 nN/μm2. This was similar to the traction forces generated by fibroblast lamella (Galbraith and Sheetz 1997), and was ∼75% less than the smallest force measured with deformable substrata (Lee et al. 1994). Thus, keratocytes, like fibroblasts, pull rearward under their lamella, change traction force direction near the nucleus (Galbraith and Sheetz 1997; Dembo and Wang 1999), and pull forward under the nucleus (data not shown).

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