CCR7/CCL19 controls expression of EDG-1 in T cells.
ABSTRACT T lymphocytes circulate between the blood, tissues, and lymph. These T cells carry out immune functions, using the C-C chemokine receptor 7 (CCR7) and its cognate ligands, CCL19 and CCL21, to enter and travel through the lymph nodes. Distinct roles for each ligand in regulating T lymphocyte trafficking have remained elusive. We report that in the human T cell line HuT78 and in primary murine T lymphocytes, signaling from CCR7/CCL19 leads to increased expression and phosphorylation of extracellular signal-regulated kinase 5 (ERK5) within eight hours of stimulation. Within 48-72 h we observed peak levels of endothelial differentiation gene 1 (EDG-1), which mediates the egress of T lymphocytes from lymph nodes. The increased expression of EDG-1 was preceded by up-regulation of its transcription factor, Krüppel-like factor 2 (KLF-2). To determine the cellular effect of disrupting ERK5 signaling from CCR7, we examined the migration of ERK5(flox/flox)/Lck-Cre murine T cells to EDG-1 ligands. While CCL19-stimulated ERK5(flox/flox) naïve T cells showed increased migration to EDG-1 ligands at 48 h, the migration of ERK5(flox/flox)/Lck-Cre T cells remained at a basal level. Accordingly, we define a novel signaling pathway that controls EDG-1 up-regulation following stimulation of T cells by CCR7/CCL19. This is the first report to link the two signaling events that control migration through the lymph nodes: CCR7 mediates entry into the lymph nodes and EDG-1 signaling controls their subsequent exit.
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ABSTRACT: Previous studies have demonstrated that, once released into the extracellular environment, the systemic sclerosis (SSc)-associated autoantigen DNA topoisomerase I (topo I) binds specifically to the surface of fibroblasts via an unknown receptor. We extended these results by identifying topo I-mediated cellular effects and characterizing the specific target of topo I on fibroblast surfaces. Purified topo I was used to investigate intracellular signaling pathway activation and tested for cell migration. To demonstrate the expression of specific chemokine receptors on fibroblasts, we performed immunoblotting and flow cytometry. To evaluate the direct interaction between chemokine receptor and topo I, a protein-protein based enzyme-linked immunosorbent assay (ELISA) was used. Finally, topo I coupled to the fluorochrome phycoerythrin (PE) was used to investigate competition of topo I specific binding on fibroblast surfaces with chemokine ligand. Topo I stimulated the phosphorylation of phospholipase Cγ1, c-Raf, ERK-1/2, and p38 MAPK, intracellular signaling pathways that stimulated fibroblast migration via a G(αi) protein-coupled receptor. CCR7 was found to interact directly with topo I. Furthermore, its ligand, CCL21, competed in vitro for this interaction and in vivo with the binding of PE-coupled topo I to fibroblast surfaces. These new roles of topo I in fibroblast physiology and the identification of its target on the cell surface demonstrate that topo I is a bifunctional autoantigen and open up new perspectives of study in the field of SSc-associated anti-topo I autoantibodies.Arthritis & Rheumatology 03/2012; 64(3):826. · 7.48 Impact Factor
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ABSTRACT: Interleukin 7 is essential for the survival of naive T lymphocytes. Despite its importance, its cellular source in the periphery remains poorly defined. Here we report a critical function for lymph node access in T cell homeostasis and identify T zone fibroblastic reticular cells in these organs as the main source of interleukin 7. In vitro, T zone fibroblastic reticular cells were able to prevent the death of naive T lymphocytes but not of B lymphocytes by secreting interleukin 7 and the CCR7 ligand CCL19. Using gene-targeted mice, we demonstrate a nonredundant function for CCL19 in T cell homeostasis. Our data suggest that lymph nodes and T zone fibroblastic reticular cells have a key function in naive CD4(+) and CD8(+) T cell homeostasis by providing a limited reservoir of survival factors.Nature Immunology 12/2007; 8(11):1255-65. · 26.20 Impact Factor
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ABSTRACT: Mature single-positive (SP) T lymphocytes enter a "resting" state in which they are proliferatively quiescent and relatively resistant to apoptosis. The molecular mechanisms regulating this quiescent phenotype were unknown. Here it was found that the expression of a Kruppel-like zinc finger transcription factor, lung Kruppel-like factor (LKLF), is developmentally induced during the maturation of SP quiescent T cells and rapidly extinguished after SP T cell activation. LKLF-deficient T cells produced by gene targeting had a spontaneously activated phenotype and died in the spleen and lymph nodes from Fas ligand-induced apoptosis. Thus, LKLF is required to program the quiescent state of SP T cells and to maintain their viability in the peripheral lymphoid organs and blood.Science 10/1997; 277(5334):1986-90. · 31.03 Impact Factor