Hyun Y-M, Sumagin R, Sarangi PP et al.Uropod elongation is a common final step in leukocyte extravasation through inflamed vessels. J Exp Med 209:1349-1362

Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, NY 14642, USA.
Journal of Experimental Medicine (Impact Factor: 12.52). 06/2012; 209(7):1349-62. DOI: 10.1084/jem.20111426
Source: PubMed


The efficient trafficking of immune cells into peripheral nonlymphoid tissues is key to enact their protective functions. Despite considerable advances in our understanding of cell migration in secondary lymphoid organs, real-time leukocyte recruitment into inflamed tissues is not well characterized. The conventional multistep paradigm of leukocyte extravasation depends on CD18 integrin-mediated events such as rapid arrest and crawling on the surface of the endothelium and transmigration through the endothelial layer. Using enhanced three-dimensional detection of fluorescent CD18 fusion proteins in a newly developed knockin mouse, we report that extravasating leukocytes (neutrophils, monocytes, and T cells) show delayed uropod detachment and become extremely elongated before complete transmigration across the endothelium. Additionally, these cells deposit CD18(+) microparticles at the subendothelial layer before retracting the stretched uropod. Experiments with knockout mice and blocking antibodies reveal that the uropod elongation and microparticle formation are the result of LFA-1-mediated adhesion and VLA-3-mediated cell migration through the vascular basement membrane. These findings suggest that uropod elongation is a final step in the leukocyte extravasation cascade, which may be important for precise regulation of leukocyte recruitment into inflamed tissues.

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    • "The mechanotransduction in the uropod is dependent on substrate stiffness because neutrophil crawling and TEM on stiff surfaces generate larger forces in the uropod than on softer surfaces (Oakes et al., 2009; Shin et al., 2010; Stroka et al., 2013). Human neutrophils and T cells showed impaired uropod retraction during TEM across inflamed HUVECs when their contractile forces were blocked by inhibition of myosin II or its regulator myosin-lightchain-kinase (MLCK) (Hyun et al., 2012; Stroka et al., 2013). "
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    ABSTRACT: The breaching of cellular and structural barriers by migrating cells is a driving factor in development, inflammation and tumor cell metastasis. One of the most extensively studied examples is the extravasation of activated leukocytes across the vascular endothelium, the inner lining of blood vessels. Each step of this leukocyte transendothelial migration (TEM) process is regulated by distinct endothelial adhesion receptors such as the intercellular adhesion molecule 1 (ICAM1). Adherent leukocytes exert force on these receptors, which sense mechanical cues and transform them into localized mechanosignaling in endothelial cells. In turn, the function of the mechanoreceptors is controlled by the stiffness of the endothelial cells and of the underlying substrate representing a positive-feedback loop. In this Commentary, we focus on the mechanotransduction in leukocytes and endothelial cells, which is induced in response to variations in substrate stiffness. Recent studies have described the first key proteins involved in these mechanosensitive events, allowing us to identify common regulatory mechanisms in both cell types. Finally, we discuss how endothelial cell stiffness controls the individual steps in the leukocyte TEM process. We identify endothelial cell stiffness as an important component, in addition to locally presented chemokines and adhesion receptors, which guides leukocytes to sites that permit TEM. © 2015. Published by The Company of Biologists Ltd.
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    • "To directly investigate the role of GzmB CTLs in transmigration, we imaged differentially labeled Gzmb À/À and WT CTLs in inflamed cremaster muscle by multiphoton microscopy (Hyun et al., 2012). This model allows precise application of proinflammatory mediators and covisualization of differentially labeled CTLs in the same postcapillary venules. "
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    • "To understand the mechanism that might underlie the effect of PKCθ on migration to lymph nodes, we determined the effect of PKCθ on uropod formation. Migrating T cell uropods have recently been shown to be crucial for migration into lymph nodes via transendothelial migration, likely through a role in force generation [6], [30]. Uropod formation is regulated in part by specific cytoskeletal protein localization to the uropod which can control both uropod formation and migration [6]. "
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    ABSTRACT: Cell motility is a fundamental process crucial for function in many cell types, including T cells. T cell motility is critical for T cell-mediated immune responses, including initiation, activation, and effector function. While many extracellular receptors and cytoskeletal regulators have been shown to control T cell migration, relatively few signaling mediators have been identified that can modulate T cell motility. In this study, we find a previously unknown role for PKCθ in regulating T cell migration to lymph nodes. PKCθ localizes to the migrating T cell uropod and regulates localization of the MTOC, CD43 and ERM proteins to the uropod. Furthermore, PKCθ-deficient T cells are less responsive to chemokine induced migration and are defective in migration to lymph nodes. Our results reveal a novel role for PKCθ in regulating T cell migration and demonstrate that PKCθ signals downstream of CCR7 to regulate protein localization and uropod formation.
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