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A Rac switch regulates random versus directionally persistent cell migration.

Pankov R, Endo Y, Even-Ram S, Araki M, Clark K, Cukierman E, Matsumoto K, Yamada KM - J. Cell Biol. (2005)

Bottom Line: In three-dimensional rather than traditional two-dimensional cell culture, cells had a lower level of Rac activity that was associated with rapid, directional migration.In contrast to the directed migration of chemotaxis, this intrinsic directional persistence of migration was not mediated by phosphatidylinositol 3'-kinase lipid signaling.Total Rac1 activity can therefore provide a regulatory switch between patterns of cell migration by a mechanism distinct from chemotaxis.

View Article: PubMed Central - PubMed

Affiliation: Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.

ABSTRACT
Directional migration moves cells rapidly between points, whereas random migration allows cells to explore their local environments. We describe a Rac1 mechanism for determining whether cell patterns of migration are intrinsically random or directionally persistent. Rac activity promoted the formation of peripheral lamellae that mediated random migration. Decreasing Rac activity suppressed peripheral lamellae and switched the cell migration patterns of fibroblasts and epithelial cells from random to directionally persistent. In three-dimensional rather than traditional two-dimensional cell culture, cells had a lower level of Rac activity that was associated with rapid, directional migration. In contrast to the directed migration of chemotaxis, this intrinsic directional persistence of migration was not mediated by phosphatidylinositol 3'-kinase lipid signaling. Total Rac1 activity can therefore provide a regulatory switch between patterns of cell migration by a mechanism distinct from chemotaxis.

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Four stages of Rac-GTP regulation of cell morphology and types of cell motility. The amount of Rac localized in lamellae as shown by anti-Rac1 antibody localization (left) and depicted schematically in the diagram (red) with increasing levels of Rac activation (broad gray arrow) from state I to state IV. Increased levels of total cellular active Rac produce characteristic increases in the extent of random cell motility accompanied by varying velocities of cell migration in 2D versus 3D culture or after experimental manipulations of Rac activity. Rac activation that is too low or too high leads to immobilization, with stunted lamellae at low levels and continuous, circumferential lamellae or cell rounding at very high levels (Discussion). The cells shown in the examples were primary human fibroblasts stained for Rac1 after culturing on a 2D substrate (state III) or in a 3D matrix (state II) compared with effects of extensive knockdown of Rac1 using 200 nM Rac siRNA (state I) or overexpression of constitutively activated Rac QL after transient transfection (state IV).
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fig8: Four stages of Rac-GTP regulation of cell morphology and types of cell motility. The amount of Rac localized in lamellae as shown by anti-Rac1 antibody localization (left) and depicted schematically in the diagram (red) with increasing levels of Rac activation (broad gray arrow) from state I to state IV. Increased levels of total cellular active Rac produce characteristic increases in the extent of random cell motility accompanied by varying velocities of cell migration in 2D versus 3D culture or after experimental manipulations of Rac activity. Rac activation that is too low or too high leads to immobilization, with stunted lamellae at low levels and continuous, circumferential lamellae or cell rounding at very high levels (Discussion). The cells shown in the examples were primary human fibroblasts stained for Rac1 after culturing on a 2D substrate (state III) or in a 3D matrix (state II) compared with effects of extensive knockdown of Rac1 using 200 nM Rac siRNA (state I) or overexpression of constitutively activated Rac QL after transient transfection (state IV).

Mentions: As depicted in Fig. 8, we suggest that there may be at least four distinct levels of Rac activity differentially regulating the speed and pattern of intrinsic cell migration. As described by others (e.g., Glogauer et al., 2003), very low levels of active Rac result in immobilization of the cells (Fig. 8, state I). Naturally occurring levels of active Rac higher than this extreme state, but still ∼30–50% lower than in cells cultured on a 2D fibronectin substrate, were found in fibroblasts grown in 3D (Fig. 8, state II). Under these conditions, cells retained a spindle-shaped morphology, but developed a stable, single lamella in the direction of migration containing membrane-localized Rac1. These state II cells demonstrated both the highest directionality and highest velocity of migration. We suggest that this condition would be ideal for cell migration in vivo; e.g., during neural crest and myoblast cell migration in embryonic development. Elevation of Rac levels by extrinsic or intrinsic factors could disrupt these processes. In addition, our finding that chemotaxis can be stimulated by a moderate reduction in Rac suggests that the specific level of overall Rac activation may also influence chemotactic efficiency in vivo.


A Rac switch regulates random versus directionally persistent cell migration.

Pankov R, Endo Y, Even-Ram S, Araki M, Clark K, Cukierman E, Matsumoto K, Yamada KM - J. Cell Biol. (2005)

Four stages of Rac-GTP regulation of cell morphology and types of cell motility. The amount of Rac localized in lamellae as shown by anti-Rac1 antibody localization (left) and depicted schematically in the diagram (red) with increasing levels of Rac activation (broad gray arrow) from state I to state IV. Increased levels of total cellular active Rac produce characteristic increases in the extent of random cell motility accompanied by varying velocities of cell migration in 2D versus 3D culture or after experimental manipulations of Rac activity. Rac activation that is too low or too high leads to immobilization, with stunted lamellae at low levels and continuous, circumferential lamellae or cell rounding at very high levels (Discussion). The cells shown in the examples were primary human fibroblasts stained for Rac1 after culturing on a 2D substrate (state III) or in a 3D matrix (state II) compared with effects of extensive knockdown of Rac1 using 200 nM Rac siRNA (state I) or overexpression of constitutively activated Rac QL after transient transfection (state IV).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171343&req=5

fig8: Four stages of Rac-GTP regulation of cell morphology and types of cell motility. The amount of Rac localized in lamellae as shown by anti-Rac1 antibody localization (left) and depicted schematically in the diagram (red) with increasing levels of Rac activation (broad gray arrow) from state I to state IV. Increased levels of total cellular active Rac produce characteristic increases in the extent of random cell motility accompanied by varying velocities of cell migration in 2D versus 3D culture or after experimental manipulations of Rac activity. Rac activation that is too low or too high leads to immobilization, with stunted lamellae at low levels and continuous, circumferential lamellae or cell rounding at very high levels (Discussion). The cells shown in the examples were primary human fibroblasts stained for Rac1 after culturing on a 2D substrate (state III) or in a 3D matrix (state II) compared with effects of extensive knockdown of Rac1 using 200 nM Rac siRNA (state I) or overexpression of constitutively activated Rac QL after transient transfection (state IV).
Mentions: As depicted in Fig. 8, we suggest that there may be at least four distinct levels of Rac activity differentially regulating the speed and pattern of intrinsic cell migration. As described by others (e.g., Glogauer et al., 2003), very low levels of active Rac result in immobilization of the cells (Fig. 8, state I). Naturally occurring levels of active Rac higher than this extreme state, but still ∼30–50% lower than in cells cultured on a 2D fibronectin substrate, were found in fibroblasts grown in 3D (Fig. 8, state II). Under these conditions, cells retained a spindle-shaped morphology, but developed a stable, single lamella in the direction of migration containing membrane-localized Rac1. These state II cells demonstrated both the highest directionality and highest velocity of migration. We suggest that this condition would be ideal for cell migration in vivo; e.g., during neural crest and myoblast cell migration in embryonic development. Elevation of Rac levels by extrinsic or intrinsic factors could disrupt these processes. In addition, our finding that chemotaxis can be stimulated by a moderate reduction in Rac suggests that the specific level of overall Rac activation may also influence chemotactic efficiency in vivo.

Bottom Line: In three-dimensional rather than traditional two-dimensional cell culture, cells had a lower level of Rac activity that was associated with rapid, directional migration.In contrast to the directed migration of chemotaxis, this intrinsic directional persistence of migration was not mediated by phosphatidylinositol 3'-kinase lipid signaling.Total Rac1 activity can therefore provide a regulatory switch between patterns of cell migration by a mechanism distinct from chemotaxis.

View Article: PubMed Central - PubMed

Affiliation: Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.

ABSTRACT
Directional migration moves cells rapidly between points, whereas random migration allows cells to explore their local environments. We describe a Rac1 mechanism for determining whether cell patterns of migration are intrinsically random or directionally persistent. Rac activity promoted the formation of peripheral lamellae that mediated random migration. Decreasing Rac activity suppressed peripheral lamellae and switched the cell migration patterns of fibroblasts and epithelial cells from random to directionally persistent. In three-dimensional rather than traditional two-dimensional cell culture, cells had a lower level of Rac activity that was associated with rapid, directional migration. In contrast to the directed migration of chemotaxis, this intrinsic directional persistence of migration was not mediated by phosphatidylinositol 3'-kinase lipid signaling. Total Rac1 activity can therefore provide a regulatory switch between patterns of cell migration by a mechanism distinct from chemotaxis.

Show MeSH