title: Signaling through L-selectin mediates enhanced chemotaxis of lymphocyte subsets to secondary lymphoid tissue chemokine.
abstract: L-selectin functions as an important adhesion molecule that mediates tethering and rolling of lymphocytes by binding to high endothelial venule (HEV)-expressed ligands during recirculation. Subsequent lymphocyte arrest and transmigration require activation through binding of HEV-decorated homeostatic chemokines such as secondary lymphoid tissue chemokine (SLC; CCL21) to its counterreceptor, CCR7. Importantly, L-selectin also functions as a signaling molecule. In this study, signaling induced by ligation of L-selectin using mAb or endothelial cell-expressed ligand significantly enhanced the chemotaxis of murine T cells and B cells to SLC but not to other homeostatic chemokines. Consistent with the expression levels of L-selectin in different lymphocyte subsets, L-selectin-mediated enhancement of chemotaxis to SLC was observed for all naive lymphocytes and effector/memory CD8(+) T cells, whereas only a subpopulation of effector/memory CD4(+) T cells responded. During in vivo mesenteric lymph node migration assays, the absence of L-selectin on lymphocytes significantly attenuated both their ability to migrate out of the HEV and their chemotaxis away from the vessel wall. Notably, ligation of L-selectin and/or CCR7 did not result in increased CCR7 expression levels, internalization, or re-expression. Pharmacologic inhibitor studies showed that L-selectin-mediated enhanced chemotaxis to SLC required intact intracellular kinase function. Furthermore, treatment of lymphocytes with the spleen tyrosine kinase family inhibitor piceatannol reduced their ability to migrate across the HEV in peripheral lymph nodes. Therefore, these results suggest that "cross-talk" in the signaling pathways initiated by L-selectin and CCR7 provides a novel mechanism for functional synergy between these two molecules during lymphocyte migration.
authors.affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
authors.forename: Hariharan
authors.initials: H
authors.lastname: Subramanian
authors.forename: Jamison J
authors.initials: JJ
authors.lastname: Grailer
authors.forename: Kimberly C
authors.initials: KC
authors.lastname: Ohlrich
authors.forename: Amy L
authors.initials: AL
authors.lastname: Rymaszewski
authors.forename: Jessica J
authors.initials: JJ
authors.lastname: Loppnow
authors.forename: Masanari
authors.initials: M
authors.lastname: Kodera
authors.forename: Rochelle M
authors.initials: RM
authors.lastname: Conway
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Steeber
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects; D054421:Chemokine CCL21 / Q000502:physiology*; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D042783:Endothelial Cells / Q000166:cytology; D007156:Immunologic Memory; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D019041:L-Selectin / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D008198:Lymph Nodes / Q000166:cytology; D008643:Mesentery / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D054400:Receptors, CCR7 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D019718:Receptors, CXCR4 / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D013047:Specific Pathogen-Free Organisms; D013267:Stilbenes / Q000494:pharmacology; D000072377:Syk Kinase; D016176:T-Lymphocyte Subsets / Q000166:cytology*
chemical_list: D000911:Antibodies, Monoclonal; C514936:CXCR4 protein, mouse; C515371:Ccr7 protein, mouse; D054421:Chemokine CCL21; D047908:Intracellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; D054400:Receptors, CCR7; D019718:Receptors, CXCR4; D013267:Stilbenes; D019041:L-Selectin; C041525:3,3',4,5'-tetrahydroxystilbene; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse