Limits...
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.

Show MeSH

Related in: MedlinePlus

Keratocytes bind FN-coated beads preferentially at the leading edge. Ligand-coated beads were presented to different regions of the keratocyte lamella. a, Approximately 70% of FN-coated beads bound and moved rearward when presented at the leading edge of the cell. The percentage of bound beads decreased to ∼30% when the beads were presented 0.5–1.0 μm behind the leading edge. FN-coated beads placed on the leading edge, n = 43; FN-coated beads placed behind the leading edge, n = 43; BSA-coated beads, n = 40. b, Immunofluorescent labeling of a fish keratocyte stained with an antibody against the cytoplasmic region of the β1 integrin. Note the preferential localization of integrin along the leading edge of the lamella. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2168090&req=5

Figure 6: Keratocytes bind FN-coated beads preferentially at the leading edge. Ligand-coated beads were presented to different regions of the keratocyte lamella. a, Approximately 70% of FN-coated beads bound and moved rearward when presented at the leading edge of the cell. The percentage of bound beads decreased to ∼30% when the beads were presented 0.5–1.0 μm behind the leading edge. FN-coated beads placed on the leading edge, n = 43; FN-coated beads placed behind the leading edge, n = 43; BSA-coated beads, n = 40. b, Immunofluorescent labeling of a fish keratocyte stained with an antibody against the cytoplasmic region of the β1 integrin. Note the preferential localization of integrin along the leading edge of the lamella. Bar, 10 μm.

Mentions: To examine ligand binding to the dorsal surface, polystyrene beads coated with either a small fragment of FN (FNIII 7–10) or with BSA were held against the cell surface by the laser trap for three seconds and then released (Fig. 5). Most of the FN-coated beads, ∼63%, bound and started to move rearward along the cell surface. In contrast, 78% of the BSA-coated beads did not bind to the cell surface, and almost none of the bound BSA-coated beads exhibited retrograde movement. Binding of FN-coated beads was not uniform across the surface, showing preferential attachment at the leading edge of the cell. The binding and retrograde movement of FN-coated beads decreased to ∼30% when the beads were placed 0.5–1.0 μm behind the leading edge of the cell (Fig. 6 a), consistent with earlier observations on fibroblasts (Nishizaka et al. 1999).


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

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

Keratocytes bind FN-coated beads preferentially at the leading edge. Ligand-coated beads were presented to different regions of the keratocyte lamella. a, Approximately 70% of FN-coated beads bound and moved rearward when presented at the leading edge of the cell. The percentage of bound beads decreased to ∼30% when the beads were presented 0.5–1.0 μm behind the leading edge. FN-coated beads placed on the leading edge, n = 43; FN-coated beads placed behind the leading edge, n = 43; BSA-coated beads, n = 40. b, Immunofluorescent labeling of a fish keratocyte stained with an antibody against the cytoplasmic region of the β1 integrin. Note the preferential localization of integrin along the leading edge of the lamella. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Keratocytes bind FN-coated beads preferentially at the leading edge. Ligand-coated beads were presented to different regions of the keratocyte lamella. a, Approximately 70% of FN-coated beads bound and moved rearward when presented at the leading edge of the cell. The percentage of bound beads decreased to ∼30% when the beads were presented 0.5–1.0 μm behind the leading edge. FN-coated beads placed on the leading edge, n = 43; FN-coated beads placed behind the leading edge, n = 43; BSA-coated beads, n = 40. b, Immunofluorescent labeling of a fish keratocyte stained with an antibody against the cytoplasmic region of the β1 integrin. Note the preferential localization of integrin along the leading edge of the lamella. Bar, 10 μm.
Mentions: To examine ligand binding to the dorsal surface, polystyrene beads coated with either a small fragment of FN (FNIII 7–10) or with BSA were held against the cell surface by the laser trap for three seconds and then released (Fig. 5). Most of the FN-coated beads, ∼63%, bound and started to move rearward along the cell surface. In contrast, 78% of the BSA-coated beads did not bind to the cell surface, and almost none of the bound BSA-coated beads exhibited retrograde movement. Binding of FN-coated beads was not uniform across the surface, showing preferential attachment at the leading edge of the cell. The binding and retrograde movement of FN-coated beads decreased to ∼30% when the beads were placed 0.5–1.0 μm behind the leading edge of the cell (Fig. 6 a), consistent with earlier observations on fibroblasts (Nishizaka et al. 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.

Show MeSH
Related in: MedlinePlus