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A talin-dependent LFA-1 focal zone is formed by rapidly migrating T lymphocytes.

Smith A, Carrasco YR, Stanley P, Kieffer N, Batista FD, Hogg N - J. Cell Biol. (2005)

Bottom Line: Talin is essential for the stability and formation of the LFA-1 zone.Disruption of the talin-integrin link leads to loss of zone integrity and a substantial decrease in speed of migration on ICAM-1.This adhesive structure, which differs from the previously described integrin-containing attachments displayed by many other cell types, we have termed the "focal zone."

View Article: PubMed Central - PubMed

Affiliation: Leukocyte Adhesion Laboratory, Cancer Research UK London Research Institute, London WC2A 3PX, England, UK.

ABSTRACT
Cells such as fibroblasts and endothelial cells migrate through the coordinated responses of discrete integrin-containing focal adhesions and complexes. In contrast, little is known about the organization of integrins on the highly motile T lymphocyte. We have investigated the distribution, activity, and cytoskeletal linkage of the integrin lymphocyte function associated antigen-1 (LFA-1) on human T lymphocytes migrating on endothelial cells and on ligand intercellular adhesion molecule-1 (ICAM-1). The pattern of total LFA-1 varies from low expression in the lamellipodia to high expression in the uropod. However, high affinity, clustered LFA-1 is restricted to a mid-cell zone that remains stable over time and over a range of ICAM-1 densities. Talin is essential for the stability and formation of the LFA-1 zone. Disruption of the talin-integrin link leads to loss of zone integrity and a substantial decrease in speed of migration on ICAM-1. This adhesive structure, which differs from the previously described integrin-containing attachments displayed by many other cell types, we have termed the "focal zone."

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IRM reveals the areas of direct contact between migrating T cells and ICAM-1. (A) The DIC image compared with the IRM image and the ICAM-1 binding focal zone (red). The IRM image identifies the total area of the T cell in direct contact with ICAM-1 in the bilayer and demonstrates intermittent, close, and lack of attachments in lamellipodia, focal zone, and uropod, respectively. Double-sided arrow, closest attachment to the substrate; black arrow, the leading edge; white arrow, the uropod of the migrating T cell. Overlaying the ICAM-1 and IRM images shows that the area of uniform attachment colocalizes with the focal zone. (B) Quantification of the area in contact with the bilayer compared with the area of the focal zone (n = 10; ±SD). All images were taken with a 63× oil immersion objective. Bars, 10 μm.
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fig4: IRM reveals the areas of direct contact between migrating T cells and ICAM-1. (A) The DIC image compared with the IRM image and the ICAM-1 binding focal zone (red). The IRM image identifies the total area of the T cell in direct contact with ICAM-1 in the bilayer and demonstrates intermittent, close, and lack of attachments in lamellipodia, focal zone, and uropod, respectively. Double-sided arrow, closest attachment to the substrate; black arrow, the leading edge; white arrow, the uropod of the migrating T cell. Overlaying the ICAM-1 and IRM images shows that the area of uniform attachment colocalizes with the focal zone. (B) Quantification of the area in contact with the bilayer compared with the area of the focal zone (n = 10; ±SD). All images were taken with a 63× oil immersion objective. Bars, 10 μm.

Mentions: The focal zone is an area of direct contact between LFA-1 and ICAM-1, but it is also possible that ligand engagement occurs in other areas of the cell. To further examine the contacts between T cell LFA-1 and ICAM-1, we used the lipid bilayer model together with interference reflection microscopy (IRM). The IRM images revealed a pattern of intermittent contact in the lamellipodial area (Fig. 4 A, black arrow), whereas the mid-cell region displayed uniformly dense contact with ICAM-1 (IRM; Fig. 4 A, double arrow), indicating that this region was the most firmly attached area of the cell. This latter area was coincident with the focal zone (Fig. 4 A, ICAM-1 and merge) and comprised 22% (equal to 20.7 μm2) of the total area in contact with the bilayer (Fig. 4 B). Our findings show that the lamellipodia region provides adhesive interactions between LFA-1 and ICAM-1, but these interactions do not result in an accumulation of ICAM-1 that is distinguishable from the level in the lipid bilayer. Therefore, as the total area making adhesive contact was greater than the focal zone, attachment to ICAM-1 must be mediated by distinct membrane distributions of LFA-1, potentially in different activity states. Finally, although expressing high levels of LFA-1, the uropod was IRM negative, indicating a lack of interaction with ICAM-1 (Fig. 4 A, white arrow). Despite the focal zone and uropod containing high levels of LFA-1, the lack of ICAM-1 binding activity in the uropod indicates differential control of integrin activity between these two cellular locations.


A talin-dependent LFA-1 focal zone is formed by rapidly migrating T lymphocytes.

Smith A, Carrasco YR, Stanley P, Kieffer N, Batista FD, Hogg N - J. Cell Biol. (2005)

IRM reveals the areas of direct contact between migrating T cells and ICAM-1. (A) The DIC image compared with the IRM image and the ICAM-1 binding focal zone (red). The IRM image identifies the total area of the T cell in direct contact with ICAM-1 in the bilayer and demonstrates intermittent, close, and lack of attachments in lamellipodia, focal zone, and uropod, respectively. Double-sided arrow, closest attachment to the substrate; black arrow, the leading edge; white arrow, the uropod of the migrating T cell. Overlaying the ICAM-1 and IRM images shows that the area of uniform attachment colocalizes with the focal zone. (B) Quantification of the area in contact with the bilayer compared with the area of the focal zone (n = 10; ±SD). All images were taken with a 63× oil immersion objective. Bars, 10 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2171377&req=5

fig4: IRM reveals the areas of direct contact between migrating T cells and ICAM-1. (A) The DIC image compared with the IRM image and the ICAM-1 binding focal zone (red). The IRM image identifies the total area of the T cell in direct contact with ICAM-1 in the bilayer and demonstrates intermittent, close, and lack of attachments in lamellipodia, focal zone, and uropod, respectively. Double-sided arrow, closest attachment to the substrate; black arrow, the leading edge; white arrow, the uropod of the migrating T cell. Overlaying the ICAM-1 and IRM images shows that the area of uniform attachment colocalizes with the focal zone. (B) Quantification of the area in contact with the bilayer compared with the area of the focal zone (n = 10; ±SD). All images were taken with a 63× oil immersion objective. Bars, 10 μm.
Mentions: The focal zone is an area of direct contact between LFA-1 and ICAM-1, but it is also possible that ligand engagement occurs in other areas of the cell. To further examine the contacts between T cell LFA-1 and ICAM-1, we used the lipid bilayer model together with interference reflection microscopy (IRM). The IRM images revealed a pattern of intermittent contact in the lamellipodial area (Fig. 4 A, black arrow), whereas the mid-cell region displayed uniformly dense contact with ICAM-1 (IRM; Fig. 4 A, double arrow), indicating that this region was the most firmly attached area of the cell. This latter area was coincident with the focal zone (Fig. 4 A, ICAM-1 and merge) and comprised 22% (equal to 20.7 μm2) of the total area in contact with the bilayer (Fig. 4 B). Our findings show that the lamellipodia region provides adhesive interactions between LFA-1 and ICAM-1, but these interactions do not result in an accumulation of ICAM-1 that is distinguishable from the level in the lipid bilayer. Therefore, as the total area making adhesive contact was greater than the focal zone, attachment to ICAM-1 must be mediated by distinct membrane distributions of LFA-1, potentially in different activity states. Finally, although expressing high levels of LFA-1, the uropod was IRM negative, indicating a lack of interaction with ICAM-1 (Fig. 4 A, white arrow). Despite the focal zone and uropod containing high levels of LFA-1, the lack of ICAM-1 binding activity in the uropod indicates differential control of integrin activity between these two cellular locations.

Bottom Line: Talin is essential for the stability and formation of the LFA-1 zone.Disruption of the talin-integrin link leads to loss of zone integrity and a substantial decrease in speed of migration on ICAM-1.This adhesive structure, which differs from the previously described integrin-containing attachments displayed by many other cell types, we have termed the "focal zone."

View Article: PubMed Central - PubMed

Affiliation: Leukocyte Adhesion Laboratory, Cancer Research UK London Research Institute, London WC2A 3PX, England, UK.

ABSTRACT
Cells such as fibroblasts and endothelial cells migrate through the coordinated responses of discrete integrin-containing focal adhesions and complexes. In contrast, little is known about the organization of integrins on the highly motile T lymphocyte. We have investigated the distribution, activity, and cytoskeletal linkage of the integrin lymphocyte function associated antigen-1 (LFA-1) on human T lymphocytes migrating on endothelial cells and on ligand intercellular adhesion molecule-1 (ICAM-1). The pattern of total LFA-1 varies from low expression in the lamellipodia to high expression in the uropod. However, high affinity, clustered LFA-1 is restricted to a mid-cell zone that remains stable over time and over a range of ICAM-1 densities. Talin is essential for the stability and formation of the LFA-1 zone. Disruption of the talin-integrin link leads to loss of zone integrity and a substantial decrease in speed of migration on ICAM-1. This adhesive structure, which differs from the previously described integrin-containing attachments displayed by many other cell types, we have termed the "focal zone."

Show MeSH
Related in: MedlinePlus