CXCR3 internalization following T cell-endothelial cell contact: preferential role of IFN-inducible T cell alpha chemoattractant (CXCL11).
Chemokine receptors are rapidly desensitized and internalized following ligand binding, a process that attenuates receptor-mediated responses. However, the physiological settings in which this process occurs are not clear. Therefore, we examined the fate of CXCR3, a chemokine receptor preferentially expressed on activated T cells following contact with endothelial cells. By immunofluorescence microscopy and flow cytometry, we found that CXCR3 was rapidly internalized when T cells were incubated with IFN-gamma-activated human saphenous vein endothelial cells (HSVEC), but not with resting HSVEC. Similar results were obtained using human CXCR3-transfected murine 300-19 B cells. CXCR3 down-regulation was significantly more pronounced when T cells were in contact with HSVEC than with their supernatants, suggesting that CXCR3 ligands were efficiently displayed on the surface of HSVEC. Using neutralizing mAbs to IFN-induced protein-10 (CXCL10), monokine induced by IFN-gamma (CXCL9), and IFN-inducible T cell alpha chemoattractant (I-TAC; CXCL11), we found that even though I-TAC was secreted from IFN-gamma-activated HSVEC to lower levels than IFN-induced protein-10 or the monokine induced by IFN-gamma, it was the principal chemokine responsible for CXCR3 internalization. This correlated with studies using recombinant chemokines, which revealed that I-TAC was the most potent inducer of CXCR3 down-regulation and of transendothelial migration. Known inhibitors of chemokine-induced chemotaxis, such as pertussis toxin or wortmannin, did not reduce ligand-induced internalization, suggesting that a distinct signal transduction pathway mediates internalization. Our data demonstrate that I-TAC is the physiological inducer of CXCR3 internalization and suggest that chemokine receptor internalization occurs in physiological settings, such as leukocyte contact with an activated endothelium.
Sauty
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A
Division of Rheumatology, Allergy, and Immunology, Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Colvin
R A
RA
Wagner
L
L
Rochat
S
S
Spertini
F
F
Luster
A D
AD
D002448:Cell Adhesion; D002478:Cells, Cultured; D054357:Chemokine CXCL10; D054371:Chemokine CXCL11; D054370:Chemokine CXCL9; D019743:Chemokines, CXC / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D002634:Chemotaxis, Leukocyte; D017077:Culture Media, Conditioned / Q000494:pharmacology; D015536:Down-Regulation; D004705:Endocytosis; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007371:Interferon-gamma / Q000494:pharmacology*; D007700:Kinetics; D008856:Microscopy, Fluorescence; D021381:Protein Transport; D054367:Receptors, CXCR3; D019707:Receptors, Chemokine / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology*
C515202:CXCL11 protein, human; C080810:CXCL9 protein, human; C515187:CXCR3 protein, human; D054357:Chemokine CXCL10; D054371:Chemokine CXCL11; D054370:Chemokine CXCL9; D019743:Chemokines, CXC; D017077:Culture Media, Conditioned; D036341:Intercellular Signaling Peptides and Proteins; D054367:Receptors, CXCR3; D019707:Receptors, Chemokine; D007371:Interferon-gamma; D006493:Heparin