CD73 is involved in lymphocyte binding to the endothelium: characterization of lymphocyte-vascular adhesion protein 2 identifies it as CD73.
We have recently described a monoclonal antibody (mAb) 4G4 recognizing a 70-kD molecule constitutively expressed on human endothelial cells and on subpopulations of lymphocytes. We showed that this molecule, which we named lymphocyte-vascular adhesion protein 2 (L-VAP-2), mediates lymphocyte adhesion to cultured endothelial cells. Protein sequencing of tryptic peptides from immunoaffinity-purified L-VAP-2 revealed sequence identity between L-VAP-2 and CD73 (ecto-5'-nucleotidase, E.C.3.1.3.5), and COS cells transfected with a CD73 cDNA were positively stained with the mAb 4G4, which recognizes L-VAP-2. mAb 4G4 was also able to partially inhibit the ecto-5'-nucleotidase activity of peripheral blood lymphocytes. Moreover, cross-precipitation studies performed with mAb 4G4 and a CD73 workshop mAb 1E9 showed that these two antibodies recognize the same molecule. Since the tissue distribution and biochemical characteristics of the two molecules are also similar, we conclude that L-VAP-2 and CD73 are the same glycoprotein. Adhesion experiments showed significantly increased binding of freshly isolated lymphocytes to COS cells transfected with a CD73 cDNA, as compared to mock-transfected COS cells, and binding of lymphocytes to CD73-expressing COS cells was inhibited by the presence of mAb 4G4 in the adhesion assay. CD73 is a glycosyl phosphatidylinositol-linked molecule previously shown to have a cosignalling role in T lymphocyte proliferation. Our data suggest that it also has a function in mediating lymphocyte adhesion to the endothelium.
Airas
L
L
National Public Health Institute, Turku University, Finland.
Hellman
J
J
Salmi
M
M
Bono
P
P
Puurunen
T
T
Smith
D J
DJ
Jalkanen
S
S
D015720:5'-Nucleotidase / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001483:Base Sequence; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D018076:DNA, Complementary / Q000235:genetics; D004730:Endothelium, Vascular / Q000166:cytology*; D006801:Humans; D008214:Lymphocytes / Q000166:cytology*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D018076:DNA, Complementary; D015720:5'-Nucleotidase