Galectin-1, a natural ligand for the receptor-type protein tyrosine phosphatase CD45.
Galectin-1 binds preferentially to N-acetyllactosamine residues on oligosaccharides associated with several cell surface glycoconjugates. In the present work, placental galectin-1 has been identified to be a natural ligand for the receptor-type protein tyrosine phosphatase CD45. The binding of galectin-1 to CD45 was detected by affinity chromatography of NP 40 solubilized Jurkat T cell membranes on galectin-1 agarose followed by immunoblotting of the galectin-1 agarose bound fraction applying monoclonal antibodies to CD45 isoforms. The PTPase activity of the galectin-1 agarose binding membrane fraction could be inhibited by sodium orthovanadate. Preincubation of Jurkat T cell membrane preparations with galectin-1 decreased the membrane-associated PTPase activity in a concentration-dependent manner. Incubation of Jurkat cells with galectin-1 suppressed the immunoprecipitated PTPase activity of CD45. Galectin-1 stimulates the cell surface expression of phosphatidylserine an early indicator of apoptosis. In CD45+ Jurkat T cells, galectin-1 induces higher levels of phosphatidylserine when compared with CD45- Jurkat cells. These observations indicate that galectin-1-mediated ligation of CD45 is involved in the induction of apoptosis in Jurkat T cells.
Walzel
H
H
Institute of Medical Biochemistry, University of Rostock, Germany.
Schulz
U
U
Neels
P
P
Brock
J
J
D017209:Apoptosis; D005434:Flow Cytometry; D037483:Galectin 1; D006388:Hemagglutinins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D019169:Jurkat Cells; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D008024:Ligands; D010718:Phosphatidylserines / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*
D037483:Galectin 1; D006388:Hemagglutinins; D008024:Ligands; D010718:Phosphatidylserines; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases