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Transcellular migration of leukocytes is mediated by the endothelial lateral border recycling compartment.

Mamdouh Z, Mikhailov A, Muller WA - J. Exp. Med. (2009)

Bottom Line: Depolymerization of microtubules has no effect on ICAM-1 enrichment but blocks targeted trafficking of LBRC membrane and transcellular migration by >90%.Similar to their effects on paracellular transmigration, antibodies against PECAM or CD99, but not JAM-A, block transcellular migration.We conclude that similar molecular mechanisms promote both para- and transcellular migration.

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Affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.

ABSTRACT
Leukocyte migration across endothelial cell borders (paracellular) and through endothelial cells (transcellular) appear to be distinct processes. During paracellular migration, membrane from a parajunctional reticulum of interconnected vesicles, the endothelial lateral border recycling compartment (LBRC), moves to surround the leukocyte in a kinesin-mediated, microtubule-dependent manner. We show that transcellular migration likewise requires targeted trafficking of LBRC membrane. We show that in addition to platelet/endothelial cell adhesion molecule (PECAM; CD31), CD99 and junctional adhesion molecule A (JAM-A), but apparently not vascular endothelial cell-specific cadherin (cadherin 5, CD144), are components of the LBRC. During transcellular migration, LBRC membrane invests the transmigrating leukocyte. Intracellular adhesion molecule 1 (ICAM-1) on the apical endothelial surface is enriched around adherent leukocytes. Depolymerization of microtubules has no effect on ICAM-1 enrichment but blocks targeted trafficking of LBRC membrane and transcellular migration by >90%. Similar to their effects on paracellular transmigration, antibodies against PECAM or CD99, but not JAM-A, block transcellular migration. We conclude that similar molecular mechanisms promote both para- and transcellular migration.

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Caveolae do not comprise the membrane that forms the transmigration pore. Leukocytes fixed in the act of transcellular migration were stained for caveolin-1 (red in merge), PECAM (green in merge), and DNA to label nuclei (blue in merge). PECAM forms a definite ring around the leukocyte (arrow), as seen in Fig. 1. In this image, several vesicular structures staining for caveolin-1 are seen distributed in a circular fashion around the transmigrating leukocyte as well (arrow). However, when the images are overlapped (merge), it is clear that the caveolin-1 staining is peripheral to and not overlapping with the PECAM staining. (inset) An enlargement of the transmigration pore displaying just the caveolin-1 and PECAM staining for clarity. In the inset, the brightness of the caveolin-1 staining was artificially raised to enable better visualization of caveolin-1. Data are representative of three independent experiments. Bar, 10 µm.
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fig2: Caveolae do not comprise the membrane that forms the transmigration pore. Leukocytes fixed in the act of transcellular migration were stained for caveolin-1 (red in merge), PECAM (green in merge), and DNA to label nuclei (blue in merge). PECAM forms a definite ring around the leukocyte (arrow), as seen in Fig. 1. In this image, several vesicular structures staining for caveolin-1 are seen distributed in a circular fashion around the transmigrating leukocyte as well (arrow). However, when the images are overlapped (merge), it is clear that the caveolin-1 staining is peripheral to and not overlapping with the PECAM staining. (inset) An enlargement of the transmigration pore displaying just the caveolin-1 and PECAM staining for clarity. In the inset, the brightness of the caveolin-1 staining was artificially raised to enable better visualization of caveolin-1. Data are representative of three independent experiments. Bar, 10 µm.

Mentions: A previous study provided evidence that ICAM-1 was recruited into caveolae, which were relatively enriched at the site of transcellular migration (Millán et al., 2006), although others studying the same phenomenon found caveolae to be only partially (Carman and Springer, 2004) or not enriched (Carman et al., 2007). Similar to the latter study, we rarely detected caveolin-1 staining around leukocytes migrating transcellularly. When we did, however, the staining was weak and clearly outside the zone of PECAM staining that encircled the transmigrating leukocyte (Fig. 2). Because there was no overlap of the green and red fluorescence (Fig. 2, inset), the membranes bearing PECAM and caveolin-1 should be at least 200 nm (approximately four caveolae diameters) apart.


Transcellular migration of leukocytes is mediated by the endothelial lateral border recycling compartment.

Mamdouh Z, Mikhailov A, Muller WA - J. Exp. Med. (2009)

Caveolae do not comprise the membrane that forms the transmigration pore. Leukocytes fixed in the act of transcellular migration were stained for caveolin-1 (red in merge), PECAM (green in merge), and DNA to label nuclei (blue in merge). PECAM forms a definite ring around the leukocyte (arrow), as seen in Fig. 1. In this image, several vesicular structures staining for caveolin-1 are seen distributed in a circular fashion around the transmigrating leukocyte as well (arrow). However, when the images are overlapped (merge), it is clear that the caveolin-1 staining is peripheral to and not overlapping with the PECAM staining. (inset) An enlargement of the transmigration pore displaying just the caveolin-1 and PECAM staining for clarity. In the inset, the brightness of the caveolin-1 staining was artificially raised to enable better visualization of caveolin-1. Data are representative of three independent experiments. Bar, 10 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2806621&req=5

fig2: Caveolae do not comprise the membrane that forms the transmigration pore. Leukocytes fixed in the act of transcellular migration were stained for caveolin-1 (red in merge), PECAM (green in merge), and DNA to label nuclei (blue in merge). PECAM forms a definite ring around the leukocyte (arrow), as seen in Fig. 1. In this image, several vesicular structures staining for caveolin-1 are seen distributed in a circular fashion around the transmigrating leukocyte as well (arrow). However, when the images are overlapped (merge), it is clear that the caveolin-1 staining is peripheral to and not overlapping with the PECAM staining. (inset) An enlargement of the transmigration pore displaying just the caveolin-1 and PECAM staining for clarity. In the inset, the brightness of the caveolin-1 staining was artificially raised to enable better visualization of caveolin-1. Data are representative of three independent experiments. Bar, 10 µm.
Mentions: A previous study provided evidence that ICAM-1 was recruited into caveolae, which were relatively enriched at the site of transcellular migration (Millán et al., 2006), although others studying the same phenomenon found caveolae to be only partially (Carman and Springer, 2004) or not enriched (Carman et al., 2007). Similar to the latter study, we rarely detected caveolin-1 staining around leukocytes migrating transcellularly. When we did, however, the staining was weak and clearly outside the zone of PECAM staining that encircled the transmigrating leukocyte (Fig. 2). Because there was no overlap of the green and red fluorescence (Fig. 2, inset), the membranes bearing PECAM and caveolin-1 should be at least 200 nm (approximately four caveolae diameters) apart.

Bottom Line: Depolymerization of microtubules has no effect on ICAM-1 enrichment but blocks targeted trafficking of LBRC membrane and transcellular migration by >90%.Similar to their effects on paracellular transmigration, antibodies against PECAM or CD99, but not JAM-A, block transcellular migration.We conclude that similar molecular mechanisms promote both para- and transcellular migration.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.

ABSTRACT
Leukocyte migration across endothelial cell borders (paracellular) and through endothelial cells (transcellular) appear to be distinct processes. During paracellular migration, membrane from a parajunctional reticulum of interconnected vesicles, the endothelial lateral border recycling compartment (LBRC), moves to surround the leukocyte in a kinesin-mediated, microtubule-dependent manner. We show that transcellular migration likewise requires targeted trafficking of LBRC membrane. We show that in addition to platelet/endothelial cell adhesion molecule (PECAM; CD31), CD99 and junctional adhesion molecule A (JAM-A), but apparently not vascular endothelial cell-specific cadherin (cadherin 5, CD144), are components of the LBRC. During transcellular migration, LBRC membrane invests the transmigrating leukocyte. Intracellular adhesion molecule 1 (ICAM-1) on the apical endothelial surface is enriched around adherent leukocytes. Depolymerization of microtubules has no effect on ICAM-1 enrichment but blocks targeted trafficking of LBRC membrane and transcellular migration by >90%. Similar to their effects on paracellular transmigration, antibodies against PECAM or CD99, but not JAM-A, block transcellular migration. We conclude that similar molecular mechanisms promote both para- and transcellular migration.

Show MeSH
Related in: MedlinePlus