Mitogenic lectins bind to the antigen receptor on human lymphocytes.
The specificity of interactions between mitogenic and non-mitogenic lectins and disulfide-linked cell surface receptors on human lymphocytes was explored. Lysates (Nonidet-P40) of surface-radioiodinated tonsil lymphocytes and T lymphoblastoid cells (HPB-ALL) were absorbed with lectin-agarose derivatives (or bovine serum albumin, BSA-agarose) or immunoprecipitated with appropriate monoclonal antibodies (mAb). Lectin eluates and solubilized immunoprecipitates were analyzed by two-dimensional (nonreduced/reduced) sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Radiolabeled polypeptides were visualized by autoradiography. Among the various lectin-binding polypeptides, two disulfide-linked heterodimers (II and III) and two apparent homodimers (I and IV) are bound by pea lectin, concanavalin A and lentil lectin on tonsil lymphocytes; II, III and IV are bound both leukoagglutinating (L)- and erythroagglutinating (E)-phytohemagglutinins from Phaseolus vulgaris (PHA). Pokeweed mitogen recognizes only II and III. These molecules are weakly bound by peanut agglutinin, soybean agglutinin, Ulex europaeus agglutinin-I, Dolichos biflorus agglutinin, Vicia villosa agglutinin and Sophora japonica agglutinin, but are not bound by Helix pomatia agglutinin or BSA-agarose. Heterodimer II (82-88 kDa), comprised of 50-55-kDa and 40-43-kDa subunits, probably represents the alpha/beta T cell antigen receptor (TcR alpha/beta). Heterodimer III (64-72 kDa), comprised of 41-kDa and 37-kDa subunits, may represent TcR gamma. The homodimers, I (120-130 kDa) and IV (55-61 kDa), comprised of 55-60-kDa and 30-kDa polypeptides, respectively, have apparently not been previously described. Evidence that H1-2D4, a mAb directed against the antigen receptor on HPB-ALL cells, and E-PHA interact with a common molecule includes: (a) immunoprecipitation of TcR with H1-2D4 from the glycopeptide fraction specifically eluted from insolubilized lectin with N-acetylgalactosamine; and (b) adsorption of TcR from a solubilized H1-2D4 immunoprecipitate by E-PHA-agarose. Recognition of CD3 by E-PHA is indicated by immunoprecipitation of CD3 protein by UCHT1 from the glycopeptide fraction specifically eluted from E-PHA. The results are consistent with the view that mitogenic lectins interact with certain disulfide-linked molecules on human lymphocytes, including the TcR alpha/beta and perhaps TcR gamma; while some nonmitogenic lectins also recognize these receptors, the interaction is of low affinity.
Chilson
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Department of Biology, Washington University, St. Louis, MO 63130.
Kelly-Chilson
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D000373:Agglutinins / Q000378:metabolism; D001666:Binding Sites, Antibody; D002458:Cell Fractionation; D003208:Concanavalin A / Q000378:metabolism; D004220:Disulfides; D006388:Hemagglutinins / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000378:metabolism; D007962:Leukocytes; D008214:Lymphocytes / Q000378:metabolism*; D014066:Palatine Tonsil; D019887:Peanut Agglutinin; D010455:Peptides / Q000378:metabolism; D010835:Phytohemagglutinins / Q000378:metabolism; D037121:Plant Lectins; D011043:Pokeweed Mitogens / Q000378:metabolism; D011506:Proteins; D011946:Receptors, Antigen / Q000032:analysis*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D011975:Receptors, Mitogen / Q000032:analysis*; D030262:Soybean Proteins
D000373:Agglutinins; D004220:Disulfides; D006388:Hemagglutinins; D037102:Lectins; D019887:Peanut Agglutinin; D010455:Peptides; D010835:Phytohemagglutinins; D037121:Plant Lectins; D011043:Pokeweed Mitogens; D011506:Proteins; D011946:Receptors, Antigen; D011948:Receptors, Antigen, T-Cell; D011975:Receptors, Mitogen; D030262:Soybean Proteins; C100155:leukoagglutinins, leukocytes; C028824:soybean lectin; D003208:Concanavalin A