CX3C-chemokine, fractalkine-enhanced adhesion of THP-1 cells to endothelial cells through integrin-dependent and -independent mechanisms.
Leukocyte adhesion and trafficking at the endothelium requires both cellular adhesion molecules and chemotactic factors. A newly identified CX3C chemokine, fractalkine, expressed on activated endothelial cells, plays an important role in leukocyte adhesion and migration. We examined the functional effects of fractalkine on beta1 and beta2 integrin-mediated adhesion using a macrophage-like cell line, THP-1 cells. In this study, we report that THP-1 cells express mRNA encoding a receptor for fractalkine, CX3CR1, determined by Northern blotting. Scatchard analysis using fractalkine-SEAP (secreted form of placental alkaline phosphatase) chimeric proteins revealed that THP-1 cells express a single class of CX3CR1 with a dissociation constant of 30 pM and a mean expression of 440 sites per cell. THP-1 cells efficiently adhered, in a fractalkine-dependent manner, to full-length of fractalkine immobilized onto plastic and to the membrane-bound form of fractalkine expressed on ECV304 cells or TNF-alpha-activated HUVECs. Moreover, soluble-fractalkine enhanced adhesion of THP-1 cells to fibronectin and ICAM-1 in a dose-dependent manner. Pertussis toxin, an inhibitor of Gi, inhibited the fractalkine-mediated enhancement of THP-1 cell adhesion to fibronectin and ICAM-1. Finally, we found that soluble-fractalkine also enhanced adhesion of freshly separated monocytes to fibronectin and ICAM-1. These results indicate that fractalkine may induce firm adhesion between monocytes and endothelial cells not only through an intrinsic adhesion function itself, but also through activation of integrin avidity for their ligands.
Goda
S
S
Departments ofInternal Medicine and Periodontology, Osaka Dental University, Hanazono-cho, Hirakata-shi, Osaka, Japan.
Imai
T
T
Yoshie
O
O
Yoneda
O
O
Inoue
H
H
Nagano
Y
Y
Okazaki
T
T
Imai
H
H
Bloom
E T
ET
Domae
N
N
Umehara
H
H
D000276:Adjuvants, Immunologic / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D054428:Chemokine CX3CL1; D020523:Chemokines, CX3C; D019743:Chemokines, CXC / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004727:Endothelium / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D004800:Enzymes, Immobilized / Q000235:genetics; D005353:Fibronectins / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000276:immunology / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000502:physiology*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007951:Leukemia, Myeloid; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009000:Monocytes / Q000276:immunology; D037342:Pertussis Toxin; D011485:Protein Binding / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012995:Solubility; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000276:Adjuvants, Immunologic; C515538:CX3CL1 protein, human; D054428:Chemokine CX3CL1; D020523:Chemokines, CX3C; D019743:Chemokines, CXC; D004800:Enzymes, Immobilized; D005353:Fibronectins; D016023:Integrins; D007527:Isoenzymes; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; D010566:Virulence Factors, Bordetella; C055791:germ-cell AP isoenzyme; D018799:Intercellular Adhesion Molecule-1; D037342:Pertussis Toxin; D000469:Alkaline Phosphatase